Vortec heads spark plugs and dieseling

Foursightho · Sep 13, 2022

In need of some help. Just got my rebuilt motor back from builder. I asked the builder for two things for my build 1) vortec heads on my original 85 block and 2) to be able to run pump gas 87 octane.

Got the motor up, broke in, and running but plugs are real black and sooty. Also engine is dieseling with 87 octane gas.

Any advice on what to do to help run regular gas? Also do I need to use the later model spark plugs for the vortec heads (mine came off a 98 Yukon he said) or can I use the shorter plugs that were factory for 1985?

CalSgt · Sep 13, 2022

Did you confirm if it still does it with high octane fuel?

TBI or EFI would probably eliminate dieseling, not an easy remedy though.

Vbb199 · Sep 13, 2022

64cc chambers on a sbc are pretty small, what piston did he use and what deck height ?

Foursightho · Sep 13, 2022

CalSgt said:
Did you confirm if it still does it with high octane fuel?

TBI or EFI would probably eliminate dieseling, not an easy remedy though.

It doesn't do it with 93. I really would like to add efi but that another 2k at least.

77 K20 · Sep 13, 2022

Not sure if this helps or not but on the GM crate engine I bought with vortec heads (HT383) they said to set timing to 10 degrees BTDC at 650 RPM with the vacuum advance line to the distributor disconnected and plugged. They want 32 degrees of total advance when using HEI distributor P/N 93440806 (at 4,000 RPM). The HEI vacuum advance canister should remain disconnected.

This engine was 9.1:1 compression. Designed to run on 87 octane.

Spark plugs: R44LTS gapped at .040"

But I don't know what cam you are running or know what carb you are running.

fast 99 · Sep 13, 2022

Assuming a carb? If yes, does it idle slow enough? If automatic shut it off in gear.

Plugs should never be black. Too much fuel?

87 octane is low. Try 91 or whatever is available.

Do not allow the dieseling to continue. Immediate engine damage can occur.

Foursightho · Sep 13, 2022

77 K20 said:
Not sure if this helps or not but on the GM crate engine I bought with vortec heads (HT383) they said to set timing to 10 degrees BTDC at 650 RPM with the vacuum advance line to the distributor disconnected and plugged. They want 32 degrees of total advance when using HEI distributor P/N 93440806 (at 4,000 RPM). The HEI vacuum advance canister should remain disconnected.

This engine was 9.1:1 compression. Designed to run on 87 octane.

Spark plugs: R44LTS gapped at .040"

But I don't know what cam you are running or know what carb you are running.

I'm running an Edelbrock 1406 600 cfm carb. I don't have the lts plug in using my original plugs maybe that could be part of my issue

Foursightho · Sep 13, 2022

fast 99 said:
Assuming a carb? If yes, does it idle slow enough? If automatic shut it off in gear.

Plugs should never be black. Too much fuel?

87 octane is low. Try 91 or whatever is available.

Do not allow the dieseling to continue. Immediate engine damage can occur.

I don't know how to fix the rich carb. Is it just the idle screws or Do I get a larger carb with more cfm. Right now I got a 600 should I get a 650 or 700? Do I need to jet the carb.

fast 99 · Sep 13, 2022

600 is fine, need to know what brand carb. We can help you through it provided you have basic knowledge. There should be u tube videos as well.

Running a new motor rich and dieseling is a recipe for disaster.

QBuff02 · Sep 14, 2022

my money is on checking and verifying the timing first. What was the condition of the distributor that you put in the engine? Black and sooty plugs is an obvious rich condition. Could be as simple as tuning the carb and making sure the timing is right for the engine. What was the cam that was installed in the engine?

Vortec heads spark plugs and dieseling

Foursightho

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CalSgt

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Vbb199

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Foursightho

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77 K20

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fast 99

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Foursightho

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Foursightho

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fast 99

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QBuff02

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