The Stovebolt Site Forums The Shop Area Engine Shop fenton exhaust with heat riser

Ive got an older set of fenton exhaust manifolds that have the heat riser section that connects to the intake... (similar to original intake/exhaust connection) Has anyone used a setup like this? My question is will the heat riser (without heat riser flapper) add too much heat to the intake if used with a 1 bbl original intake? There is no heat riser flap to control how much heat is supplied to intake. Would it cause problems the same as if heat riser is stuck in position to direct heat to intake?

they don't make this version anymore... was it known to have problems or is the heat riser section on fentons a benefit?

My goal is dual exhaust with a single 1bbl carb for good drivability. I have considered going with a modified original exhaust manifold to provide dual exhaust and have the heat riser still functional but the dual exhaust added section is usually for the back 2 cylinders on modified originals, and the fentons use the 2 front cylinders for the second header... my present truck has dual carb/dual exhaust setup with normal fenton exhaust manifolds... if I change from fentons to modified originals I would need to modify my exhaust pipes also... preference is to not change exhaust system also.

truck is a 1940 chevy 1/2 ton with 1957 235. all original other than dual intake/exhaust added.

thanks..

I vote for a heat riser, if you can find one.

The bar/post and spring are available as replacement parts (Chevs of the 40s - over-sized diameter). The flapper comes off the bar/post fairly easily. Try posting a parts-wanted ad for the flapper and screws?

Not having the flap valve will limit the effectiveness of manifold heat during warmup, but any heat is better than none. There shouldn't be a problem with overheating the intake because there will be a non-restricted flow down the rear pipe even when the engine is at normal running temp. A stock manifold with a second outlet added and the original heat riser flap is still the best choice, as long as a baffle is welded into the manifold between the 2nd. and 3rd. exhaust ports. The baffle doesn't even have to be a total seal- - - -it just needs to block most of the flow between front and rear. That's the way the 6 cylinder Corvettes did it, and those manifolds are scarce and expensive now. Far more of them were sold over the counter at Chevy parts departments than were ever installed on Corvettes.
Jerry

Those fentons may be set up for the earlier 216/235 and may not bolt up to a later (like 55-62 intake manifold) so you will have to check to see if what you have will bolt up. Frankly, you may be better off converting a stock manifold just to retain the stock exhaust manifold function given you want to retain the stock I bbl carb set up. Just as an aside on the converting the stock exhaust manifold, I have done this conversion a couple of times. There are three approaches. The first and easiest is to simply install/weld an additional outlet. Years ago the parts houses use to sell the outlets (think jc whitney, gotha others). This is the quietest of the setups also. The nest is to split the manifold, and install a plate just inside one of the halves with a hole, 1 inch or so, in the middle, weld the halves back together, and add an outlet on the other half. This is a truer dual set up but a little more louder (a little more rappy really) then the stock set up with an outlet added. The third version is split the manifold and weld plates to each half, ground a little clearance between the halves and add an outlet to the half that needs one. This is a true dual set up and the loudest/rappiest of the versions.

Thanks for responses... the fenton will bolt to a newer intake manifold.. not a 216 specific unit
There is no provision in the fenton casting to install a heat riser flapper - its not a missing piece, it was never designed with one in place.

I also am leaning towards a modified original ( I already have a set) though that would involve changing some exhaust piping... probably better to do it right the first time.

I am changing from a set of dual carbs on a fenton intake as I don't like the drivability for around town and lower speed cruising... it seems to run fine on top end, and out on the road but low speed operation and putting around in high gear isn't as "user friendly"

anyone have one of these older heat riser fentons on a running motor?

Simply drilling holes in the right place and installing the flapper valve and shaft would probably convert the Fenton to have the heat riser function. Press fit a couple of steel bushings into the hole to support the shaft and add the snail shell bimetal spring on the outside. I've fabricated heat riser flappers and shafts from stainless steel- - - -they last about 3 days past forever.
Jerry

Have you considered changing from two I bbl carbs to a pair of 1974 ford pinto Holley/weber 5200 carbs (using adapters for your intake). They run pretty good around town. I ran that set up for a good many years on a 235 motor and a weiand 2x1 before I moved up to the cliford 2x2 and 38 mm webers for the 261 motor.

as for the 216/early 235 vs later 235, the bottom of the intakes for the earlier motors were flat while the later motors had an angle to them which is why there may be a difference. I have two weiand intakes, one meant for the early 235 and one later. the pads to attach the exhaust manifolds are different.

Dirball,

I have a 55 Chevy 2nd series with a 235 engine and I am running an set of the original old school Fentons with the heat riser casting. I'm running it with the original intake and single Rochester B carb.

Smart move- - - -two carbs is either one too many, or one not enough.
Jerry

Jaydee5150
That's the setup I'm looking to install.. I have all the pieces and I won't need to change my exhaust piping ( already has newer style fentons without heat riser)
How does yours run.. I assume if you are in Southern California you would see any issues with excessive heat to intake. Did you do any rejetting of carb with dual exhaust?... thanks

It runs well, I didn't need to do anything at all the the carb. I'm running 1.5" straight pipes to the back of the truck.

I just swapped out the old single flapper exhaust with the Fentons. Excessive heat has not been a problem and I've run it in 100 degree weather with traffic.

If you have a set of the old Fentons with the heat manifold cast into them you've found yourself a gem. They are very hard to find...and when you do find a set in decent condition, people want an arm and a leg for them.