What Heads To Use With Supercharger?

You will have higher compression with PI heads on a NPI shortblock. But with a safe tune and 6-8 pounds of boost you should be fine. Especially if you're using meth injection or an aftercooler (Vortech) or innercooler setup. I think the compression would be around like 10.1:1 - 10.5:1 somewhere around there. You should be safe with a mild tune. I personally would not hesitate to use boost. Plus different head gaskets will decrease or increase the compression a little as well. Look at it this way, if a PI swap gets you 10.1:1 CR, then consider the fact that the non-Termi Cobras and the Mach 1s have about 9.85:1 - 10.1:1 compression and they see boost all the time...some of them up to about 12 pounds. Stick with 6 psi (PD blower) - 8psi (centri blower) and you'll be ok.

Dont worry about the compression. If you have a tuner who knows ANYTHING about tuning, he'll be able to compensate for the compression. Personally, I think 10:1 is PERFECT for boost. It isnt too high to worry about detonation. You will see some awesome power from it. As Three50 said, throw some meth or E85 at it in the future and it will fkn steam roll!!!

Yea that was like 12 years ago. Back then the PI engine was kinda where the Coyote engine is now as far as being new and relatively unknown. I mean, back then, shops all thought cam swaps were all but impossible and would give you no gains. A lot has changed since then as far as tuning and what we can do with these engines. See, back then, the oldest PI engines were only 4 years old. And there were not many PI swapped engines out there. And even supercharged New Edge GTs were not that common. I mean, they're talking about LT1 Camaros in comparison to compression ratio, lol!! And the main guy campaigning against it was even saying the stock compression is too much. Back then he may have been right. But how many of us are running stock compression and DDing our cars with 8, 10, even 12 psi? And how many Cobras are seeing the same boost levels at 9.85:1? And how many Mach 1s are out there with blowers on stock internals at 10 psi?

If you do a PI swap, and you use a centri blower which builds boost gradually, and you do a moderate tune, then I think you will be fine. Go with some ARP head studs, make sure that engine is built correctly using the correct torque specs and sequence, throw some headers on it while you're at it, run the 3.60 pulley (if using Vortech) for starters, and tune it mildly. If you want extra assurance, throw in a CX Racing intercooler set-up which goes for like $500 shipped on Ebay or a meth injection kit. But even if you keep it non-intercooled, as long as the tune is safe and mild and you're not going WOT and staying in it all day every day then I really don't see you having any problems. Your tuner should be able to keep your AFRs in the proper range. And from there just use high octane gas and throw a can of octane boost in it every now and then and I think it'll be ok. Other things you'll wanna do is run a good aftermarket fuel pump and some 60lb injectors. And if you're really worried about the compression, then run a thicker head gasket which should help out a bit.

Jesus Christ. WHY THE DO I WASTE MY TIME HERE??????

I told you what you need to know.....

People are always going to have questions and doubts...and more questions and more doubts...and for every question you answer there will be 2 more that pop up and someone somewhere who will say the exact opposite. There is nothing wrong with asking the same things over again. Nobody wants a blown engine.

Max22 said:

Thanks for all your help, that's the kind of info I was looking for. Glad someone around here understands that not everyone "knows everything" like Nightfire up there. Do you think that just stock PI heads will see decent enough gains or would it worth it to go aftermarket PI heads?

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PI heads will net you 35 hp N/A and the gains will increase exponentially with boost. 10:1 on a conservative tune up is not an issue. Remember that the coyote motors are 11:1 from the factory and fwiw, my S550 see's 11lbs regularly making 646rwhp and zero issues.

Max22 said:

Ok yeah that makes sense. Suppose I'm sitting at 240 hp at the crank pre pi heads, what kind of projected numbers would I expect to see with PI heads running 6lbs of boost? I'm just planning it all out to see if supercharging a 4.6 is worth it $ per $.

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When I had my 98 years ago, Forged bottom end DSS 4.6 with cnc ported heads, cams ect. we managed to make 495 rwhp on 12lbs of boost. With stock PI heads and cams I don't think that 350rwhp is out of the question on 6 lbs of boost, more boost more power, further upgrades, more power. I've never met anyone that didn't enjoy a boosted motor