Inliners International Forums General Discussion Engines Carb/Intake change - 235 chevy straight 6

Greetings,

I am looking for some advice. I have a dual carb setup on my 57 chevy. I could not figure out how to attach a picture. I do not have my own website at this point either. I will have to work on that.

The two rochester single barrel carbs are remanufactured. They were not the best when I purchased them. I had them rebuilt a few months ago.

I have been toying with the idea of replacing the dual carbs with a single two or four barrel. I realize that going with a single carb setup will require a Clifford intake or something other than the dual setup I have. Then if I go with the Clifford single carb intake, my fenton headers will most likely need to be replaced.

One of my reasons for exploring the idea of replacing the duals is because I am experiencing a lot of backfiring. I have adjusted the timing. The rotor and distributor cap look good. However, I have not checked to see if the valves need adjusting. I will get to that.

My gut feel tells me that the old carbs are on their last legs. Does anyone have any recommendations for a switch from dual to single? I have also priced Clifford's EFI kit. That would require a lot of money (the kit, Clifford intake, and Clifford headers). Right now I am not leaning towards spending that amount of money.

Let me know if you have any advice.

Are you sure you don't have a vacuum leak either between the manifold and head (ie maybe there is enough of a difference in the flange thickness of your intake and fentons that the washers aren't pulling square) , or at one (or both) of the carbs?

Are those the carbs with the power valve that needs a flange gasket with a cutout (and if so is the cutout oriented properly)?

Definetly check the valves (compression check too if you can).

You say the cap & rotor look good, are you still running points? Not the most likely culprit but a set of points and a condenser could do that, or an excessively worn distributor shaft or drive might as well. (again not the most likely, but wierder stuff has happened)

If all is good there and you want to try new hardware as opposed to a new overhaul shop, then there are 2 options I can think of, Langdon's Carter/Webbers and adapters, on your current manifold, if you want to stay with carbs.

If however you are interested in EFI, then might I suggest a Megasquirt kit and 2 single barrel TBI units off early to mid '80s econ-o-boxes, each on a home made adapter and bolted to your current manifold.

There is a thread here about retrofitting TBI onto a factory single manifold (I'll see if I can find it for you). The dual would be slightly different in the plumbing and wiring, but not exceptionally so.

Either way should be cheaper than the Clifford setups you mention, if you do most of the work yourself.

If it's what you are after, the Clifford setup should make more peak power though.

Here's one.


https://www.inliners.org/ubbthreads/ubbthreads.php?ubb=showflat&Number=42661&fpart=1

I am running dual carbs on my inline and couldn't be happier. Typically backfiring isn't caused by a carb problem as much as by a vacuum leak as indicated or ignition timing or valve lash being too tight.

Thank you very much for responding to my post. You have given me some good information.

Eddie

I am going to have my mechanic check the valve lash and all. The last time I attempted to adjust the valves myself, on another car, I screwed things up. So I have gotten shell-shocked in terms of valves.

But I will get things taken car of soon.

Forgot to mention that I am using Petronix instead of points.