PI Heads With Supercharger?

98GTVortech · Dec 10, 2003

I have a 98 GT with a s trim vortech i am wondering if I install a set of pi heads will the compression in the heads cause damage? I am wondering if anyone has done this before and what they did to make it work. I heard alot of good things about the pi heads and the gain that the 96-98 gt's see. Thanks for the help you guys really clear up alot of questions...

FastRedPonyCar · Dec 10, 2003

no it'll be fine. just make sure you do't go past about 420 ish RWHP. That's about as much as the stock rods and pistons can take.

My advice would be to throw in a set of blower cams. Check with scott from VT engines.

98GTVortech · Dec 10, 2003

Thanks for the advice...

BTW-Sweet Car--- i saw that burn out

98superstangGT · Dec 10, 2003

FastRedPonyCar said:
no it'll be fine. just make sure you do't go past about 420 ish RWHP. That's about as much as the stock rods and pistons can take.

My advice would be to throw in a set of blower cams. Check with scott from VT engines.

whoa whoa....before you give that advice you might want to know what your talking about man. If he already has a blower on his 98 GT and throws the PI heads on there without any bowl work then the compression will be way to high for the car and the engine will start detinating and blow. 10.5:1 compression is WAYYYYY to high for a blower. You can use the heads but you will have to do some bowl work to get the compression back down to about 9.4:1 or lower.

blown98gt · Dec 10, 2003

98superstangGT said:
whoa whoa....before you give that advice you might want to know what your talking about man. If he already has a blower on his 98 GT and throws the PI heads on there without any bowl work then the compression will be way to high for the car and the engine will start detinating and blow. 10.5:1 compression is WAYYYYY to high for a blower. You can use the heads but you will have to do some bowl work to get the compression back down to about 9.4:1 or lower.

not necessarily...his cushion will be much less but with a tuner that knows what he is doing he will be fine. get the AF to ~11.5 and no more than 14* total timing. its all in the tune...but if you are the kind of guy that beats on the car then you may want to get some head work done or get some thicker gaskets to drop the compression a point or so. cometic makes some .078" gaskets that will drop your compression to about where the 01+ GTs are now. a tune is a must...

98superstangGT · Dec 10, 2003

blown98gt said:
not necessarily...his cushion will be much less but with a tuner that knows what he is doing he will be fine. get the AF to ~11.5 and no more than 14* total timing. its all in the tune...but if you are the kind of guy that beats on the car then you may want to get some head work done or get some thicker gaskets to drop the compression a point or so. cometic makes some .078" gaskets that will drop your compression to about where the 01+ GTs are now. a tune is a must...

true but i still wouldnt trust it. I mean who would throw PI heads and a supercharger on and NOT beat on the car to have some fun? i mean thats the point of increasing your hp so you can increase your fun. I know if i spent all that money on a blower im not going to be shifting at 2K. I would play it safe and get some bowl work done. Even if you dont get any head work done the best you could probably do is MAYBE 5psi at best. Its the same reason the Vettes can only run a max of 5psi or so without head work done because of the compression.

FastRedPonyCar · Dec 10, 2003

i know lots of guys who have headswapped and added blower and no problems yet. wouldn't the blower cams affect the comp ratio or no?

besides, everyone i know who has done the headswap has had at least a little maching work done to them. I'm planning on getting mine lightly polished and mabey ported a hair. When I get a supercharger though, I'll have a new bottom end and fully ported heads so no worries.

98superstangGT · Dec 10, 2003

FastRedPonyCar said:
i know lots of guys who have headswapped and added blower and no problems yet. wouldn't the blower cams affect the comp ratio or no?

besides, everyone i know who has done the headswap has had at least a little maching work done to them. I'm planning on getting mine lightly polished and mabey ported a hair. When I get a supercharger though, I'll have a new bottom end and fully ported heads so no worries.

that little bit of machine work they had done might have been some bowl work to drop down the compression a bit. I ported/polished my 01 heads but didnt have any bowl work done since i was staying N/A so i still have the full 10.5:1 compression ratio. I personally would NEVER throw a blower on my car with that compression till i bring it down to under 9.4:1 or less. I will be pulling the heads back off next year and doing this before i throw my blower on.

also the cams in no way whatsoever effect the compression ratio. the only way you can change that is to do some sort of modification to the combustion chamber area, such as bowl work, increased or decreased thickness of head gaskets and so on. The cams cant change anything in terms of CR.

billyfe390 · Dec 10, 2003

98superstangGT said:
that little bit of machine work they had done might have been some bowl work to drop down the compression a bit. I ported/polished my 01 heads but didnt have any bowl work done since i was staying N/A so i still have the full 10.5:1 compression ratio. I personally would NEVER throw a blower on my car with that compression till i bring it down to under 9.4:1 or less. I will be pulling the heads back off next year and doing this before i throw my blower on.

also the cams in no way whatsoever effect the compression ratio. the only way you can change that is to do some sort of modification to the combustion chamber area, such as bowl work, increased or decreased thickness of head gaskets and so on. The cams cant change anything in terms of CR.

General rule of thumb
short duration=higher cylinder pressure, more power at low rpm's
long duration=Lower cylinder pressure, less power at lower rpm's higher power band

An extremely long duration cam can lower the cylinder pressure enough to cause some driveability problems which can and will help a boosted application.

Basically your CR is fixed and can only be changed by bowl work, thicker head gaskets etc. etc. however the the cylinder pressure is what counts and that is variable and can be changed by longer duration cams.

