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Fri Jun 20, 2003 11:46 am

I see plenty of people running a merged headers in the magazines but not at the shows that I go to. Most people run a street header. I've seen that Dave Cormack used to run one before he installed the heater boxes on his Oval. I would assume he drives the car quite a bit and California's climate is hotter than it is here in N.J.. Is is possible to run a merged header for normal street use? The tubes run right under the heads and you have to remove the lower half of the cooling tin. Wouldn't this make your jugs and heads run even hotter? How much more H.P. is to gain with a merged anyway? Has anyone swapped one for another and felt a difference?

Sat Jun 21, 2003 2:29 pm

You will get a very small gain with merged headers. Some years back we did a lot of dyno testing on different ex. We found all 4 into 1 performed just slightly better then 2 into 1 or 4 separate. The largest difference we found is Looks, cost, sound and performance. And in that order. We recommend the smaller diameter for torque and not matching the head to the pipe dia. Also the one ex that always gave HP was the Anti-reversionary ex. developed by Rodene and later sold to Cyclone Ex. Hard to find and expensive but really works. Vic. "Parts Book" Schematics and VW part numbers. -> http://www.vwhelp.com
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Sat Jun 21, 2003 5:13 pm

Thanks for that info. What about the temp. increase. I have both a merged and street header. I was wondering which one would be better to run. The heat increase is what bothers me, I don't want to overheat it. Anyone have any trouble with a merged setup?

Sun Jun 22, 2003 6:31 pm

Whatever happened to the RX dual stinger exhausts?? Those were supposed to be a pretty effective design, but were pricey.

Tue Jun 24, 2003 9:45 am

My views on Merge headers. They really dont begin to shine unless you are looking at performance set up's where larger cams are conserned. when larger cams (bigger durations) come into play, the valves are actually open at the same time during part of the cycle. also called valve overlap. sounds funny, but what a merge header is designed to do is pull a vacuum on the tube that is not currently expelling gases. thus when the valves are both open for that brief time, (the exhaust is on its closing run and intake is opening) the vacuum in the header asssist in pulling an intake charge from the carb into the chamber, thus more air/fuel to burn.
So it is definitly application oriented. put one on a small motor with an Engle 100 and you probably wouldnt see any difference. put one (and a big one at that) on a 2332cc with an FK-89 (heads and carbs to match) and then they work wonders. Then you get into different designs, steps, diameters, etc.