The Stovebolt Site Forums The Shop Area Engine Shop Header Choices Fenton VS ???

I'm looking to put split exhaust headers on my 235, are Fentons the way to go or are there tube headers that work better?

Any recommendations?

Thanks,

Tom

"Split" the original manifold and run the right kind of heat riser. "Fenton" clones made offshore are worse than useless, and tube steel headers are even worse than Fentons. What kind of race car are you building?
Jerry

Thanks, not making a race car, just a mild period mod.

I have both Fenton’s on my 235. A duel exhaust and dual intake. Heated the intake with water. It is the system Tom Langdon sold and recommended for my truck. With the dual Weber progressive two barrel carbs. All I can say it works flawlessly. No hesitation or dead spot. Very strong running engine. The two Weber 32/36 two barrel is not over carbureted for my 235. It is only 28% larger in the primary Venturi’s than the stock one barrel carb. The Fenton duel exhaust sounds great. I have 2” pipes all the way back to the rear bumper. I could not be more pleased with this set up. I have had it up to 70mph easily. I have the stock 4.56:1 rear end but with a Gear Vendor overdrive. That gives me a final ratio of 3.55.

Friend of mine is running a set of the cheap eBay tube headers on his 235 with a mild cam, some head work, and a Tattersfield dual. He's got 2" pipe out to the back with no mufflers on his 58 Apache. It's louder than I would want on my own truck, but seems to run pretty good.

Headers raise the underhood temperature 100 degrees, burn you whenever you work on the engine, and only last a few years (vibration cracks, rust).
Without a hot cam, headers add no power.

Either way, don't join the 2 exhaust pipes, leave them separate.


BTW: half of all engines & cars sold "have a mild cam".
No, they don't, it's just what people like to say & hear. A cam hot enough to make a difference is a PITA to drive in traffic.

A mild cam is easily streetable and adding 30-40HP is plenty to make a difference in everyday driving.

A mild cam for a stovebolt might not be worth it due to the supporting airflow mods that are required to take advantage of it, but that is not a true statement for "engines and cars".

In over 200 dyno tests on "streetable" engines over a span of 25+ years, I don't think I've ever been able to gain 30-40 HP with just a cam change. I'd really like to see some documentation of someone doing that.
Jerry

There are not that many alternatives. Of course, you can cut the stock manifold and make a true split unit by welding on an additional outlet, and then welding the ends of each half. You can also cut it in half, add a baffle with a hole in it, 1 inch or smaller, to mellow out the sound, add the outlet and weld it all up. You get to keep the stock heat riser with this set up. That is assuming you have the skill and tool box to do that kind of work. Most don’t.

So one alternative is to beat the bushes pretty hard and dig up a corvette factory dual outlet manifold. these are relatively expensive but are easy to install and you get the stock style heat riser. $$ are the issue her as I have seen them go for a few hundred.

Next, vintage fentons with the heat riser. Really hard to come by. Really hard. Vintage fentons without the heat riser. More reasonable and they come up for sale once in a while.

Aftermarket fentons currently on the market. I have seen them installed on quite a few motors they seem to be reasonable quality. No heat riser.

Don’t like the fentons, then Williams headers.

https://www.hillchevy.com/product/williams-exhaust-headers/

Then there are the really crappy cheap sort of tube headers sold all over the internet. I think they are a terrible design. Don’t waste your time or money.

https://www.suncentauto.com/product...&utm_content=exhaustmanifoldsheaders

Real tube headers are sold by Clifford. Prior to Jack Clifford’s death, Jack sold true long tube headers. I have run the same pair of Clifford long tube headers since 1983 or so. They also turn up on eBay and Facebook market place. These are application specific. They work good, sound great. One issue, they warp on the ends. So once they cycle a few times, you have to add some weld to the flange to build it up and make it straight. There was apparently a big brew haha when Jack passed away and somehow the guy who was making Jack’s Viper brand headers destroyed all of Jack’s jigs. So there will never be any additional long tube offerings from Clifford.

