Removing the computer on an 81 Vette
Thread Starter
Melting Slicks
Joined: Oct 2005
Posts: 2,056
Likes: 8
From: Redruth Cornwall
Removing the computer on an 81 Vette
Is it as simple as changing out the carb and the distributor?
Ive seen threads saying that if the prom dies, a new one can be bought from Hypertech but for the same price I could get a new distributor and I already have a good rebuilt Qjet.
Im thinking of upgrading to new heads, cam and dual exhausts and have heard the computer can get confused by a low vac signal ( easily addressed with a MAP sensor voltage adjuster circuit ). Also I like the idea of being able to dial in the timing rather than have the comp do it.
Just throwing it out for ideas.
Ive seen threads saying that if the prom dies, a new one can be bought from Hypertech but for the same price I could get a new distributor and I already have a good rebuilt Qjet.
Im thinking of upgrading to new heads, cam and dual exhausts and have heard the computer can get confused by a low vac signal ( easily addressed with a MAP sensor voltage adjuster circuit ). Also I like the idea of being able to dial in the timing rather than have the comp do it.
Just throwing it out for ideas.
Last edited by jotto; Aug 24, 2012 at 02:31 PM.
Racer
Joined: May 2007
Posts: 370
Likes: 0
From: Cherry Hill N.J.
This is the tech forum.......
I believe your transmission is also controlled by the computer if original..
I'm not sure, but I know someone with more knowledge than me will respond...either way!!!
I believe your transmission is also controlled by the computer if original..
I'm not sure, but I know someone with more knowledge than me will respond...either way!!!
Thread Starter
Melting Slicks
Joined: Oct 2005
Posts: 2,056
Likes: 8
From: Redruth Cornwall
Thread Starter
Melting Slicks
Joined: Oct 2005
Posts: 2,056
Likes: 8
From: Redruth Cornwall
Drifting
Joined: Aug 2009
Posts: 1,635
Likes: 8
From: Enid Oklahoma
Yes, you are correct. Dist and Carb. A good dist can be bought for cheap. Set it all up right and an easy swap, did mine in less than an afternoon including setting the timing and carb all to Lar's specs and HAVE NOT HAD A SINGLE NEED SINCE TO TOUCH EITHER OF THEM. I also removed ALL of my smog crap and have headers and true duals. And for a point of reference, my mileage is as good or better than any 81 with the CCC. I have no regrets.
Thread Starter
Melting Slicks
Joined: Oct 2005
Posts: 2,056
Likes: 8
From: Redruth Cornwall
Yes, you are correct. Dist and Carb. A good dist can be bought for cheap. Set it all up right and an easy swap, did mine in less than an afternoon including setting the timing and carb all to Lar's specs and HAVE NOT HAD A SINGLE NEED SINCE TO TOUCH EITHER OF THEM. I also removed ALL of my smog crap and have headers and true duals. And for a point of reference, my mileage is as good or better than any 81 with the CCC. I have no regrets.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
Best bet is a stock GM HEI setup. They are cheap, very reliable and will do the job just fine. Might not be as fancy and pretty as Pertronics and the like, but unless your racing all out there is no reason to run something like that. That is unless you just like the look and spending the money.
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Thread Starter
Melting Slicks
Joined: Oct 2005
Posts: 2,056
Likes: 8
From: Redruth Cornwall
Best bet is a stock GM HEI setup. They are cheap, very reliable and will do the job just fine. Might not be as fancy and pretty as Pertronics and the like, but unless your racing all out there is no reason to run something like that. That is unless you just like the look and spending the money.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
That computer just contols the primaries mixture of your carb.
What this means is that when u go WOT the secondaries still control the mix.
Do u really want to do this? Computer controls carb from idle to cruise only - doesn't control timing at all.
cardo0
Do u really want to do this? Computer controls carb from idle to cruise only - doesn't control timing at all.
cardo0
Drifting
Joined: Aug 2009
Posts: 1,635
Likes: 8
From: Enid Oklahoma
Last edited by 81pilot; Aug 28, 2012 at 04:17 PM.
Drifting
Joined: Aug 2009
Posts: 1,635
Likes: 8
From: Enid Oklahoma
Drifting
Joined: Aug 2009
Posts: 1,635
Likes: 8
From: Enid Oklahoma
All of the harness related to the computer in the engine compartment can be easily unlugged. There are connectors at the firewall. So your not "ripping" out anything, but merely removing them. I removed mine along with the smog crap and EGR crap. I will never put any of it back on, I can hand to someone if I sell it though.
Racer
Joined: Aug 2012
Posts: 427
Likes: 20
All of the harness related to the computer in the engine compartment can be easily unlugged. There are connectors at the firewall. So your not "ripping" out anything, but merely removing them. I removed mine along with the smog crap and EGR crap. I will never put any of it back on, I can hand to someone if I sell it though.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Ok i looked that up.
Sure it does. The ECU controls the timing just like a vacuum advance can does, that is why you need a new dist when you take it out. These 81 motors will never get a Qjet to open the secondaries all the way, it ain't gonna happen even at WOT unless they are beefed up, And since most of us spend very little time at WFO if any then the comp controls things most of the time.
'81 does have a computer controled dist where '78-'80 do not.
But there is support out there with a just an EPROM chip upgrade for a performance tune. Though i never installed one in an '81 i did one for my '90 pickup - simple and cheap.BTW a common complaint is the air valve and secondaries - need to be adjust correctly regardless electric Qjet or not.
cardo0
Drifting
Joined: Aug 2009
Posts: 1,635
Likes: 8
From: Enid Oklahoma
'81 does have a computer controled dist where '78-'80 do not. But there is support out there with a just an EPROM chip upgrade for a performance tune. Though i never installed one in an '81 i did one for my '90 pickup - simple and cheap.
BTW a common complaint is the air valve and secondaries - need to be adjust correctly regardless electric Qjet or not.
cardo0
But there is support out there with a just an EPROM chip upgrade for a performance tune. Though i never installed one in an '81 i did one for my '90 pickup - simple and cheap.BTW a common complaint is the air valve and secondaries - need to be adjust correctly regardless electric Qjet or not.
cardo0