BJ8 Rebuilt Engine and Carbs - Vapor Lock and Misfires when hot

[curly02161]

This is a very frustrating issue and I have read other posts and threads.

67 Healey 3000 MK III BJ8

1. Engine was rebuilt and SU Carbs were rebuilt less than 2K miles on engine
2. Car ran very hot so installed electric fan to help cool. Also new radiator.
3. On hot days in traffic car will start to gasp ( vapor lockish) and occasionally misfire.
4. Took on long open road drive keeping at 3500 RPM. Ran well as i thought engine was staying cool.
5. Engine began to gasp/vapor lock and misfire after about 70 miles.
6. Once engine cooled off, I was able to drive again. But clearly unreliable.

I need some kind of order to troubleshoot this problem and ideas/tips as to what may be causing this?

Thanks

 

[Brinkerhoff]

Re-check your timing and change the coil even if its new, its probably breaking down causing the misfire which too often is diagnosed as vapor lock.

 

[andrewss]

I had exactly the same problem on the same model about 2 months ago. I reset TDC advanced as per the book, changed the points and solenoid. Checked the pump and fuel lines for fuel flow/starvation, cleaned the fuel filter and reset the float bowl height in the SU's. I still had the problem !!! The problem in the end was the plate in the distributor that was moving/oscillating as the bushes were worn.. I had the distributor rebuilt with new bushes and the problem went away..

 

[bob hughes]

I go with Andrew, give the distributer a good looking at, is there movement in the shaft, see if you can rock the top plate on the bottom plate - if the answer is yes then the sprung star washer under the fixed plate is damaged, advance the top plate by hand and examine the connections to the vacuum mechanism to see if there are any loose connections. Also look at the earth- (ground) lead from the condenser to the fixed plate screw. Examine the low tension lead to the points - if the insulation is iffy - suspect - get a new lead. Lastly examine the low tension lead on the outside of the dizzy back to the coil - see if the connections are sound.

Best of luck



Bob

 

[British_Recovery]

A bad condenser can give the appearance of running out of fuel as it heats up, only to be normal again after cooling.
Bob

 

[andrea]

Your engine have the original Heath shield over the exhaust manifold and the carbs? in this cars they are very important -
https://picasaweb.google.com/112770...6RICOSTRUZIONECARBURATORI#5476707139836297490
I have somewhere one photos with the exhaust warmed so much that have cherry color (600/700°C, I suppose)

 

[steveg]

I had the same problem and replacing the coil fixed it. IMHO coils and condensers are flaky enough these days, one should have spares of both.

 

[BoyRacer]

Over time crud builds up around the weights and springs in the distributor and this prevents proper advance of spark. In which case, your timing is retarded and your engine will run hot. Check out your distributor.