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IFS/SLA Hypothetical Roll Axis Diagram
When I started my independent rear suspension installation I gave very little consideration to the relationship of the IRS to the front suspension. I simply started with a car having a solid live axle and an independent front suspension; figuring any IRS would be an improvement. Since then, I have learned; maybe, maybe not. It is all about achieving a balance between the front and rear suspensions, tuning the suspension system to the intended purpose of your vehicle.
My intention is to build a street driven car. But, I am not against applying what we can learn from a road race vehicle in an effort to know what to expect when we do a bit of spirited driving. I have read articles pertaining to roll centers and roll axis in circle track racing, road racing, drag racing, and to a limited extent on production vehicles. I have a great respect for Steve Lyman's production car orientation. In his slide presentation, Collegiate Design Series Suspension 101*, he states in regard to roll center heights, "avoid rear heights that are much higher than the front, slight roll axis inclination forward is preferred". Although I find his presentations on roll centers, spring rates and motion ratio to be quite clear, this statement is ambiguous. How does one know how much is slight and whether or not the slope forward is up or down?
So, where do we start with an initial setup of our IRS? Rear roll center level with the front? Higher or lower in back?
*For a power point presentation or a .pdf version, Google; Steve Lyman Suspension 101.
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Yes - The front - first determine what it is. If satisfied -- Lucky you!
The incline of the roll axis is desired as you've drawn - angled down toward the front. You'd probably shoot for an RC about ground level to just below, with good migration qualities - e..g. none.
The rear - same exercise in determining the RC - and get it to maybe less that 4 inches AGL. And little migration.
As you've indicated -- its all about "balance."
For a track car you'll probably focus on less Bump and Droop - fewer potholes and curbs when on track. As a consequence, you can get very tight roll center placement. Moving to the street with its challenges - not so tight. There are several good and cheap/free software programs (there is a thread here and I'll be adding more) to help you do the analysis -or SolidWorks, or make a String Computer for a hands on approach.
Cheers - Jim
Last edited by phantomjock (4/12/2012 3:45 am)
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Here's Steve Lyman's work, in a PDF file.
PJ, irstang and I talked about the axis angle. He mentioned the axis even being level. Going back I think he was referring to a race configuration being level. Your mentioning for the street the axis should be higher to the rear. This all makes sense, since for a race application your on a smooth consistent surface. Plus racers are always dialing in the chassis. For street application I guess you would need to find a happy medium. I guess I'm just reiterating what you said. From what I have read and can see in my head, the IRS design already offers a lower RC than the leaf spring solid axle design. I'm not sure where a 4 link solid axles RC would be. So in this respect you have a gain here going to an IRS. If your RC becomes to much to low? An anti-swaybar would be needed at the rear.
Another factor that plays into this is the CG height, lower being better. The distance between RC and CG!
Trying to wrap my head around this topic you and irstang give focus to.
Last edited by Ralphy (4/12/2012 6:19 am)
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Gentlemen, thank you for the help so quickly. All else being correct, does a roll center lower in the front than the back induce a bit of understeer as you enter a turn a bit too fast? I will do a RC diagram of my front MII suspension and see where I am. Looks like everyone should be doing the same early on in their installation.
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Actually, at "less spirited"driving the roll axis could tend towards level - as I get it. One purpose of the "nose down" incline is to take advantage of the aerodynamic loading generated by the relative angle of attack. Like at Track Time!
Remember as a kid? Hand out the window? Now turn it 90 degrees pointing into the "wind" lengthwise like a car. Try and turn it with your finger tips front - but higher than palm -- whoops there it goes!!
Try again tips down - that's where the tarmac is -- and the suspension, the wheels for grip, etc... That's the picture!
Understeer - Oversteer - both can be generated by a number of factors - staggered tire widths - fatboys on the back, roll (anti) bars, chassis stiffness, etc. So many factors to consider - it may be best to set a few then make adjustments and then correct.
Start at the front - be satisfied and move to the rear!
Check out www.onedirt.com You can crawl around in th emud a bitthere -- some good stuff - but check out /Bing-or-Google "Finding Your Roll Center" by Curtis Dietzsch -- he give some hands on tips on measuring it -- if your car is still together - not torn up like mine.
TerrellRacing - You too Buddy!! Maybe measure your Griggs when it stops snowing!!
