60 Lower Choke Tube

[Pete P.]

I decided to replace the lower choke tube on my 1960, base 283/230. I removed the RH exhaust manifold and can see what appears to be like a small insert with about a 1/16" hole. I measured the hole where the upper choke tube inserts and it's .250" diameter. The new lower choke tube that I bought from Paragon p/n 4003 is for 57-65 Corvettes and is larger than the hole in exhaust manifold. My manifold appears to be correct with GM p/n 3750556. I included some photos of the top manifold hole and also the best that could get of the inside. Also attached is a sketch of the Paragon tube with dimensions. I've read the archives which mention inserting the new tube from the top and tap it in carefully. But, the new tube is quite bit larger in diameter than the hole in the manifold. Am I supposed to drill out the hole to make it larger or did I get the wrong replacement tube or is there something else I'm not aware of?

Any help is appreciated.

Pete
20800100_4443.jpg100_4452.jpg100_4436.jpgParagon Tube Dimensions.JPG

[Richard M.]

Re: 60 Lower Choke Tube

Pete, Your photos didn't appear.

But it sounds like your original tube end piece is still there and rusted into the hole in the manifold. Try using a hammer and drift to drive it out. If you drill it do not enlarge it.

Rich

[Pete P.]

Re: 60 Lower Choke Tube

Rich,

I uploaded my pictures again.

Pete

[Richard M.]

Re: 60 Lower Choke Tube

Ah there they are. To me it definitely looks like part of the original tube is in there. I'd try to tap it out(actually "in") with the drift.

Rich

[Pete P.]

Re: 60 Lower Choke Tube

Rich,

The problem I have is the hole in the EH manifold is only about .250" and the new tube is about .340" at the expanded end. It won't fit. Another thing to note, that I didn't mention above is, the EH manifold doesn't have a lower hole. There appears to be a "blind pocket inside. I'm stumped because the GM p/n is correct, but it only has the top hole which is small.

Pete

[Richard M.]

Re: 60 Lower Choke Tube

Hmmm, A picture of the lower area where the hole should be? It should have a hole there for the tube to insert into.

I'm wondering if someone before you drilled out the top area from a Fuelie Manifold. Ouch! They had no holes or tube.

Here's the actual tube pic from the paragon site. The ends are a little oversized so they fit tight when driven in.

4003.jpg

[Pete P.]

Re: 60 Lower Choke Tube

Here are 2 pictures of the outside lower section of the 2" manifold showing a "bulged" area. Could this be a FI manifold as you mentioned? Did the FI have the same p/n?

Pete


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[Richard M.]

Re: 60 Lower Choke Tube

Bingo....That was a 0556 FI manifold and someone drilled the top of it. From 1958-1961 the same casting number was used for both FI and Carbureted. They machined the holes for the carb versions and had a new part# for the assembly with the tube. But cast#'s were the same for both.

Tough call now. Rock and hard place scenario.

Since the top hole is now drilled, you can drill the bottom out and make it a NON-FI 0556. Drill alignment will be tricky. A long jobber bit should be used if you decide to do that.

....Or you can get the top hole filled in and sell, as-is, with the bottom as-is for posterity. Then find a non-FI 0556 and use that one.

Rich

[Joe L.]

Re: 60 Lower Choke Tube

Bingo....That was a 0556 FI manifold and someone drilled the top of it. From 1958-1961 the same casting number was used for both FI and Carbureted. They machined the holes for the carb versions and had a new part# for the assembly with the tube. But cast#'s were the same for both.

Tough call now. Rock and hard place scenario.

Since the top hole is now drilled, you can drill the bottom out and make it a NON-FI 0556. Drill alignment will be tricky. A long jobber bit should be used if you decide to do that.

....Or you can get the top hole filled in and sell, as-is, with the bottom as-is for posterity. Then find a non-FI 0556 and use that one.

Rich

Rich and Pete------


I agree; this had to be an original FI manifold that someone "converted". I would not even attempt to further convert this manifold. For one thing, you know it's not original to the car anyway (unless the manifold is original but the engine is not). For another thing, drilling this correctly is going to be fraught with problems and you only get one shot to get it right. I'd look for another manifold that's already drilled properly for the tube.

[Stuart F.]

Re: 60 Lower Choke Tube

What year did they start using the fresh air supply tube, 63? The only ones I've ever changed were from about 1957, and they used the open bottom end tube and some of the tubes were pressed into an "X" shape for all but the ends I suppose to restrict (slow) the air down to ensure full heating. These tubes were prone to burning through causing the choke to draw exhaust into the carb and really making a mess.

Stu Fox

[Richard M.]

Re: 60 Lower Choke Tube

Stu, '63 still had the fresh air tube inside the manifold setup, like '62 IIRC. It used the extra tube to the carb/air cleaner vent area though.

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[Pete P.]

Re: 60 Lower Choke Tube

Rich, Joe and Stu,

Thank you for the replies. I'm just getting back to check on this post after sweating my gerbs off outside redoing my deck stairs.

It's amazing how much I keep learning about my car, especially after owning it for 39 years. I don't think I'll attempt to drill the holes through the bottom. I'm going to look for a correct RH manifold.

I appreciate your feedback. Have a good weekend.
Pete

[Stuart F.]

Re: 60 Lower Choke Tube

Rich;

Your pics are a lot like my 63, only I no longer have the choke tube in place as I use an electric choke conversion controlled by a thermo sensor. I still keep the tube in place to change back if desired, but I cap it off on the top side, but retain the fresh air connection to the carb. I was just wondering what year the fresh air tube started.

Stu Fox

[Jim D.]

Re: 60 Lower Choke Tube

Rich;

I was just wondering what year the fresh air tube started.

Stu Fox

I believe the clean air tubes were used from 62 to 65.

[Stuart F.]

Re: 60 Lower Choke Tube

Thanks Jim.

Stu Fox