PI Head Swap Question

[VTGT91]

I know there are a lot of threads out there telling about how to do a PI head swap. However, there is a piece of information that I can't seem to find. After doing a PI head swap is it necessary to get the car tuned? Its obviously a good idea, but will I be running the risk of tearing something up if it is not tuned. Also if I borrowed a SCT or Diablo tuner from someone and just set it to the preloaded 93 octane tune would that suffice?

Also does anyone know where to get a good PI headswap kit for a decent price? Going through the local auto parts stores, it looks like the cheapest I can do is about 220 for the gaskets and the bolts which is a lot. Not the hard parts, but like gasket set, head bolts, water pump nipple and hose, etc. etc. Thanks for the help.

 

[wmburns]

Just to make sure we are on the same game page. You have a 1996 SOHC GT and the plan is to remove the NON-PI heads and replace both heads and manifold with the PI versions.

This is a great swap. However, it is VERY important to remember this swap will raise the compression ratio by a FULL POINT. While many ppl will disagree, stong consideration should be given to running only higher octane fuel.

The PI heads do flow better, but because the air is metered (via the MAF) a re-tune is not needed.

Regarding your questions about a "canned" tune. Do not do this. The reason is that your engine is no longer a "canned" engine. Remember the thing about the 1 point increase in CR? All of the after market tuners increase HP by changing the timing curve (adding timing). Adding timing increases octane requirements. Your motor combination is already octane hungry. So unless your plan is to run race gas, run the motor as it is.

Otherwise, have the entire package professionally dyno tuned.

Good luck.

 

[fast97gt]

+1 up on the tune question, its not necessary but it wont hurt later down the road to have it chassis dyno tuned. that will help see a few more horses but other then that youll love that thing will run. doing a pi swap does increase compression, thus this gives you more hp than a pi engine. a 96-98npi with pi h/c/i swap=more hp then a 99-04pi engine, not sure but i think it nets around 20hp more.

 

[fast97gt]

Cylinder Head Changing Kit 2V Modular Depot - Your source for Modular Performance parts and service $105 bucks aint bad

 

[trinity_gt]

I'm with wmburns. Normally-aspirated "tunes" almost always crank the spark timing which can lead directly to detonation and on a 10:1 PI-swap, this would be suboptimal. Remember, the 2V doesn't have knock sensors so you need to err on the side of caution when it comes to spark timing.

If you do have it "dyno tuned", you might consider going in with a mid-grade fuel in the tank and have them tune it such that you don't get tip-in spark knock (i.e. a burst of knock related to big transitions of throttle angle, especially at low RPM and under load.)

But I'd start by just driving the thing with the factory tune and see how it does.

 

[Midnight2V]

Keep in mind that if you ported your NPI heads and added a PI intake, you could run a much more aggressive cam profile and make more power than ported PI heads....both are about even on flow in ported setups. Even taking into account the compression bump and performance cams in PI profiles, the NPI will hold up against a PI setup. And you maintain a positive displacement supercharger or turbo friendly CR of roughly 9.2:1 as opposed to 10.4:1 (which would be good for NA). You would need to notch your pistons in order to run an aggressive enough profile to match a properly cammed and ported NPI setup that is using a PI intake.

 

[bnmc98]

PI head and NPI spark tables are very different, especially at the part throttle applications. its like throwing a bunch of global timing in there. That being said, I have run a PI engine on a hot NPI tune in a heavy car and been fine with 91 octane. I did retard the timing 2 degrees, also because I deleted the egr as well. You should be fine if you bump the octane a bit, but to get the most out of your combo a tune would be recommended.

 

[Winters98GT]

I have done 2 full PI headswaps on my NPI cars, and one partial swap. (2 on my 98, and 1 intake on my 97). I drove my 98 with PI heads for 30k or more in miles, hard miles. Tracks times, etc. Car never had any problem, trapped 105 with stock headers/cams/ and no tune. 264rwhp. No drivability issues. Years later, We added Erson reground cams, at the time, I was the first to do it if I can remember. We had to use lash caps under the lifters to adjust for the cams. Needless to say, that didn't work and the motor blew.

I installed a junkyard NPI 2v in the car. A couple months later, we swapped another set of PI heads on the car. It ran completely fine and also ran 104-105mph in full street trim with chrome wheels.

I am sure a dyno tune might pick up some hp. For me, I just used the track and a steeda timing adjuster to do the trick. Car was always a low 13 second car with crappy c springs, stiff tokico non adjustable shocks/struts, and chrome wheels. Not exactly a drag setup, but it did ok