Hey Gang, Lately there seems to be a fair amount of discussion behind the scenes about the best way to build our beloved Big Block Buick. Gary Kubisch and I were discussing our engines and our past experiences with the cars trying to come to some sort of an answer and the best way to build our next engines. So... anyone who has any thought on this subject please chime in and give your thoughts. From my experience I would say build the largest cubic inch engine possible but make sure there is still enough room in the cylinder walls for the next rebuild. I think this goes for stock BBB block and aftermarket. My example is this..... With my 464 engine in the 70 Skylark we typically went low 9.50s to high 9.40s. It did manage a 9.39 once but the air was terrific. When I went to the 523 engine the car went right into the 8.90s. So... that is about .40 to .50 quicker than my 464. Then when we switched to the 535 the car went into the 8.70s and I have no doubt in my mind that the car would have gone 8.60s and maybe even 8.50s on a good day on the east coast. So.... Engine Differences... The ETs below were from my data in my log book where I do track weather and Density Altitude. For every 1000 ft of DA higher the car will usually slow down a tenth. For every 1000 ft lower the car will typically pick up a tenth. 464 = 9.53 @ 2000 ft of DA 523 = 8.97 @ 1700 ft of DA 535 = 8.78 @ 2100 ft of DA 464 Crank is 3.90 stroke 523 Crank is 4.40 stroke 535 Crank is 4.50 stroke Cylinder heads 464 Stg 2 heads with great low numbers 225 @ .300 and 330's @ .600 523 Stg 4 heads with so so low number 210 @ .300 and 340's @ .600 535 Stg 4 heads with better low numbers 217 @ .300 and 353 @ .600 Almost identical exhaust numbers. Camshafts 464 was a solid cam 263/272 @ .050 523 was a roller cam 276/276 @ .050 535 is now a 286/296 @ .050 Also the 535 engine had quite a bit of work done to the rotating assembly to remove weight. The other components were close to being the same. So... when going from the 464 to the 523 there wasn't much difference in the cylinder head air flow and the biggest difference was in the crank stroke. When going from the 523 to the 535 the biggest change was reducing the reciprocating mass of the rotating assembly and putting the correct camshaft in the engine. Once while having a conversation with Mike from T/A, he explained that he decided to sell the 4.40 stroke cranks because of a computer program that said the 4.40 stroke would cause less stress on the block than the 4.50. I do know that this particular program is no longer sold but it could certainly be possible because of side thrust loads on the cylinder walls. Well I have ranted long enough... Anyone care to give there opinions and WHY they would make there decision?????????? Later :3gears:
John, same here. When I went from my 464 to my 535, I never looked back. I loved what the longer stroke did to my already stout Buick motor. I love torque. I figure with the extra cubes, 573, the thing should be even torqueier. My build for my car will revolve around a lower compression 573. I want a pump gas motor that will out run my 13 to 1 535. My car was built as a prostreet car and I want to be able to drive it on the street. I figure if my car will run in the 9's at my altitude on pump gas, I'll be a happy camper. The new engine will have better heads than the old one so I think the goal will be easily obtainable. And at least now I won't have to worry about the block every time down the track. I was reading somewhere awhile back that anything much over 4.5 inches in bore is not as efficient as 4.5. I believe the article was comparing a 4.5 inch bore to a 4.6 inch bore. The only substitute for cubic inches in my book is a blower. Jim Burek
Jim, I can understand your situation for wanting to build a low compression street engine that is a torque monster. If your looking to go mid nines that is typically around 140 mph. For the average tire diameter and rear gear ratio the engine will have to turn around 7000 rpms. Where I see a much different situation is where guys are looking to go into the low 9s or even faster. I used to bust Doug Hecker's chops all the time about spinning his engine so hard. But I never realized that I am not going to go low 9s at 6400 rpms with a car that weighs in at 2800 lbs. To do this you need to start going with 4.33 gears and up and then you try to use a bigger tire to get the car to hook. This combo dictates an engine rpm that is higher than 7000 rpms. Its simple math..... When we were going 8.80 to 8.90 we had a 4.33 rear gear with 32 inch tall tire. With a converter that slipped 5-6% the engine was spinning at 7500-7600 rpms. Now.. this is where I ask you guys to start thinking about crank stroke... At some point you have to start thinking RPM!!!! If you want higher RPM then it would probably be best to sacrifice some crank stroke to reduce loads on the block. What do you think Jim? and anyone else??
