292 Stalling out when stopping

[1973straightsix]

Hey guys I have been having a weird issue with my 1973 Chevrolet C20 with a 292 straight six and 4 speed manual with granny low. Just installed a new single barrel carb on the original intake manifold and a HEI distributor. Got the timing set to factory setting (4 degrees before top dead center) and I adjusted the idle mixture with a vacuum gauge (only getting 15" of vacuum at best) Before the truck ran Ok.

But now the truck will idle and rev up fine when stopped but when I start driving and start braking the truck will stall out every time. I tried checking for vacuum leaks and haven't really found anything yet. Wondering if anyone has had a similar issue and found a fix for this.

Wondering if the distributor is off by 1 tooth could that cause this issue where it will stall out only when slowing down?

 

[DoubleDingo]

Maybe vacuum check valve(s)? Sounds like pressing the brake pedal causes issues. I've also heard of new I-6 HEI distributors having bad vacuum advance canisters right out of the box too.

 

[DoubleDingo]

Do a search over on stovebolt or inliners, I thinking that's where I saw that about the vacuum advance

 

[1973straightsix]

Maybe vacuum check valve(s)? Sounds like pressing the brake pedal causes issues. I've also heard of new I-6 HEI distributors having bad vacuum advance canisters right out of the box too.

I haven't thought of vacuum check valves so I'll start there. I'll have to check out those websites you were telling me about too. Thanks for the info!

 

[DoubleDingo]

I haven't thought of vacuum check valves so I'll start there. I'll have to check out those websites you were telling me about too. Thanks for the info!

You're welcome. I have been trying to find the thread, but I cannot find it. Although, after doing some searches, I think it was more of the vacuum advance curve of the new HEI didn't jive with the I-6 engine. The springs were too stiff or too weak, the canister was wrong, etc. It's been a while since I saw it, but someone had similar issues you are having after installing HEI. In that thread there was talk about the timing as well, I think they suggested going with 10 or 12 degrees BTDC and not 4 degrees BTDC. If I find it I'll post the link here. I know I'll most likely be in this same boat when I swap in the HEI to my 292. I may just run the points distributor for a while, and send in my HEI to be curved before I install it.

 

[DoubleDingo]

Just to let you know, those old boys over at stovebolt don't mess around like we can do here to some extent. You will learn a ton over there, but no shenanigans.

Reading some info over there, you may have to investigate your timing curve, and of course vacuum leaks, etc. If you have the old distributor, try to get the mechanical advance of the new one to feel about the same as the old one does. You may need to swap springs or it may be just right. I have a feeling the mechanical and vacuum advance is not the same as the old points distributor.

And one thing I just read over there, instead of using starting fluid, carb cleaner, etc to check for vacuum leaks, use an unlit propane torch. If there is a leak the engine rpms will change and you'll where the leak is.

 

[1973straightsix]

You're welcome. I have been trying to find the thread, but I cannot find it. Although, after doing some searches, I think it was more of the vacuum advance curve of the new HEI didn't jive with the I-6 engine. The springs were too stiff or too weak, the canister was wrong, etc. It's been a while since I saw it, but someone had similar issues you are having after installing HEI. In that thread there was talk about the timing as well, I think they suggested going with 10 or 12 degrees BTDC and not 4 degrees BTDC. If I find it I'll post the link here. I know I'll most likely be in this same boat when I swap in the HEI to my 292. I may just run the points distributor for a while, and send in my HEI to be curved before I install it.

Come to think of it when I was setting the timing it seemed to run better the more I retarded the timing beyond 4 degrees before top dead to a certain extent. I'll try the things you are mentioning and let you know what works when I get it running good. Might be a few weeks out on that though I've been busy with work and such.

 

[DoubleDingo]

Do you mean advance beyond BTDC? Retarding it makes it fire later and run like crap. 10-12 BTDC, and just like the other engines, 36* total all-in at 3,000 rpm.

 

[1973straightsix]

Do you mean advance beyond BTDC? Retarding it makes it fire later and run like crap. 10-12 BTDC, and just like the other engines, 36* total all-in at 3,000 rpm.

I mean going from 4 degrees BTDC to 12 degrees BTDC. That's what I get for trying to sound smart on the internet.

 

[Shorty81]

The 292 is a awesome engine by the way.

 

[sirweesarunch]

You installed an HEI. Did you use the old wire from the coil to go to the new distributor ? That is a resistor wire and drops volts to the coil after the vehicle is started. Wire a nice thick 10 guage wire to the HEI because it requires full voltage to operate correctly. The symptoms are of a HEI operating at low voltage. Continuing with this will even damage your HEI.


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[DoubleDingo]

You installed an HEI. Did you use the old wire from the coil to go to the new distributor ? That is a resistor wire and drops volts to the coil after the vehicle is started. Wire a nice thick 10 guage wire to the HEI because it requires full voltage to operate correctly. The symptoms are of a HEI operating at low voltage. Continuing with this will even damage your HEI.


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Thanks for that, I forgot about the resistor wire to mention don't use it.

 

[1973straightsix]

You installed an HEI. Did you use the old wire from the coil to go to the new distributor ? That is a resistor wire and drops volts to the coil after the vehicle is started. Wire a nice thick 10 guage wire to the HEI because it requires full voltage to operate correctly. The symptoms are of a HEI operating at low voltage. Continuing with this will even damage your HEI.


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I was thinking of doing this initially but my dad didn't run a new wire on his 350 when he put a HEI in and it has been running for the last 25 years that way. Makes sense why this would cause issues though, I'll have to do that next. Thanks for the info

 

[sirweesarunch]

I’m confident a full 12 volts will have you buzzing down the road like a champ. If not swap a different control module after eliminating the resistor wires and some even have a porcelain resistor with a spring like thing. The module may have gotten damaged.


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[DoubleDingo]

I’m confident a full 12 volts will have you buzzing down the road like a champ. If not swap a different control module after eliminating the resistor wires and some even have a porcelain resistor with a spring like thing. The module may have gotten damaged.


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But also adjust timing and carb for maximum vacuum/performance while you're in there tinkering