I plan on making my stock fuel pressure regulator adjustable this weekend. Being that I'll have my intake plenum off, I got to thinking about siameseing the top of the runners and the plenum to match. I don't want to port the lower runners or the intake because I'm afraid I'll give up WAY TOO MUCH low end. I was thinking that by just porting up top to effectively shorten the runner lenth by an inch or so, it would give me a little better breathing on the top end (my trans shifts to 2nd around 5,600rpm's) without sacrificing any low end.

Is the time and trouble worth it for a possibly very small gain up top?

Will my low-end suffer too much afterwards?

If it matters, my mods are below.

Thanks:rockon:

 

If you can do it yourself and for free, go for it. From just doing the upper you won't see much of a gain, but if you plan to do future mods it's a good start.

 

Not going to make a differance.

Your time is better spent raidusing the transitions between Plenum and runner, and removing the EGR wall at the front of the plenum.

 

Having personally wasted an afternoon doing exactly what you are proposing http://home1.gte.net/res0t8sj/inj/ , IMHO it's a waste of time. As in, if i had another TPI car, i would not even consider it as a useful idea. I'd just radius the inlets as radically as possible and leave it at that.

As for siamesing the base, the jury is still out on that one. Definitely not a good idea if you aren't into programming and have a decent converter as well as some big plans. It didn't really lose any low end, that is a myth. TPI's long runners are detrimental at low RPMs just as they are at high rpms because the incoming air has to move that whole long runner. Short runner V8s have had all the low end in the world since the advent of the ICE. TPI is only good for extreme mid range torque. But i still ran basically the same ET/mph with a siamesed base as without, with no tuning even. And low end as expressed with a locked torque converter on the highway is still as alive as ever.