Well I don't have the expertize that many here do, but I know that in Pro Stock they use a short stroke big bore and spin the engine high to get the required horsepower needed to run the times they do. In IHRA the smaller displacement motors don't seem to have a problem with the mountain motors. So if you want the opinion of someone who follows drag racing, but has never built an engine the likes of which you guys do, I'd say that block strength and airflow to turn high rpm in a 500 cid engine will get you farther then huge cubes spinning lower RPM would. Besides using forced induction or NOS the only way to get maximum air into an engine is to spin the heck out of it.
My opinion isn't so much cubic inches as it is bore/stroke ratio. For unlimited drag racing, a big bore, shorter stroke (oversquare) will always be faster than the opposite at the same cubic inch. Like John said, it's simple math. Someone mentioned Pro Stock NHRA vs. IHRA. The NHRA guys are making the bores as big as they can within the rules. NHRA limits the blocks to 4.90" bore centers. IHRA has much higher CI limits and larger bore centers, but the block architecture still limits the largest possible bore/stroke. The IHRA cars have about 250-300 more cubic inches, but I believe they are only about 2-3 tenths quicker. Why? RPM's and cylinder heads. They can't get a port and valve configuration to support 800 ci and 9,500 RPM's. On a more realistic level, I lost the romance with "low-end torque" a long time ago. My previous racecar was a Oldsmobile 455. With a 4.155 bore and 4.25 stroke it had plenty of low end torque. Great if you're towing a trailer. Big headache if you want to go fast. Most of the really fast (8,9 second) Olds use the small block at about 400-410 ci. I also learned that "low end torque" doesn't mix well with 9" slicks. Let it hook, THEN bring on the power. If you're driving on the street and doing burnouts, stay with low end torque. If you want to build a serious drag car, spin it hard. Just my opinion. Have fun.
Yeah, I know. My car has 4.30 gears and 32 inch tall tires. It had gone a best of 10.17 at 134 not hooked up yet, just before it broke an axle. It broke an axle when the vht'd the track and the tires hooked, that problem should now be solved. I twisted my 535 to 7000 rpm. Like I said, I am not looking to be anywhere near the fastest guy out there, I simply want my car to run 9's here at home. Jim Burek
Jeff, I agree that the 700 to 800 cubic inch IHRA engines do not have the cylinder head to support the CID and that they are ONLY .20 to .30 quicker than the 500 CID NHRA engines but yet they are still faster. o No: Why?? This is what I am questioning. The Olds guys that are going so fast with smaller 416 to 434 CID engines are doing this with higher compression and internal parts that are much much lighter than our Buick stuff. For example the crankshafts... our stock crank is 72 lbs and a Moldex in anywhere from 77 to 90 lbs. The Olds cranks are anywhere from 42 lbs to 50 lbs. Thats a great deal less weight to be spinning and thus creating some great ET numbers. So.... is going with an extremely lightweight BB Buick crank the way to go and keep the engine at 500 CID? Also another idea.... If the deck height on the new block is still around 10.600 would it be smarter to remove some of the deck surface and take that down to say 10.500 or 10.400. That is .100 or .200 thousands of connecting rod that you dont need to be dragging around. Jim B., At 6000 feet above sea level where you live can a NHRA Pro Stock in the 9s?? :laugh: Come on other engine GURU's.... whats your opinion here. Jim W. what do you think?? Mike from T/A???? Brian Earick??? Rob C.??? Bob Mackley... come on man... I know your getting bored sitting at home.. talk with me LOL. Knowing that we may now be able to go to 572.. Dreams still... maybe.. But if everything goes right how would you build your engine and why? Lets even pretend for a bit that we have a cylinder head that will flow up to 400 CFM. Later
John, For a strip only motor, your thinking is correct. Consider how well the oversquare 455 based (462,464) runs. Also that 470 combo some guys are running. Your correct, you have to spin the death out of them to go fast, one thing we won't due with Sweesy's motor, preferring to be a few tenths off where it could run, to keep that stock block motor together, and let him have some fun with it for a change. Now with that rpm limitation gone with a stronger block, I would prolly build a 540" motor (4.25 stroke- 4.500 bore). Bigger motor would be good for a street deal, with plenty of torque, but that's not what your after. No, I would not whack the deck, I would get a piston built with about twice as much skirt as the typical stock block based strokers. They are tough on the cylinder walls with that tiny skirt length, and with the typical .009-.010 piston to wall on those motors, I feel we are losing some power with piston rock. I am certain that is why the race motors respond to the addition of a vacuum pump motor, more than the street motors do. I think a light billet crank with smaller mains, alum rods, lightened pistons with more skirt, bigggg roller cam and paper thin stage 4's would be the ticket. Buzz it thru the traps with some good gearing. Also a good candidate for a tunnel ram with a pair of alcohol 4150 1000's on it. Alky will bring the torque up to near what a bigger motor would put out (typically a 6% increase over gas) Keep the runner length at about 5" with lots of volume. 