Th-200 R4

[Paul J.]

We decided we are going to install a stock Th-200 R4 transmission into our 1961 Corvette with the stock 283 engine. Can anyone point me to any technical threads or readings on the conversion? I know the TV cable is very important, and We have selected a TV cable for an Edelbrock 4 barrel. There doesn't appear to be one available for the stock Carter carburetor.

Paul
Parker, CO

[Duke W.]

Re: Th-200 R4

We decided we are going to install a stock Th-200 R4 transmission into our 1961 Corvette with the stock 283 engine. Can anyone point me to any technical threads or readings on the conversion? I know the TV cable is very important, and We have selected a TV cable for an Edelbrock 4 barrel. There doesn't appear to be one available for the stock Carter carburetor.

Paul
Parker, CO

There were five "stock 283" configurations in 1961, so I hope you are talking about one of the three that doesn't have a Duntov cam.

Duke

[Paul J.]

Re: Th-200 R4

We have a 3:55 rear end.

[Terry D.]

Re: Th-200 R4

Duke
Could you expand on your statement about not having a Duntov came with the automatic in a 61?

Terry

[Duke W.]

Re: Th-200 R4

High overlap cams yield a rough idle and need much higher idle speed than the base engine cam, and the effect of a given high overlap is exacerbated by shorter strokes, so a high overlap cam like the Duntov is not at all friendly to automatic transmissions, especially in a 283. That's why GM never offered Powerglide on OE Duntov-cam engines.

Notwithstanding the handfull of L-88/TH400 combinations, which were meant for serious drag racing, the first time GM offered an auto trans with a SHP engine was the L-82/TH400 and the L-82 cam has less overlap than the Duntov, so GM was able to engineer an acceptable auto trans configuration on the longer stroke 350 with a "moderate overlap" cam for retail sale to the general public.

Well engineered combinations of high overlap cams and automatics incorporate "high stall" converters - typically 3000-3500 RPM versus the typical 1800-2000 on OE engines with low overlap cams. This can make for a good drag racing combination, but it will have really atrocious fuel economy in normal road driving, which is something to consider at today's fuel prices.

A few years ago I helped out an owner of a '62 with overheating and idle stability problems. It turned out the cam was a 30-30 with a 700R4. Some spark advance map modifications helped (It had a "B1" VAC and I replaced it with a "B28), but it was still a cantakerous beast in normal driving and the owner eventually followed my advice and installed a base engine cam, which made it a much more pleasant cruiser, which was his primary use.

Duke

[Paul J.]

Re: Th-200 R4

I don't believe the new cam is to the spec of a Duntov cam. At least I never selected anything like that.

I am researching the Tru-Shift solution for my project from Bowletransmissions.com. They claim that it is the simplest setup you can purchase and requires no pressure testing when installing. I have not found a solution for my stock Carter carb, it appears I need to install a Edelbrock or Holley.

Can someone tell me if you need to change the whole stock 'rod' throddle mechanism? It appears that the TV set-up that I read from Bowtie Overdrives uses a cable system from the pedal to the carb, and from the carb to the tranny. Is there any connection from the TV cable the the shift linkage on the TH-200 RV?

Paul

[Michael S.]

Re: Th-200 R4

Is there any connection from the TV cable the the shift linkage on the TH-200 RV?

Paul

Makes no sense?

Call a company called Lokar out of Knoxville Tennessee. They make aftermarket throttle cables for all sorts of applications including old Corvettes that are modified with new engines or transmissions. They will have something that works with your gas pedal.

Talk with Bowler Transmissions as they have a new bolt on system for carbs that allows the installation of a throttle cable and TV cable to several different types of carbs. You will need to call Bowler and talk to them not look on their website. Bowler definetly has a carburetor throttle cable/TV cable adapter for the Carter type of carb as produced by Edelbrock. Depending on the configuration of the butterfly arm where your current rod attaches, their kit may also fit an early Carter 4 jet.

[John H.]

Re: Th-200 R4

If they don't have a bracket arrangement for the stock Carter WCFB and you decide to use the Edelbrock AFB clone instead, you'll also need a new intake manifold, as the one you have will ONLY accept a WCFB.

[Paul J.]

Re: Th-200 R4

A new intake manifold is NOT an option. I need a carb that will work for the stock one.

[John H.]

Re: Th-200 R4

A new intake manifold is NOT an option. I need a carb that will work for the stock one.

Then you'll have to fabricate a TV cable bracket arrangement (possibly using some Lokar parts) that will work with the WCFB you have, as that's the ONLY carburetor that will fit on your existing intake manifold - it won't accept an AFB, Edelbrock, Holley, or anything else.

[Paul J.]

Re: Th-200 R4

I think a manifold is now an option. Any recommendations on a stock carb and manifold setup to look as original as possible?

Paul
Parker, CO

[Paul J.]

Re: Th-200 R4

Dave,

It sounds like you have done this conversion before. I sent you a message with our plans. Does anyone else have first hand experience (successful experience) with this conversion?

Paul

[Edward M.]

Re: Th-200 R4

If they don't have a bracket arrangement for the stock Carter WCFB and you decide to use the Edelbrock AFB clone instead, you'll also need a new intake manifold, as the one you have will ONLY accept a WCFB.

Rochester 4GC will also bolt on, won't it? Does that help the situation any?