rlsterling3

Hey all, OK. I can't identify the dizzy thats in this 81 vette. It's got wires coming off the top and side which I was told is for the computer, yet it also has a vac advance on it. I understand that vac advance distributors ca be hooked up to either a ported source or the manifold. This dizzy has a vac line going to the thermostat housing. What the hell am I missing? Why is this as confusing as it is? This is the only problem with buying someone else's project, trying to "decode" everything they were doing can be a headache at times! So I guess the question is this: What distributor are other 81 owners out there using? Are you happy with it?

Jig A Low

a "true" '81 dist. does NOT have a vacuum advance can on it, besides the spark plug wires there is a connector with 4 wires coming off the side.

I have seen some dist. (not '81's) that the vacuum advance line is routed through a thermal switch that is on the thermostat housing, basically, it won't let the dist. advance until the engine is warmed up.

rlsterling3

Yeah there is absolutely a vac advance here. I'm going to have to check the shop manual when I get home and see what the original part was. Any high performance elect. controlled cas out there that would play nice with the computer?

rlsterling3

So I finally got the 1981 shop manual. Looking at the book it appears there are 2 distributors listed. One is an hei with a vac advance, the other is an est controlled by the ecm. So the hei looks like what I have now, so why is everyone saying that the 1981 only had the est model and no vac advance? I'm confused as hell now... Any clarification?

Easy Mike

Does your shop manual include cars other than Corvette? Some of them do. Your 81 had HEI from the factory.

qwank

because it did. your shop manual isn't the correct one. it should look like this:

rlsterling3

[hQUOTE=qwank;1586746697]because it did. your shop manual isn't the correct one. it should look like this:

[/QUOTE]

that's the exact shop manual that I had. In the section talking about distributors in ignition and talk about an HEI it has a vacuum advance as well as an HEI est which is all electronic controlso the 1981 hea hadd both these distributor?

qwank

I'll double check when I get home, But I dont ever remember reading that.

can you post some pictures up of your engine compartment and distributor?

the lines going to the thermostat housing control the smog pump and charcoal canister i think, I cant remember off the top of my head

rlsterling3

Here is a link to some pictures I posted a fe days ago. Let me know if the link doesn't work. I'm doing this on my cell phone
https://www.corvetteforum.com/c3-tech-performance/3454897-carb-and-dizzy.html

qwank

looks like someone swapped out your electric distributor for a vacuum advance style

Easy Mike

Post #7 in your link answered your question. The distributor in your pic in that thread is not a correct 81 distributor.