safe compression for supercharged 5.0

[red03terminator]

Hi I have a 1990 mustang that will be getting a block soon. I have afr 165 heads (61cc), Holley systemax intake, comp cam. Will 8.25/1 compression be good for a street car? I plan to put a v3 vortech with 10psi. The most i want to see is 425-450rwhp.

1. will 425-450rwhp be safe on a stock block with forged internals?
2. is a 306 block from chp with 8.25 compression good?
3.what size injetors would u recommend?

 

[blownfox]

I dont understand why you would buy a 306 from chp when you could buy a 347 for a little more.

I will be running a 347 with 6 or 7 psi and I should be right around 430ish rwhp. My compression should be close to 9.1 or 9.2. Using 42lbs for the injectors will work. The block should be OK as long as the tune is dead on.

 

[red03terminator]

the only thing that is keeping me back is that my heads are too small for a stroker.

 

[4valvemach]

I agree with "blownfox" and get the 331/347 unless you are on a budget then the 306 will do.Also go for around 9.0:1 compression on your motor since that is the factory ratio and what the supercharger was based on.

a stock 5.0 at 10psi should make around 320rwhp

a full bolt on 5.0 (heads,cam,intake,exhaust etc etc)should be around 420-450rwhp at 10psi

 

[blownfox]

the only thing that is keeping me back is that my heads are too small for a stroker.

It is always easier/cheaper to add heads down the road than CI's. Either way you should be able to get to your numbers by adding more boost.

 

[red03terminator]

ok so the stock block should be fine with about 450rwhp max

 

[blownfox]

It is all in the tune. So the answer too your question is yes, but if the tune is off you will break it.

 

[red03terminator]

on chp's website the flat top pistons with (61cc) heads will have a compression of 9.30:1
is there any way to lower the compression a little?

 

[4valvemach]

You can get the main girdle for some added strength but I think CHP short blocks come with one.They should also be able to change the pistons for the compression ratio you are looking for.

You just need to call them and find out what can be done even if your not ready to order.

 

[trendkilllx]

I also recommend the stroker motor over the 306. Don't worry about your heads being to small. You could still make more then enough power to kill the block if you wanted to. Just get a good tune, go easy on the timing and limit your RPM. I'm in the middle of building a 331 myself. Using CHP streetfighter rotating assembly. TFS 170cc heads, Systemax intake, S-trim. ARP main studs. Compression should be around 9.10:1. Shooting for about 450-475. I haven't done the math yet but 42lb inj will probably do the job.

 

[blownfox]

I also recommend the stroker motor over the 306. Don't worry about your heads being to small. You could still make more then enough power to kill the block if you wanted to. Just get a good tune, go easy on the timing and limit your RPM. I'm in the middle of building a 331 myself. Using CHP streetfighter rotating assembly. TFS 170cc heads, Systemax intake, S-trim. ARP main studs. Compression should be around 9.10:1. Shooting for about 450-475. I haven't done the math yet but 42lb inj will probably do the job.

I think 42's are good for 500 rwhp, well that is what I am hoping for. How much boost will you be running? I'm doing a 347 with TW heads and 7psi. I'm hoping for 430-450 rwhp.

 

[trendkilllx]

I'll probably start at 8psi and go from there. I also think 42's will be good.