00_blackgt · Dec 10, 2003

Josh Harris had MV Performance put the PI heads on his 98' GT and then he eventually added a supercharger. The shop told him his motor would not last long with the setup simply because of the compression. At first he ran 12.5's but eventually his motor started wearing out and he eventually only ran 13.7's. Some people said that if he leaned it out some that it would be ok but he didn't to try to keep it from detonation. It drove terrible and smoked like crazy.

mrvax · Dec 10, 2003

Do NOT supercharge a PI swapped 4.6L. You will blow the engine almost right away. A c/r of 10.5:1 is totally wrong for supercharging. No magical tuner in the world will be able to prevent a sudden and quick end to that engine.

If you have the swirl dams removed on the heads, the c/r can drop back to about 9.4:1 when a good tuner can keep the car alive.

Still not sure? PM "Cobra Killer" and ask him. He's probably installed more s/c on 4.6L Mustangs than anyone.

MUSTNAG 03 · Dec 10, 2003

mrvax said:
Do NOT supercharge a PI swapped 4.6L. You will blow the engine almost right away. A c/r of 10.5:1 is totally wrong for supercharging. No magical tuner in the world will be able to prevent a sudden and quick end to that engine.

If you have the swirl dams removed on the heads, the c/r can drop back to about 9.4:1 when a good tuner can keep the car alive.

Still not sure? PM "Cobra Killer" and ask him. He's probably installed more s/c on 4.6L Mustangs than anyone.

PM Tim he can tell yo for sure.

RedGTvert · Dec 10, 2003

mrvax said:
Do NOT supercharge a PI swapped 4.6L. You will blow the engine almost right away. A c/r of 10.5:1 is totally wrong for supercharging. No magical tuner in the world will be able to prevent a sudden and quick end to that engine.

Bull. You can supercharge a headswapped car. There are numerous people who have done it, and I don't need Tim to tell me if it can be done or not.

You cannot get greedy with it. Get plenty of fuel, keep the timing reasonable, and you should be fine.

stangman · Dec 10, 2003

well you can "do" anything you want to, to it. now whether it will hold up for any period of time & be reliable is a whole different ball game. the people talking about the swirl dams are right. another option would be to put a different piston in it, to lower the compression. but that's prolly going to be more work than he wants to get into. because if you get that far you might as well go all out

but when in doubt talk to cobrakiller

98superstangGT · Dec 11, 2003

RedGTvert said:
Bull. You can supercharge a headswapped car. There are numerous people who have done it, and I don't need Tim to tell me if it can be done or not.

You cannot get greedy with it. Get plenty of fuel, keep the timing reasonable, and you should be fine.

sorry man but your advise sucks! please do some more research and learn a little bit about engines and superchargers before you come spitting out some **** like that. The 10.5:1 compression ratio is WAY to high and would blow the engine in no time. How many engines have you ever built yourself? how many have you supercharged? didnt think so.....ive done plenty of both and compression and superchargers do not go together. Your right though, there are plenty of people that are headswapped and have superchargers....you know why though? they have done bowl work of some kind and have lowered the compression back down to a safe area so they wouldnt have any detination to destroy the engine. No tuner could safely make up for the increased compression. Atleast not for long. Please go dig up and find me atleast 1 person who has 10.5:1 compression or better in their stang with a blower if you think its possible. The reality of it is that you wont find even one, because people just know better not to do it.

FastRedPonyCar · Dec 11, 2003

lets start a thread and see who responds. my bet is that it won't be many.

mrvax · Dec 11, 2003

98superstangGT said:
Please go dig up and find me atleast 1 person who has 10.5:1 compression or better in their stang with a blower if you think its possible. The reality of it is that you wont find even one, because people just know better not to do it.

Again, I agree 100%. Last year there were 2-3 people who posted on Corral that tried it anyway. One of them was a fairly famous engine builder. The car grenaded in all cases almost right away. Sure if you tune it down to 1-2lbs you might get away with it, but then the blower becomes useless.

If anyone knows someone who has a S/C 10.5:1 compression PI swap 4.6L, please post up details. I'm very confident if you know someone who has a cousin who has a friend that did this, you will find they had the c/r lowered somehow.

cobra killer · Dec 11, 2003

First off,Rich (RedGT)you do need me to tell you what to do..Your wife had to post instructions above the head board for gods sake....

It can be done.I did it with 10 psi,no headwork and also ran a shot of nitrous.Car went 11.40's..
Now,is it smart.NO..Do I recommend it ,hell no..I ran a very conservative tune.I also ran 100 octane when spraying to keep it safe.The key is alot of fuel and little timing.Detonation is what will kill the engine.Mine never was hurt,but I wan't stupid either..It requires alot of tuning and care..Its not a car you beat on daily and I highly recommend running Torco accelerator and get a 96-100 octane in there when beating on it..
It can be done on pump gas,but get a 11-11.5 A/f down low quickly then maintain it..Alot of times detonation starts low in the rpm..Then as pressure builds it increases.If you head it off low with a rich A/F and basically stock timing,you can increase the timing to around 14 degress @ 5-6 K and be o.k.I would run 10-11 degress from 2500 - 4500.Then 12 @ 5000 14 @6000.

IMHO,I wouldn't do it unless you have a tuner willing to spend ALOT of time on the car.With 10:5.1 your flurting with death.Your car is on the ragged edge of grenading anytime.
My best advise,if your gonna do it,run 100octane..

Tim

cobra killer · Dec 11, 2003

FWIW,my car made 456rwhp and 454 TQ on a stock bottom end..Ya,Im retarted..

Tim

onlyme · Dec 11, 2003

im curious

Im curious thought the lt1's in the 93-97 camaro had over 10:1 cr and they supercharged them no probs and the new ls1's are suppose to be 10:1 and they supercharge them, how do they keep the motor from detonating and blowing to kingdom come?

PI Heads With Supercharger?

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