L6's with Offenhauser 4 barrel

[old51sedan]

Just curious how many of us are running a 250/292 with an Offenhauser intake and a 4 barrel carb along with cast iron headers. Mine is cold blooded as can be so I just ordered a plate to mount under the carb. It talks about running water through it to warm things up. My idea is to run the exhaust vapors through to do the same thing. Would appreciate any input.

[Palf70Step]

I never ran it on mined. However it is a lot warmer down here. To me If you have it stored away during your winters and only run it in the summer months, forget it. Remember, we try to keep the carb and it's mixture as cool as we can. Just have a good electric choke for those initial startups. I ran a phenolic space on mine to help keep carb cool

[old51sedan]

I understand the warmer weather in the south, it seems like my truck is on fast idle for such a long period of time, it also has an electric choke. I'm sure there are a few people that are running some form of heat to the bottom of their carb. I have a 51 sedan with a 235, has Fenton headers (they are drilled and tapped for heating) with just the original carb. I ran copper tubing from the headers to a plate on the bottom of the manifold right below the carb. With the manual choke I just start it and after it's ran a few minutes I can push the choke back in and it's good to go. I believe the heat is better than water simply because it's instant heat, you don't have to wait for hot water. Any thoughts appreciated.

[Palf70Step]

I would double check the 12 and ground on the choke to make sure power is right, then watch it as it runs o see if the choke opens. All I can think of. I have done them with maunal chokes and carbs were the choke is wired open alll the time, but it doesn't get cold here very often, so I just dealt with the pickiness of no choke back then.

[old51sedan]

Originally Posted by Palf70Step

I would double check the 12 and ground on the choke to make sure power is right, then watch it as it runs o see if the choke opens. All I can think of. I have done them with maunal chokes and carbs were the choke is wired open alll the time, but it doesn't get cold here very often, so I just dealt with the pickiness of no choke back then.

Thanks for the input, It is wired right, the choke is working fine, I just want to get this thing off from the high speed idle a little quicker, at 1500 RPM's it seems like it's running awful fast to me.

[RichardJ]

1500 ? High speed idle screw and choke valve misadjusted. You may even want to take a second look at the Holley Electric choke installation.

https://documents.holley.com/199r11046.pdf

At hot idle do you have a good 600 rpm idle with no vacuum leaks?

I've never been a fan of the electric chokes so I adapted the Carter AVS to manual choke for my 292.

['68OrangeSunshine]

Originally Posted by old51sedan

Just curious how many of us are running a 250/292 with an Offenhauser intake and a 4 barrel carb along with cast iron headers. Mine is cold blooded as can be so I just ordered a plate to mount under the carb. It talks about running water through it to warm things up. My idea is to run the exhaust vapors through to do the same thing. Would appreciate any input.

On my 292, I have the Offy intake and Clifford Headers. Four Bbl Edelbrock Performer EDL-1404, 500 CFM. I have no carb heat set up.
Running in Southern AZ, I don't think I need it. But it does perform better in high summer -- when the Snowbirds are longgone.

[old51sedan]

Originally Posted by '68OrangeSunshine

On my 292, I have the Offy intake and Clifford Headers. Four Bbl Edelbrock Performer EDL-1404, 500 CFM. I have no carb heat set up.
Running in Southern AZ, I don't think I need it. But it does perform better in high summer -- when the Snowbirds are longgone.

I received the plate, now I believe I'm going to drill a hole in each one of the exhaust pipes just below the headers and weld a nut on similar to the way they install an oxygen sensor , then run some 3/8 copper to the plate. This is what I used on my 51 sedan and it worked well.

['68OrangeSunshine]

The Clifford L6 intake is plumbed for water I believe. One is supposed to divert a water hose from the heater core lines. Not sure which one, or if it makes a difference.
Offenhauser chose to copy the GM manifold [except for the 4V] but in aluminum alloy so it would mate with the GM cast iron exhaust manifolds.
Clifford makes headers which do not interfere with their intake. But the Clifford intake will not work with stock OEM exhausts.
I guess you see some deep winters in Michigan.

