need help building a 347 for my procharger

wadman1 · Jan 27, 2010

I have a car set up for the strip it is a 95. i am rebuilding my motor from my 86 it is a 347 stroker. the motor is a work in progress right now. i don't know much about motors other then i like when they have a lot of power. i need help picking and deciding on a few things for it. The 347 was built in 1999 and has probably 6000-8000 miles on it. i was going to just put it in this car and run it but now that it is apart and i have the procharger for it i think i need to chang a few things to make it better and safer to run with the charger. tell me what you think. here is a list of what it was.

93 cobra block
the block is o ringed
ARP head stud kit
main cap girdle
28 oz imbalance
cast scat crank part # 93023
forged i beam rods 5.400
comp cams adv. der. 274/282 der. 6.050 224/232 .555/.565 lobe sep angle 112
keith black Hypereutectic flat top pistons 4.030
Windsor senior heads, stage 3 port and they are 61cc
head gasket .047" thickness i was told this combo made it 10.5 to 1 compression?
ported cobra intake
Electric water pump

but now i will be adding a p-1c Procharger kit with intercooler, i need to know if there is some internals i need to change, what injectors to get, should i lower compression? should i run the meth kit?

thanks in advance for any help.

BlownFiveLiter · Jan 27, 2010

I wouldn't change a thing personally. You'll make more than enough power to split the block in half with the Procharger and the current parts. You could do that with a Procharger and stock heads/cam/intake. In my opinion, it would be a waste to throw more parts at a factory block. Now if you wanted to change anything for longevity's sake, I'd pick up a Dart block and put that rotating assembly into it. That would be the most worthwhile thing you could probably do, but it wouldn't be cheap with the initial purchase price of the block and the subsequent machine work that it'd need, you're easily looking at $2500 before you've changed a thing, except the block.

wadman1 · Jan 27, 2010

ok i forgot to say i was only going to run 5 pounds. do you think even if i put a thicker head gasket on there and get to 9 to 1 it will still split the block? is there nothing i can do other then getting a built block or not running the charger?

Tanus · Jan 27, 2010

personally Id drop compresion to 8.5 to 1, get a fresh set or bearings too. definatly a meth or H20 kit. 8-10 psi should be safe. 42-60lbs injectors

BlownFiveLiter · Jan 27, 2010

wadman1 said:
ok i forgot to say i was only going to run 5 pounds. do you think even if i put a thicker head gasket on there and get to 9 to 1 it will still split the block? is there nothing i can do other then getting a built block or not running the charger?

Boost is a measure of restriction. 5 pounds on your engine might be 10 on a stock one. Just something to keep in mind.

You can run the charger and not crack the block, but you'll want to go lower on the boost, which it sounds like you have the idea of doing just that anyhow. Once you start getting into the 475-550HP range, the block starts becoming a liability. Once I finally decide to fix my electrical issues that I'm having, I should be in the 475ish HP range on a stock rotating assembly.

Tanus said:
personally Id drop compresion to 8.5 to 1, get a fresh set or bearings too. definatly a meth or H20 kit. 8-10 psi should be safe. 42-60lbs injectors

With 6-8,000 miles? I'd leave it alone, honestly. Dished pistons and 8-10 PSI of boost on that engine is probably going to be well over 500HP. That's an awful lot of power for a stock block. Some guys get lucky and they survive, but just how long are you willing to risk it? I have a DD and another 302 sitting on a stand, so I'm a little more willing to take a chance.

giddyup306 · Jan 27, 2010

I'm with tanus on lowering the compression. You build an engine for a supercharger, not the other way around.

Methanol injection is some really cool stuff. With a boosted application you can expect to see a nice power increase. I first got into methanol injection as an alternative to mixing toluene and xylene on a high comp NA engine. I'm in the developmental stages of building my own kit with a hex fet and opto isolator... need to find a pump that is more tolerable to the water tho... But what is really nice is the CLEANING benefits that it has. You can run a race car all season then disassemble it and it will look like a drag engine with two passes.

wadman1 · Jan 27, 2010

StangGT1995 said:
Boost is a measure of restriction. 5 pounds on your engine might be 10 on a stock one. Just something to keep in mind.

i have a 5 pound pulley for a 302. and i have been told it will be less boost on a 347. the kid i bought it from had it on a 331 and it was just under 4 pounds. they say the more displacement the less boost with same pulley. have you found this to be true?

i plan on doing Methanol injection with a inline presser switch hooked up to a light so i know i have the meth at all times. i will also go to the dyno and get the car tuned and drop power if it is making to much power for a stock block. i want a reliable set up.

7upstang91 · Jan 27, 2010

wadman1 said:
i have a 5 pound pulley for a 302. and i have been told it will be less boost on a 347. the kid i bought it from had it on a 331 and it was just under 4 pounds. they say the more displacement the less boost with same pulley. have you found this to be true?.

No my stock 5.0 made 6psi and now with the 331 and same pulley it made 7psi. Not really a big deal. But look into a set of longtube headers, I have heard they will help lower boost about 1-2psi depending on the set up. BUT I have only heard this, not sure if its true or not.

Tanus · Jan 27, 2010

I think the volume of the intake manifold plus the intake ports in head have more effect on psi then the displacement(but I could be wrong) Like if you have 10psi with stock heads/intake, then swap for a trickfow setup you'll lower the psi.

wadman1 · Jan 28, 2010

well i can always take the belt off if it hits over 5 pounds. i will bring it to the dyno and see where i am at, if i'm over 450 hp then i will take the charger off to save the motor. (or just run it till it lets go) i will build a real motor mid summer.

2000xp8 · Jan 28, 2010

Run it as is, if you are going to change it any way to make it better it's going to require a race block, like a Boss, dart, A4 or R.
No sense investing more money in something you are probably going to blow up anyway.

I'm with tanus, with a pulley rated for 5psi on stock engine, if your heads and intake flow well, you normally wouldn't see much boost, but with a ported cobra and unknown head porting the SC still may give you a few pounds.
If that was an rpm II and cnc wedges or 185 afrs, you'd probably see 0 pounds.

cjrpony · Jan 29, 2010

This is something I have been mulling over for a while also. My 331 is at 10.5 compression with the RPM heads and intake. I know that the compression is a little on the high side for supercharging, but have been wondering if anyone is doing it and what the setup was? I would think 5-6 lbs max at that compression. I have less than 5K miles on this motor (DSS ProBullit) so I don't want to blow it up. In the end, I probably would just leave it NA for now, but still the HP bug keeps biting! Any thoughts on this?

wadman1 · Jan 29, 2010

i already have the charger so i might bolt it up and just see where it hits boost wise and go from there. i guess from what you guys say a stock block is junk unless you want under 500 hp, so who cares if i blow it up? i will start looking in to other motor options so i can find what i want for this car. maybe i will sell this 347 motor whats it worth?

need help building a 347 for my procharger

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