Valve shims/gaps

[DaveT]

Have opened up a can of worms trying to get the 1750 engine (currently residing in my Giulia Sprint GTV) up and running properly. I've gone and done a naughty thing and bought a Twin Spark for it, but the plan is to get the 1750 running properly so I can register it and get it on the road and have some fun whilst I continue to bash my shins on the Twin Spark lying dormant in the shed for the next decade or two.

So the 1750's symptoms were: Hard to start, rough running - sometimes on 3 cylinders (fouling plugs), down on power, noisy tappets.

So I got rid of the dirty filter socks, checked compression (hot, throttle open: 198/205/170/210, not bad I thought except 3rd down a bit) cleaned/adjusted the distributor/points, new leads, adjusted the ignition timing, cleaned carbs/checked jets, replaced missing carb support rod, syncronized carbs, replaced leaking inlet manifold gasket and stripped studs, new spark plugs, new accelerator linkages/rods.

Result: idles and revs smoother, still hard to start, still noisy and still down on power.

So next was check the valve clearances, inlets .175/.280/.114/.178mm, exhausts .584/.330/.305/.553mm, hmmm.

Then I checked the numbers on the camshafts and realised it's running 2ltr (1052003) camshafts. Managed to source a very good pair of 10548 cams from a very good forum member (thank you Martyn).

Checked the clearances again and now I don't have any... the base circle diameters of the 10548 cams are 2.4mm(approx) larger than the 2ltr cams, hmmm.

So then I took the shims out and measured the gaps without shims and the resulting calculations are that I need the following size shims:

Inlet 1.050/1.200/0.925/1.350, Exhaust 1.375/1.450/0.825/1.375

The conclusion being that pretty much all of my valve seats have recessed or been ground/cut beyond their limits.

Now I know that ideally I should be taking the head off and having new seats put in, but I'm trying my best not to take the head off because I'd rather spend the money on the suspension, interior and the naughty Twin Spark. I know if I pop the head off I'll open much bigger cans of worms and before I know it I'll be stripping the engine and polishing things with toothbrushes...I've been here before with another car and 6 years later the car was on the road in concourse condition and I was in need of treatment for OCD.

So back to the shims, I read a post on the AlfaBB forum (from a bloke who seems to know a lot) that even though the lowest new shims available are 1.3mm you can get away with running shims down to about 0.760mm (.030"). The lowest I need to go is 0.825. What are peoples thoughts about running shims this thin? Does anyone have shims this thin that I can buy or swap for my fat ones, or will I have to grind my own down if I want to take the thin shim punt?

Phew that was long winded, sorry about the waffle.

Dave

[AikenDrum105]

HI Dave -  was that you snaffled the cheapie TS on ebay yesterday ?    wish I'd had somewhere to hide it.

It's interesting that all your seats would have recessed or been cut that deep...   I've experienced the other side of the coin on one engine where the valve stems were ground down a little to allow clearances with the existing shim set...       You get an interesting problem there as some shims have deeper skirts than others and ride along on the top of the collets instead of the valve stem... eeek   Still a fun dodgy brave MacGyver option if you're just trying to get a few more miles out of the engine in it's current trim.   Might be entertaining cleaning all the ground off material out of the head afterwards...    Dont grind too deep on those sodium filled exhaust valves mind ....

another (pretty remote) possibility might be that you have oversized cam follower buckets installed (perhaps as a matched set to go with reground cams if the clearances are that much tighter )  .  I know you can mix and match followers a little too to get more options with your existing shims when required... if you pop one out and measure it's thickness I could compare with some I have in the shed...  see if it's stock-ish

I have a bag of shims you're welcome to swap in/out with (in box hill)  but I think only one of them has been ground down past 1mm....  there's an old surface grinder you can use too if that helps.   

USB endoscopes are $40 or so at jaycar / supercheap these days - stick one down the spark plug holes and see how deeply recessed the valves look...

a few options anyway,  I've probably missed something obvious - hopefully the other denizens of the forums will chip in

[DaveT]

Hey Scott, thanks for your very informative reply and your offer of shim swaps and surface grinding, I think I'll take you up on that...good opportunity to check out your Super too!

So my understanding is that to keep the old girl going for a few more miles I'm better off giving the thin shim thing a go rather than trying to shave a bit off the valve stems...not sure how this would be done in the car anyway without creating a serious mess??

Didn't realise there was such a thing as oversized cam follower buckets, I haven't got a caliper that will measure them...when I go to Supercheap to check this USB endoscope thingy, what the?! sounds like my kinda gizmo...I could see if they have a caliper thingy that will measure my buckets too.

Oh and no it wasn't me who bought the TS on ebay recently, mine's been sitting in the shed gathering dust and shin skin for a good while now.

Thanks again, be in touch.
Dave