540 BB The hard way

scottcleaver · Aug 31, 2002

I have been thinking again, which usually means expensive. I always hear about how tough it is to get a high torque big to hook up on the street. I agree. Now the hypothesis, could I take the normal 540 combo that is a 4.25 stroke and 4.50 bore and do some rearranging. I was think getting some of the stroke out and adding more bore. Destroking should get some of the torque out and I like a motor that has a slightly narrower power band. If you go with a 4.00 stroke and 4.65 bore it's just about the same cubes. It's kinda like building a big block with smallblock thinking but getting the benefits of the much better heads. What do ya think of the theory?

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SCOTT
69 RS-SS 396 4-SPEED

OCRacer77 · Aug 31, 2002

Your bore/stroke would just be like an overbored 502, therefore id say would have similar torque characteristics of a 502. The 502 is still a torquebeast. With that id go with a lot of cam (270@.050) and large (330+CC) intake runners to cause the torque curve to move upward. IMO id actually go with a 482 instead which is a 4.50 bore and 3.76 stroke(396/427crank.) That would be a bitchen high revvin BB good for 7k rpm blasts on the street. Gotta luv the high rpm, its so awesome. I always laugh at these goofs at the track that run a 12.30 at 104mph with their bb chevelle. Then there is a 327 guy running 13.50 at 110. On the street, the car with a faster trap speed wins the race.

phel69 · Aug 31, 2002

<BLOCKQUOTE>quote:</font><HR>Originally posted by OCRacer77:
I always laugh at these goofs at the track that run a 12.30 at 104mph with their bb chevelle. Then there is a 327 guy running 13.50 at 110. On the street, the car with a faster trap speed wins the race. [/B]<HR></BLOCKQUOTE>

I don't buy that statement no matter where you race and you shouldn't race on the street. 12.30 at 104 is way more hooked up than 13.50 at 110. A car that hooks wins. At 12.30 he beat you by 1.2 seconds.

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Bob
Garnet Red 69/SS396/TH400/355 Posi ( 454 now)
94 HD Dyna Wideglide

pdq67 · Aug 31, 2002

A 4-5/8" x 4" = 537.6"!

And a mag. did an article on it and did call it a poor-mans stroker due to the size approaching the 4.5" x 4.25" = 540" engine!! It is indeed a good combination..

This is the same stuff that I have been mouthing about when I say I want to build a 4.75" x 4.375" = 620" engine using a standard deck Merlin block that would pass a sonic check! It would look just like a 396!!!

Guy's say that a short stroke engine doesn't produce enough torque b/c they look at the little Z-28, 302 engine. But if you up the cubes using the same bore/stroke ratio, you can make plenty of torque just b/c the sucker is BIGGER!! Not b/c of it's stroke.

Of course if you keep the cubes the same but build it by stroke, it WILL make more torque and at a lower rpm which makes such an engine a more street friendly driver!! Imho. pdq67

OCRacer77 · Sep 1, 2002

To phel69. I understand your point... but let explain why a car with more trap speed would win. On the street, most of the races are from a roll or even at some speed, therefore leaving the first 60 feet out of the equation. With that wouldn't you agree that the higher trap car is quicker to get from 50mph to 100mph? With that it would have an ability to pull away. In a flagged street race, the et car would smoke the trap car ONLY if it were able to get the same traction it does at the track which is highly unlikely. ie a car running 12.30 at 104 would have to have a 60 foot in the 1.6's or better.

CamaroNOTcamero · Sep 1, 2002

We here dont race on the street, its a BS match on the street. I do understand your point, but IMO we are talking about drag racing at the track from a dead stop. The 12.0 on a 13.5 is going to win reguarless of trap speed.

