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I have a 72 BB 4spd. Engine rebuilt about 700 miles ago. I have put in a petronix ignition and a set of GM rapid fire plugs at that time. Car starts and runs smoothly except when pulling towards 5K rpm. When you start it when it's cold , the drivers side has lots of vapor (natch) but not the right. When the car is fully warmed up (180 thermo), the passenger side exhaust is quite cool (?). The drivers side seems comfortably warm, but the other side is noticably cool. Whats up? Does this have something to do with the breakdown at high rpm's? Thanks Ray
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Re: one side cooler
'Part' of this symptom is something judges check for during Performance Verification. The RH exhaust has a heat riser valve between the exhaust manifold and the front pipe. During cold start there SHOULD be asymmetric exhaust flow as the heat riser on the RH side is closed blocking exhaust flow to speed warm-up and force the carb's choke stove bimetal to heat and open the choke.
Now, when the engine is fully warmed up, the heat riser should have fully opened (crawl under and look/watch the heat riser's counterweight arm change position with respect to cold/warm engine operation) and there should be little/no difference in bank to bank exhaust flow. If not, you've got a defective heat riser that's restricting RH exhaust flow and should be replaced. No big deal--a $30 item at your local auto parts store. -
Re: one side cooler
Ray: If judging, originality, and COLD weather are not a consideration. Replace that heat riser with a spacer. They are a pain, and serve no purpose other than prematurely rotting the right side exhaust. Regards Jay.Comment
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Re: one side cooler
And you can just wire it in the open position.Comment
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Re: one side cooler
Thanks guy's, Yes the riser was closed even when the car was hot. I wired it tempo like you recommended and it goes like a scalded dog. It ran ritght up to 5k no sweat. I have 4:11 in the rear so you eat up the rpm's pretty quick. I still however have this odd thing, when in fourth and you get on it, it seems reluctant to go past 4200 or so?? You feel the initial surge when you floor it, then it kind of backs off by itself. ?? any ideas ? Thanks RayComment
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