Missing at full warm up

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Jun 12, 2020 | 09:52 PM

alan600

Thread Starter

Intermediate

Joined: Jun 2019

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Missing at full warm up

I have a 1980 L82 with a new 383 Blueprint stroker. I live in Alabama and now that the temps have gotten to mid 80's and 90's, I have a miss when warmed up completely. When cruising at about 2500 to 3000 RPM, with no load on the motor, it has a slight miss. You can here it surge and fall back a little like the fuel flow is not keeping up. But when you punch it, it runs great. Last week I ran it about 20 miles with the same miss but it was the hottest day I had driven it. I parked it in the hot sun for 20 minutes and it started fine . But before I got out of the parking lot it died. When I tried to restart it was a little slow and I smelled a little gas. It went about a block and died. It was a little hard to start but it cranked and I was able to make it about 15 miles and I decided to see if it would still take off when you punched it. It started to go but spit and sputtered like it ran out of gas. Now it seems to be missing more before it is even warmed up good. I can't figure out if it's a fuel or distributor heat problem. Any thoughts would be appreciated.

Jun 12, 2020 | 10:17 PM

gjohnson

Drifting

Joined: Mar 2008

Posts: 1,812

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From: Denver CO

Check the plugs. BluePrint recommends a cold plug which can lead fouling.

Jun 12, 2020 | 11:07 PM

forman

Melting Slicks

Joined: Mar 2010

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From: Randolph nj

could be a bad coil

Jun 12, 2020 | 11:09 PM

MelWff

Race Director

Joined: May 2006

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Did you look down the carburetor when the engine is hot and off to see if gasoline is dripping into the engine?

Jun 13, 2020 | 02:51 AM

OldCarBum

Race Director

Joined: Mar 2016

Posts: 14,444

Likes: 8,239

From: Napa Valley California

Could be a dying coil.
They seem to function normally when the engine is cold and will start to fail as the engine heat warms the coil.
Coils are cheap and easy to replace.

Jun 14, 2020 | 10:47 AM

Big2Bird

Le Mans Master

Joined: Dec 2006

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Change the HEI module.

Jun 14, 2020 | 11:13 AM

CanadaGrant

Safety Car

Joined: Apr 2006

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From: BC

You can also check your plug wires. I had something similar a few years ago. Missed slightly on one cylinder but only when hot. One of the metal plug connectors that crimp onto the plug wire end had slipped off the wire. It worked great when cold but when the wire heated up and expanded from the arcing it would fail causing a miss.

Jun 14, 2020 | 02:46 PM

7T1vette

Team Owner

Joined: Jan 2006

Posts: 37,637

Likes: 3,118

From: Crossville TN

If you have an HEI ignition system, the ignition module may be showing its age with some additional heating. There is supposed to be some heat-transferring grease placed on the base of that module, so it will not over-heat. If that is missing or has dried up, you may need to refresh it.