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Re: Heat Riser Valve
Right side muffler will last longer without the restriction function of the heat riser.Comment
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Re: Heat Riser Valve
Brad;
Now we have gone down the path of confusion on a simple issue. If you refer back to what I said in post #8; If you can move it by hand without an apparent binding, and it has spring tension to return it "UP" when you push it "DOWN", you are good to go. Don't sweat it. I'm sorry if a threw a monkey wrench into the mix by saying anything about wiring it open. Don't do it, not yet anyway. Get it functioning as stock first - which it sounds as though you have.
As for the cross over; yes you do have it if your engine has stock intake manifold and gaskets, as well as a stock carburetor and base gasket. Here again, leave it alone if it is this way for now. The cross over in point should not be confused with a cross over pipe used on some models between both left and right head pipes. It was used to balance the exhaust gases between the dual exhaust system pipes both for sound limiting and to reduce condensation in the right side due to the heat riser butterfly forcing gases through the manifold cross over for intake preheat.
For now, make sure it is functioning correct as stock, and leave it that way until you study and learn more about it. Then you can evaluate the modifications described herein by other posters and decide whether any of the these changes are worth your while. Many of us have done different things to our car's engines to compensate for the gas that is available today, most have done things which are intended to improve their operation while retaining the stock appearance. You too can try some in the future, but I stress that you should get your's running right first.
Stu FoxComment
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Re: Heat Riser Valve
Take Duke's advice and wire it in the full open position. You'll be glad you did. Fuel percolation in the carb bowls after shutdown will be gone and hot starts will be a breeze.Comment
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Re: Heat Riser Valve
Wire it totally open or bust out the flapper or better yet why put the damn valve in anyway. Early corvette engineers, flunked math 101. Thanks for all the diversified input. BradComment
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Re: Heat Riser Valve
Brad -
You need either the valve or the F.I. spacer in place so the "donut" on the exhaust pipe has a chamfered surface to seal against; the RH exhaust manifold outlet surface is flat, to accept the triangular gasket between the flat top of either the valve or the spacer. Only the LH exhaust manifold outlet is chamfered to accept the "donut".Comment
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Heat Riser Valve
I would hesitate to say that if you remove the butterfly restriction provided by the heat riser valve in the closed position that no NCRS judge would be able to tell the difference in a judging environment.
Any experienced, competent operations judge would or should spot it in a heart beat on cold start up just by checking the exhaust flow difference (or lack thereof) at the exhaust exit tips.
A "qualified" PV judge should never miss this "abby-normal" function during judging.
It's easy - just study and follow the rules... and spend a lot of time behind the wheel. Besides, it's fun...
Best, DennisComment
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Re: Heat Riser Valve
In my opinion, from the experience I've had of late with fuel percolation, wiring open the heat riser valve is NO panacea. By itself, it did nothing to cure my percolation problem as evidenced by only a drop of 10 degrees in temperature across the cross over passages of my intake manifold. It did not help my hot starting that I can say for certain. What it does is make a nicer sounding exhaust note, specially when backing off the throttle.
The main thing I've done to help the percolation problem is putting a phenolic spacer under the carb. Temperature differential between the carb and intake manifold went from about 7-10 degrees to 35-40 degrees. I also use a fuel hose in place of the steel line between the filter and carb, primarily due to the raised carb height, and an electric choke which provides better choke control from startup thru warmup (choke spring pushes and pulls the pull-off piston lever).
I still have my heat riser wired open and I have a F.I. spacer ready to install, but I'm not convinced that that is the way to go. We have cooler ambient conditions here in Florida now and I'm seriously thinking about removing the wire until the hot season.
Stu FoxComment
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Re: Heat Riser Valve
Stu,I now have two heat riser units that work on the bench just fine using torch to lightly heat spring. kept the one that opened in twenty seconds vs forty seconds, reinstalled and yes they both worked by hand great opening and closing but there is very little movement none at all during warmup on both units and just a little bit of opening when fully warm. Not enough heat gets to the spring on outside lie a torch would, so my question is what I should of asked from the get go, Will it hurt anything if these things don't open at all or minimally or will it hurt to wire or weld in open position ( or can it be in any position) so which is best on the motor, cars are kept inside at 60 degrees anyway during cold months, and does this affect the thermostat from opening later by having in open or closed postion, so which will be best for a cars overall performance. Thanks to all again, I'm stuffed Brad
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Re: Heat Riser Valve
As long as the valve operates freely, it's exhaust volume/pressure that opens it, not just the spring; that's why the butterfly is asymmetrical with respect to the shaft. If you drive your car in cold weather such that the design feature improves cold fuel vaporization and cold driveability, leave it alone. Otherwise, wire it open and your passenger side exhaust system will last longer. If you have your car judged, make sure the valve is operational or you will fail the Ops item on exhaust.Not enough heat gets to the spring on outside lie a torch would, so my question is what I should of asked from the get go, Will it hurt anything if these things don't open at all or minimally or will it hurt to wire or weld in open position ( or can it be in any position) so which is best on the motor, cars are kept inside at 60 degrees anyway during cold months, and does this affect the thermostat from opening later by having in open or closed postion, so which will be best for a cars overall performance. Thanks to all again, I'm stuffed BradComment
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Re: Heat Riser Valve
Brad;
Listen to John. You don't have a problem. Use it as is if you live in the fridged north (pun intended) and it will work fine (as nature, God and GM intended). If you're down here in the south at this time of the year, there are some days you might want it wired open and some not. Like I said, mine is (wired), but I'm not sold enough on the idea to replace it with an F.I. spacer which I have ready to install. On that baby, I even ground it out round too (no butterfly flats). Hope I didn't add to your confusion. Put it in and drive it!
Stu FoxComment
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