The Stovebolt Site Forums The Shop Area Engine Shop Headers for 235

I would like to change from stock exhaust manifold with single exhaust pipe to headers with dual exhaust. I currently have a Weber 32/36 carb setup on stock manifold and it is running well. I have an oil filter setup on the stock manifold.

I am planning on running the stock intake manifold with one carb, after market heat plate, then dual exhaust with glass packs late in the exhaust run.
I may upgrade the stock intake manifold to a dual carb setup at a later date.

The corvette 55 intake for the 235 is probably the best, but I probably won't be able to find or afford one.
I've heard conflicting reports regarding fit for Williams headers. I've also read they fit the stock intake as well as the Offenhauser. I kind of like this as it allows me to upgrade to dual carb setup in the future, if I decide to do that. Langdon and National Chevy Association both sell Williams headers.

I have read a lot of threads about header choices but nothing too recent.

Is there any experience lately with the Williams headers? Did anyone with this setup run the oil filter mount?

Thanks,
Joe

I would ditch the oil filter. Find a good 848 head. I have done 2 of these on my 49 and 1951. One has the 32-36 weber carb. Both are rebuilt 1954 235 engines. Just change your oil every 1000 miles.--Bill

Gotcha on the 848 head, I've read that the 848 head gives higher compression and better exhaust note.

My current 235 block is 57 and the head is a 54/55 standard 235 head.
I am just looking to update the exhaust this winter.

better exhaust note

How?

The 848 head thing is based on the 58 and engine specifications as 8.5 CR compared to the 56-57 8.0, and I guess the 54-55 7.5. A good number of years ago, Tom Langdon and I were discussing the CR of the various heads. Tom was still at GM before he retired and he actually looked the numbers up with the 848 heads (which entered service for the 1956 model year) at 79.1 cc and I think 86.0 for the 5913 head. I have to check my notes on the exact cc so If I am off a little I will correct it. One of these days I will have to cc one of my 56-57 heads and a later 61 head and see if there is any difference because I have never been able to sort out where the 8.5 CR for the 58 and up motors vs. the 56-57 motors came from. That being said, by the time you deck a block during a rebuild, and surface a head, I think the difference in CR between the 848 and 5913 heads becomes negligible.

Btw, I ran a 5913 head on a 57 block for quite a few years with dual carbs, hot cam, headers and it ran really good (I still have the motor) so I would not be overly concerned about sourcing an 848 head. As for headers, you have Fenton and Williams as the cast iron possibilities, Clifford for the true tube header possibility (although they only sell a shorty header these days no long tube versions like they used to have years ago, and not cheap at any rate), the crappy tube manifolds you see on ebay (both plain steel and stainless, I would take a pass on these), and finally, converting a stock manifold to dual outlet or true split.

As for the intake, you can use exhaust gas to heat the bottom of the manifold, but frankly the two little copper tubes for the fentons and Williams are not all that efficient. Hot water is better.

Why would hot coolant-water be much better than exhaust gases, unless your intake manifold was a properly installed Offenhauser-style intake?

The Offenhauser intake allows the correct use of a dual-port bottom-plate (they are now hard to find - images are attached) : the plate allows an inlet port/fitting and an outlet ports/fitting - for two water hoses (properly plumbed to engine coolant ports)?

The Offy intake also allows flow from one side of the intake manifold to the other side of the intake manifold, through internal passages.

If there is no flow of exhaust gases or of coolant - neither heat-source is as good as having engine-coolant or exhaust-gas flow.

I ran such a "coolant flow" set up on a 261, until I worried about providing more opportunities for breaks in coolant hoses. I now have two exhaust gas lines attached to the plate under the Offenhauser intake. It has worked fine for a few decades.

I think someone posted long ago a description of an original Fenton set-up that somehow allowed exhaust gas flow for heating the intake?

My personal favorite.

Hi. I am bringing back an old thread about exhaust that I started last year. I ended up just driving my truck all year with single exhaust, but I would like to convert to dual exhaust this winter. Does anyone make those altered stock single manifold to dual - like Curt posted above?
They look great.
Thanks,
JD

Water heat: takes longer to have any effect, but final temperature is pretty close to what you want, effect can be reduced to below actual water temperature with a restrictor in the line, can be completely shut off by bypassing the water inlet & outlet. A serious leak will overheat the engine eventually.
Exhaust heat: takes effect more quickly, but final temperature is too much for high air temperature, more difficult to regulate or shut off. A leak won't harm the engine but will make the passengers sick.

Converting a stock manifold to a split system and retaining the original heat riser is by far the most effective way to get dual exhausts that work- - - -sort of. It doesn't really improve performance, unless rattling windows a block away with harmonics is considered to be an "improvement"- - - - -but you'll create fewer problems that way. The trick is finding an old geezer welder who is good at welding cast iron. They're pretty scarce these days!
Jerry

I have to say the stock manifold posted earlier really does look nice. My current single exhaust manifold works well with the "flapper". My performance is fine and I'm not looking for a performance gain but I do like the dual exhaust sound.

I would bet there is an old hotrod guy close by that knows exactly where to cut to make them and probably can weld or knows someone who can. Check around with your local car clubs.

In the forum classifieds one of these single to split conversions show up from time to time.

The 235 Corvettes had a factory split manifold. Hotrodders bought thousands of them from Chevy parts departments, so there were a lot more manifolds than there were Corvettes.
Jerry

I have a complete set up with dual carbs and water heat from Langdon's. No problems for 12 years. Also have not run an oil filter for the same length of time. I put about 3000 miles a year on it.