Cheers - Jim
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Thanks, again. Maybe we can get Daze to measure his front roll center with the Shelby drop, too.
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The way I have always understood the inclination of the roll axis was to make the entire suspension package more predictable when pushed to the point of oversteer. The inclination was put there by the engineers on purpose to give the illusion of a higher polar moment of inertia. Please note I said illusion, The mustang is light in the rear to begin with, not only that the front has more weight ahead of the front axle than the rear has behind the rear axle. If the roll axis was level the transient handling would be so erratic, the initial loss of traction would occur more quickly with out warning causing the more unskilled the driver with slow reactions to crash. Another way of looking at it might be that the roll axis when viewed from the side is a graph of the weight distribution. The higher the roll center, the lower the percentage of weight on that axle. The affect the inclination has on how the car handles is primarily in the transient handling area when the slip angle breaks the rear tires loose. The quicker this happens the less likely the driver will recover. The design basically slows this initial break in traction enough that an average driver can recover. As the percentage of rear axle weight is increased the roll center can be lowered with out loosing this effect as long as the ratios are kept equal. A high polar moment of inertia at the rear can make a car behave very similar initially, However the penalty of poor weight distribution and a high rear polar moment is if the driver gets into a oversteer slide and then chickens out by lifting off the throttle, the weight behind the rear axle will pull the car around like a pendulum into a spin. The raised rear roll center combined with a low rear polar moment of inertia will allow car the ability to correct its self if the throttle is lifted in the same situation. On my car I moved the engine to the rear 6 inches and down 3 inches in the chassis . This put the engine from the harmonic balancer back behind the front axle centerline and that made enough difference that when I was setting up my IRS I did my best to lower my rear roll center 1.5 inches to compensate. I was pleased with my results it handled better when I was done than it ever did with the live axle. This information is just what I have found reading suspension books and tuning cars for road racing and should be considered my opinion
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Thank you tyrellracing for your help. It is time for me to do my homework and see where I am with the front roll center. I plan on installing the engine light and as far back as I can, also. Sounds like the heavier sprung weight of the Jag diff in the rear will help a bit, too.
Last edited by irstang (5/04/2012 10:48 pm)
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I can't tell you where I read this yesterday. But it was a quote from a chassis builder. Saying a properly set up chassis will not need a rear anti-sway bar. It only adds more parts you carry around. We had so many customers ask why there was not one. We just started installing them because.
Also on Club Cobra a few guys that track their cars would chime in with newbies tracking theirs. Saying to remove the anti-sway bar and see if your times don't improve.
I guess I should add. A sway bar gives a sense of a higher RC. So removing the sway bar falls in line with the thought of a more level RC axis. The point made in an article irstang sent was. A level RC axis would remove any or more chassis flex. This was submitted to the NASCAR guys and I guess being used. So understand even NASCAR has been running a higher RC to the rear previously or still. The article also did not specify if they run this level RC axis on all tracks or which tracks.
Last edited by Ralphy (4/16/2012 8:21 am)
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Most people using front and rear sway bars on the track use them as tuning aids to combat over steer and under steer. The guys at club Cobra are correct in that you should not need a rear sway bar if the vehicles basic geometry was set up correctly. The reality is most track and street cars have flawed suspension geometry due to the lessor of two evils thinking. But if you are fighting a problem of under steer at corner entry the least expensive way to solve this problem is with a rear sway bar or a more effective rear sway bar. In an ideal world the rear sway bar would have little reason to exist, but in reality every ones vehicles are slightly different and when employed correctly the rear sway bar can be a useful tuning aide.
Since even consecutive vin numbered cars from the same assembly line the will have minute differences that will affect their ability to grip the tarmac, tuning aids will be necessary to obtain parity between them.
Their are a lot of people that think: since their car came with a front sway bar and that was good, getting a bigger front sway bar and a rear sway bar is better. In my opinion that is rarely the case. Since most performance cars have some form of negative camber gain designed into their suspension the bars will reduce this aspect of the suspension package while overloading the out side tires in a corner. Putting this into practice these two issues will create a corresponding reduction in the lateral grip previously available.
IMHO, the car may corner flatter but it will not necessarily corner faster or generate a greater lateral "G" force.
