Wondering if anyone has tried to adapt a Chevy SB header to a b20. Obviously new mounting plates would have to be fabricated, but the manifold tubes seem to be in the right place. Wish i had one to measure..that's why i ask.

On a separate but not unrelated note; Does most of the reistriction in our stock FI exhaust systems happen in the down pipe where the dual tubes meet? Or rather is most of the restriction due to our cast iron manifold?

They shold work, the spacing seems good(I compared 2 stock manifolds one 350 one b20f) the only concern would be clearence. Have fun

merci

Yvan
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65 122s/73 1800es/80 262c(350ci v8)/89 745t/87 780/89 740/89 740t/ 86 745 and too many parts cars and projects to list

thanks Yvan. There are so many SB header styles out there hopefully one will work.

Most of the restriction is in the exhaust ports in the head.

are the valves a factor?

I believe large exhaust valves would do just about nothing without first reworking the ports. The exhaust ports are the main factor limiting how much power a B20 will make. Only after having them improved does it make any sense to look at valve, cam, and other options.

http://www3.telus.net/public/iadr/V/porting%20pics/vizard1.jpg
http://www3.telus.net/public/iadr/V/porting%20pics/vizard2.jpg
http://www3.telus.net/public/iadr/V/porting%20pics/vizard3.jpg
http://www3.telus.net/public/iadr/V/porting%20pics/vizard4.jpg
http://www3.telus.net/public/iadr/V/porting%20pics/vizard5.jpg

Useful theory in those links. I tend to think a larger valve is, infact, the first step.

We distribute Hedman, Flowtech, and Hooker headers at work, for a large portion of Canada. There was only one SBC design that had a ghost of a chance to fit on Volvo chassis, and that has been revised/discontinued! (old p/n hedman 68310, new part has same number, but different tubing routing). Check with IPD regarding the pending deal they have on Thunderbird headers. I think the intention was to have them in 1.625" tubing. That 1 5/8" size is too big, but other than that it is a matter of supply.

The b20 header Stahl makes is (almost) worth the price, and is available in the correct size- 1 3/8" for stock motors and 1.5" for street performance.

I found 1&3/4"x29" better than 1&5/8"x32" on my big cammed engines.

Stock or mildly cammed engines are better with 4-2-1 or the standard layout.

Putting a header on a stock head is mostly just for the visual effect. Unless you are replacing a single downpipe manifold, as in my case. The dual downpipe manifolds are quite nice as is.