[old51sedan]

Originally Posted by '68OrangeSunshine

The Clifford L6 intake is plumbed for water I believe. One is supposed to divert a water hose from the heater core lines. Not sure which one, or if it makes a difference.
Offenhauser chose to copy the GM manifold [except for the 4V] but in aluminum alloy so it would mate with the GM cast iron exhaust manifolds.
Clifford makes headers which do not interfere with their intake. But the Clifford intake will not work with stock OEM exhausts.
I guess you see some deep winters in Michigan.

I'm not sure about Clifford intake but I know the Offenhauser I have is. I don't care for the looks of the water lines around the engine, that's why I'm thinking of using the exhaust heat. I believe I can drill a hole in each of the exhaust pipes just below the cast iron headers, weld a nut on there such as is done for an oxygen sensor and run two pieces of 3/8's copper tubing up to the plate below the carb and have instant heat for the carb, no waiting for the engine to get up to temperature to have heat. That is the way it is on my 235 six in my 51 sedan, it works great.

['68OrangeSunshine]

If it works, go for it.
TBH I have never seen a Clifford intake in real life. What I know is from reading catalogs.

[MikeB]

Originally Posted by old51sedan

I received the plate, now I believe I'm going to drill a hole in each one of the exhaust pipes just below the headers and weld a nut on similar to the way they install an oxygen sensor , then run some 3/8 copper to the plate. This is what I used on my 51 sedan and it worked well.

Have you thought about a way to block-off that tubing when the engine warms up? Might be something out there that would work, like one of the 80s emission control doo-dads.

[RichardJ]

>>sedan with a 235, has Fenton headers (they are drilled and tapped for heating) with just the original carb. I ran copper tubing from the headers to a plate on the bottom of the manifold right below the carb.<<

I've seen plenty of pictures of the Chevy 235 Fenton cast headers, but never with the carb heat tubes connected. In order for the hot exhaust gases to pass through the tubing, one tubing end will have to be connected to a location with lower pressure, than the feed tubing.

You could use a angled tube like used for Crankcase Evacuation Systems. You wouldn't use the one-way valve because you're connecting exhaust to exhaust.

Yes, the 292 is cold blooded and I bet you'd do better with a manual choke, rather than the electric.

['68OrangeSunshine]

Times two on Manual Choke.
I found ''Automatic'' chokes went off at all the wrong times, atmospheric conditions and pressures.
But then Arizona is a unique environment.
Hot desert days, cold nights.
Hot in the Valley, then super-chilled in the mountains. Once the auto choke went off on my '67 K/10 Sub after spiralling down a few levels [couple thousand feet] of a pit mine, while on location. I had to take off the air cleaner, and jam a screwdriver butt into the throttle body to keep the butterfly open.
With a manual choke, I can pull the knob if I need it. But it stays off when I don't want it.

[old51sedan]

Originally Posted by RichardJ

>>sedan with a 235, has Fenton headers (they are drilled and tapped for heating) with just the original carb. I ran copper tubing from the headers to a plate on the bottom of the manifold right below the carb.<<

I've seen plenty of pictures of the Chevy 235 Fenton cast headers, but never with the carb heat tubes connected. In order for the hot exhaust gases to pass through the tubing, one tubing end will have to be connected to a location with lower pressure, than the feed tubing.

You could use a angled tube like used for Crankcase Evacuation Systems. You wouldn't use the one-way valve because you're connecting exhaust to exhaust.

Yes, the 292 is cold blooded and I bet you'd do better with a manual choke, rather than the electric.

I cannot think of any reason as to why I would want to block it off. I say this because of the way my 235 runs installed this way and the fact that if I was running this intake with the original exhaust they would be mated together anyway. My 235 has a manual choke and works well, if I do this I can tell how well the automatic choke does compared to the manual.Here's a silly question, with 2 lines running to this plate each from different cylinders, will the air circulate with the opening and closing of the exhaust valves at least to some extent? It would have to in order to keep warm air under the carb correct?