My question to the NASCAR guys would have to be, How did they move the rear roll center height with a truck arm rear suspension? They all use them with a pan hard rod and I always thought the roll center was more or less non adjustable with that set up. I could be mistaken but as I recall that set up puts the roll center on or about axle center. Doesn't it?
I never thought of the affect of a rear sway bar being similar to having a more level roll axis, but that seems logical since when taken to the extream they can both produce the similar results.
Last edited by tyrellracing (4/16/2012 12:17 pm)
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If you want to build to turn left (mostly) then any NASCAR idea will work I suppose. Let's say corner weighting, stagger in the wheels/tires, etc.
OTOH - if you want to Drag race - you wouldn't be here worrying IRS either! (And that good old trick of removing the front anti-roll bar to improve launch weight distribution, heaps of caster to keep going straight, etc. would be in the repertoire.)
And so here I am, trying to build a road/road race car. And no doubt a series of compromises will most likely be necessary.
Entry and carry through the turn - adequate control on exit stable with lots of throttle- all designed as close as possible and then tuned to "what works best."
No doubt it won't be right when first launched.
These comments are not meant to "pooh-pooh" any of these well made points, I think a balanced approach is what I'm seeking.
I'm not sure the anti-roll bar so much as gives a "sense of a higher RC," as much as it loads the chassis -- Is that what you meant Ralphy?
tyrellracing - ever use wheel tire combos to tune in/out understeer/oversteer? Theoretically possible - just wondering about the practical application.
Good conversation and thought points here - thanks guys.
Cheers - Jim
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If your RC height were equal to the CG the chassis would not want to roll in a turn right? If your CG were below the RC the chassis would actually want to roll opposite, like a pendulum. To high of a roll center will make your suspension more ridged in a turn. Same holds true for the sway bar, increases ridged. The purpose of lowering the RC is to reduce weight transfer onto the outside wheels as TR stated. Trying to keep the inners planted also.
NASCAR controls RC through the track bar/panhard. The trailing arms are not where roll center is achieved. Like the C3, we have trailing arms however our RC is set by the half shaft and camber rod angles. Drawing a straight line off both gives you the instant center. Then back down to the tire center for the RC. So when you see a NASCAR team pit and adjust the track bar? They are changing the RC.
The Mustang using leaf springs has an imaginary line from the leaf springs front and rear mounting bolts. Already in your mind I think you are seeing a much higher RC. This reads odd? Hmmm........
Up early today in Ohio, going west soon. Landed in one hell of a high wind yesterday, white caps on Lake Erie. That was an experience! Going to check out Shelby American this week. Not much of a gambler.
Last edited by Ralphy (4/17/2012 1:32 am)
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Using the rear sway bar to add roll stiffness to the rear suspension is a common way to reduce understeer on corner entry. Using a front sway to control over steer on corner exit is another commonly used method. Neither of these methods it the best way to solve these problems, rather they are common track side methods of solving underlying design flaws. These are as old of tuning methods as the sway bar design and should be considered tuning aids not permanent fixes. The right way of solving the problem is through design. That means no race car builder has ever built a suspension completely right because they all have to tune the suspension to existing track conditions. My point being that the best designs are tuneable to suit conditions at all tracks and not build a car for just one particular track. That is of course unless you have the funding of a top NASCAR team and have a different car for each track. I dont. LOL
Yes on the pan hard height controlling rear roll center height. I just looked it up and thats exactally how the roll center is adjusted. My Bad. I dont work with truck arm type suspensions much and had completely forgotten that the intersection of the pan hard rod with the C/L of vehicle is how the r/c is determined.
I have many hours of diagnosis time driving vehicles to try to sort them out. Much of my seat of the pants methods of fixing handling problems are from first hand experiences. I dont claim its scientific nor do I claim my conclusions are always correct. The only thing I know I can rest my laurels on is my success rate. I have always found some of the methods of finding the roll center height on some of the different designs to be questionable but accept them as true for design proposes.
More later I have got to get my ass to work.
Last edited by tyrellracing (4/17/2012 6:36 am)
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Interesting comments. I might as well chime in. May not add much but we'll see. We've had an interesting experience with the MG-Roadmaster, and it shares many characteristics with the Cobra, particularly the Arntz-Butler variety. About the same size, weight and power, same suspensions basically, and weight distribution is probably very similar. One significant difference is increased rear suspension travel (8") and another is air suspension at the front.
