1.5"(SSI's) vs 1.63" headers in a 3.4 conversion?
 

I am in the process of a rebuild and conversion of my '87 3.2 to a 3.4 using the Mahle 98mm P+C's (9.8 CR) and 964 cams. This will be a street car. I have learned that Brian at RarlyL8/M&K can build a set of 1.63" headers with heat and was wondering if that is a better option for this build over the SSI's? Thanks for sharing any thoughts you have on this, or better yet any dyno information that can shed light on this question.

Went through the same debate, heard that the majority think that the larger headers are the way to go, but I opted for SSI's, still have to do my build.

But then again, I am seeking good strong midrange power rather than ultimate high end HP. Engine will have PMO throttle bodies, 10.3 compression, Mahle 98mm P/C, Turbo crank, Carillo rods, DC35 cams.

Keen to hear opinions....

Dennis

I have 1-5/8 headers that my daughter will fab and weld heater boxes onto. Everything is have read is that the 1-1/2 is just too small for the 3.4.

I have a 3.2 to 3.4 conversion, 964 cams, 98mm wedge dome Mahle single plug...

Using 1.63" headers. Keep in mind this is also the factory heat exchanger size. I wouldn't go smaller.

Everything I have read and searched through indicates that 1.5" is too small for this setup.

Now that said, I wouldn't turn right around and sell my 1.5" SSI's either. A 964 is a pretty mild cam, and the performance gain with a header is said to be negligible anyway.

1.625"od will have an id of 1.5", not enough exhaust flow for your engine size. Check this header set up at MSDS Inc. -* HIGH QUALITY HIGH PERFORMANCE ACCESSORIES
Marty

Those are nice, I looked at those for my own car, they won't work for him because he said wants heat. That is the only reason I didn't consider them.

Thanks all for your input. Brian at Rarly8 has been very responsive to my inquiries and has informed me that for my intended use that emphasizes mid range torque over max HP, that 1.63 inch headers with long tube primaries are what I would need and these are not available with heat. The medium length tube headers move everything up the RPM curve - not what I am looking for. Will go with the SSI's.