How to Choose Bore and Stroke for BIG POWER!!

Discussion in 'Race 400/430/455' started by Philip66, Jan 21, 2018.

  1. Philip66

    Philip66 Well-Known Member

    I get more excited every time I think about the new Stage 6 Aluminum Heads from TA Perf and the Billet Aluminum Heads from Ken Betts!! To be able to make BIG power, and N/A too is nothing short of amazing!! A big round of applause to everyone who has been involved in these projects from the research and development aspect to the reworking of port profiles, and everything in between; thank you for your dedication!!

    I know how to take an engine apart and put it back together, and it will run. But when it comes to planning and designing a specific engine, I'm lost. I know that these heads will provide remarkable increases in power output because of the flow potential of the head.
    And that is due to the design and size of the intake ports as well as larger valves?
    Due to the shear size of them, do they also allow for the possibility of larger bores? If so, is the maximum possible bore size limited by the block or the head?
    For a 455 the factory Buick bore is 4.31" with a stroke of 3.90". I have read a lot of threads that talk about a square engine, where the bore and stroke are the same or close, with 4.5" used as an example. An engine with 4.5 bore and stroke will give you 572.5566 cubic inches.
    Is it more desirable to have "square" engine?
    By being square, does that affect the balance of the engine or is it more an issue of ???
    A 4.5 bore and a stroke of 4.36 gives you 554.743 cubic inches.
    Is this the layout of Guy's engine? JW mentions that it's a 555 in the thread about the first install of the billet heads.
    Is it necessary to have the tall deck Tomahawk in order to have a 4.5 stroke?
    What is the maximum stroke possible with the tall deck?
    Are there pistons and rods available now to allow choosing the biggest possible bore and the longest possible stroke?
    Is it beneficial to go as big bore-wise and as long stroke-wise as possible?

    I guess I'm really just thinking out loud with all of this, but I've never learned anything by listening to myself talk. I'm trying to form my random thoughts into questions.

    To me, if these heads are going to flow big numbers, it seems that it's going to take as big an engine as the Tomahawk can provide in order to take advantage of the flow.
    What are the other concerns when trying to plan for the size of a BBB in a race car?
    Price??
    Type of fuel...Corn or Petrol?
    Induction Type...naturally aspirated or forced induction? NOS?
    Carb or Fuel Injection?
    Or is it more a function of rotating weight, balance...whether internal or external? Or harmonics?
    Longevity...does choosing one bore or stroke over any other drastically affect how long it will stay together?

    Or will the longevity be directly tied to your machinist and who you have put it together? Price and lifespan are going to matter because without a sponsor, I'm looking at spending BIG BUCKS!

    But as I read in DragZine,
    "Money can't buy you happiness...But it can buy you horsepower
    and that's kind of the same thing!"

    Thanks for reading, thanks for trying to understand, and thanks for everyone's patience, especially if all of this has been covered and beat to death before!
     
    Last edited: Jan 20, 2019
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  2. cjeboyle

    cjeboyle Gold Level Contributor

    Many good questions asked here. I can answer none of them BUT I will follow this thread to see what the experts have to say.
    Cliff
     
  3. hugger

    hugger Well-Known Member

    If I was going to go for big NA power, and spend the money on either of those heads, I would have a tall deck block with 632cid minimum
     
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  4. Briz

    Briz Founders Club Member

    With the introduction of the S6 head and it being of a cast construction a Buick based engine could possibly be competitive in the PDRA's 632 class. Those guys are going 4.20's @ 165 mph in the 8th. I know the engine is only a small part in going that fast. Lots of other things play into it all which require stupid large amounts of money
     
  5. hugger

    hugger Well-Known Member

    The new heads would be really at home on a heavy Hitting N20 setup too, 3 kits on a 572+ would be a scary piece of equipment.

    As far as turbo goes idk, the conventional heads will take you to well on the other side of 2k HP imo, look at Big Chief his Pontiac is well over 3k HP and with a Edelbrock Victor Head, I'm Sure they are MAXED out but I wouldn't imagine they are much better than the 400cfm capable heads we have now.
     
  6. Jim Weise

    Jim Weise EFI/DIS 482

    David Rehr said it better than I can parrot it back at you, so you might as well read his thoughts:

    http://rehermorrison.com/tech-talk-66-go-big-or-go-home/#more-381

    Now that you have read that, you should be convinced that the biggest bore possible is the way to go, I strongly believe that is true. It's free cubic inch and airflow.

    The Tomahawk retains the 455's 4.750 bore centers, so the largest practical bore size is 4.500. You could push it a little farther for rebuilds, but your not going to gain any appreciable amount more size or performance past 4.500 in this block. We will need a block with a wider bore center to get into the really big cube motors.

    My 555 combo is a 4.500 bore, with a 4.365 stroke. I chose this stroke for two reasons.. the first is the obvious marketing one, (455-555) ... and the second is to provide as much rod/cam clearance possible, for alum rod bracket motors, that will become very popular builds for this block. 555cid is plenty enough to produce over 1000 HP NA with these new generations of cylinder heads, so I chose that for my everyday bracket motor build.. remember the K.I.S.S. rule, it will serve you well.

