So here I am tearing apart my engine and I get the rear exhaust manifold off and WOW I took it off the head and there is a 1/8" or bigger spot all the way around the hole where it is just black from exhaust. Evidently the holes in the manifolds are smaller than the holes in the heads. It looks like if someone ground those out to be even with the heads that it could provide some decent power gains. One one of the holes there was a 1/4" all the way around the hole...thats a BIG restriction. Now I realize the rest of the exhaust needs help as well, but this will definately help for faster spooling if nothing else. (not that we need faster spooling)
Now I will definately be grinding that off because I have to match the manifolds to the 3100 heads anyways, but if someone is looking for more performance anywhere they can find it, this might be a good place. You can grind down the manifolds yourself and the gaskets are under $20 each so you could gain a few horsepower for about $40.
Just a suggestion...
Shawn
Yeah exhaust is our biggest restriction. I'd do that, but I'm scared that I'd break a bolt off in the head...
:lol:
Quote from: no1kickerYeah exhaust is our biggest restriction. I'd do that, but I'm scared that I'd break a bolt off in the head...
:lol:
I knew our exhaust was our biggest restriction, but I didn't know that the holes in the manifolds were smaller than the holes in the heads (which are already small enough). I just though the manifolds and crossover were really restrictive. Good thing I have a dremel. I will be AMAZED if this car doesn't turn some 13's now!
Go ahead and try it. I didn't break any bolts off and my engine bay is really rusty (even though the body isn't...its weird). If you do break off a bolt, I have a set of heads sitting here that I don't need...
Shawn
Well, if I pull the heads for any reason I'll do that also. The STE will be off the road in a bit, and the new rockers are going in. (Problem is, If I pull the heads I'm gonna want a 3100 top end also). Don't know if it's worth it at 135k though. I'm very interested to see how your car turns out. I'm gonna take your advice and get rid of the cat very soon. I think that's my biggest drawback now besides my dead struts.
Don?t port out the exhaust manifold as is being discussing here 8) !! The exhaust manifold is matched rather nicely to the exhaust port of the head! The carbon you found is because of the exhaust manifold gasket hole is bigger than the exhaust port of the head or the exhaust manifold! The gasket is designed this way to keep the gasket?s leading/exposed edge from being to close and getting heated up enough from the hot exhaust gas to become a source of ignition should the engine experience an excessively rich condition such as a neglected weak ignition side! If we were to have combustion in the exhaust, the explosion would be hard on the turbine wheel, and what would go back into the head/engine and wham up against the piston as it approaches Top Dead Center/TDC would not be good either, ouch!! Last, the exhaust flow capabilities of the exhaust manifold and crossover pipe are not a problem at all :? , the problem/restriction in the TGP is the exhaust trying to get through/out of the turbine housing 8) !
Back to work, just wanted to clear things up before anyone got too much going on this :) .
Jeff M
Um, Jeff, I REALLY hate to contradict you, but porting my exhaust manifolds DID help a good bit. I did them while I had the heads off the first time, before I did the head porting.
Had mine done too when i sent he heads into the shop......for rebuild...
they matched the heads-manifolds and gaskets
just my 2 cents...
Quote from: maximageUm, Jeff, I REALLY hate to contradict you, but porting my exhaust manifolds DID help a good bit. I did them while I had the heads off the first time, before I did the head porting.
That's good 8) :D , but as you can see I was trying more so to head off other guys from hogging things out the size of the exhaust gasket :wink: , or thinking something was whack with their engines. I have done quite a few of these heads over the years and found the very large bolt holes of the exhaust manifolds relative to the size of the bolts can have the exhaust manifold located in many different positions when tightened down, making port matching a real challenge. If you try to port match these it requires a lot of marking the positions, having the head off the engine block so you can take out the exhaust valve to feel the port lips needing to be ground, or spraying a small amount paint to mark it for you, or use grease between the exhaust manifold and head to mark the areas of contact/areas sticking out, or make a template, lot of work. Even after a lot of good port matching, it all boils down to the assembly part (stock as assembled from the factory too :shock: ), and since you cannot see all the port matching in there when assembled, you have little way of knowing if you or someone else did it good :!: . It?s very a painstaking task with these over-size bolt hole, but I believe some of the reason for this is to allow expansion and contraction from heat cycles the exhaust manifold experiences more so than the water cooled aluminum head.
Jeff M
It's no different than porting the heads and manifolds on just about any other turbo'd factory car. They do make the larger manifold bolt holes to allow for expansion during heat cycles. I've been doing porting for a while myself.
You are right though, I wouldnt recommend this to a novice.
Quote from: maximageIt's no different than porting the heads and manifolds on just about any other turbo'd factory car. They do make the larger manifold bolt holes to allow for expansion during heat cycles. I've been doing porting for a while myself.
You are right though, I wouldnt recommend this to a novice.
Ok 8) , yep, that be my main reason for straightening some things out here, don't want other people/novice types (the bulk of what we have) or someone that might be good at engines but end up missing this :) The iron heads (not aluminum yet :twisted: ) on my Typhoon did not have nearly this much slop, I don't think the GNs/T-Types are as bad as the TGP? Chris A and I found this slop problem with the bolts back a while ago when we had some fitment problems, really had us bummed till that issue came up.
Later
Jeff M
Quote from: maximageYou are right though, I wouldnt recommend this to a novice.
Porting is not for anyone who does not know what they are doing!! Practice on your 4 stroke lawn mower or go-kart...then practice on your neighbors import car...then you might be ready for your TGP motor!! :lol: 8)
Quote from: TGPilotQuote from: maximageYou are right though, I wouldnt recommend this to a novice.
Porting is not for anyone who does not know what they are doing!! Practice on your 4 stroke lawn mower or go-kart...then practice on your neighbors import car...then you might be ready for your TGP motor!! :lol: 8)
Hey now that's the right combination!!! I like it :lol:. Porting intakes is easy as things stay put, little tricky with our long runners, but things shifting really makes for some challenges, can do more harm that good if not sure!
Jeff M
Quote from: TGPilotQuote from: maximageYou are right though, I wouldnt recommend this to a novice.
Porting is not for anyone who does not know what they are doing!! Practice on your 4 stroke lawn mower or go-kart...then practice on your neighbors import car...then you might be ready for your TGP motor!! :lol: 8)
I have a neighbor with a nasty looking riced out Civic(like an '87 Civic base model...). I wonder if I could convince him to "learn to port" on that head, so I dont have to watch him go racing through the residential area we live in......
Btw, Jeff, what state do you live in? For some reason MN sticks in my head. If it's near Wisconsin, we should get together sometime and comapre notes on TGP tuning. I do a lot more than I let on here.