2-1/4 headers with 4" collectors. Scotty has always turned them hard, that's why his car sounds (and runs) like it does. JW
Here's some food for thought......... I've seen 500 inch motors make well over 1000HP and 632's that come up short of 1000HP....... What does this tell us..........? I believe parts selection and operating parameters are more important than the cubic inch. I ordered the 4.5 bore and have been running the 4.25 stroke so that is what I was leaning toward,A 540 combo with rpm potential of 7800 or so....... So much for the valve spring life I've been enjoying below 7000rpm,It's all about steppin' up........Can't wait. So who's gonna step up with heads????
John, hundreds of millions of R&D dollars spent.short stroke big bore.fastest and quickest naturally aspirated door cars on the planet. There must be a correlation somewhere? Cylinder heads are only a phone call away.
Brian, I understand that when limited to 500 CID that a short stroke big bore combo is the best way to go. This is kind of the scenario we are faced with... If NHRA told the Pro Stock engine builders... We have decided to raise the CID rule to a 4.600 bore and a 4.600 stroke which equals 612 CID... OH... and you still have to use the same cylinder head. Would the NHRA guys stay at 500 CID or would they go to 612 CID???? Just food for thought!
John, hope you appreciated my humorous answer to your question. The new block now opens up many new options for us. One extremely important factor that I havent seen anyone talk about yet is the bore center. Without going to at least 4.840 you wont be able to have adequate cylinder head flow for both high RPM and big cubic inches. As to your NHRA pro stock engines, they would and some already have increased the cubic inches. The reason that the 815 cid IHRA engines work is because the bore center is 4.900. After they stretched the bore center we were able to develop an adequate cylinder head for the engine. One other factor is that the larger the engine displacement is the exponentially more difficult it is to achieve high efficiency numbers.
I'm with Jeff and others who favor small cubes on the Big Bore(over-square). Unless you find more gears to keep the rpms low the Buick heads at the moment are the limit. YOu can only go so big and still feed it at rpm. The faster you go the more rpm you need for 2 to 3 gears with out slowing it down by a rear gear drop. YOu could go to a liberty, lenco, ect. but the rear gear is still a multiplication of HP so dropping it in favor of more foward gears I feel is counter effective to a point. On a naturally aspirated car I feel you can feed the @535 but only with a newer 55mm cam where you can get the "lobe area" needed without excessive power robbing overlap. Of coarse then there's the T&D race rockers to keep it stable and together. THis is a pretty broad discussion to cover on a short note but worth talking about. I'm a "power-adder" guy so it will be a while before, if ever, I go bigger. Turbos with the current head flow and 470 cube will make well over 2000Hp so after the nitrous thats where I'll be instead of more cubes. Cam specs is another thing of thought being the 55mm is available. You can get so much better of a cam now that the small base circle is gone. Its not just overall lift but the ramps can be so much more aggressive giving the the lobe on the cam more area with out going crazy with duration. Since all this would require the high dollar race T&D's, I would opt. for the 1.7-1.8 rocker ratio. Be ready to get tappered $$$ big pushrods to keep it sable along with$$$ springs. So who wants to go FAST!?! Another opinion on "BIG 500+ cube" setups is that they are more forgiving on combination "flaws". A little off on the cam, gear, converter, ect will not be as bad as if it was done on a small cube race motor. THere is less Hp loss on a small motor and with the same airflow you could essentially make the same or more HP if it was done right at less weight and with more gear to multiply the power more. Heads-Up racer >>>> Smaller motor more $$$$ Bracket racer >>>>> Bigger Motor less $$$