    Ken's head will support a 555ci at 8500+rpm, I am sure Mike's will be similar, so we are right in the sweet spot with that cid, for dyno performance that will translate to the race track. Mega compression, super long camshafts, and a light rotating assembly will produce some very fast race cars.

    Ken asked me to build him a dyno mule, to show the max potential of his heads, so for that, we are going to build a 604.. that's 4.500x4.750. Ken has a raised cam block, and with some small journal steel rods we should be able to fit it all in the package. The 455's 10.570 deck height is plenty big, remember the "tall deck" BBC's used for their 632's are 10.200. The difference is that the BBC has a 4.840 bore center, so they can use 4.650 bores.

    The first test shorblock will be a 555, with a moderately size cam (278/284@.050 .766/.766). Right at 14-1 compression so it's a good realiable bracket motor, exactly what is it designed to be. Low maintenance and 500 runs between freshening.

    Ken's motor will test the same set of heads, on a 604ci, with everything much more toward the ragged edge... more cubes, more cam and more compression. We will find the limits of the heads at this CID, and those two motors should provide good information for those of you going forward, as we step into this new realm of BBB performance.

    Stay tuned.

    JW
     
    Last edited: Jan 21, 2018
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  7. Philip66

    Philip66 Well-Known Member

    So if a 305 Chevy is considered a pig with its small bore--long stroke, would that same principal apply to a 604?
    And if the 604 seems to have a longer stroke than bore, where do you go bore and stroke wise to come up with a 632?
    Now I do understand we're looking at an engine with twice the cubes of the 305 and I am sure the valves are significantly "unshrouded"!

    The 555 looks like a different animal!! More like the heralded 302 with a large bore and shorter stroke. Currently we discuss the merits of a 464 versus a 482 or 494 and that seems like a substantial increase over our beloved 455. But now we're looking at a 555!! That's almost like adding half of a 231 Buick V-6 in additional cubes!!
    Unbelievable!!

    So we have these two new awesome styles of heads on the horizon, their baseline flow numbers are going to blow away the max we could push for yesterday! And looking at the article you linked above, the Tomahawk block, by allowing us the larger bores you're working with; can actually make the already stout new heads even more efficient flow-wise!?!? That's exciting!!

    Mike T., thanks for bringing us the Tomahawk!! Where it is leading us and the performance potential it is unleashing is definitely exciting!!

    You better believe, that I for one will be staying tuned!!
     
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  8. JESUPERCAT

    JESUPERCAT No Slow Boat

    Phillip the engine I'll be running in the dragster is a Tomahawk at 477 cu.in..
    3.750 stroke and 4.500 bore with the billet heads.
    This is most likely one of the smaller builds out there.
    Not to worried about HP output we will have plenty for this year. Blown 12:1 on alcohol should be enough.
    We will be winding it up in the lights at times to run the class.
    Looking forward to seeing several record breaking fast Buicks real soon.
     
  9. Gallagher

    Gallagher Founders Club Member

  10. 8ad-f85

    8ad-f85 Well-Known Member

    To the OP...using BBC 572 and 565 as examples, the smaller has a .100" bigger bore with short stroke (short deck) and revs up faster than the other one (long stroke, tall deck).
    You can find close enough flow into the cylinder between them to make similar hp on the dyno, but that's still misleading.
    The dyno numbers are calculated after inertial calcs are considered, and this power level of engine isn't held at a steady state during the tests (steady state testing negates the inertial correction).
    This can be important with both drag or circle track when there's a need to rev up through the powerband, where even a lesser hp numbered engine might run from the slower revving one even having more power.
    Some vehicles run a very narrow powerband, like down the track 'on the converter', so the engine doesn't grab R's .
    There are times in which bigger is still better.
     
    Last edited: Jan 21, 2018
  11. Philip66

    Philip66 Well-Known Member

    So John Everett has a motor that is right in line with the Rehrer article, a larger bore with a shorter stroke. Which should be an easily high revving engine to take advantage of the big flow billet heads!

    Bore: 4.500 Stroke: 3.750 Cubic Inch: 477


    This would seem to validate the point of optimizing your overall package to work together as a package.
    So with a higher revving engine, would you want that utilize a Powerglide or maybe a 2-Speed TH-400? Or would that depend on the weight of the car? Since it's a dragster anyway, probably has a Glide.
    So then you have to be cautious about rear gear selection?!
     
  12. Bens99gtp

    Bens99gtp Well-Known Member

    We gave to remember that hp isn't measured it's calculated. Hp is basically work overy time.....work being the torque the motor can make, time being the rpm's the motor spin. (Rpm x Tq)/5252 =hp

    So a motor making 500 ftlbs or Tq at 5500 rpm's equal out to 523hp.
    Take the same torque at 8500 rpm and it's 809 hp.
    Now take the first rpm of 5500 but a motor making 775 ft lbs or torque there, it comes out to 811.
    Almost the same hp as the previous randomly picked numbers just to show a point in the formula.

    Basically to make more power to either need to make more torque, or turn more rpms, or some combination or both.

