plentum porting

[clarkey3]

has any body with a ecotec ever taken off the cover of their plentum(intake manifold)and seen the dirty little bits of carbon/fuel build up? its worth cleaning it out.i was wondering has anybody ever tried porting their intake manifold? or dose this upset the computer?due to a factory set measurment of air flow.

[HoZy]

If you clean it or port it, remove the plenum & the manifold from the car so u dont get metal shavings an shit down in ur motor!

Cheers
MaT

[immortality]

cleaning it iseasy, just a rag and some solvents will do the trick. there isn't probably a lot of porting to do in the plenum end of the manifold as it already has large radiused edges going into the runners. maybe port matching the runners to the head would be of more benefit but would require removing the intake manifold from the engine. some have suggested that the plenum could use a little more volume and that the runner need to be longer but unless your going to design an entirely new manifold and produce it there isn't a lot that ca nbe done. maybe have look at the walker V6 manifold. top righthand picture. link below

http://www.walkerperformance.com/index.html

[sircruisealotVS]

that walker manifold is so crazy, i should have saved my money and bought that, it would be wicked.
as for the topic at hand, like immortality said, port matching the manifold and runners is said to give some gains so it would be a case of both or dont bother.
as for the crap inside the manifold, if you feel like pulling it off (its not hard) go nuts with some throttle+carby cleaner, it gets most of it off....remembering it'll probably be back to how it was in a couple of months though.

[immortality]

weird looking thing ain't it. love to see somoene put it on there engine with some before and after results etc. i probably wouldn't bother port matching the intake untill you have ported the heads as well

[sircruisealotVS]

weird looking thing ain't it. love to see somoene put it on there engine with some before and after results etc. i probably wouldn't bother port matching the intake untill you have ported the heads as well

damn straight its weird looking, but it would be so awesome.
i actually emailed walker today, lol...i couldnt help myself. unfortunately anthony tells me they are no longer available ...."due to the extensive fabrication required, only a few V6 crossrams manifold were made"
so even if i did come up with the dosh they dont have any left to sell!
oh well.

[immortality]

damn straight its weird looking, but it would be so awesome.
i actually emailed walker today, lol...i couldnt help myself. unfortunately anthony tells me they are no longer available ...."due to the extensive fabrication required, only a few V6 crossrams manifold were made"
so even if i did come up with the dosh they dont have any left to sell!
oh well.

would still be interesting to see how they perform vs the stock manifold

[sircruisealotVS]

yeah, definately..the torque would be great with those long runners!
while the dont manufacture those particular ones anymore, anthony did say he could design a similar type of twin plenum manifold if i was interested.
might be something i look into next year.

[chook231]

If/When you remove your lower intake you can see the parts of the lower intake that is actually overhanging the ports entering the heads , as there wil be a carbony deposit left from the blow back (but the gasket surface should be clean, it will be obvious once you take it off) as un-burnt air/fuel mix escapes back into the plenum.

If your interested there is a small (upto 20 hp -according to COME RACING on the 4.3 ltr) to be gained from porting the lower ends of the ecotec intake/runner area on the ecotec motor.

also try port matching the plenum to the lower intake (runners).
You could also try extending the runners inside the plenum by tack welding a few bellmouth extensions to the base of the plenum.

hope that helps cheers
Chook

[immortality]

If/When you remove your lower intake you can see the parts of the lower intake that is actually overhanging the ports entering the heads , as there wil be a carbony deposit left from the blow back (but the gasket surface should be clean, it will be obvious once you take it off) as un-burnt air/fuel mix escapes back into the plenum.

If your interested there is a small (upto 20 hp -according to COME RACING on the 4.3 ltr) to be gained from porting the lower ends of the ecotec intake/runner area on the ecotec motor.

also try port matching the plenum to the lower intake (runners).
You could also try extending the runners inside the plenum by tack welding a few bellmouth extensions to the base of the plenum.

hope that helps cheers
Chook

basically you mean port matching the intake runners to the head? this is common. that is probably 20hp on there 4.2 stroker which i bet had a bigger cam in it also and probably a really good tune. i recon you wouldn't see even half of that on a near stock engine. tack welding extensions into the runners would be very dificult and time consuming as you would need to make sure there sealed properly to the original base. i'd maybe suggest using a product like "knead-it" it sets as hard as metal alsmost and you could form it into the shape you like and then leave it to set. and if it doesn't work out as you though it would require a lot less effort to remove it. using this technique i guess you could get maybe another 1" to 1 1/2" off runner legth. another thing to maybe consider is trying to increase the volume of the intake manifold?

[chook231]

basically you mean port matching the intake runners to the head? this is common. that is probably 20hp on there 4.2 stroker which i bet had a bigger cam in it also and probably a really good tune. i recon you wouldn't see even half of that on a near stock engine. tack welding extensions into the runners would be very dificult and time consuming as you would need to make sure there sealed properly to the original base. i'd maybe suggest using a product like "knead-it" it sets as hard as metal alsmost and you could form it into the shape you like and then leave it to set. and if it doesn't work out as you though it would require a lot less effort to remove it. using this technique i guess you could get maybe another 1" to 1 1/2" off runner legth. another thing to maybe consider is trying to increase the volume of the intake manifold?

Hey immortality,
you do make a good point there, and yes it was on one of come's mega dollar 4.3 ltr engines with a cam and their sissy tuning, and knead it would probably work better than tack welding, just passing on information that has been passed to me and has by word of mouth worked pretty good.

cheers Tim.

[immortality]

true, but for most that doen't have a workshop avail, getting things welded would be a costly exercise. i'm thinking of trying the "knead it" technigue on the missus VS but it's fairly much stock and i have no way of tuning it without paying someone which i'm not goingto be doing any time soon so i don't see much to be gained there at the mo. places like COME tend to do really good tunes on in house built engines that they show case but when they do a tune that will be sold with something like there stroker kit it is actually "detuned" because of the many variables that are out of there hands when people use there kits otherwise if it was a reallyhot tune and someone put to much compression in there engine it would detonate itself to death and they don't want a bad rap.

[chook231]

Hey immortality,
with your come racing tuning theory you are spot on the money with their in house built engines and not wanting a bad rap from something that is out of their control.

With welding the plenum, they may not do it , as the welder who does my jobs would nt weld up the breather hole (22mm)in a set of vn alloy rocker covers as the alloy is to thin and would distort or burn. - so the knead it solution sounds like a good idea , or you could use hi-temp silicone (was succesful in the build of a mild ford 289),or gasket goo would probably work better.

Extending the runners will probably only result in more torque(not dyno kw's) and a better 1/4 mile time.

cheers
Tim

[1991_Vn2nV]

Since when does COME have a 4.3 litre kit

Its a 4.2L unless im very mistaken.

[immortality]

Extending the runners will probably only result in more torque(not dyno kw's) and a better 1/4 mile time.

cheers
Tim

i wonder if it would make any difference without it being retuned. last i checked it was a 4.2 stroker from COME. i believe the bradley stroker is 4.3 but i've heard it's weak

[IBLOWN]

Do what i did and die grind with a polishing wheel (flap wheel) on the inner plenum until smooth and matchport.

[Michelson4301]

Remove the plenum chamber and refit the lid. Hold the plenum up to the sun with the runner inlets facing upward then look through the intake where the T/B bolts on. It's a tad on the small side aye. I ported this section out and with the standard throttle body i noticed a definate increase in accelaration, not bad for $2 of threebond and 2hrs of my time.