i am having my brothers engine rebuilt. so i have a few questions i am unsure of. its a 1988 GTU N/A (this will be a street car / everyday driver)

1) anyone on here have had their exghuast diffusers/splitters removed? 1,with no porting? 2, if you did get them ported could you still pass smog test (ca smog)

2) when you get a 4port conversion what does that intail?
i know the Turbo 4 ports do not have the diffusers but do you keep the stock 6 port intakes? when using them? and if you changed so it was 4 port intake would that interchange with the stock intake manifold?for the standerd 6 port manifold? or do you have to go carb or custom intake?

 

Everything i have read is that the diffuser is very hard to get rid of. Its evidently incredibly tough steel.

If you went to a 4 port you would be changing the irons AFAIK. You wouldnt be able to use a 6 port intake mani if you did that. It would involve finding a 4 port intake mani.

BC

 

The 4-port conversion has nothing to do with the diffusers. The diffusers are in rotor housings, while the intake ports are in the side housings (irons.) I would not recommend getting a4-port conversions. I've never even heard of anyone doing it unless they built the motor for a turbo then changed their minds at the last minute.
If you want to get rid of the diffusers, you can either grind them out (which I have heard is hard, but other people have done it without a problem), you can switch in the sleeves from a turbo motor (which I think can be tricky to do, bu I have no experience with it) or you can use turbo rotor housings if you have access to them. On my motor I used turbo housings and ported the exhaust as well as the intake.

 

could you pass smog with exhaust ported?

 

Don't remove the diffusers. They cut down on the noise A LOT. Impact to flow in a stock ported engine is negligible.

Converting to 4 port (why?) would require changing the irons and intake manifold. You would end up having to use something aftermarket. The only aftermarket choices are carb manifolds (though you can use an EFI throttle body....) and the IDA kits...

None of this has any hope of passing smog.

 

Yeah, do help a lot with noise. Mine is crazy loud without them. And if you end up porting the exhaust, it depends on how it is ported as to whether you can pass emissions, but theres a good chance you will have a hard time.

 

if you don't port it, then leave the splitters in there. the only thing you will gain is more noise - as has been amply stated.

if you port it, go with a mild streetport. the only thing i know about CA emissions laws is that they appear to be more strict than the other 49 states. i cannot and will not try to speak on if a streetport will pass the tests there. i simply don't know.

i don't know if i'm reading this wrong, but you seem a little confused (not trying to be facetious). so here goes ... the ports are in the side housings, not the rotor housings.

if all you do is use T2 rotor housing on your brother's engine, then yes, it's still 6-ports. no new manifolds required for this.

if you do, indeed, convert it to a 4-port engine using T2 side housings, then the simplest thing would probably be to get the T2 intake manifold/throttle body assembly with the housings and go from there. carbies and custom intakes are simply not necessary unless you have reasons/goals that would more than likely yield an engine that wouldn't pass CA emissions.

 

yes, i went to the block and can see exactly what the case was.. intakes are on the irons and exh ports are just on the rotor housings.. i didnt know why i didnt see it before while tear down. thanks you guys