Thread: BBC power estimate

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Hello all: As you can see from my name I'm into European stuff: Alfa, Porsche, Ducati, etc. However I respect American Iron. Please Help: What kind of power could I expect from this combo: 4.5in bore/3.76in stroke with a low 9.0 comp. ratio? (aka 502bore/427crank. I chose the shorter stroke for higher RPM potential.) Assume all the good (race quality) stuff is in it... High flowing Aluminium heads... Forged aluminium pistons... Forged rods(or titanium) and crank... Roller cam... aftermarket programmable electronic fuel-injection, etc. I'm shooting for 6500-7000 RPMs. I'd like a life-span of 75-100K miles, not a dozen 1/4 mi. passes. Cost is no object 'cuz this is a strictly imaginary project. I know this is probably not the rat motor y'all would build, but humor me! Thanks in advance.

what may stop you is valve springs you will need the best and not to big on the lift on the cam640 lift. this may keep the HP down with the low cr but it can be done . i would go with a 4.1/4 crank and a4.600 bore this may give you565 cid. more TQ at lower rpms and keep the rpms down to 6500 or so it will be easer on parts in the long run HP? 750 it would be easer to do this with a bit more cr like 10to1 and you will need a very good EX step tube headers would be good and a X cross in the EX run the 4-7 swap on the cam . or the ls1 race cam firing order . this stuff here will help with the hp. and tq .have done this before with a bigger engines

Pat, i hate to mark out to you.. but when it comes to big block chevys ..you da man..

I am building my first engine ever, I was told by an engine builder that I won't get over 600HP with this combo, but I would like to know two things: 1) is it possible to build a stroker with stock pistons, and 2) what does your magic computer say for HP/TQ?

We'll start at the top and work down
2 Edelbrock 600CFM carbs
Edelbrock C66-O oval port dual carb low rise manifold (not tunnel ram)
Brodix RaceRite Oval port heads (271cc intake, 119cc chamber)
Comp Cams XR270HR hydraulic roller (p/n 01-414-8)
Aluminum roller rockers 1.7:1
GenVI 502 block, 4 bolt main
Eagle stroker crank, 4.25"
Scat 6.385 rods
OE pistons

May be a little more torquey for some of your tastes, but I want something that will be streetable. Are the pistons going to be smacking valves? If not, what kind of compression will I get, and what are my HP/TQ #s?

Good info Pat, as usual! When I build a big block, I think of lower rpms and mega torque. If I was gonna build a high rpm screamer, I think I would go with a 427 small block! Or maybe even bigger. But I just dont think of BBC's as high revving powerplants...and they dont have to be either!!

502Cobra, you might want to start another thread with you info, so as not to steal the thunder from EuroCarGuy, but to answer a little for you....No, stroker pistons have the pin at a different location because of the longer rods....if you didnt move the pin hgt, the piston would come right up out of the block at TDC. You chose good heads, but why would you want to run two carbs? It will work, but will require more tuning and messing around, and it wont result in more power. But it does look cool as heck!! I would stick with one carb. The only other thing with the heads is the 119cc chamber. It's big, which will require you changing to a dome piston to get a decent compression ratio...With flat tops in there (similar to the original), you will be lucky to hit 8.2/1 or so. If you want to build a blower motor, you're all set! But be prepared to change pistons...you have to buy them anyway for the stroker rods. Something around a 27 or 30cc dome should get you up around 9.5 or 10/1......... Cam is OK, although Im not a Comp Cams fan...just a personal preference. But a roller cam is the way to go. If you're going with Scat rods, why not a Scat crank also?? Im not an Eagle fan either! And the engine builder is right, you'll likely be around 520 HP or so, maybe little more, and maybe 580 Tq.... But if it's a street car, dont worry about the HP numbers...It's the torque that you feel. No, you shouldnt have piston/valve problems with that cam, it's not too big...not really high lift, and duration is reasonable. John