The current offerings from Clifford are “shorty” tube headers. Jack’s son-in-law Larry told me those shorty headers make the same power as the long tube headers but fit better. He may be right, I don’t know, but the truth is, when the Clifford headers are open, what a sound. Not cheap but they are real headers.

https://cliffordperformance.net/store/ols/products/52-0025-chevy-235-dual-outlet-street-rod-headers

Clifford Performance Engine Tuning Video


If you are really handy, you can make your own tube headers. Here are some flanges

https://davisspeedequipment.com/pro...s-for-1937-62-216-235-261-chevy-engines/

https://www.hellsgatehotrods.com/shop/chevrolet-early-6-cyl-216-261-exhaust-flange/

http://www.headersbyed.com/__chevrolet.htm#Early

So a few choices.

You show me your dyno results and I will show you mine. I my daily driver dynoed at 285, I changed the cam and tuned it and it dynoed at 319. That is a 32HP gain.

And I still drive it to work literally every day.

How do you get a stovebolt six to produce 300+ HP? Nitrous? Or are we comparing apples and oranges? 440 MOPAR- - - -714 HP @6500 RPM on a single Quadrajet and gasoline, but it cost $12K to build it that way. 355 Chevy small block- - - -526 HP @ 7500 RPM- - - -one Holley 650 and 102 octane Pure Firebird gasoline- - - construction cost $15K. 426 MOPAR hemi- - - -dry sleeved with an epoxy filled cooling system- - - - -1400 HP on alky/nitromethane. None of those engines lasted past 500 miles between rebuilds. The hemi was lucky to make it 1000 feet total travel distance at a time before a freshen-up or a blowup. The billet crankshaft alone on that one was $7K. It's always more fun to go racing on the other guy's money!
Jerry

Yeah, 40hp is very common gain when installing a modern day camshaft into an old 500cid Cadillac; replacing the tired, emissions friendly 1970s grind. My point here isn't to talk about non-Chevy engines but to illustrate the fact that camshaft tech has come a really long way since the 1960s when 'mild cam' meant poor manners in a daily driver. Might not see that much gain on a Stovebolt, but I'd buy 20-25hp improvement pretty easy versus a cam grind designed before Eisenhower was president.

That's what I did. Works like a charm.
Not a ton of power gain, but at least not as restrictive as the stock system.

Does anyone know of a source for weld on outlets for an original exhaust manifold?

Gentlemen! Please, you are straying way off the OP’s question. We are not debating how much HP gain you can get from an engine. Stick to the headers!

I documented the process I used here a long time ago for anyone who wishes to attempt to split a stock manifold:

https://www.stovebolt.com/ubbthread...more-split-manifold-info.html#Post470651

Pictures are gone after being held for ransom so I've attached the limit of 5. With more experience it was found that doing most of the welding while bolted to a scrap head minimized movement.

I cut the flange off a broken exhaust manifold and graft it onto an original manifold with the factory heat riser. There also needs to be a slit cut into the original manifold with a cutoff wheel on an angle grinder to install a baffle just ahead of the heat riser to split the exhaust stream between the two flanges. Leave 1/4" or so gap at the top of the passageway to allow for pressure equalizing instead of doing a full blockage. As always, preheat, peen, post heat, and bury the modified manifold in a pile of sand overnight to prevent cracks beside the welds as it cools. It's also a good idea to keep the manifold bolted to a junk cylinder head when welding to avoid warping the assembly. Use nickel-alloy arc welding rod.
Jerry

thanks will have to try that procedure

What Lumbersayer said. I have been running the sameset up for 13 years, bought from Langdons.

I have some aftermarket Fentons. They have threaded bungs into which I screwed brass pipe fittings for tube to carry hot exhaust to the bottom of the Offy intake plenum. I fabricated a plate for the bottom of the intake and threaded a couple of holes to receive the tubes. I've been told over and over that this cannot work but it does and has for 20 years. I did have to tighten the fittings once though.

Do you have a picture of that setup? I am having a hard time visualizing it.

Is the goal to replicate the effect of the exhaust riser?

Mine is a variation on EchoBravaSierra photo. Shorter tubes.