Hey all, I have standard SBC exhaust manifolds on my 41 Coupe. I have a DIY 2.5” exhaust from Speedway that I am attempting to hang this weekend. I ran into an issue though with the collector reducers I am using. From my measurements the manifold is 2.5” outlet, so I bought a 2.5 to 2.5 collector reducer. However the flange is no where near fitting on my manifolds. The bolts on my manifold are 2.5” apart as best I can measure. The holes on the flange for the reducer I was recommended at 3” apart. Anyone have any idea where I can source the correct ones that will work? Car is going for an alignment Monday, so if it’s an off the shelf option would be great! Thanks!
Helen, You should mod your profile to include your location, a member down the street may have a set of collectors on their wall you could obtain.
Back in the day used to get them from the muffler shop. I'm sure a parts store can get them through Walker.
As always, pictures would be helpful. But if the bolts on the manifold outlet are 2.5" apart there is no way the exhaust outlet itself is 2.5", more likely 2.25" or even 2".
Stock sbc will be smaller than 2 1/2 not sure what size, but a muffler shop should be able to form up the reducers and sell the flanges
Collector reducer's are for header's, not exhaust manifold's. You used to be able to get headpipe starter kits from Walker, don't know about now-a-days...
This is what I measured. The output opening I believe was Looking at it correctly. But I have had a few beverages haha
What are the manifold's off of? You're going to need the doughnut's, heat riser gasket , and heat riser/heat riser delete spacer. Depending on application, you may not need the heat riser/delete spacer. Once you get all of that sorted out, you can start with the factory style head pipe flange's.
Most old Chevy manifolds have a 2” head pipe with a slip-over donut for a gasket. Corvette versions were for 2 1/2” pipe. If you have the factory flanges, donuts and the old pipes you can work with that and adapt it to the new 2 1/2” system. If not, you will have to find a good old muffler shop and buy some flanges that fit your manifold outlets and some tubing for stubs.
If it's your run of the mill, standard SBC manifold, it's usually a 2" outlet. How much of a headache is it to remove a manifold and take it to a local NAPA and match up what you need to what you have? Does Summit give any critical dimention's for the manifold's? Or do what @bchctybob said, because he type's faster than me! LOL!!!
Thank you all. Looks like in the interest of time I will take a manifold off and bring it to the shop Monday and go from there. Thanks!
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