The Stovebolt Site Forums The Shop Area Engine Shop split manifold, what exactly does that mean??

I have heard of split manifolds before from other inliners, but what exactly is entailed in doing this? I am by no means a mechanical expert, so I hope this doesn't sound like to lame of a question.

I assume you are asking about exhaust manifolds. Simply stated, the manifold is cut into two halves, with an exhaust flange on each half. For sixes, it allows greater flow. You can split a stock manifold or buy headers whach are usually split.

dubie, Here is a link to a picture of my engine. It is a GMC with a pair of Fenton Headers. Installing the headers is the easy part, then you need to customize two pipes and mufflers to complete the set-up..

So basically, this is a way of making your own headers. Is it very hard to do this? or would i be better off buying a set if name brand headers?

All depends on your abilities. How are you at welding cast iron? I'm not, so I leave it to others.

The Fenton headers in that picture are a name brand piece, namely Fenton. They are in the catalogs for about $239 The rear outlet hooks up to your stock pipe without any modification necessary and the front outlet will need a new pipe bent. But there is plenty of room and any pipe jockey can do that.

There is also a company that will cut and weld your manifold into dual exhaust. This is a bit more of a stock look. They charge $165 and they use your manifold. They advertise on the Inliner page.

That sounds like a reasonable price. Unfortunatley I would have to pay double that amount because I live in Canada. I'm gonna check with a local exhaust guy and see what he can do for me first. Thanks for all the input guys.

I had the guy split my manifold that Tony mentioned--he did a great job. TIG welded, bead blasted, painted with high temp. paint and guaranteed for one year. Yes it's expensive, but I get to use the original pre-heat chamber (very important) and it's still $70 less than Fentons. Appears stock other than the extra pipe. I have his address if you want it. I used 30" Smitty mufflers and does it sounds great!!

PS: DON'T let some amateur welder mess with your manifold!!! Old cast iron that has been heated and cooled numerous times is tricky to work with--make sure they know what they're doing!

Since you have the split manifold. I was wondering, if you ever wanted to upgrade to a different intake and carburator or add a second Rochestor, then the new intake won't have the heater box correct?

So, for those situations you want either the Fentons or the Fake Fentons the guy makes out of your manifold upon request. (heater box removed).

The reason I ask is because in the future I wouldn't mind upgrading my carburator and manifold so don't want to buy the wrong exhaust manifold.

I emailed the guy that modifies those manifolds and asked him some questions. He said he is a bad salesman and told me to get regular Fentons. I emailed back agreeing with him, yes you are a bad salesman. But, it still didn't answer my questions.

For looks I'd run a stock split before I ran Fentons....They are just too easy to get
I run Nicson in and out on the 39 Kidda different and old (Like Me)

Smitty are just too quiet!!!

Sorry 12" glasspacks or nothing is better!!!

Dual intake will bolt to the stock heater box providing they are for the same engine, 235/261 or 216. I run dual intake with my '54 Vete dual exhaust, which is another option for a Chevy dual exhaust system.

Tony - If you live in a warm climate a manifold heater isn't needed. I have seen older aluminum intakes set up for use with the original exhaust heater, and most aluminum intakes can be set up or adapted for water heat, if needed.

Tony;
I don't understand your comments re your conversation. I have talked with Mike numerous times and he has always been very polite and very helpful--he even bead blasted the intake and primed it free--- the guy I bought both manifolds from shipped them to Mike together!
Yes, you can run dual carbs with a split--I have them on my 235 using an Edelbrock intake (two 216 Rochesters), which has a heat chamber. And yes, you need a heat chamber---regardless of your climate, your car starts at ambient temperature--100 degrees or less--which is much too cold for proper fuel atomization. To run without heat will result in hesitation and excessive choking wich will wash down the cylinders with raw, unatomized gas, removing any top cylinder lubrication. If you talk to someone who knows, like Tom Langdon of Stovebolt, he will quickly tell you of the need for heating the manifold. These manifolds were not designed by idiots! Also, you can go to the Inliners site and click on Tech info--then "Improving driveability with multiple Rochesters". :rolleyes:

Well, I took his comment about being a bad salesman to be a joke. And I responded in kind agreeing since he was recommending Fentons that he must be bad.

But, he also sells his Fake Fentons and I emailed again to ask some more questions. But, I haven't received a response that time. I figured I will just call when I get closer to deciding.

I still might go that route just because its cheaper than Fentons.

So, I could have my manifolds split and keep the heat riser and then later upgrade to a different intake manifold and go for dual Rochesters, which is what I have my eye on.

RE:The problem you described about no heat and cyl. washdown. Does it act like a mid-range stumble? On my 250 L22

I have a spot in the RPM range at about 2000 to 3500 that feels "flat" and acts like a miss. The plugs look rich (black sooty and dry). The spring is missing on the heat valve on the exhaust manifold.

Once I run the truck down the highway or on warmer days (above 70*) it's fine, unless it idles too long or sets for a few minutes.

It has a Holley Rebuilt Rochester "B" on the right P/N and I was thinking it was improperly jetted. Now I'm thinking cold charge and poor atomization.

What do you guys think?