Technical Fitting the head back on and the shims!!

[oldskoolmk1unoturbo]

I've put my cylinder head back on after i've had it skimmed,

and i have a problem as when i took the head off i didnt label up the shims, can i just put them back on and hope for the best? what do i do?

Alex could you help?

Thanks

Mark.

 

[SteveNZ]

put them back anywhere, then measure the clearence and figure out where they should go. you may need to change a few as they may have been out originally anyway.

 

[dave]

put um back any where measure the gaps then swap them around and get it right

 

[alexGS]

As Steve says, and as Dave says... just put 'em in anywhere to start with

But measure the thickness of the shims first before you put them in (or read off the numbers, they're usually accurate since they don't wear much) - and write them down with space for writing measured clearances etc. and doing your working-out later. I find that writing everything down is the only way to go - too many mistakes otherwise, like putting in a thicker shim when actually a thinner shim was required, and without the numbers in writing, it can be really confusing!

Then install them and measure clearances. That way, you can work out which shims need to be changed and to what, and you know which tappet to get the required shim from. Clearances are 0.40mm inlet, 0.45mm exhaust. It can be very tedious to get them exactly right, +/- 0.05 is good enough in my opinion, but I always end up trying for better anyway...

Unless you have been saving these special coins since you were a little boy, you'll probably have to visit a FIAT specialist who will no doubt laugh at your attempts and tell you to do it some other way...

BTW thanks for asking
meanwhile I'm still waiting for advice on my Uno Turbo's low-idle speed when cold... basically it tends to stutter to a halt if the throttle is sharply closed... maybe I'll start a new thread

-Alex

 

[oldskoolmk1unoturbo]

Thing is alex i was told that the cam is not standard, it apparently has a piper fast road cam but i have no proof of this apart from it sometimes runs lumpy at idle.

would the shims still be the same size?

 

[alexGS]

Hmmm... non-standard cams are sometimes specified with tighter clearances, e.g. 0.20/0.25, but without any info I'd start with standard clearances as it can do no harm that way.

Turbocharged engines are supposed to have non-symmetrical timing (or so I've read), so let's hope the cam was intended for a turbocharged engine... also I don't think it would be a question of 'sometimes' idling unevenly - it would be like it all the time... all the usual culprits still apply (vacuum leaks, fuel pressure, airflow meter...)

-Alex

 

[unoracer]

I just thought I would throw this one in! (sorry if a bit off topic tho!) When I was having my uno race 1500cc engine rebuilt recently, the engineer (who is used to building race engines) noticed that with very little machining of the cam carrier bores, BMW M3 buckets and shims could be used, which are an awful lot lighter! Having said that, the wall between the central two bucket 'bores' would have been a tad on the thin side, and so in the end I did not take the risk due to using engine for racing!

 

[unoracer]

Thing is alex i was told that the cam is not standard, it apparently has a piper fast road cam but i have no proof of this apart from it sometimes runs lumpy at idle.

would the shims still be the same size?

If you look on the Piper cams website, they give you the required valve clearances and other data for the various fiat cam profiles.

Also, if you have the camwheel removed, you should be able to see the Piper markings/profile number on the end of the cam if it is from piper, or poss other markings denoting Kent or other manufacturers etc,