We have no roll bars on the car whatsoever. Now mind you this is not a track car. It is a street car and cannot be said to have finished evolving. So we have no competitive track times thus far and that has not really been a focus. However, it has been on the track, in the hands of an experienced race car driver (Hal Waldrop), and it has been driven by a number of our members who are very competent and fast drivers. Our general consensus is that the car seems to be quite fast, could use a little less body roll but is not generally excessive, turns in quickly and is very controllable. However I'm quite sure that nobody has well and truly put it sideways yet. I've slid it a little. The suspension is very compliant and it takes the worst road irregularities in stride without getting the least bit upset. An almost dangerous characteristic as you begin to think you can ride over anything at any speed.
But the point here is that it has no sway bars, either on the rear or the front. Handling is pretty neutral with just a hint of being nose happy. My opinion is that just a little more rubber on the rear might balance it out perfectly.
In my experience with these cars, which handled pretty darned good before we ever did the first thing to them, handling is a very relative thing and depends on the objectives and the type of driving, but almost across the board if you can lower the body and widen the track the outcome is positive in a bunch of ways, one of which is decreasing the stiffness needed in the roll bar(s). Stiffer roll bars incrementally destroy almost all of the advantages of independent suspension by coupling motion from side to side, so it should be crystal clear that in terms of the roll bars, less is more. Unless you have to keep your skirts firmly planted, and have the glassy smooth surface to do it, in which case a go kart suspension would work.
There is a large faction that insists on the "larger is better" school of roll bars. Once the front is fitted with a bar suited for a Mack truck so that there is no detectable body roll, and a suitably hefty item fitted to the rear so that the car will turn, you have your flat cornering car which is pretty quick, but you're wondering why it has to ride so rough and tends to skate over bumps. It might be a pretty good track car but as a daily driver, well it sucks.
I've always been a bit of an outlaw so I never bought into that scheme. To me, the smart thing is to keep the ride, and widen the track to get the handling. Granted that's a fairly major undertaking but I'm not above body mods to get there, and all of this is perfectly acceptable for a street car. With track cars you have more rules. But if you can play with the CG, RC, a bit of geometry and tire stagger to get the handling without any roll bars at all it seems to me the car is going to be faster just because it doesn't transfer motion from wheel to wheel. And it'll certainly ride nicer.
Jim
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I have a Sunbeam Tiger that I ve owned for 15 plus years and it has no rear sway bar either. The last thing I would want to do is add more rear roll stiffness. It doesnt understeer going into turns but you have to pay close attention on the corner exit because if you try to accelerate away from the apex it likes to snap oversteer. In my opinion it has too high of percentage of it's weight on the front axle combined with a real short wheel base and a low rear polar moment. This makes driving it fast a real test of ones reaction skills. Kind of like standing on a basket ball.
When I worked at Oregon Auto Spring we made all of Quickors sway bars. About once a month we would get a custom order from Quickor for a 2 inch dia.front sway bar for a Camero or Mustang and a week or two after the customer installed it they would be at the front counter trying to get their money back. We got to the point where we would not make such ridiculous parts with out speaking directly to the end user first so we could explain what they were doing wrong and that all custom orders are non refundable.
I have seen too many vehicles that had too big of bars installed that felt like they cornered better but that was because the car had higher roll resistance. On a skid pad nearly every time the performance was worse. There is a lot of improvement that can be done by going to larger sway bars but like anything good there is a limit where you hit diminishing returns. Keeping a car level can help but not at the price of overloading the out side tires.
Last edited by tyrellracing (4/18/2012 5:20 pm)
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Anti sway bars do not couple the two sides of an IRS together like say a De dion tube would. They tend to add roll stiffness to the chassis through the bars resistance to torsional load. When a vehicle is in a constant state of cornering load the center of vehicle mass will act on the roll axis to in most cases compress the outside springs more than the inside springs. The sway bar simply adds more of the vehicle weight to the outside lower control arm as close to the tire as possible to hold the vehicle more level. . That is how they can overload the outside tires if too big of a bar is used.
