Q-Jet Block Off Plate

[TravisUT]

Hey all, I have a stock intake on my 454, and currently the Q-jet uses the hot air stove system for the choke (see pic). I purchased an electric choke conversion, but need to block off those hot air holes. I found this from Edelbrock (https://www.summitracing.com/parts/edl-8961/make/chevrolet) that looks like it might work.

My questions are: 1- Is Edelbrock the only ones that make a block-off plate, or am I just not finding them? 2- Are there other ways to block off those holes?

Thanks!

 

[fast 99]

Unless installing a plate for appearance just leave stock one on and proceed with choke conversion. It is a tube preheated by the exhaust. Will not affect drivability in any way unless rotted out.

 

[PrairieDrifter]

Hey all, I have a stock intake on my 454, and currently the Q-jet uses the hot air stove system for the choke (see pic). I purchased an electric choke conversion, but need to block off those hot air holes. I found this from Edelbrock (https://www.summitracing.com/parts/edl-8961/make/chevrolet) that looks like it might work.

My questions are: 1- Is Edelbrock the only ones that make a block-off plate, or am I just not finding them? 2- Are there other ways to block off those holes?

Thanks!

Buy the edelbrock or weld up what you've got. A good welding shop should probably get that done for you for free in less than 5 minutes. Or cut out your own from flat plate steel.

Haven't seen a hot air choke in a long time!

 

[legopnuematic]

An alternative if you don’t weld/don’t want to find someone to weld them up, drill and tap them for npt pipe plugs.

 

[DoubleDingo]

Unless installing a plate for appearance just leave stock one on and proceed with choke conversion. It is a tube preheated by the exhaust. Will not affect drivability in any way unless rotted out.

I believe this method would cause an exhaust leak at the plate.

 

[fast 99]

I believe this method would cause an exhaust leak at the plate.

No, exhaust [for preheat] is on the outside of the tubes never inside. Any tube leak would be an unregulated EGR. However it is possible to have an exhaust leak at the gasket where the tube assembly attaches to the manifold. The 2 tubes that run to the carb can be removed. The vacuum port on carb can be plugged or used for other purposes.

 

[DoubleDingo]

No, exhaust [for preheat] is on the outside of the tubes never inside. Any tube leak would be an unregulated EGR. However it is possible to have an exhaust leak at the gasket where the tube assembly attaches to the manifold. The 2 tubes that run to the carb can be removed. The vacuum port on carb can be plugged or used for other purposes.

I understood it that those pipes went down into the head as part of the heat crossover? When I took mine out they were down in there pretty good and went into the head. If that is not actually the heat crossover or part of the heat crossover, then I guess there wouldn't be any leaks. I personally would just buy the plate and would suggest the OP do the same. Or maybe I misunderstand the heat crossover. I thought it had actual exhaust gasses passing through it as it gets coked up pretty good inside there.

 

[fast 99]

That's correct, there is exhaust within a manifold passage, but it never blends with the intake charge unless EGR equipped. Exhaust should never enter those tubes. If present they are broken or rotted out. I have done countless carb conversions and left that plate in the manifold. Like I said if the appearance bothers you get a plate. Otherwise, it isn't needed.

 

[TravisUT]

That's correct, there is exhaust within a manifold passage, but it never blends with the intake charge unless EGR equipped. Exhaust should never enter those tubes. If present they are broken or rotted out. I have done countless carb conversions and left that plate in the manifold. Like I said if the appearance bothers you get a plate. Otherwise, it isn't needed.

So I could just remove the tubes, leave the existing plate in, with the 2 small holes in it, and the only "down side" would be a small amount of extra heat coming from the manifold?

 

[DoubleDingo]

That's correct, there is exhaust within a manifold passage, but it never blends with the intake charge unless EGR equipped. Exhaust should never enter those tubes. If present they are broken or rotted out. I have done countless carb conversions and left that plate in the manifold. Like I said if the appearance bothers you get a plate. Otherwise, it isn't needed.

I wasn't meaning blending with intake charge. I am talking about the exhaust gasses in the manifold that goes from one head to the other via the heat crossover. Oh, wait, as I typed that I see what you mean. I forgot about the tubes being part of that plate, and thus, no exhaust gasses should come out unless the tubes are rotted out, but they shouldn't be rotted out as they are never exposed to the elements. Yes, the tube goes into the head on the passenger side, but only exhaust heat passes through it/them, and the hot air choke setup on the carburetor has ports that circulate that hot air through the choke. Actually the hot air choke works just fine, just seems the electric choke is opted for on these, and I am guilty of doing that, but only because I swapped to vortec heads that have that have no heat crossover because they are technically FI heads.

 

[DoubleDingo]

So I could just remove the tubes, leave the existing plate in, with the 2 small holes in it, and the only "down side" would be a small amount of extra heat coming from the manifold?

Yep, but doubt you would notice the heat coming from the openings. If it were me, I'd order that plate, but leave the original one on there until you were in there for something that required undoing stuff in that area, and then remove the old and install the block off plate.

 

[TravisUT]

Thanks everyone! Great tips, and help, as usual!

 

[fast 99]

I wasn't meaning blending with intake charge. I am talking about the exhaust gasses in the manifold that goes from one head to the other via the heat crossover. Oh, wait, as I typed that I see what you mean. I forgot about the tubes being part of that plate, and thus, no exhaust gasses should come out unless the tubes are rotted out, but they shouldn't be rotted out as they are never exposed to the elements. Yes, the tube goes into the head on the passenger side, but only exhaust heat passes through it/them, and the hot air choke setup on the carburetor has ports that circulate that hot air through the choke. Actually the hot air choke works just fine, just seems the electric choke is opted for on these, and I am guilty of doing that, but only because I swapped to vortec heads that have that have no heat crossover because they are technically FI heads.

I do like the electric thermostats better if one can be found that unwinds at the correct speed for the application. They are not dependent on a clean intake passage or working heat riser.

 

[DoubleDingo]

I do like the electric thermostats better if one can be found that unwinds at the correct speed for the application. They are not dependent on a clean intake passage or working heat riser.

On my application it opens too quickly. Late Spring, Summer, and early Fall and it's fine as it's warm enough outside. But during the wintertime, if the engine doesn't have a chance to get up to operating temperature, it doesn't run right, especially from a stop.

 

[fast 99]

On my application it opens too quickly. Late Spring, Summer, and early Fall and it's fine as it's warm enough outside. But during the wintertime, if the engine doesn't have a chance to get up to operating temperature, it doesn't run right, especially from a stop.

As manufacturers consolidated part numbers this became a problem. Either too fast or too slow however the adjustment can help the situation provided it isn't one with an index tab. Best option is a GM stat. Any pick and pull yards nearby?