I had a stock L98 TPI base custom ported that I am going to be installing along with 22lb injectors in the next 1 - 2 weeks. I've attached a photo of the portwork for reference. The port diameters are actually a little larger than meets the eye as I haven't matched the gaskets yet.

While I have the top end torn apart, I was wanting to do some portwork to my SLP runners. Currently, they are sporting the stock siamese with the plenum portmatched. I was thinking of enlarging the siamese area and taking the divider back another inch or so, effectively shortening the total runner length from the plenum to the heads. I am also planning on smoothing out the inner diameter of the runners by removing the cast finish.

My ultimate goal is to get a bit more RPM out of my intake. I know that TPI needs a MASSIVE amount of work to hit the 6k mark. I am hoping to get the motor to pull strong to about the 5500 mark. Currently it peeters out around 4700ish RPM and goes into cardiac arrest by about 5k. Given my future goals with this motor if I could make it to 5500ish rpm I would be ecstatic. You guys can hate all you want but eventually I want to build a 335 with a good set of 1.94 heads and a 268XE cam.

I've done some searching but haven't found much info on the subject. I know names like DynoDon and Kevin91Z could really shed some info on this matter. Thanks guys.

 

What exactly is your question?

 

Not sure how I could have worded that any differently.

I'm trying to get my motor to pull to a higher RPM rather than the 4600 - 5000rpm wall TPI is famous for. I want it to pull to a higher RPM for more peak horsepower without sacrificing too much bottom end (Daily driven street car).

Extrude honing looks nice but I'm doing this on a budget. I'm thinking a flex shaft and carbide cutters are going to be my friend here.

 

Do this to the runners, but go back a total of 3.5" - 4".>>>
https://www.facebook.com/photo.php?f...type=3&theater

Match the plenum like this.>>>
https://www.facebook.com/photo.php?f...type=3&theater

What cam are you running?

 

I think I get it. So you are saying enlarge/radius the runners inlets and take the divider back so the runners start their path going straight down instead of taking that initial curve from the Plenum? Then finish off with a nice 80 grit finish to the inlets and outlets?

Right now I am running the stock TPI Cam that was used in 85 (NOT the peanut Cam) so I know I am not going to see substantial gains up top right now. I do see 1.6 roller rockers as a good possibility in the near future.

EVENTUALLY when I build the 335 I am looking at an XE268 package

 

Yeah, you got it.

You really need to upgrade your cam to get the best results though. The stock cam is pretty weak. 1.6 rockers at least. Also, do you have an adjustable fuel pressure regulator? If so, pressure should be raised. The early TPI engines had low fuel pressure. Raising pressure to 45-50 will yield big gains, even on a stock motor.

 

When I brought my car back from the dead I found out the diaphragm in the stock regulator was toast after searching for the cause of all 8 spark plugs AND the O2 being fouled out so I junked it and tossed in the holley regulator. It's set at 45PSI now and I'm going to do a bit of track testing and some dyno pulls after the 22lb injectors to see what it likes best.

Before the end of the year I'm getting it tuned but paint and bodywork is of the highest priority after this.

 

a old set of my runners mid way thru porting

 

Exactly what I had in mind.

How did that end up working out for you?

 

Running an XE268h cam in my rebuilt 355 and am absolutely stoked with it, no vices and will pull from 1000rpm in top with stump pulling power and as sweet as around town.Got 1.6 rockers so nearly half an inch of lift and 24lb injectors, has a nice lumpy idle that goes smooth by about 1000rpm.

 

Thanks for those pics. I will be doing this to mine soon. I ported the lowers already but wanted to wait on the tops and run the car on the new engine. That way I can see what gains I got just from the porting when I do it.