Van engine cuts out from high revs, but idles fine

[Termite]

Hi,

I have a problem with my engine at the moment where it will cut out pulling up to traffic lights etc.. I fitted a new engine that I built and it has done 200 miles since fitting. It has been running sweet, but has developed this issue:

I first noticed it about a week ago going up a hill in 3rd gear, pulling up at the end of the road with the engine revs high. Dipping the clutch cut the engine out. I hadn't realised it had cut out as the new engine is so much quieter than the old! It didn't cut out again after this.

Now yesterday I used it for running around in and it was an absolute pig, cutting out almost every time I stopped at lights, but now and again not cutting out. I seemed to narrow it down to if the engine was reving high and I braked and pressed the clutch down it would cut out. The van doesn't have a brake servo.

I also revved it when stationary and letting off caused it to cut out as well. The van restarts every time and ticks over fine at Idle, only appearing to cut oput if revved high and letting off the throttle.

What could be causing it? It looks like I have a bit of an exhaust leak as there is soot around where the heat exchangers fit into the exhaust. Could a leaky exhaust be causing these symptoms? I plan to take off and refit the exhaust this weekend, but I am wondering if that is likely to solve it or if I should be looking at something else while I am at it.

Thanks in advance,
Termite

 

[Termite]

Checked some more last night and it definitely doesn't cut out from low revs or if you let it drop gently from high revs.

 

[ozziedog]

It's really hard to work things out if you have leaks as well. So first port of call has to be to sort out the basics like leaks. Then go through the regular stuff first, tappets for clearances points plug gaps etc, have a real good look at plug leads etc , power cable to the dizzy, inside the dizzy etc, even have a look with it running in the dark for stray sparks etc.
Does sort of sound like fuel starvation but I can't see how unless the floats are jamming in the raised position by suction.
Ozziedog,,,,,,,, good luck with this one.

 

[Termite]

So it appears to have been fixed. Took it for a 20 mile test run on Sunday after doing the following:
- check tappets (number 1 valves were a touch tighter than others, might not have set them correctly first time)
- changed the oil
- removed the exhaust and engine support bar
- fitted a new gasket to the oil pump cover plate that was weeping. Torqued that correctly
- re-fitted the exhaust with paste around every joint/gasket this time!
- wrestled with getting the support bar back on after the exhaust.
- I also noticed a Snell of petrol in the engine bay all day and found that petrol was dripping out of the carb. The gasket in the 13mm bolt for the main jet was leaking. This might explain why it had been a pig to start after leaving it a week or so as the carb bowl would've been dry
- at the same time noticed the vacuum hose on the dizzy and carb wasn't a very tight fit, so renewed that

Something out of that little lot sorted it !

 

[IZZYBAY]

I was going to suggest fuel filter and vac pipes. Glad its sorted