PI HEAD QUESTION FOR ALL YEARS!

TopDeadCenter · Aug 3, 2004

Wheres KBOY when you need him..

How many horses would i be robbing from myself if i dont do the PI Headswap..if i just go with the PI Intake and Cams...what would this give me..the reason im asking is changing to PI heads in a 96-98 motor will really bump your compression right? Well what do you do if your looking to eventually charge or spray? I am really thinking of staying with my heads..cause they're really not that bad..going with the PI Intake and probably Comp Cams..worth it?

RysRed96GT · Aug 3, 2004

you'll loose about 10-15 HP without the head castings. if you're gonna use nitrous, the added compression will benefit more than lower, but not if you're going to super/turbocharge it. i think if u get aftermarket cams with more lift you'll need new springs too.

i had just the pi intake before and definattly wasnt the power i have now. more torque throughout now and much more pull uptop. why not get the full headswap, sell the PI cams and get comp cams in the pi castings as well? then that would be sweet.

TopDeadCenter · Aug 3, 2004

hmm maybe..theres a big debate on all of this..i wish more people would reply..but i guess if ur gonna do one might as well do all..free up some power

mogs01gt · Aug 3, 2004

You are going to loose a lot more than 10 or 15 rwhp. You will loose the same amount the heads will give you.
pretty simple to figure out.

RysRed96GT · Aug 3, 2004

mogs01gt said:
You are going to loose a lot more than 10 or 15 rwhp. You will loose the same amount the heads will give you.
pretty simple to figure out.

nah, he'll get power from the manifold and cams. he'll loose some from the heads due to stock compression and less port-flow

tangerine · Aug 3, 2004

most people with the heads dyno around 250 at the wheels but with the cams and intake I have seen numbers around the 225 range so there is about a 25 rwhp difference.

TopDeadCenter · Aug 3, 2004

blowing that much money might as well

mogs01gt · Aug 3, 2004

RysRed96GT said:
nah, he'll get power from the manifold and cams. he'll loose some from the heads due to stock compression and less port-flow

You are missing two big components with the swap from the Non PI to the PI. A. higher compression(more power) B. BETTER FLOW.

The cams wont do **** in the stock non PI heads. It would be a lot more worth it to get the PI heads over the cams in the Non PI heads.

billyfe390 · Aug 3, 2004

There is about a 10-20hp difference depending on who you talk to and what mood they are in when they post it.

TopDeadCenter · Aug 3, 2004

lol aint that the truth

RysRed96GT · Aug 3, 2004

mogs01gt said:
You are missing two big components with the swap from the Non PI to the PI. A. higher compression(more power) B. BETTER FLOW.

The cams wont do **** in the stock non PI heads. It would be a lot more worth it to get the PI heads over the cams in the Non PI heads.

thats exactly what i said . you'll retain stock 9:1 compression by staying NPI and you'll lose CFM airflow. the cams will do some gains, bout 8-10 rwhp alone on average i've read.

COramprat · Aug 3, 2004

mogs01gt said:
The cams wont do **** in the stock non PI heads. It would be a lot more worth it to get the PI heads over the cams in the Non PI heads.

I beg to differ...

Now we don't have dyno results but we do have car(mine 96GT) vs. car (his 98GT). Before the cam swap, me and kboy ran a couple of times. His car at the time just had complete exhaust swap, I had midpipe, pullies, and 4.10 gears. I had no problem walking away from him from a roll or a dig. After his cam swap we ran again. I would take him from the dig but from the top of 2nd on he ate my lunch. We did runs from a roll and it was no contest. He would immediatly pull away. So just cams DO have an effect on non PI heads. I don't even want to try now that he had done the intake swap. He will have dyno results later this month when he goes to Atlanta for a duno tune.

The complete PI headswap is worth 10-15 HP tops over just an intake swap. Compare $1200 for parts and another $1000 for labor on a complete headswap or $600 for the intake swap kit and another $600 for labor and decide for yourself if 15 HP is worth it. In fact...PM Johnny Langton and let him give you his results on the intake swap. There is also and article in a recent issue of 5.0 Mag discussing Livornois intake swap kit and gives dyno results there. The results were a 10 HP difference between a complete HS vs just an intake swap. Granted you can get the above done cheaper if you do the work yourself and find used parts but $ for $ you will still gain good HP numbers with just the intake swap.

GDawg · Aug 3, 2004

billyfe390 said:
There is about a 10-20hp difference depending on who you talk to and what mood they are in when they post it.

I agree... and since I eventually plan on putting in a S/C I am leaving my NPI heads in.

billyfe390 · Aug 3, 2004

GDawg said:
I agree... and since I eventually plan on putting in a S/C I am leaving my NPI heads in.

You can use the PI heads if you wanted to all you have to do is grind out the swirl dam and you will be back to stock compression.

mogs01gt · Aug 3, 2004

Put a .500 & a .550 lift cam in both heads

see which one of the two will perform better stock for stock. Its a waste of money putting cams into the Non PI heads when you have the option of the PI heads. 5-10 rwhp on a cam swap is worthless.

Jake795 · Aug 3, 2004

i actually saw an article on MMFF website where livenois flow tested pi and npi heads on a flow bench with several different cams. the npi heads actualy outflowed the PI heads when the lift got over .500 below that the pi heads out flowed the npi.

Jake

FallenPhoenix · Aug 3, 2004

There's a few threads over on mod depot claiming that ported non-pi heads will flow better than ported pi heads. If it were me, I'd get the PI intake and when you want to go blown, swap for some fully ported and polished heads later on. 15hp isn't worth that much more money to me but you'll see huge gains with ported heads and a blower.

LI98GTStang · Aug 3, 2004

On a budget, you go can with just PI cams, no springs needed and a PI intake you can install it yourself relatively easy with the help of the AFM cam tool. With PI cams/intake installed, I dyno'd at 229 rwhp on my NPI headed '98GT. Only other major mods being catted X, FRPP catback and Pulleys. Most 99+ stock stangs (with PI heads) dyno in that range. I am still using 87 octane gas and stock timing. PI heads will give you more hp than what I have in the range of 10-15rwhp, but will require premium gas due to the increase in compression. Only way to go wrong is to leave the stock cams and intake IMO.

fstnfuriusgirl · Aug 3, 2004

FallenPhoenix said:
There's a few threads over on mod depot claiming that ported non-pi heads will flow better than ported pi heads. If it were me, I'd get the PI intake and when you want to go blown, swap for some fully ported and polished heads later on. 15hp isn't worth that much more money to me but you'll see huge gains with ported heads and a blower.

<---rysred96gt

ported NPI's will not outflow ported PI's. the big debate is between ported NPI's and regular PI's.

FallenPhoenix · Aug 3, 2004

fstnfuriusgirl said:
<---rysred96gt

ported NPI's will not outflow ported PI's. the big debate is between ported NPI's and regular PI's.

I guess I read the thread wrong, why would there be any question if fully ported non-pi will outflow stock pi?

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