Jim you said the MG's you helped build produced neutral cornering with a big block Buick for power? Is your entire engine behind the front axle center line? Have you put your MG on a scale to see how the weight is distributed front to rear? On the Cobra the entire engine is behind the front axle and that makes it a mid engine car. I dont know how much room the MG's have but my Tiger has the two rear cylinders behind the firewall to get the engine to fit in the tiny engine compartment and it is not a mid engine. When I was in high school I built a Fiat 124 spider with a 289 and a 4 spd and had to do the same thing. I cut out a huge hole in the fire wall to fit the rear cylinders past then fabbed up a new floor and trans tunnel. It was nose heavy and under steered on corner entry too. The 289 in that car put my feet in a awkward angle like the Cobras have but you get use to having your feet pointed to the left of forward.. There isnt much choice in the matter if you want the engine to fit. Your MG was a pretty good handling car from the factory. That had a lot to do with their light weight and nimble size. Then you added more than 400 lbs and most of that must be on the front axle. I am guessing on the weight and its distribution but my experience with nose heavy sports cars is they do not have neutral cornering ability's what so ever. At least none of mine ever did. I would be very curious to see how your MG does on a 300 ft.skid pad. My bench racing guess would be the front tires will break loose first. Neutral steering cars will break all four tires simultaneously on a skid pad. The idea of a skid pad is to go as fast as you can with out sliding at all. if a tire breaks traction , that was the limit of the vehicles grip and the test is over.
Widening the track with wheel offset alone will create a larger scrub radius and that is a bad trait. If you ever drove a car with a large scrub radius and hit a large pot hole it will nearly break your wrists ripping the wheel out of your hands. The only way to widen the track correctly is to move the knuckle out with the tire by building longer control arms. That way the center of the tire is on or near the king pin line and scrub is kept to a minimum. I know of no exception to this basic rule.
Last edited by tyrellracing (4/19/2012 5:54 pm)
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Making a few assumptions I see. Allow me to clear up some of the confusion. Stock weight distribution of an MGB is 51/49, about as close as it's ever realistically going to get. We've done a lot of engine swaps and that was a heavy 4 cylinder. The typical Rover V8 swap ends up about 30 pounds lighter.
The Buick BB was chosen for several reasons but light weight was at the top of the list. We weighed a similarly equipped original 4 and a 430 BBB with iron heads and intake. The BB was 200 lbs heavier on the money. We swapped to aluminum heads and intake on a lighter '71 455 block for an overall weight increase at the front of under a hundred pounds. On an MGB you have to be very good indeed to feel the difference of that much weight when driving.. To fit the engine in we notched the firewall behind the passenger's side head, moving that small section back 1/2". Low on the driver's side we increased the diameter of the tunnel opening by a similar amount, and lowered the steering cone, requiring a small reposition of the gas pedal, only noticeable if you have really big feet. We also lowered the steering rack, and more dramatic changes were needed at the front to accommodate the oversized radiator. I don't recall the exact size, but something like 17 x 32 double row aluminum.
But we didn't stop there. By adding the Jag IRS at the rear we increased the weight at the rear of the car by 90 lbs, while of course greatly reducing unsprung weight, greatly increasing suspension travel, and widening the track by nearly six inches, also allowing us to fit wider tires. (fenders were flared of course) So the overall weight balance is the same as original, just a couple hundred pounds heavier. In return for that we got better suspension and brakes, plus somewhere in the neighborhood of 400 extra horsepower. That's a trade I'll take nearly any day.
Now at the front. you are quite right, and the only thing we did there was increase the width of the tires. Though we may have moved them out just a little in the process, if we did it wasn't by much and the steering is light. But a wider tire does increase the width of the stance and although it was not as large a change as in the rear, even a couple inches helps.
Jim
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The Buick is much lighter than I ever imagined a GM big block engine ever could be. On the Fiat I had to intrude 10 inches into the fire wall to fit a 289 and on my Tiger they moved the fire wall back 6 inches when compared to an Alpine. In both cases the foot boxes were reduced by a substantial amount. I dont recall how far I had to move the trans tunnel on the Fiat but my tiger's driver side foot box was reduced by at least 5 inches because the clutch and brake pedals were factory bent to provide adequate spacing when compared to an Alpine.
