I'd like to start trying some porting of my intake plenum, runners, base, etc. but I was wondering... if I don't have any internal mod like a cam or anything, and I have the stock throttle body, can porting hurt my performance?

Will I be getting too much gas/air? I'm affraid that it would run like crap! (Well, more crappy lol)

 

nah from what i've heard you can only get better performance. BUt i'm not completely sure. This'll help bring it back to the top of the list for more views.



Shane

 

It own't really hurt anything, if done properly.

Your stock throttle body isn't a limit to your car's performance, so don't worry about that.

The thing that are its limits (apart from the general design features of TPI) are the cam, the exhaust, and the intake base.

 

Don't "siamese the runners". You'll gain top end HP but loose low end torque.

 

now see i dont get why it hurts the low end but help the high end. It should, in theory, help both. Your increasing air flow at both rpm ranges. I'll never get that.



Shane

 

really? didn't notice that when i completely siamesed my intake. or when i completely siamesed the SLP runners. dyno didn't show it either. well maybe a little. but hey 20ft-lbs is nothing.

 

Seems like RB has the right order. The restrictions are:

1. The plenum directly behind the throttle body;
2. Casting mismatch between the runners and plenum;
3. Casting mismatch between the runners and intake base;
4. Exhaust manifold restrictions;
5. Intake base/head mismatch and runner sizes;
6. Intake ductwork restriction;
7. Valve sizes and lifts;
8. Head runner volumes.

I think I have those in the correct order. Just opening the area behind the throttle body can help a bit. I left out the last restriction, since it's fairly obvious that ths TPI is designed to support lower RPM cylinder charging, and falls off in effectiveness at upper RPMs, even if modified. Long runners are simply tuned to charge better at lower RPMs. Gear your car accordingly.

 

If you open it up too much and start to lose velocity you start to lose power, or something like that.

 

Bes217 has it exactly right. Bigger does not always equal more air. The diameter of the runners is a set diameter to get maximum velocity at a certain rpm range. If you change the runner size or lenth you might loose hp.

 

20 Ft/lbs is a lot. Especially when it's right in the rpm range that you usually drive. (low rpm.)
On a basicly stock motor with stock low gears and low stall, its quite noticable.

Unless you're going to do other mods like increased compression, head porting and a larger cam, it could slow you down. (on a stock motor).
You'd want to speed up the motor (rpm range) with more gear and a higher stall.

 

Looks like you changed cam and changed the chip also between those runs.

Siamesing the base is nothing new,,, I knew a couple guys that did it back in the late 80s. One hurt his engine as Mike Davis did (not very long ago) and the other slowed down,, got ticked off about it and carbed the thing. Not saying that everyone has bad results,,, I just haven't seen good results with my own eyes.

Siamesing the runners is a differnt story though. I took and inch at the time off a set of SLP runners and the et and mph increased each inch removed until about the 1/2 way point in the runners. There's no question if I had removed more, the car would have slowed down. The long runners is the best thing going for the TPI system,,, if you totally kill that,, all you end up with a terribly inefficient (the absolute worse) short runner intake on the planet.

 

i read a bunch on this, in a book that i have, actually... right next to me, :-D.

basically, if you port too much, you can hurt it, like the... one guy, forgot who said it said, you can loose some of your pressure & vacuum essentially, that sucks in the air. basically.. .. you know how, when you blow into a small straw(wendy's), you can feel how much your forcing, and the speed at which it's going in & out? then you blow into a big 3 diameter tube, & it's like, wtf, no air is comming out the other side. it's about the same. you wanna get everything matching up right, flowing good, but not too much. if you don't, then you could screw stuff up. Also, if you grind out too much, you could basically funky junkie up your heads. aka, buy new ones, :-D. it's easier to just let a pro do it, or get some spare heads, play around w/ it until you really know how to do it. Also using different stones, bits, & different tools does alot as well, there are certain tools you use for certain areas, and different metals, ie iron or aluminum, heads/chambers. Stock heads... i think it could help.. but is it honestly worth having your car down for a few days? and possibly screwing it up?

just my .25 cents, not .02 cents, cuz i actually have read up quite enough on this stoof. :-P.

btw, i'm talking heads, not plenum or runners, i duno about them, rofls. i'm doing away w/ tpi asap so i havn't given them much thought. i've heard praises about siamese & i've heard no no's about it too.

OHYA, last note.. you can only port out until where the gasket is at.. & you shouldn't port it out to exactly where the gasket is on the bottom... you should have it alittle above.. also talking about heads.

& with the chamber... dang it's a hard job, i havn't done it, but the pix i've seen are enough to make me say, ok, helo, your going to shop for this.

/me fears doing porting/polishing work. cuz it has to be exact, or close to it...all has to be same size.

good luck w/ it though.

k, i've rambled enough, bye.