jocww

Time to start building the engine for our race car itll see light street duty, the parts i have so far is a stock nickel 4 bolt block with stock 192 heads. the blower is a 174 i believe, it is a weiand havent really taken it apart yet, would like to run this mainly on regular or 89 for street and 91 when racing. so compression will be low im thinking 8.5.1 or there abouts, this is a budget build so nothing to exotic. im thinking about keeping the stock heads and giving it 202 valves. what kind of stick should i put in. i am thinking about stroking it to a 383/385 with cleanup. what kind of crank should i get and does have to be forged same with the pistons.
Jon

AFBCamaro

I would suggest you run nothing but premium gas on your motor. If you are dead set on running low octane then I would go no higher than 8:1 compression on the motor, and no more than 6 psi. I am using 7.5:1 for mine right now. Forged pistons are a must, a crank use anything you can find. I run a crank cut 20 under with a 6-71 Blower running 13 psi. We run a cast crank on our digger with an 6-71 running about 20 or so psi of boost. The blower really does cushion the hit the crank takes. (We spin it to a ceiling of about 7800 at the end of the strip). But it is a light car.

If you want to keep the heads I would suggest leaving the intake valves as they are and going up in size as much as you can on the exhaust, and if you know how, port the exhaust as much as you can. (Properly though). :-) By the end of this keep in mind you might be close to the price (including time) of a good aftermarked head. But if you can get the valves cut bigger for cheap and dont ming the work then the stock heads will do just fine.

Oh and by the way if you descide on stroking the motor that will make it very hard to keep a lower compression ratio since you want to go with regular gas. I say, save some money keep the a 350 with a stock crank and with the money you save get a good aftermarket head 70-76cc range if going with iron.

jocww

ok so a cast steel crank will work fine i thought the blower would hit it harder than cushion it? the reason i want to keep low octane as an option is that in cal the gas for regular is already 350 and its gonna go up and this will see more light street cruising that it will the race track. the car is a 72 vega. im thinking of 6-8 psi the heads will be iron unless i find a great deal on a set of aluminum heads
jon

slapi01

i second everything afb had to say especially with the gas being premium. i went with afr 76cc heads due to my blower and it dropped cp down a whole point to 8.2-1. keep the timing down and if you must not go with premium gas stock up on additives. there are always decent aluminum heads on ebay, but i understand that is more money than you planned on spending. believe me, my credit card are still burning -lol

Damon

Another one agreeing with above posts. I've tried 8.7:1, even with aluminum heads and a rooots blower- it was MARGINAL on pump gas. I eventually blew it up when I got greedy- not safe. And you won't like the results of detonation on a boosted motor (think "ka-boom").

8:1 squeeze is where I'd start my thinking with a roots blower. If you're going to go higher you damned well better know exactly why and how or you'll end up in trouble.

The compression issue now being beaten to death, here's a combo that will work.....

Comp Cams 262NX hydraulic flat tappet cam (218/230 on a 113* LSA). Biggest headers and exhaust you can reasonably fit. Biggest carb you can put on top of the blower (~800 CFM), pulley the blower to hit about 6 PSI of peak boost, 26-28* of max ignition advance at WOT (good condition HEI driving .035" gapped plugs at a minimum, ignition amplifier box system preferred- MSD, etc.), port the crap outta the heads- as much as money will permit, especially on the exhaust side. Don't skimp on the fuel system- don't EVER run lean on a boosted motor. Don't ever get greedy with ignition advance on a boosted motor.

Look out- it'll rip your head off. Don't try to compare a mild blower motor making 450HP to a N/A 350 making the same power. It's apples and oranges. A roots-blown 350 making that kind power will generate mind-bending amounts of low end grunt and be very drivable on the street. High stall converters and steeep rear gears are not needed.