I have a friend that owns two 455 GS convertibles and I was there when he installed his fresh rebuilt stage II 455 and I could have swore that engine weighed in at 600 lbs if it weighed an ounce. But having never seen it on a scale that was a guess. He also did not have aluminum heads which make a substantial reduction in weight. I know that 289's weigh 450 lb. full dressed and a small block Chevy weighs in at 500 lbs so that must have been a heavy four cylinder and a light BBB
I too have done many engine swaps. I own a 65 FJ 45 land cruiser that I built a full tube frame and installed a Chev 454, my daily driver is a 48 Volvo with a inter cooled turbo charged Toyota 3.4 V6 and Tacoma 4x4 running gear with TRD electric lockers at both ends. I have done several average swaps, V8 Vegas and V8 pintos and one mid engine 65 falcon wagon. The Falcon was my street racing sleeper from hell. I built a firewall behind the front seats and blacked out the rear glass so the engine wasnt visible. I coupled a built 351 C and C6 trans directly to the narrowed four link 9 inch rear. No drive shaft! Sounds goofy but it could do high 8's and low 9's all day long with the front tires aloft through first and second! That was back in my Pro street days when gas was cheap.
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Not as light as you might think? I just looked the weight of the 455 Buick thin wall casting type engine. According to the GM archives the Buick 455: From air cleaner to oil pan and from fan to flex plate weighs 770 lbs! That is still 150 lbs lighter than a 454 but almost three times the weight of the MG four cylinder it replaced. GM claims that the Buick 455 was cast with new techniques that made the new engine much lighter than their other big blocks due to a thin wall method of sand casting. However at 770 lbs it's no lightweight!
Your aluminum intake and heads are good for a max reduction of 150 lbs. That still leaves a 620 lb engine .
I am not trying to criticize or any thing of that nature. I think your MG project is cool , this is just what Google turned up
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Apples and oranges TR. There are other weight charts that show other weights. 600 lbs shows up a lot. For 770 lbs that must be a really heavy air cleaner. We did corner weights on the car before the interior and glass went back in and it was fairly well balanced. Next month at the annual BritishV8 meet they will corner weigh the car again for a total weight and corner numbers. I'll let you know what they get. The other mods also add up of course. We dropped some weight with the tubular exhaust, alloy water pump and the mini starter of course, but the front brakes added a few pounds. All I know for sure is the numbers I got weighing both engines. Now the way it stacks up is, the aluminum BOPR (215/Rover) is -30lbs. The '64 Buick 300 and SBF are +50 at around 400 lbs. The BBB adds another 50, as does my Buick 340 with Eaton blower and intercooler. Weights are approximate of course.These are all fitted with the light weight parts.
Jim
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No that came from a GM archival document not a chart. The pages described bore/stroke rod length,crank type, as well as internal architecture, type metal, and casting method. These were broken up in category's by make (Buick, Olds, Pontiac, ect.) then each engine by family then increasing displacement. I think their weight figures included the exhaust manifolds but was specific that no assessory's were included. From what I found GM never made any production big blocks that weighed 600 lbs. The ZL1 aluminum block 427 weighed in at 525lbs on the same site. Their description was air cleaner to oil pan and fan to flex plate.
Dont get me wrong. I am not putting a 455 an a scale and reporting the results nor am I criticizing your build. I just thought your numbers seemed light so I googled it and that was what I found. I would be very interested how the scale tips on the vehicle weight as well as the front to rear bias. More than anything else I like the work you posted on your build and think the BBB MG was a difficult engine swap if there ever was one. I dont care for the body work mod's but that is just my personal taste and I cannot think of a better way to make the tires fit inside the fenders
Last edited by tyrellracing (4/21/2012 8:31 pm)
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Mr Jim Blackwood. I owe you a sincere apology. I dont know how but I found the only place on the internet that claims the Buick 455 weighs 700 lbs. Since then I have found no fewer than 12 different unrelated sites that claim the BBB weighs 600 with a default figure of 640. The documents I found photo images of appear to have been original so the only way that could be possible is with all accessory's attached.
The best site I found was for Morgan sports cars and had a chart that covered more engines than all the others combined. The chart covered the weights of every thing from ww1 aircraft and motorcycles to modern F1 engines.
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My FE428 as best as I can glean weighs app. 550 lbs., 700 sounds a little high.
Ralphy
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I've seen on www.348-409.com the early chevy big blocks weighted 640 lbs as a long block assembly. I don't have the link off hand but I'm sure the bigger big blocks wouldn't weigh much more. In some cases, the 348s & 409s can be bored .125 over, which is a thick, thick cylinder wall. Having a 348 and seeing how wide it is, I'd believe the 640 weight.
