CAM BELT SNAPPED ON MY 1.8 NON TURBO VAN SO I HAD A REMOVED THE HEAD AND REPLACED WITH A HEAD FROM A TURBO VAN ASSUMING THEY ARE THE SAME,THE VAN NOW HAS NO oomph AND TOP SPEED IS 70 AS OPPOSED TO 85 BEFORE ,ARE THE HEADS DIFFERENT AND CAN I DO ANYTHING TO IMPROVE PERFORMANCE,JOHN.

Edited July 31, 201114 yr by stef123
Please mind your language

I suspect the compression ratio is lower on the turbo engine and they may have lowered it by using bigger combustion chambers. Turbo engines on petrol engines usually have a lower compression ratio before the turbo boosts it, but after being boosted it's obviously higher. Does it seem to turnover faster, easier?

You could skim the head, if the comp ratio is the problem, but by how much is hard to say.

You could try googling the compression ratios of turbo and non turbo to check.

Other than above: did you take the fuel pump off and if you did is the pump timing correct now? I assume the head gasket is OK. No bad air leaks or blocked fuel filters?

Your bang on the money ,turbo head is lower compression,we are going to rebuild original head to save any further aggro,many thanks.

Your bang on the money ,turbo head is lower compression,we are going to rebuild original head to save any further aggro,many thanks.

You're welcome. The only thing is if the valve stem guides have been damaged they might be hard to get out of the head or even have damaged the head its self, i.e. slotted the valve guide holes.

Good luck with it any way.

Here's a picture of what happens when a two vale 4 cylinder (bored out to 1200 with high comp pistons) bike engine drops a valve whilst doing 10,000 rpm.