69 L-89 Choke Question

[Stuart F.]

I recently rebuilt a set of Holley tri-power carbs for one of my sons cars, a 1969 with the L-89 Big Block engine. We have the engine running quite well with the exception of Initial cold start and warm up. We are here in Central Florida, so our ambient conditions are still very warm and humid. This unit uses the divorced type choke which does not seem to respond to normal book spec adjustments very well.

It is not a big deal as I guess we should expect a beast like this to be some what temperamental, but we'd like to get it to run as "streetable" as possible.

My thoughts were that perhaps the divorced type choke may not be the best design for use on the aluminum intake manifold, specially with the aluminum heads. This car has been "bubbaized" some as well as the exhaust system was changed to the 2" side pipes. There is also a heat riser valve on the right side manifold that doesn't seem to function very well as it seems sloppy and sticks part way through it's travel. I can't help but wonder if the aluminum heads even have an exhaust cross over in the first place, and that perhaps the valve is just being used as a dummy spacer.

Any insight on this will be appreciated.

Stu Fox

[Joe L.]

Re: 69 L-89 Choke Question

I recently rebuilt a set of Holley tri-power carbs for one of my sons cars, a 1969 with the L-89 Big Block engine. We have the engine running quite well with the exception of Initial cold start and warm up. We are here in Central Florida, so our ambient conditions are still very warm and humid. This unit uses the divorced type choke which does not seem to respond to normal book spec adjustments very well.

It is not a big deal as I guess we should expect a beast like this to be some what temperamental, but we'd like to get it to run as "streetable" as possible.

My thoughts were that perhaps the divorced type choke may not be the best design for use on the aluminum intake manifold, specially with the aluminum heads. This car has been "bubbaized" some as well as the exhaust system was changed to the 2" side pipes. There is also a heat riser valve on the right side manifold that doesn't seem to function very well as it seems sloppy and sticks part way through it's travel. I can't help but wonder if the aluminum heads even have an exhaust cross over in the first place, and that perhaps the valve is just being used as a dummy spacer.

Any insight on this will be appreciated.

Stu Fox

Stu-------


Assuming the aluminum heads are the ORIGINAL ALUMINUM HEADS, they absolutely do have an exhaust crossover passage. The GM casting #14011077 replacement heads also do have an exhaust crossover passage. Many GMPP and Edelbrock heads do not have a crossover passage even though they APPEAR to have one. Most other aftermarket aluminum heads do not have a crossover passage.

Keep in mind that even though original heads will have a crossover passage, it is possible to effectively deactivate it by using manifold gaskets with a blocked crossover (e.g. like L-88 intake manifold gaskets).

[Stuart F.]

Re: 69 L-89 Choke Question

Joe;

Thanks for your valuable insight on this. I admit, I never got into Big Blocks much. They came into being when I was out of the country, and all I knew was what I gleaned from car mags.

In the case with this car, my son is still in touch with the former local owner, and got the car from him with a lot of documentation including Bloomington and NCRS judging sheets. He had the side pipes put on it to further his enjoyment in local car shows. So if I had to bet, I'd say it's pretty certain it is a factory L-89 equipped with the aluminum heads, and it has the TI ignition system.

How much more we do with and to the car depends on my son. He has several interested buyers, but I would still like to tweak the start and warm up. If he decides to keep it for a while and have some fun with it, I have a great divorced electric choke kit I'd love to try on it. For that matter, a new repro choke stove unit is rather inexpensive. So far, What I can tell you is this baby will hall the mail!

Thanks again;

Stu Fox

[Joe R.]

Re: 69 L-89 Choke Question

Stu-------


Assuming the aluminum heads are the ORIGINAL ALUMINUM HEADS, they absolutely do have an exhaust crossover passage. The GM casting #14011077 replacement heads also do have an exhaust crossover passage. Many GMPP and Edelbrock heads do not have a crossover passage even though they APPEAR to have one. Most other aftermarket aluminum heads do not have a crossover passage.

Keep in mind that even though original heads will have a crossover passage, it is possible to effectively deactivate it by using manifold gaskets with a blocked crossover (e.g. like L-88 intake manifold gaskets).

Hi Joe,

Could you please tell us the GM number for the L88 intake manifold gaskets?

Thanks!!!
Joe

[Joe L.]

Re: 69 L-89 Choke Question

Hi Joe,

Could you please tell us the GM number for the L88 intake manifold gaskets?

Thanks!!!
Joe

Joe-------


GM #3955528