Well, I was hell bent on building a 489 stroker this fall for a pure street car, until I started thinking about going with a 4.37" crank instead of a 4.25" piece. Now I might want to go bigger!!!

Here is the basic fantasy combo:

1971 454 bored .030" over (2-bolt block)
Standard 9.8" deck height
063 GM iron Closed Ovals (101cc's)
Standard Size Valves
4.37" Crank/6.385" Rods
Flat top pistons (-3cc's)
LUN 272/282 Small Solid Cam (112 LSA)
Edelbrock RPM Intake
800 CFM Qjet
1 3/4" Hedman Headers, 2 1/2" exhaust
Flowmaster Big Block Mufflers
HEI Distributor
TH400 w/B&M 2400 Converter
3.31 12-bolt Posi

I should get about a 9.8 CR and a 7.9 DCR as per Pat Kelly's DCR program using steel head shims and decking a little. This will be a great big street tow-truck motor (PDQ67?) and should run on pump gas.

Anyone have any comments on this combo or see any potential problems with the engine building process? What about the stock suspension not being adequate for the huge torque output?

Thanks, Charles

I suggest using a 6.440" long custom rod in it and the needed pistons..

That way, you will hold cylinderwall/piston thrust sideloading to a minimum..

And I have reaaly thought about a 588" motor using a Dart or Merlin-Pro block that will go out to 4.625" along with a 4.375" stroke so it would be a standard deck height motor, but yet still be able to rpm half way OK....

Talk about a 396" "stealth" motor!!!

pdq67

Pdq67, yep, that would be the ultimate stealth motor. Don't forget to use the "396-325HP" air cleaner on it.

I think I understand what you mean about that side thrust issue and the need for 6.44" rods. But, where would I get those rods and pistons? Would there be clearance issues associated with the 4.37" crank and 6.44" rods?

Thanks, Charles

My '74/'75 454 core P/U block swallowed my 496 rotating assembly like it was made for it!!

NO clearancing/grinding at ALL except a schosh at my oil-pump nut's location!!

I figure it can take a 4.375" crank easy, with minimal clearancing..

As for rods, any custom rod maker should be able to make a set in a heartbeat if you have the money..

And try JE for pistons with a compression height dimension in the 1.145" range and shoot for a zero piston deck height using the stock, 9.8" block dimension so you can squeeze a 6.440" long rod in there with the needed minimum ring stack measurements!!!

Get your needed quench by headgasket thickness...

pdq67

PS., Speed-O-Motive sells 4.375" stroked rotating assemblies too but not with a 6.44" rod unless you negociate with them, I bet??

Wow. Sounds like I might be pushing the limits going the 503 route! I may want to think about this some more.

By the way, would that small LUN 272/282 solid be enough for that large of a street motor? I only want it to go up to about 5500 RPM's.

Charles

I don't think you will have enough bore to power the 4.375" stroke. The motor will probebly have more low end torque than you can hook up, but will run out of breath 4800 - 5000. Take a look at the power curve of GM's 8100 truck motor to see what I mean. Personally, I wouldn't do the 4.375 stroke unless I had a 4.5" bore to push it with. It's basically what I found out when looking into a 434 / 402 motor. I even looked into putting a 4.25 stroke crank in the 4.155 bore 402 block. For performance usage, the motors run best with bore/stroke ratios of at least being equal, but always better with a bore larger than the stroke.

That's not always true!!

It is the rod/stroke ratio that governs a motors ability to rpm!!

Check out the Honda S2000 motor's rod/stroke ratio b/c If not mistaken, the little jewel has an 8200rpm redline or maybe even higher AND it most certainly is a small bore/long stroke, "under-square", motor if you doubt me here. (I.e., the 302", Z-28 motor is an "over-square" motor and a 400" Ford motor is a "square" motor)..

And since the 2.19"/1.88" valved BB heads were installed on the smaller bore 396"/402" motors, they are valved and ported big enough to still breathe although not the best such as like the afore mentioned 4.5" bored aftermarket blocked motors..