I am actually using Williams headers on a 261 with an 848 head and an oil filter. I did relocate the oil filter to the inner fender. Worked out pretty good. I didnt install any heat riser setup at all to the bottom of the intake. The exhaust is still rather quiet unless you thump on it. I think they are 30 inch glass pacs. I bought the whole kit from National Chevy. Included everything from the headers to tailpipes with hangers and clamps. Ive been running it for They Probably wont have a set up for application tho. Not using that restriction of an air cleaner anymore either.

There are actually three ways to use a stock exhaust manifold in a split configuration, but as Jerry notes, you need someone who can braze up the cast iron. I am sure arc welding or maybe tig welding may also be a possibility but with so much carbon in the cast iron I would imagine you would have to weld like I dry wall, 5 pounds on and sand 4 off.

So method one is a true split where you are splitting the manifold and welding the ends shut or weld in a baffle that essentially shuts off half the manifold, weld the halves back together, and then add an additional outlet on the half that needs one. This will result is a true split with the true split sound.

Method two, split the manifold, weld in a baffle with say a 1 inch hole in the baffle, weld the halves shut and add an outlet to the side that needs an outlet. This type split results in a somewhat tamer sound.

Method three, just add an additional outlet. Not a true split but allows for dual exhaust and is the quietest of the three methods.

I have never actually had a vette exhaust manifold in my possession. Fentons and clifford tube headers so I do not know what the vette exhaust manifold is, true split or just an additional outlet.

I have run Clifford headers since the late 70s. I like tube headers so I put up with the issues that can arise with them. But if I had to choose today between the fentons and maybe splitting a stock exhaust, I might go with splitting the stock exhaust particularly if the choke butterfly was still functional in order to retain th4e stock carb and choke heat functions.

Splitting a stock manifold isn't impossible, but the welder definitely has to know what he's doing. It isn't necessary, or desirable to completely block off the halves of the manifold- - - -leaving a small gap to allow a pressure relief is best. With a thin cutoff wheel on a small angle grinder, a gap about 1/4" wide needs to be created in three sides of the manifold just ahead of the heat riser, and a piece of cast iron cut from a junk manifold is inserted, leaving maybe a 1/8" gap inside at the top where the manifold doesn't get cut. Grind the area to be welded down as smooth as possible for about 1/2" on both sides of the baffle and chamfer the edges a little. Now, use nickel-alloy welding rod to make about 1/2"-3/4" of weld bead, after preheating the manifold with a rosebud torch until it's almost, but not quite red. Stop welding and peen the bead for about 5 minutes with the pointy end of a slag hammer to stress-relieve the weld. Heat- - - -weld- - - -peen- - - -"rinse and repeat" until the whole baffle is welded into place. Post-heat the manifold, not quite as hot as the preheat and bury it in a pile of sand overnight to cool slowly. It's also a good idea to have the manifold bolted to a junk cylinder head, or at least a piece of thick steel plate to prevent warping while you're welding.

Once the baffle is welded in (and the weld bead didn't crack) use a hole saw to make a hole in the front of the manifold and weld another pipe flange on, using the same procedure you did to install the baffle. Have fun!

I found a roll of nickel-alloy wire for my MIG welder, so the next time I have an occasion to weld cast iron, I'm going to experiment a little to see if I can develop a procedure for using MIG instead of stick welding.
Jerry

Here's the Corvette, notice the intake manifold heat provision.

Obviously there is no tuned length.
However, other minor benefits:
1. the flow from each port of the front (1, 2-3) or rear (4-5, 6) cylinder group occurs in rotation (front - rear - front), each cylinder is not fighting gas pressure from the next cylinder in firing order - it's in the other group
2. separate outlets for each group reduce internal pressure, produce stronger pulse at the tailpipe
3. less heat soak into the engine bay vs. tube headers
4. 50 year life expectancy vs. 3-5 years for un-coated tube header

The Austin Healey 3000 I drove back in college had a split manifold, and when the muffler and tailpipes were removed for SCCA club racing, the exhaust pipes and manifold were the right tuned length for good breathing with the engine wound up close to its horsepower peak- - - - -I'll bet some Limey engineer figured that out when they decided where to locate the muffler!
Jerry

Jerry's weld procedure is pretty close to what my welder used and he stick welded with nickel based rod. That being said the welding is only a third of the project as making a flange and shaping the elbow for a good fit are more work than finding a welder. I always used a heavy wall 90 deg. steel pipe elbow and made flanges with a bevel to accept a donut. Some process pics:

that looks terrific!

It's also possible (but not as pretty) to simply cut a flange off of a cracked/broken junk exhaust manifold and weld it on.
Jerry

Spool up the mig gun and show us! More pics:

No matter what, it cant be all that beneficial to the actual drivability of the motor. Theres no flow. Its probly creating more turbulence and restriction than realized. Id like to see a cut down Corvette manifold. Im not sure GM thought it out either??

Separating exhaust pulses from cylinders next to each other in the firing order into separate pipes will reduce back pressure. Whether or not that's a good thing, and what RPM ranges, if any, where there's a benefit is a job for a dyno pull. (Or somebody who likes to pull imaginary horsepower figures out of his ear, or some other body orfice)! That's how Clifford does it!
Jerry

Lol.