Help with crate engine for 81
Thread Starter
2nd Gear
Joined: Jun 2012
Posts: 2
Likes: 0
Help with crate engine for 81
Hello guys,
I have a 81 model that the engine needs replacing. I've been working on this car for a little over 3 years now and I have the ECM working great, with good/no codes and no check engine light. The engine however is shot and now I need to replace it.
Looking at GM Performance 260hp and also the 290hp crate engines. I'm leaning toward the 290hp, Summit says the old carb, dist., intake and ECM will work fine with this engine.
Jegs however says I may have issues with the ECM because of the cam and they suggest the 260hp engine.
Here's what I know about the cams: 290hp engine: Lift: .450"intake, .460" exhaust - Duration: 222* intake, 222* exhaust @ .050" tappet lift - Centerline: 114* ATDC intake, 114* BTDC exhaust
On the 260hp engine this is what I know: .383"/.401" and 112* lobe separation.
Question is do any of you run a modified cam with the original ECM? Any problems? Can the carb be adjusted to fix any idle problems, maybe a new prom chip for the computer?
Any help will be greatly appreciated.
Jeff
I have a 81 model that the engine needs replacing. I've been working on this car for a little over 3 years now and I have the ECM working great, with good/no codes and no check engine light. The engine however is shot and now I need to replace it.
Looking at GM Performance 260hp and also the 290hp crate engines. I'm leaning toward the 290hp, Summit says the old carb, dist., intake and ECM will work fine with this engine.
Jegs however says I may have issues with the ECM because of the cam and they suggest the 260hp engine.
Here's what I know about the cams: 290hp engine: Lift: .450"intake, .460" exhaust - Duration: 222* intake, 222* exhaust @ .050" tappet lift - Centerline: 114* ATDC intake, 114* BTDC exhaust
On the 260hp engine this is what I know: .383"/.401" and 112* lobe separation.
Question is do any of you run a modified cam with the original ECM? Any problems? Can the carb be adjusted to fix any idle problems, maybe a new prom chip for the computer?
Any help will be greatly appreciated.
Jeff
Burning Brakes
Joined: May 2008
Posts: 1,116
Likes: 5
From: Middleburg Florida
I ran the ECM and associated sensors and carb when I swapped a big block into my car. It work fine with the exception of idle. I had to richen up the idle circuit to the point the O2 sensor didn't like it based on the parameters programed into the ECM via the prom. I ended up pulling the ECM, and the electronics out of the carb. I think you're going to see the check engine light on a regular basis, but it'll clear after you get off idle. A different prom won't help, all those do is change the distributor advance curve a bit. And that's another area where you might run into issues. The ECM controls the distributor too, and it's fairly restrictive...
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
Hello guys,
I have a 81 model that the engine needs replacing. I've been working on this car for a little over 3 years now and I have the ECM working great, with good/no codes and no check engine light. The engine however is shot and now I need to replace it.
Looking at GM Performance 260hp and also the 290hp crate engines. I'm leaning toward the 290hp, Summit says the old carb, dist., intake and ECM will work fine with this engine.
Jegs however says I may have issues with the ECM because of the cam and they suggest the 260hp engine.
Here's what I know about the cams: 290hp engine: Lift: .450"intake, .460" exhaust - Duration: 222* intake, 222* exhaust @ .050" tappet lift - Centerline: 114* ATDC intake, 114* BTDC exhaust
On the 260hp engine this is what I know: .383"/.401" and 112* lobe separation.
Question is do any of you run a modified cam with the original ECM? Any problems? Can the carb be adjusted to fix any idle problems, maybe a new prom chip for the computer?
Any help will be greatly appreciated.
Jeff
I have a 81 model that the engine needs replacing. I've been working on this car for a little over 3 years now and I have the ECM working great, with good/no codes and no check engine light. The engine however is shot and now I need to replace it.
Looking at GM Performance 260hp and also the 290hp crate engines. I'm leaning toward the 290hp, Summit says the old carb, dist., intake and ECM will work fine with this engine.
Jegs however says I may have issues with the ECM because of the cam and they suggest the 260hp engine.
Here's what I know about the cams: 290hp engine: Lift: .450"intake, .460" exhaust - Duration: 222* intake, 222* exhaust @ .050" tappet lift - Centerline: 114* ATDC intake, 114* BTDC exhaust
On the 260hp engine this is what I know: .383"/.401" and 112* lobe separation.
Question is do any of you run a modified cam with the original ECM? Any problems? Can the carb be adjusted to fix any idle problems, maybe a new prom chip for the computer?
Any help will be greatly appreciated.
Jeff
Keep the shiny side up!
Scott
Le Mans Master
Joined: Feb 2011
Posts: 5,943
Likes: 61
From: Southern NH
Get the 260 HP and like already said, convert it to a roller cam. You could probably even find a roller cam that will make good power and idle well enough to keep you ECM happy.
Anyone try a ZZ4 in an '81 with stock ECM?
Anyone try a ZZ4 in an '81 with stock ECM?
Burning Brakes
Joined: May 2008
Posts: 1,116
Likes: 5
From: Middleburg Florida
These ECM's can't be "tuned", and a smooth idle won't make it happy either. If you want to keep the ECM, I suggest you learn a bit more about it. It will take some mods like a cam and headers, but you have to work the carb and use a differnt PROM to take advantage of the different advance curve. Like I said in an earlier post, teh ECM controls the distributor too, it also controls the lock up of your trans if you have an automatic.
The best place to learn about this system is the factory service manual. It has a whole section on it and the carb too.
The best place to learn about this system is the factory service manual. It has a whole section on it and the carb too.
Melting Slicks
Joined: Feb 1999
Posts: 2,473
Likes: 10
From: New Paltz, New York USA
Yes, the ECM can be eliminated. I bought a crate engine from Paceperformance. Its a 300HP/350, I eliminated the computer, got a new carb and distributor and am VERY happy with the set up. I used the opriginal intake and everything worked fine.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
Drifting
Joined: Dec 2011
Posts: 1,742
Likes: 289
From: Chardon Ohio
I have the older GM 290 or 330 (don't know) crate engine in mine, replaced by PO in 2005, and am not using the ECM. It runs great. You don't need it. Toss all the smog stuff while you're at it.
Had a 1976 L-82, 4-sp
Joined: Mar 2011
Posts: 5,338
Likes: 1,213
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
That would be the route I'd take if I had an ECM.
Thread Starter
2nd Gear
Joined: Jun 2012
Posts: 2
Likes: 0
Many Thanks!
Thanks for all the replies! Certainly a lot to think about. I'm convinced I want more hp than the original engine had. So, if I go with the 350/290 and I can't get the carb, dist., and ECM working I can change them and lose the ECM (as a last resort).
I think I'll try to make it work with them and see what happens.
Bill...I believe the original l81 is shot because I've developed a real bad "knock", I'm losing oil pressure (down to 0) when sitting still or coasting into a turn and when I changed the oil last Friday, I've got a lot of metal shavings showing up in the filter...took it to the shop to have them listen to the "knock" and between that and the metal in the filter they think its time for a rebuild.
I think I'll try to make it work with them and see what happens.
Bill...I believe the original l81 is shot because I've developed a real bad "knock", I'm losing oil pressure (down to 0) when sitting still or coasting into a turn and when I changed the oil last Friday, I've got a lot of metal shavings showing up in the filter...took it to the shop to have them listen to the "knock" and between that and the metal in the filter they think its time for a rebuild.