I will definately go along with it being a lower rpm torque motor if stroked b/c it is true that it is stroke that governs the cam rpm range a lot more then BORE!!

That's why a long stroke motor can always use a schosh more cam then the same cubic inch sized motor, but one with a shorter stroke....

pdq67

I don't have the exact figures handy, but on the Honda S2000, at 8000 RPM, the piston velocity in realtion to RPM is a lot slower than would occur in a BBC. Years ago I had a 289 Ford motor, it seemed that the piston hardly moved at all at 2.875". Also, the Honda has a very small piston mass to deal with. If the Honda motor were oversquare, it would be a 10,000 RPM motor.

GRN69CHV, a small bore/big stroke street motor is exactly what I want to run, sorta like the '70 OLDS 455HO. As you may remember, those cars were absolute monsters on the street and very few cars could beat them. I don't need a high winder with that many cubes.

What cam would you recommend to "power" a 503 stroker for the street? Would that small Lunati 272/283 solid I mentioned do the job, or maybe go up to the 276/284F10?

Charles

......276/284F10----

UDHarold

Hmmm, if I step up to the 276/284F10 solid for a 503 street stroker, would I need more than the 9.8 CR for that cam? Anybody?

Charles

The honda S2000 started out as a 2.0L I4 with a 9000rpm redline that needed 7000rpm clutch drops to get its best times at the track. The new one is a 2.2L version [just a stroked 2.0, thats it] and it has the 8300rpm redline. Hondas normally run either sqaure or undersqaure motors, the exceptions being their high performance v6's [like the 3.2L 270hp acura motor, 89mm bore and 86mm stroke]

They get the revs not because of rod length vs stroke IMO, but in their lack of piston weight, high compression and huge flowing 4v heads.

Originally posted by 1967chevelless396:
Hmmm, if I step up to the 276/284F10 solid for a 503 street stroker, would I need more than the 9.8 CR for that cam? Anybody?

Charles =
No, big engines like cam. That cam will be very mild in a 503 ;)

Originally posted by 1967chevelless396:
Well, I was hell bent on building a 489 stroker this fall for a pure street car, until I started thinking about going with a 4.37" crank instead of a 4.25" piece. Now I might want to go bigger!!!

how much of a differance could 14 cubes make in a street motor?

Would it be worth the little bit of extra hp to have to buy one-off pistons and/or rods? I realize it would be unique, but what kind of return could you get on your investment - probably pick up less than .05 and a couple of mph. IMHO, unique is for the rich boys to deal with, I can spend my money elsewhere and get the same or better results with an HP carb, hydraulic or solid roller cam, etc. Just my .02, of course. My local shop had a fresh turned Cola 4.375 crank last time I visited and I could check on it for you if you like, though.

Young Gun '71, I won't even try to debate the rationale for 14 extra cubes on the street with you. What I can say is that its' merely for the fun and an additional cube won't hurt at all in a heavy street Chevelle!

MyBoTy, we're all after an extra 1 or 2 horsepower lurking somewhere, right? No, I'm not a rich guy,
I only have a bare 454 block and bare 063 closed ovals sitting on the shop floor, that's all. Since I have to buy crank, rods, pistons, valves, etc., I figure, hell, why not build it big?

I think I might be able to get this 503 built for under $5000. I wonder how it would compare to a $6500 crate ZZ502 if I used the LUN 276/284F10?

Thanks, Charles

Had to delete my earlier response. Spoke too soon, Speedomotive has a 510CI (4.310 x 4.375) rotating assembly for 1875.00.

edited 8/6/04

My mistake, that kit has a forged crank.

Back again.

Onna last months or maybe even this months mags says you can buy a BB piston with a 1.105" compression height so with the pistons at zero, (i.e., even with the deck), and a stock, 9.8" tall block you can spec. a 6.5" long custom rod and use the headgasket to create the quench number you want to run..

Rod/Stroke ratio comes up to 1.4857 using a 6.5" rod and a 4.375" crank....

Try JE/SRP for these pistons...

pdq67