Hey gang, I may have an issue. When porting my 2200 head the shop hit a problem. They are porting it to my pacesetter gasket to insurre i get a good port match witht he header im gonna use. Now, they have hit a couple small holes in the casting that go through to the water ports! well they welded those up but are affraid to continue to port it any further. It seems thay have taken a good amount of materiral out but is it enough?!
the ports are now 1 1/4 and 1 1/8 in size. I did not measure stock so i dont know what is removed.
you really don't want to have the exhaust ports totally gasket matched to the header, because if the port is the same size(or bigger) as the header primary, you can get reversion, exhaust backpulses that can sometimes get back into the cylinder... the step keeps that from happening... or at least thats what i've gathered from my research thus far, but i'm sure if i'm wrong that MadJack will step in to correct me.
Arrival Blue 04 LS Sport
Eco
Turbo
Megasquirt
'Nuff said
Yea, keep in mind this motor will be N/A with nitrouse. And I do remember hearing tat fully opening the exhaust IS a bad idea.
Scarab (Jersey Jay 1.8T) wrote:you really don't want to have the exhaust ports totally gasket matched to the header, because if the port is the same size(or bigger) as the header primary, you can get reversion, exhaust backpulses that can sometimes get back into the cylinder... the step keeps that from happening... or at least thats what i've gathered from my research thus far, but i'm sure if i'm wrong that MadJack will step in to correct me.
I think that's more for turbo'ed engines, but it probably applies on a smaller level here. However, you normally want the step on the bottom of the port, not the top, as the exhaust tends to flow more towards the top of the port than the bottom. At least that's what I've gathered. I'm kind of curious as to why pacesetter used such large ports..? Is that designed for the 2200, or the earlier engine?
I just went out and measured the ports on my pacesetter and the heads I have (all 90-97 unfortunately), and I'm getting 1.320" for the pacesetter and a tiny bit larger on the heads, so I would actually have to remove material from the header...I don't have an exhaust gasket lying around, so I don't know how the placement is.
fortune cookie say:
better a delay than a disaster.
the newer pacesetters have very larg ports so that they will match up to the 2200 and older 2.2's
im gonna be pissed if i can use this head after getting this far!
event has got to have an answer
Scarab (Jersey Jay 1.8T) wrote:you really don't want to have the exhaust ports totally gasket matched to the header, because if the port is the same size(or bigger) as the header primary, you can get reversion, exhaust backpulses that can sometimes get back into the cylinder... the step keeps that from happening... .
That is the same thing I thought..
Hope you can find a fix
http://registry.gmenthusiast.com/images/importkilla32/Bullit.JPG
Scarab (Jersey Jay 1.8T) wrote:you really don't want to have the exhaust ports totally gasket matched to the header, because if the port is the same size(or bigger) as the header primary, you can get reversion, exhaust backpulses that can sometimes get back into the cylinder... the step keeps that from happening... or at least thats what i've gathered from my research thus far, but i'm sure if i'm wrong that MadJack will step in to correct me.
You're right on the money!
OHV notec wrote:I think that's more for turbo'ed engines, but it probably applies on a smaller level here. However, you normally want the step on the bottom of the port, not the top, as the exhaust tends to flow more towards the top of the port than the bottom.
That goes for all boosting(S/Ced or turbo) or nitrous. Booth power boosting meathods put more oxygen into the combustion chamber, which is why more fuel is needed. After combustion you have allot more exhaust to get rid of, so you need more exhaust volume to expell all of it.
Yessir, you'll be A -ok
I was a retard, and now I'm permanently banned.
Silver Streak wrote:Would it not affect daily driving since he is not going to be on the N20 all the time?
No...
I was a retard, and now I'm permanently banned.
i would sit the heat up like how it goes on the car and slot the bolt holes until the gasket hole is centred better.
see ya!
i;d actually use a stock gm MLS gasket. and then bolt (just the gasket) on...
personally i didnt take much out, i simply smoothed it out and gave it a mirror finish.... basically to decreaase carbon buildup on rough porous surfaces.
the intake side should remain rough, like 80 grit rough...
the exhaust side, all places i have seen basically mirror finish em for those reasons...
like most have already said, you need a wall for the exhaust to pulse against....
also keep in mind in alot of cases with a header, the header will actually be a larger opening than the gasket, which can increase the pulse wall, and keep velocity up better as well.
i cant remember if my p-setter gasket was off or not, but i think it was, so i used a stock gm one and used black perm marker to scribe off how much wall was inside the opening of the gasket.
with a GM gasket, you know its gonna be dead on.
