HI I was just currious what you all think about a moded TPI and the rpm level it should pull to. My set up is going to be a VERY ported base/ highly ported SLP runners/ and much worked over plenum/ and 52mm throttle body. So in theory if I have the correct cam/heads combo, what do you think the best rpm the set up could pull to. Also if anyone has a like combo on the induction set up, what has your experiance been with the tpi, and rpm range...THANKS

 

You're going to have some fuel reprogramming to do. There's nothing wrong with shifting a TPI at 5,800 with the right setup.

 

I'm shifting at 5850rpm on the 1-2 shift and 5600 on the 2-3 shift. With my next set of mods I will try to up that around 250 rpm. See signature for details.

 

Thanks VADER, 1989GTA, I know I will have to do some programming thats why I am getting a APUI moates set up as soon as he has them off of backorder, hopefully very soon. So with the mods im looking at it you are saying that with the correct cam/heads that it should pull to at least 5800 or so. Thats good so I guess my gear that I have will work just fine. I was just currious because the cam that comp had suggested to me will pull to 6200 and I thout that was a little high even for a XFI cam and so I was wondering why they would reccomend one that big for a MODED TPI. Later I will figure out a way I can make me a HSR work for me but was just looking for some people that has had experiance with some higher reving TPIs...If anyone else can give me some real world examples of the RPM range they have gotten out of there TPI then please let me know. Thanks

 

Which XFI cam did they suggest? Also Dyno Don has almost the same combination as myself and he shifts at about the same rpm range. Just a matter of how well your moded TPI breathes. Kevin L also has a highly moded TPI but I'm not sure of his shift points.

An Extrude Honed TPI aftermarket manifold will flow around 270 CFM. That is enough to make some serious horsepower. Just have to make sure the aftermarket runners will do the same and the plenum. Siamesed runners will do it and just match the plenum to the runners.

You can see where I'm at with a 212 degree cam. DynoSym has my current combination at 399 horsepower. I'm at that point or a little more. When I plug in the XFI-268HR-13 cam, raise the compression to 10.72, bore .030 over and port my heads the horsepower jumps to 510 at 6000 rpm. I can only hope. Hehehehe.

 

Thanks 89GTA, yea I have removed almost a 1-1/2 pounds out of my SLP runners and that has really opend them up, I am about to start polishing since I finished making all my rough cuts and have smoothed out all the bumps etc. Boy thats huge hp on a TPI set up for a 355, have you had any detonation problems with the compression you are running. I am going to be pushing mine to 10.35:1 and think thats ok for alum. heads. What kind of times/speed have you turned with your combo. I cant waite, test and tune starts at our track next sat, so im going to get some base numbers soon and then see what kind of difference they make afterwards. They reccomended the same one as you are looking at.......lol. Mine has to be an everyday driver so I dont want to get to crazy, I actually have a Pro Street Vega that I run at the track so I get most my thrills out of that car, but dont want my Z to be a slouch. Boy I would like to have some extrude honeing done but that seems to cost as much as I could do me a HSR for ...lol. Thanks for your imput and please let me know when you do your cam change and the other mods, and what kind of difference they make.

 

My compression right now is about 10.5:1. No detonation. With the rebuild I'm going with a quench of .038" and 10.72:1 compression. I'm also going to have the valves ceramic coated, polish the piston tops and the chambers. These items will help keep detonation in check, keep more of the heat in the combustion chamber and hopefully make more horsepower

I'm also building mine for a street application. I want a decent idle and good vacuum to run everything. Madmax has the 230XFI cam and his car seems to run quite well. However you can tell there is a cam in the car. My times are in the signature.