Dedicated offroader that I have recently built.

When I first got it I had issues after running for a while which I put thought I replaced by switching the dizzy and ignition system out for an HEI and by heat wrapping the fuel lines.

Recently did a trip where we had a relaxed drive of about 45-60 mins in on private roads before we got to the stages. After about 45 mins I started to get some mis firing and reluctance to rev out and lack of power. Pulled over and checked everything, had bonnet up for 10 mins. Jumped back in, ran fine for a few minutes then started again.

Ended my day and drove out, couldn't rev past about 1700rpm and was down on power.

It's obviously heat related but not sure if it's fuel or electrical. I am going to get a fuel pressure gauge to monitor the rail pressure and will find the test data for the MAF and check both of those next time it's playing up. I can't think of any other electrical components involved as I have the HEI now.

Thinking of putting a couple of vents in the bonnet to allow excess under bonnet temps to escape.

Anyone have any other thoughts?

Cheers
Matt.

 

it's still possible the HEI coil is giving out due to heat....get a spare and try it..

 

2 bits.. I have been fighting a similar issue for years on a project/hobby car. It is getting close to being resolved but is looking like after time/heat or combo of each something is causing the drivers in the ecu to fail to fire on two coils.

This is after the coils were replaced and there is a concern that the failed coils may have affected the ecu or even vise versa.

The shop that has the vehicle is also reporting stray voltage showing up on at least one sensor that should not be there and so this could escalate to a wire harness issue.

Though it best to share in case you have exhausted all other possibilities and have not heard of coils affecting the ecu adversely.