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Help! distributor what new one to install on 81 with all smog and computer removed new carb intake

dirtypants

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Joined
May 14, 2015
Messages
69
Location
Spokane
Corvette
81 4spd Corvette Blue dark met
as in post in title 81, std trans 4 spd..all smog stuff removed incl catalytic, now with Edelbrock Performer series, intake, carb, cam..computer to be disconnected..so what distributor to use..as the stock one was 1. controlled by computer, 2. no idea of advance when no computer, and 3. Lars says the stock OEM types in C3s prior to 81 had poor advance curves anyway..but could be made better with a kit of weights and springs..so i guess could do that with an HEI for late 70s..but why, if/.or..are some now made with the improved mech curve and vac also..ready to run with a modern curve both mech and vac, ....or...do I get a fully electronically adjustable dizzy like the MDS E Curve? will it fit..if so what tips for fitting and setting up. I am thinking the the set up now with the smog/ECM gone..and new carb..is now more like any late 70s 350...just needs correct timing / advance via a new distributor.
and...are the distrib to oil pump gears compatible...i have heard that on some..(mustangs for ex) they are not..a drive gear change is needed to not chew up gears and of course then the engine..
anyway..what dizzy to buy and install and any tips for the install and set up..not a race car..not even high mod...but all that stuff is gone/done by prior owner but dizzy never set up to match. at risk of repetition..if any late 70s HEI. ..do some not have..some do have...the improved, more optimal mech and vac advances as per Lars articles.:confused:confused:confused:confused:confused
so what next..thanks.
Nick
near spokane wa
 
Joined
Mar 9, 2009
Messages
1,026
Location
Yemen
I'm running a ProForm mechanical tach drive HEI in my '71 big block and it comes with the heavier advance weights that give a full advance by about 2800 rpm. There are many to quality brands to choose from but just make sure you order a mechanical tach drive version. And then you'll need the larger 8 mm HEI wires and common Belden is plenty good for average use.
 

GTR1999

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Joined
Sep 4, 2003
Messages
1,146
Location
New Haven CT
Corvette
1969,1972,1975
You are basically going old school, no computer. The last year a vette used a mechanical drive Tach was 1974, starting in '75 they were electronic and pretty good. There was a tap and filter for the dash tach but I'm not sure if it will work with yours. You'll have to check into that. Lars was offering them but I don't know if he still is working on them, you can contact him to ask.
 

Vettehead Mikey

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Aug 26, 2003
Messages
3,487
Location
Not that far from Ottawa
Corvette
1973 Coupe
Unless you've converted to a mechanical tach, you don't want a tach drive distributor of any type.

The GM HEI unit is as good anything in the aftermarket. It will benefit from fine tuning the vacuum advance and mechanical advance, but just about every off the shelf unit would.
 

SVO

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Joined
Jan 11, 2011
Messages
332
Location
Texas Gulf Coast
Corvette
69 L68 Vert, 72 LS-5 Cpe, 72 LT-1 Air 'Vert
I would think that one of the HEI units that GM specifies for use with the ZZ crate motors would be a good place to start.
 
Joined
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Messages
1,026
Location
Yemen
Unless you've converted to a mechanical tach, you don't want a tach drive distributor of any type.

The GM HEI unit is as good anything in the aftermarket. It will benefit from fine tuning the vacuum advance and mechanical advance, but just about every off the shelf unit would.


Oops, I forgot the later C3's used an electric tachometer. Sorry.
 

dirtypants

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Joined
May 14, 2015
Messages
69
Location
Spokane
Corvette
81 4spd Corvette Blue dark met
just to answer my own question..and thanks all for the advice posted..I went with Performance Distributors DUI for Chev 350, elect tach, no computer, mech advance of 24 all in at 3,000, vac can 8-10 hooked to manifold vac, and set timing for 36 at 3,000 so 12 static. Put on their Livewire plug wire set which come nicely heat shielded and numbered..but..were not long enough for the orig stock wire routing. Added addtl fabric heat shield near boots/exh manifold. They will custom set the mech advance when given your engine/cam/etc specs. They recommend plug gap opened to .050 to .055. I installed Autolite 25 at .053 and will check them soon.
Nick
 
Joined
Mar 9, 2009
Messages
1,026
Location
Yemen
I Recommend The usual .035" Plug Gap Even For HEI's

I recommend using a .035" plug gap regardless of what they recommend because over time the gaps will increase to the point where they quit firing. Better to start with a narrow gap and let them wear to a larger gap. I had gapped mine to the usual .045" gap for an HEI and on a trip to Los Angeles a year later 4 of the plugs quit firing. The gaps had enlarged to .055" and that was just too wide for my HEI to fire.
 

dirtypants

Well-known member
Joined
May 14, 2015
Messages
69
Location
Spokane
Corvette
81 4spd Corvette Blue dark met
since posts live a long time on the web

I recommend using a .035" plug gap regardless of what they recommend because over time the gaps will increase to the point where they quit firing. Better to start with a narrow gap and let them wear to a larger gap. I had gapped mine to the usual .045" gap for an HEI and on a trip to Los Angeles a year later 4 of the plugs quit firing. The gaps had enlarged to .055" and that was just too wide for my HEI to fire.

just in case anyone should read this..have Men in Black...zap your mind and delete your memory of it.
(but I have no doubt that...was/is not firing on at least half of "cylinders"..
N
 

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