Electronic ignition

[Buford]

Hey all, just got my Vette about a month ago, last time I had a V-8 was 20 some years ago (a '68 Chevelle 350). Question is does my '74 Vette have electronic ignition? It's not supposed to but it has that odd-looking distributor cap and honestly I don't know. The car is perfect externally but some fun projects lay ahead for many things that appear to have been Bubba'ed.:confused ;help

 

[Jack]

74 came with small cap & points. 75-up came with large cap HEI. The HEI (high energy ignition aka electronic) has a large cap about 5" diameter & it has coil inside cap ... thus, stock HEI has only 8 plug wires & NO coil wire. Points dist cap has 9 sockets ... eight plug wires & one center coil wire.

Another clue is your tach ... 74's OE in-dash tach is mechanically driven w/ large cable from dist base ... 75-up OE in-dash tach is electronic & driven via small wire from side of dist cap. Does your OE in-dash tach work?
JACK:gap

 

[Buford]

OE in-dash tach does not work, it has a Sun tach mounted on the steering wheel. Pulled the spark plugs for a clue and got R45TS, this is not a 74 motor, block is 3970010 and prev. owner says it is a 4 bolt main with L82 heads, thats all he knows.:crazy :BOW

 

[Jack]

You didn't reply if your dist matches above HEI description. If it is HEI ... you can swap in an OE in-dash electronic tach from 75 thru 77 vette. 75 thru 77 vette tach will fit right in your 74, match your other gages & work perfectly w/ HEI. Available used on ebay, vette swap meets and rebuilt from many vendors. I found a good used one 2 years ago for about $50. Or you can get a rebuilt correct-for-car mech tach drive points distributor from same sources for $200-$300. FYI ... IMHO ... HEI is best distributor chevy ever used ... excellent street performance, very reliable, low maintenance and cheap & readily available parts. All GMPP hi-po crate motors that ship with a distributor come with early-style big cap HEI.
JACK:gap

 

[Buford]

Well it is about 5" across, I think it must be what you say. I have a picture, going to try to attach it.

 

[JohnZ]

Yup, that's an HEI distributor, which is why your tach doesn't work - it needs a distributor with a tach drive gear like the original points unit had.

 

[Jack]

John Z nailed it ... that's an earlier-style big cap HEI ... that's exactly why your OE tach won't work ... as before, a 75-77 vette tach will retrofit. But I can't tell from the pic if it has vacuum advance can or not (vac can is desireable for most carbed street cars). I think about 1980-81 some big cap HEI vettes did not come with vac can? Also, I think about same era some vette did not come with a centrifugal advance (also desirable for most carbed street) ... not sure on the deleted cent though? I'm certain 75 thru 79 vette had both. Best to have both for most carbed street. GMPP dist mentioned earlier have both vac & cent advance. We run em in regional circle track cars with both vac & cent advance locked ... that's only for race cars with operating range above 3k rpm ... locked is no good for carbed street cars ... carbed street needs both operating aok.
JACK:gap

 

[Buford]

Yes it has the vacuum advance and it is hooked up.:cool