Toby Keen · Sep 1, 2002

pdq67, My machinist and I have been looking at a 4.50 bore/3.76 stroke for longevity and probably wouldn't rev it like it could. He has built several "pro stock" like motors with good luck using this method but they rev alot higher. I'm still working on the cam timing and cylinder heads to make a decent drag motor and keeping it around 7000 but the jury is still out. We can always go to a 4.0 stroke and bore it 30 over if it doesn't work out. I'm sure glad he's a friend and had these parts in his shop.

oger · Sep 1, 2002

Even a 4in stroke can be hard to hook in a street car. Have you thought about a 4.500 bore with a 3.76 stroke and atleast .250 long rods? That should take enough low speed out to make it much more livable on the street.

scottcleaver · Sep 2, 2002

I still like the idea of the big cubes but I appreciate all the responses. Would it not be possible to pull enough bottom end torque out by using big intake runners like OCracer77 mentioned or by using a different cam profile or pull enough timing out. I am not locked into my theory only, but I would like a high revving big block that would be fun on the street. I already have 4:11 gears and will keep them but probably change to a different tranny than my Muncie. Probably a 5-speed to get some taller high gear.

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SCOTT
69 RS-SS 396 4-SPEED

Eric68 · Sep 2, 2002

Thinking out of the box here . . . rather than worry about destroking a beast of a BBC to kill some torque, why not just use a little less gear?

Here's the math . . .

600 FT/LB at the flywheel X 2.52 (trans 1st gear) X 3.42 gear = 4883 FT/LBS at the rear wheels.

500 FT/LBS at the flywheel X 2.52 X 4.11 = 5178 FT/LBS at the rear wheels.

Rather than kill TQ at the flywheel why not multiply it less in the rear end? then you have a car that will lope down the road all day long and will probably be faster in the 1/4 to boot.

The Prostockers run destroked motors because they have to in order to make them live at 8000+ RPM. If you aren't going to rev it anyway why build the bottom end to rev and then not?

Just my opinion.

scottcleaver · Sep 3, 2002

Eric, maybe I'm doing it wrong but I came up with 600 x 2.52 x 3.42=5171 I really do appreciate you offering a different twist though. I wonder if the gear spacings in the tranny will put me at a strange place at the finish line though. I mean what if it's not quit a 3rd gear finish line and not a good 4th gear combo either. Do you have an idea what the finish line RPM I would have in 4th with those gears and a 27 or 28 inch tire?

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SCOTT
69 RS-SS 396 4-SPEED

460BBC · Sep 3, 2002

Im with Eric. I run a 3.42 posi with a 454 and there is still plenty of tire spin (even with bfg drag radials). You could also run a larger diameter tire and take advantage of the larger contact patch....BTW I think he meant: 500 FT/LB at the flywheel X 2.52 (trans 1st gear) X 3.42 gear = 4309 FT/LBS at the rear wheels

Eric68 · Sep 3, 2002

I meant 5171 for the first example and 5178 for the second. Either way you can see there is more than one way to skin a cat. Same TQ at the rear wheels, its just that IMO one way is more streetable than the other.

If you take my example a step further you will see that the same holds true in second and 3rd gears as well.

600 X 1.75 X 3.42 = 3591 in 2nd and 600 X 3.42 = 2052 ft/lbs in 3rd.

500 X 1.75 X 4.11 = 3596 in 2nd and 500 X 4.11 = 2055 in ft/lbs in 3rd.

These cars would probably ET the same if both chassis are optimized!

BTW There's nothing wrong with a destroked BBC - its not a "wrong way to do it" at all.

[This message has been edited by Eric68 (edited 09-03-2002).]

OCRacer77 · Sep 3, 2002

This is such a great topic! I think softening up the rear gears would definately help on traction issues...but would also soften up the "fun" factor just as much. I mean how fun is shifting at 5600rpm? I used have a SB 355 that i shifted around 6600 to 6800 and it was a blast. It wasn't the fastest car, in fact i had hardly any low end torque (200cc runners/240@.050) but it was so fun. Probably a well built 383 that shifted at 5800 would have beat me but my car still was more fun to drive. Not I am an import fan or anything but I got a chance to drive a GSR integra. These cars run high 14's. Seem boringly slow?, not quite, it was alot of fun...shifting at 8000 rpm is pretty cool even in a 4 banger. I guess I am an rpm guy. I mean once youve had an rpm motor its hard to digress to a low rpm, slow winding, torque blob. I say build short stroke BB and go through the lights at 7000rpm with your 4.11 gears.

