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DOHC advice needed - nlc NOW WITH PICS

Posted: Wed Jul 28, 2010 12:14 am
by ClarkyBoy
Righto so, at gue moment I'm in the process of changing the head on my e30 Beemer, the gasket needed replacing and I managed to pick up a lowish mile engine las week for spares that has a great ported/polished head on it, so I'm now at the stage where I have both heads off. Insert joke wherever.

I was told by the previous owner that when he put the head back on the engine after the polishing was done he reconed he got the timing a little off, the valves look visually fine with no major marks on the pistons, can I assume that they will be ok, bearing in mind the engine was only ever turned over and not actually run? Also, now that I have both of the identical heads on the bench with the cams sitting in tdc on both why do the valves not appear to be in the same position on both heads? Surely they should both look the same at the bottom of the head if they both look the same at the top???


Or can anyone local come over to give second opinion? I'm maybe missing something!
Can any one advise?

Thanks

Re: DOHC advice needed - nlc

Posted: Wed Jul 28, 2010 7:55 am
by Rich H
Beware that hydraulic tappets can do funny things when left. When you rebuld a dry K head all the valve sit open for a while...

They should be identical - can you get some pics?

Do these heads have the Vanos veriable valve timing gubbins?

Re: DOHC advice needed - nlc

Posted: Wed Jul 28, 2010 2:50 pm
by ClarkyBoy
ok, i have managed to get some pictures uploaded now, crap quality iphone ones may i add - my hands were waaaay to filthy for my camera!

original head - valves slightly open circled in red
Image

new head - again valves a little open circled in red
Image

top veiw with cam positions - both @ TDC

Image
Image

also, is there anything i should be aware of if i want to keep my cams + followers etc, from my original head and put them on the new one? purely because they looka lot cleaner as the engine was running until sunday and not sitting in a garage gathering moisture?

thanks.

Re: DOHC advice needed - nlc NOW WITH PICS

Posted: Wed Jul 28, 2010 9:11 pm
by Gourlay83
take the cams out and turn the head upside down, making sure its level. fill combustion chamber with a fluif ie anti freeze. leave it for a night and check that no fluid escapes into the ports.

A simple check for your valves/seats

Re: DOHC advice needed - nlc NOW WITH PICS

Posted: Wed Jul 28, 2010 10:28 pm
by Rich H
I think what you have is a bit of engineering tolerance
At TDC there is a bit of overlap of the valves but the cams aren't always spot on.
Basically I think it's the cams that are out relative to the pulleys.
You could measure lift at TDC with a DTI if you were worried but I'd not worry about it. If you wanted you could swap the cams over.

Re: DOHC advice needed - nlc NOW WITH PICS

Posted: Thu Jul 29, 2010 12:22 am
by ClarkyBoy
Cheers for the input guys, I will gt on the case with your test Alan, all going to plan it will be back. On the car come Sunday.

Saw your car at union square tonight, glad your doing well enough to be getting out if it was you and Jen. :thumbsup