I have a set zz4 heads that I plan on putting on my 1991 RS that I replaced the original 6 with a 350 TPI setup. I was curious about the choice of headers I have. I have been having a tough time finding D-port headers to match the heads exactly. My question was, do I have to use D-port heads or will any/certain 1-3/4 headers work. Will there be any drawbacks from using the 1-3/4s. Would I be better off sticking to the D-port headers instead. I already put a new cat and a 3" Flowmaster muffler. Please let me know if you need anymore info about the car.
Thanks guys

 

Im sure you will be fine with regular third gen headers.

 

I thought it should work too because the header should cover the exhaust port but I'm not sure if there will be back pressure problems or anything like that. Please, any info will help. I don't want to buy anything that might give me problems in the long run.
Thanks.

 

Buy the 1 3/4 ... the lower corners of the d-shape will extend very slightly beyond the 1 5/8 primary's sealing surface .....However, not the case for all exhaust ports on the d port heads..

 

1-5/8" primary headers would probably be the overall preferred choice. But, you don't want any flange sticking into the flow path, either. That sharp step sets up turbulence that doesn't do you any good at all (more of an issue than "back pressure").

An alternative to the potential low-RPM loss of 1-3/4 tubes is to port-match the headers. To do that, you have to weld around the tube on the outside of the flange to provide your sealing. Then, match to flange to D-port gaskets and blend to the tube.

Here's a thread on what I did about the headers on the '57 https://www.thirdgen.org/techbb2/sho...hreadid=171116 (includes intake port matching talk as well - sorry). As you can see in the early photos, they blocked the ports pretty bad as-received. I'm not claiming any proficency as a welder, but it got the job done.

 

I am using the Hooker 2210 1 3/4" long tubes on my Fastburns with the D port exhaust. They seem to work alright.