scottcleaver · Sep 4, 2002

I believe it's all down to personal taste, again. Tons of good theory and knowledge to work with here. I personally like a motor that has a more upper band, tight windowed style of performance. I do fully understand that it's not the most practical and we all seem to defend our personal choices most of the time. I, like a couple other guys here prefer the quicker gear changes and higher RPM's that go with compared to the more sensible stroker motors. This is all good food for thought and gonna be fun to build either way it happens.

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SCOTT
69 RS-SS 396 4-SPEED

pdq67 · Sep 4, 2002

Spend some money and pick up the latest copy's of D2K, the cam disc and Drag and have more fun then a barrel a monkey's watching the trends!!

They say my tow-truck, 496 should go like 130mph in 10.5 seconds or so if I can get it to hook!! (M-20 and 3.31's and about a 26" or so performance tire).

Heck, if it goes 120, I will be tickled pink! pdq67

Toby Keen · Sep 5, 2002

We were looking at the 4.5 bore and the 3.76 stroke for a couple of different reasons. First and foremost was longevity. The second is a little more theoretical. Building it to run 7000 through the eyes and shifting it at 7000, using a 5000 converter and leaving at 4500 and using a TH400, we SHOULD be able to keep it in the torque band if we gear it and cam it right. We were thinking a 3000 lb car SHOULD be able to run consistant 9.8's without leaning on the motor too much. Of course this is all theory at this point. My machinist is putting the pieces together, along with a set of Edelbrock rectangle heads that have already been done and we will see what happens. We'll see, I guess.

coach420 · Sep 5, 2002

After reading this post I see another reason why it's fun to have a Camaro. There's a different flavor for everyone's taste.

scottcleaver · Sep 8, 2002

I have looked at the Dart, Merlin and Bowtie block info and they all say max bore is 4.600. I am wondering if a 4.650 bore will cause to many problems and would the cylinders be to thin to keep it cool on the streets?

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SCOTT
69 RS-SS 396 4-SPEED

OCRacer77 · Sep 9, 2002

Is the 50 thousanths, or 8 cubic inches worth the trouble? Not to mention, making the block unrebuildable without sleeves?

pdq67 · Sep 9, 2002

Scott,

Go to World Castings site and check out that the Merlin Pro, (not Merlin-II), can go to 4.625" and still have .400" thick cylinder walls on the thrust side!! And I would sonic check the sucker before spending that much money!!!

I figure .275" walls are thick enough b/c a Pontiac Guru told me once that a .250" thick wall is way good enough!!! If I remember right he was running something like .150" or so in a 455 Pontiac block with a 4.21" crank!! So it should hold a stroker well... Imho. pdq67

scottcleaver · Sep 10, 2002

pdq67,
You are absolutely correct, for a mere $2769.00 I can have a Merlin Pro block that will handle the entire bore and leave plenty of cylinder wall for almost any kind of trouble that might brew up. It seems like common sense and the wallet shall never meet.

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SCOTT
69 RS-SS 396 4-SPEED

MY10secSS · Sep 10, 2002

The early CAN-AM motors were 4.40 bore and I believe the stroke was 3.6xx. These motors ruled the track. I was also under the impression that a 4.5 bore was borderline for efficient combustion due to flame travel.

pdq67 · Sep 10, 2002

Scott,

I can dream, but if I'm gonna dream, at least it's gonna be for the engine I want... He, He!!

Yes, it is alotta money, but when Pro- engine builders are getting the kinda money they want for their high-powered motors, building one like my tow-truck engine would be CHEAP!!

Lets see, crank, pistons, rods, complete heads and the good block..

Nothing you don't have to have for any engine.. pdq67

540 BB The hard way

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