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Thanks TR. I saw that heavy quote on a google search I ran yesterday, I'd guess the searches are chronological and it was recently posted.
Here is a link to a thread that has a photo of the scale used to corner weigh the car:
,27968
Now bear in mind this is with no glass or interior, and that shifted the weight rearward. But just the same, you see we're 50 lbs heavy on the driver's corner and 100 lbs heavy on the passenger's side. And of course, this is without a driver, battery or fuel which will also tend to balance out the weights. We are expecting the car to come in just under 2500 lbs when it gets weighed next month and be pretty well balanced.
Jim
Edit: It doesn't look like Pete will make Palestine so we'll have to wait on Bill to weigh the car. Probably be just a few more weeks. J
Last edited by Jim Blackwood (4/23/2012 8:39 am)
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I found it surprising that the 455 Buick weighs only 50 lbs. more than the stock 351 cleveland since it is a thin wall casting as well. I have been using C3 aluminum heads and Yates aluminum intake with Jessel valve gear on my Cleveland stroker for years but never bothered weighing it. Yesterday I got a killer deal on a rare Fontana aluminum Cleveland block. One of approximately a dozen cast the machine work was never finished so I hope I did not buy a blem. It should be here in a week. From the description I will have to rough deck the block to pressure test it. It was cast .500 above stock Cleveland deck height so I have plenty to play with If it passes pressure testing and inspection, I will do all the remaining machine work my self, . With any luck it should put my engine weight in the area of 350 lbs.
Last edited by tyrellracing (4/23/2012 7:08 pm)
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That'd be quite a feat TR, and best of luck with it. I hope it turns out as you want. The 215 Buick comes in at 318 lbs. Interestingly enough, when TAPerformance began producing their new all aluminum BBB block the weight was so close to the cast iron block that there was little if any weight savings by going to the aluminum block from cast iron. Now admittedly the TA block is a lot stronger, has reinforcements that the stock block does not, and will support displacements up to at least 700 cid. But still. That's a LOT of aluminum. The difference in weight from the 215 to the 300 and 340 (all the same series of engine) is 80 lbs. The cast iron just about doubles the weight of the block. So TA would have had to add at least 80 lbs to the block and possibly more. I guess it adds up, but it's still a LOT of aluminum.
So anyway, going to an aluminum block for the 455 will not make the engine any lighter. It can make it bigger, will make it stronger, and more reliable in most cases, definitely can make it more powerful, but lighter? Nope. Ain't gonna happen.
I just looked up some numbers. Actual weight for the stock block with caps and brass freeze plugs is 157.5 lbs. TA's aluminum block with steel main caps is 158 lbs. Without the caps it's 112 lbs. Yes, the caps weigh nearly 10 lbs each, but the block is good for 2000 hp, possibly more. Aftermarket cranks come in around 79 lbs.
Jim
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More weights: The 215 block weighs 60 lbs, with caps I believe. The 340 block weighs exactly 82 lbs more at 142 lbs. The 300 is 140 lbs. So the 455 block weighs 16 lbs more than the 340. Interestingly enough, the Buick 350 is the lightest of the iron SBB engines, excepting the '64 300 which had aluminum heads. The BBB crank is heavier by some 20-30lbs. We had all of these numbers before the engine ever went into the car the first time (except the weight of the TA block), so we knew it was going to be pretty light.
Jim
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I have no real idea of how much the cast aluminum block weighs. I am paying $150 for shipping but that doesnt mean much. I am familiar with the block from magazine articles I read over the years and always wanted one. The block has cast iron sleeves cast in and can be bored as far as 4.155 where as the cast iron Cleveland can only go 4.030 over safely. The Alum. block has 4 bolt mains on all five mains like the stock ford unit but it has splayed outer bolts that are larger than the stock units. The decks are over 9.503 and are tall enough to use 351 w rods and pistons. If I stay with my current internals I will have to mill the decks down to 9.200. The 408 stroker kit in my engine now could benefit from longer rods. I have 6 inch rods with a 4 inch stroke because I had insufficient deck height to go any longer on the rod length. I feel like a little kid 5 days from christmass.
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I bet. That will make a sweet engine. The SBF is a pretty light engine also, within 5 pounds or less of the SBB in some cases. So you do have a real potential lightweight on your hands. Let us know what it weighs when it comes in, OK?
Jim
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