    Bigger bores and stroke make more torque. This is why engines like at trains and ships are huge bore and huge stroke.......the down side comes in wanting to spin the rpm with those big bores and stroke. Now those two examples are not in the same ball park as car motors, but shows the point.

    With the longer stroke each pistons will be moving faster cause if gas to cover more length of travel in the same time. So given that it's harder to acceralate and harder to stop. Bigger bore pistons tend to be heavier, again making it harder to speed up an slow down, we help offset this some by using a piston with a shorter compression distance and a longer rod.......but going too far there can cause it's own issues with keeping the piston stable in bore.

    The more forces that are applied by the pistons in starts and stops the stronger the rod needs to be. We all know lighter parts spin up faster and can turn more rpm's with fewer side effects than heavier parts..........so in the search for something as simple sounding as 500 more rpms, everything changes.

    I have no personal experience with big cube motors, but can see how a good plan b4 starting is important and changing 1 part can be a big big deal
     
  13. JESUPERCAT

    JESUPERCAT No Slow Boat

    Some dragsters do run 3 speed transmissions. We are running a heavily modified glide for now, but we are setup to run a 10" Crower clutch in the future with a 1 or 2 speed Lenco transmission.
    Now 3:89 gears with 33 Hoosiers. Weight of the car is about 1800 with me in it.
    We will be updating to a 3:55 floating rear mid summer.
    Fuel type does make a big impact also to the math. Next year we will drop the compression down to around 7-7.25 and change fuel type.
     
  14. hugger

    hugger Well-Known Member

    Turboglides are for BIG power and heavier cars
     
  15. Philip66

    Philip66 Well-Known Member

    John, Thanks for sharing some of the specs on your rail! I wasn't trying to single you out, was trying to be hypothetical. I know a lot of people can get pretty sensitive and protective over the details of what they run. Thanks!!

     
  16. Jim Weise

    Jim Weise EFI/DIS 482

    Phillip,
    With a 4.500 bore you would need a just shy of a 5 inch stroke to get to 632...

    That's alot of arm to be swinging at big rpm.

    The reason for testing a 4.750 stroke is because that's the number that the BBC 632 uses with good success, but no parts have been ordered yet, and we may drop that back to about a 4.700 to keep the bore/stroke ratio aprox the same as the BBC 632. We just can't make that 632 number without the bigger bore.
    4.500x4.700 is a 598cid engine.

    That's what test motors are for... my production stuff will continue to be the proven 555/560 combo.

    JW
     
  17. ken betts

    ken betts Well-Known Member

    Great thread! Please understand what John and I are doing. The parts for the 477 are already here. We have heads now. Anything I make will be available to anyone. I don't have secrets. I want Buick to compete with anyone else out there. We will have an ongoing program to see what bore and stroke seems optimum for our head with bracket reliability.
     
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  18. Philip66

    Philip66 Well-Known Member

    Ken, and everyone else too,
    This is one of the things I have always appreciated about most of the Buick Community; a one for all-all for one mentality! Any time we can share secrets to beat the other camps, All the better!!

    And I think you hit on another point as well, it's probably the real reason for my questions. Sure you could build a 632 or even a 732 as mentioned in the TA catalogue, but if it has to be torn down every week then it's not practical or affordable. Pro Stock guys have to do that, and they have sponsors with deep pockets!

    I for one am definitely looking for "Bracket Reliability!" Bargain-Hunter affordability would be nice, too. But that's probably not realistic. Buying a new set of heads and a suitable block to hold them will be a major capital expense. Something I won't want to replace in short order, nor will I be able to.

    If I can land on a good foundation to best take advantage of the massive flow of a new set of heads, whether that be a 477 or a 555, so be it!! It will be a major leap forward and I am excited about the prospects!!
     
  19. JESUPERCAT

    JESUPERCAT No Slow Boat

    Phillip as Ken said we are here to assist anyone that is racing a Buick. I will show any Buick owner any part of the car or engine, as in my opinion drag racing is losing major interest.
    People need to enjoy and learn new things or the sports future is dim.
    I have driven and crewed in/on cars that are full rebuilds every pass. Fun but expensive.
    Any questions just ask.
     
  20. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    You can't really use the sbc 305 as an comparison to a 600 + cid BBB. The biggest limitation for the small bore of the sbc 305 is because the biggest valve size it can accommodate is 1.94" intake and 1.50" exhaust. That was even overcome though with the factory Vortec 305 with heads that flow some impressive air for a factory cast iron head with 1.875" intake and 1.50" exhaust valves. But even with the Vortec 305 heads the sbc 305 is probably maxed out for more upper RPM HP if more cubes were added by increasing stroke though.

    With the flow of those sweet billet heads on a 4.5" bore even if the stroke was 5.00" to add cubes the flow should be able to fill the smaller than the stroke cylinder(as long as the block can handle that stroke?).

    A better comparison would be a 5.4L Ford modular engine with a IIRC from my CRS memory 3.660" bore and over a 4.100" stroke. This engine even with its tiny pathetic bore size, the heads can flow some air to make power with such and under squared engine! Of coarse we're talking about 3 and 4 valves per cylinder to get the flow but that really doesn't matter how the flow gets there as long as it can.
     

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