Dual carbs and split exhaust installed

[steveplym]

Well I've been working on a project about a month or so. Decided to add dual B&B's with an offenhauser manifold and then decided to have Charlie Akers (aka Olddaddy) split my exhaust manifold.

After I purchased another carb and did a rebuild I was ready to install the setup. Took about two weeks to get the manifold back from Charlie with shipping and all included in the time. He does a great job and I am really happy with the results. I went ahead and used the throttle linkage in the kit and I can see I'm going to have to fine tune it a bit. Has a little too much slack for me. Car fired right up yesterday though after pumping it a bit. It runs really good. Of course it will need to be fine tuned once I get the dual exhaust installed. Hoping to do that this week.

There were a few minor modifications I had to make. The bolt holes for the intake to exhaust manifold connection were 5/16" bolts on the exhaust and 3/8" bolts on the new manifold. A 3/8" drill bit and new bolts solved that problem. Had a little trouble with it lining up on the engine studs, but used a wooden block and a rubber hammer once I had it lined up. Tapped it lightly until it lined up and I could bolt it on. Other than that things went pretty well.

The information in the offenhauser kit said that studs for the carbs and all necessary hardware were included. I had to make the carb studs out of 3/8" threaded rod and make a bracket for the lower throttle spring. Not sure what experience others have had, but those items were not in the kit. The pieces to make the fuel line in the kit actually worked well. Had to make two flares and bent a couple of lines and it worked out really well. Plus it didn't leak. Which is the most important part.

The air cleaners I purchased from summit and just added another filter to each to stack them. Have read about several on here having problems with running rich from the lack of air in the smaller filters. Hopefully I have solved or prevented that problem.

Here's some pics. I haven't road tested it yet, but I have about a 1 mile drive to the exhaust shop so I will find out a little bit then. The real fun will be coming back from the exhaust shop. I can't wait! I have two 26" smithy mufflers to put on it and chrome pencil tip exhaust tips. Included some pics of the final results.

Edited March 11, 2012 by steveplym

[Don Coatney]

Looks great! Glad that carburetor worked out for you.

[steveplym]

Thanks Don. Yeah it did work well. I cleaned out that box that it was shipped in and found the broken off idle/air screw. I guess it just got damaged in shipping. Put a good base on it from a spare carburetor I had and it took care of it. I'm very happy with it.

[claybill]

good work steve..i have been running the same setup for 7 years on my coupe. also experienced the same install problems. a new, better linkage is important, but others have used the included kit with no problems.

bill

Edited March 12, 2012 by claybill
wrong info

[steveplym]

Well back from the exhaust shop yesterday and looks like I've got an exhaust leak. It's up near the manifold and spent some time checking on it today. Seems to be leaking between the intake and exhaust manifolds, at the heat riser. Anybody with offenhauser manifolds have any trouble with these sealing up good with the original exhaust manifold?

I put the gasket between them that came in the manifold gasket kit from napa. Seemed to fit well, but looks like I will need to address it again.

[1941Rick]

Had the same issues you are having....I filed the exhaust manifold flat and no leak..only problem I am having is running rich...exhaust pipe looks like I am burning coal...

[steveplym]

Did you put a thicker gasket in there as well Rick?

I cleaned the surfaces well, but may have to file it as you say. Did you file off much?

[steveplym]

Here's how the exhaust looks from the rear. I'm really happy with it. Can't wait to be able to hear what it sounds like from the back without hearing the noise in the front as well.

[Plymouthy Adams]

[quote Can't wait to be able to hear what it sounds like from the back without hearing the noise in the front as well.

suggest you leave the wife at home...

[steveplym]

Thanks for the suggestion Tim.

[Niel Hoback]

I tried that once, but then I didn't have an airbag.

[Jerry Roberts]

Did you put a thicker gasket in there as well Rick?

I cleaned the surfaces well, but may have to file it as you say. Did you file off much?

Another option would be to have a machine shop plane it flat . ( if it isn't flat already )

[1941Rick]

same gasket just made sure it was flat by draw filing

[steveplym]

Well after a few frustrating days I got the exhaust leak fixed. Put on a new gasket between the intake and exhaust, as well as filing down the exhaust manifold surface, and using a bit of exhaust cement.

Went for a cruise today and had a blast! I really like the way it sounds and it has a bit more power too. I'm going to try to drive it as much as I can the next three weeks before taking the 5 hour drive down to Jackson, TN.

I also got a couple of videos today of the drive and how the exhaust sounds. Please excuse the quality of it. It is hard to hold the camera and drive.

http://s167.photobucket.com/albums/u122/siufan6/?action=view&current=VID_20120325_124002.mp4

http://s167.photobucket.com/albums/u122/siufan6/?action=view&current=VID_20120325_123817.mp4

[oldodge41]

Looks great! Thanks for the ride.

[Ed Griffin]

Yes, thank you for the ride, beautiful color I might add.

[greg g]

Looks and sounds great thanx for the ride.

[cole18cars]

Did the same mods and was running rich also. I ditched the individual air cleaners and made a single, larger air cleaner that covers both carbs. I used an oval, open filter, more air I think solved the rich problem.

[steveplym]

Did the same mods and was running rich also. I ditched the individual air cleaners and made a single, larger air cleaner that covers both carbs. I used an oval, open filter, more air I think solved the rich problem.

Got pics of your air cleaner?

[Don Coatney]

I bought these flexable and cleanable air filters.

[cole18cars]

I am not going to be home for a few weeks and will try to snap a few pics.

[HanksB3B]

Do you happen to know what the performance gain is with dual carbs and a dual exhaust manifold?

Very Nice,

Hank

[Rusty O'Toole]

Do you happen to know what the performance gain is with dual carbs and a dual exhaust manifold?

Very Nice,

Hank

Dual carbs and dual exhaust work best with a reground cam and high compression or milled head. This combination should be good for a 25% to 40% increase in horsepower, depending on the cam, compression, size of carbs and size of exhaust.

Should be done only on an engine that has been rebuilt, or a known good engine with less than 50,000 miles on it. An older engine might go for years if you baby it but if you hop it up, the life will be measured in weeks or months rather than years.

Another old hop up trick, not often spoken of these days, is to lighten the flywheel for snappier acceleration. Old cars typically had very heavy flywheels in the interest of smoothness and easy driving. A machinist can put the flywheel on a lathe and remove up to 10 pounds of weight. This has the same effect as removing hundreds of pounds of weight from the car.