I was digging through some old info I had saved and I ran across this post from Darin Morgan of Reher-Morrison Racing Engines on an old message board. The discussion involved comparing NHRA 500 ci motors to IHRA 800 ci motors. The info he shares here is also extremely relevent to the conversation in our thread and our Buicks: _______________________________________________ The reason they don't have any valve area is because of the ridiculous bore stroke ratio. In a two valve engine the size of the intake valve is directly proportional to the bore size. Any more than 52% of the bore in a wedge and 54% of the bore for a canted valve/Hemi design is usually detrimental because valve efficiency drops dramatically after that. The efficiency is rated as a coefficient such as CFM/INsq or mass flow in relation to a theoretical maximum also known as discharge coefficient. Look at our discharge coefficients in relation to our piston speeds and then take a hard look at what they are doing. Those things are operating at a ludicrously high piston speed range. No other engine on the planet operates in that piston speed range because its not a mechanically sound way of doing it. They do operate way out of there actual power range to get as much RPM as possible but again, its not efficient. Look at our valve size in relation to bore verses our piston speed and you will see that we can fill the cylinder quite adequately with VEs in the 115-117 range at peak power and 125+ at the torque peak. They are lucky to achieve 90% VEs and it falls off fast. I am speculating by calculating it because I have never seen what the actual VEs are on those engines. I have never seen a Mass flow meter or turbine used with one on the dyno. Even if they did have the valve area or mass flow the pistons speeds ( which are totally insane) would limit them to about the same RPM range they operate in now. It all goes back to BORE STROKE RATIO. In all other high end racing engines this is key to producing power by achieving a balance of valve area, bore diameter and stroke so as to operate the engine in an RPM range to achieve the highest VEs possible. These guys just throw Stroke at it because of bore space limitations which lowers the RPM range of the engine thereby decreasing the amount of horse power you can extract from the engine. Torque is just a static force. Horsepower is WORK being done over a giving amount of TIME. Think about it. To get from point A to point B (1/4 mile) we have to do more work in less time, don't we? So with that being said it does not make a whole lot of sense to LOWER the torque peak by throwing stroke at an engine thereby lowering the potential Horse power, Now does it? That is why they only run a couple tenths faster instead of a second faster with 300 cubic inches more. Calculate what bore size and bore spacing they would have with the same Valve area/CID ratio using the maximum 54% of bore diameter like every other engine on the planet. It will scare you. You can not build a block that big and make it usable in Drag racing. On another note. Those engines are just as expensive to build as one of our 500 inch engines. They last about one tenth as many passes as our 500 inch engine because of the insane piston speeds they run. You can not cheat the laws of physics. _______________________________________________ Very interesting! Have fun.
Jeff, That is some very good information!!! Thanks for sharing. When Gary and I had our phone conversation about this subject I brought up piston speed and rod angle and its effects on our blocks. The most interesting information is the statement that a big inch engine will get about 1/10 the amount of passes. :eek2: Great discussion everyone.. thanks for adding to the discussion. Jim W. I do like the idea of a longer skirt on the pistons. When especially when the pin is moved up near the oil ring! Take Care
One other factor is that the larger the engine displacement is the exponentially more difficult it is to achieve high efficiency numbers. that's due, in large part, to the aerodynamic drag off of the big valve diameters is it not? if so, who's planning a set of 24v / 32v big block heads? :bglasses:
John what did you mean bye this? "The most interesting information is the statement that a big inch engine will get about 1/10 the amount of passes" dont scare me here! Thanks
Shawn, They are talking about the 800 CID engines vs. the 500 CID engines. Not out BB Buicks. Also the article states that is tougher to achieve higher efficiency numbers but again.... the bigger inch engines are still faster. Later
Shawn, some food for thought: Bruce Hunters 494 Stg 2 engine made 648 HP and 657 ft-lb with a 598/584 268/274 @ 108 cam. Yesterday we were on the dyno with or 464 pump gas engine. We made 656 HP and 620 ft-lb with our 558/543 256/262 @ 110 cam. The two engines are similar other than the short block displacement. The 494s cylinder heads had been ported, the 464 has out of the box Stg 2 street eliminator heads. Both engines have the same intake, headers, and carburetor.
