valve clearance

[Aziz]

Hi

I have fitted a 284/272 shrick cam to 325i head with eta 2.7 bottom.

Can any one tell me what the valve clearance's are for hot and Cold.

Haynes manual says 0.25 cold 0.30 hot, but this is on standard BMW cam.

If I try to set it as above the too tight crank wont turn.

Cheers, Imran

[Adammcf]

Not sure what they should be for that cam but I can confirm that on a standard cam its 0.25.

[Aziz]

Anyone else know??????????????

[TVRTASMIN]

Those valve clearances are correct, although larger clearances seem to give better power.
If you cannot turn the engine over by hand (plugs out), the valve timing is out or you haven't set the clearances properly and the valves are touching the pistons.
Hope you didn't crank over with the starter or you might have a few bent valves!

[Aziz]

I know 0.25 is for a standard cam.... thank for the info.

ok...I've set the clearance to 0.40 I'm confident its set right as I am getting alittle friction on the feeler gauge when checking clearance.

The crank is turning smoothly. The only reason for this is the cam is higher, longer lift so require more clearance.

I can't see why the pistons would touch the valves as the clearance is higher not lower.
I'm only turning the crank by hand.

I know someone must have this type of cam fitted you there 325i head.

Imran

[Gt6s]

Think you need to look at your valve to piston clearances, this job should be done during build up. TDC is your cams overlap period (Hot cams use longer overlap) If head has been skimmed it wont help either. On an interference engine you need to be so carefull. The cam manufacturers tappet clearances may also differ from OE but dont think tappet clearances are your problem

[Aziz]

Think you need to look at your valve to piston clearances, this job should be done during build up. TDC is your cams overlap period (Hot cams use longer overlap) If head has been skimmed it wont help either. On an interference engine you need to be so carefull. The cam manufacturers tappet clearances may also differ from OE but dont think tappet clearances are your problem

How do I check valve to piston clearance?

[TVRTASMIN]

How do I check valve to piston clearance?[/quote]

A blob of plasticine on the end of the valve, but should have been done before final build.

Have you used a dial guage and timing wheel and did your build include a vernier pulley or modified key on the standard pulley?

[Aziz]

How do I check valve to piston clearance?

A blob of plasticine on the end of the valve, but should have been done before final build.

Have you used a dial guage and timing wheel and did your build include a vernier pulley or modified key on the standard pulley?[/quote]

No I didn't use a dial guage or timing wheel, I have used the original pulley with no modified key.

I was under the impression that I would replace the original cam with the 284/272 open all valve clearances to full set crank TDC and cam to correct firing order 152624 and fit timing belt.
This is what I have done.
The engine is still out, I think I will have to take the head off again
1st to see if I've bent any valves.
2nd to go through the process of valve to piston clearance.

Can you talk be through the process.

Imran

[gcorky]

the valve clearance is to allow for expansion in the valvetrain fullstop-if your increasing clearance your gonna loose cam lift-sorta defeating the object.
.25 cold it is.
need to check the fundamentals within your engine dude.

[Gt6s]

Just thinking about your valve to piston clearance, some head gasket manufacturers (NOT ALL) make thicker head gasket options for the M20 intended for use with skimmed heads, worth a look into, may save you a bit of machining.
BMW may also supply the thicker gaskets.
Certainly worth looking into.

[chu346]

Have you used a dial guage and timing wheel and did your build include a vernier pulley or modified key on the standard pulley?

I'm on the standard pulley on my 2.7 with a 282/272 cam, would a vernier pulley make any difference?

[Aziz]

Thanks to all for info and help.

I took the head off and checked valve to piston clearance with plastatcine tappet set @ 0.25 and the pistons don't touch the valves (visa versa).

I refit the head and turned the crank and it turns fine may be alittle stiff, but I have fit a higher longer lifting 284/272 cam and it is new.

So once its running should be better.

Imran