Alfa spider 1750 valve shims (help) - Alfa Romeo Bulletin Board & Forums

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post #1 of 19 (permalink) Old 04-15-2017, 05:28 AM Thread Starter
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Alfa spider 1750 valve shims (help)

Built my alfa 1750 series 2 motor (1971), I had some issues with what I'd done namely it ran poorly.
I decided to take the engine to a reputably rebuild shop near me and as I'm a fortune into this car which besides the engine is as new I decided to have a full build and race balance.
I bought all the parts from Classic alfa, new crank shells, new pistons and liners, new oil pump, new water pump etc, everything was given to the builder including gasket sets etc.
The head had already been rebuilt by another local specialist and was supurb, I told the latest builder this and left them to it.
I fitted the rebuilt engine and it ran terrible, I put it down tocarb settings etc and tried to get the setup better, but i then noticed a lot of oil on the floor beneath the car, I mean a lot, I ran it again to see where it was coming from and honestly looked like it was being squirted out of an oil can.
I stripped the head off and changed the head gasket, the builder had missed the o-ring out of the build, bit annoying and I told them so and carried on.
Engine now oil and water tight and it ran better, not perfect though, bogged down when setting off and a bit lumpy, a mate suggested doing a compression test which I did, no1 @ 175 psi, no2 @ 175 psi, no3 @ 175 psi and no4 @ 90 psi.
My mate did a leak down test but while working on this we noticed that the inlet valve had no gap and was always open, all the other inlets and exhaust valves have perfect gaps so its puzzling.
I have stripped the inlet cam out today and I need a shim cap of .050" or less and after looking at classic alfa I note that the smallest shim they offer are .059", I also have a spare head (for parts) and the caps in that are almost all the same and about .020" bigger than what I need.
Now then, I could easily grind one but I don't understand the issue I have, I'm tempted to pull the head again just as a precation that the head is not getting pulled off the valve.

Can anyone offer advice or guidance, I don't mind dealing with issues but I now need to move on from working on this project, its been never ending problems.

Andy
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post #2 of 19 (permalink) Old 04-16-2017, 11:14 AM Thread Starter
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I'm still not exactly sure what happened in my engine but I got a little bit lucky by investigating.
Stripped the inlet cam out, I noticed that the cam followers where now actually now at the same height, I measured then and they where.
I could't understand why the bucket had stuck so high that there was no clearance between it and the cam, I looked at the shim, all seemed ok and the valve and collet at first glance looked ok.
A pal came round with a snapon camera, we looked at the valve through the inlet port thinking the seat had come loose but everything was ok.
I'd already decided the head was coming but before I did I noticed some damage to the collet holding the valve in, I don't know how this damage happened it must have been assembled by my engine builder like that but it must have been so close to dropping a valve.

Andy
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post #3 of 19 (permalink) Old 04-16-2017, 11:56 AM
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Cam experts here know that problems are always caused by bad, Alfa camshafts....
You must replace with RJR cams.

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post #4 of 19 (permalink) Old 04-16-2017, 12:55 PM
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I have boatloads of shims if you're needing specific sizes. PM me if you want to talk further.
I have never used other than Alfa stock cams, 40 years of Alfa ownership, a total of like three bad lobes in that time. Had a bad lobe on a Fiat 124 cam too, so it's not exclusive to Alfa. All by way of saying, there are a variety of ways to go, and various opinions on cams.
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post #5 of 19 (permalink) Old 04-16-2017, 01:14 PM
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The head had already been rebuilt by another local specialist and was supurb, I told the latest builder this and left them to it.
Well, it sounds like the head wasn't "supurb" after all. Since you told the second specialist that the head was fine, he probably took your word for it; while it sounds like the second guy did make some mistakes (like leaving out the O rings!), I don't think you can pin the #4 valve problem on him.

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I need a shim cap of .050" or less and after looking at classic alfa I note that the smallest shim they offer are .059".... now then, I could easily grind one but I don't understand the issue I have
The issue is that the shop who installed the valve seats just set their heights willy-nilly, not taking into account that Alfa valve shims only come in a certain range of thicknesses. A competent Alfa head shop will know this and ensure that the valve-to-cam distance allows the use of common shim sizes.

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I noticed some damage to the collet holding the valve in, I don't know how this damage happened it must have been assembled by my engine builder like that
OK, so I think you are now saying that you don't need a shim < .050" because a damaged valve keeper was holding the cam follower too high. So the fix may be as simple as properly assembling that valve, and using shims within the normal range of thicknesses. You may need to pull the head again to re-attach the valve keepers. Set the valve clearances before re-installing the head to make sure that all is well.

Jay Mackro
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Last edited by Alfajay; 04-16-2017 at 02:22 PM.
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post #6 of 19 (permalink) Old 04-16-2017, 04:31 PM
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Yes, valve keepers need to be pretty solidly in place. Sounds like the head might need to come back off. And maybe a different shop to evaluate? You are where?
I had the head off my MGA Twin Cam in the 90s, wrong valve keepers from a 60s rebuild, half moon ones in wedge slots of vice versa, I forgot, and it hadn't come apart and blown up, but it should have. Not something to take a risk on.

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post #7 of 19 (permalink) Old 04-17-2017, 11:40 AM Thread Starter
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Well, it sounds like the head wasn't "supurb" after all. Since you told the second specialist that the head was fine, he probably took your word for it; while it sounds like the second guy did make some mistakes (like leaving out the O rings!), I don't think you can pin the #4 valve problem on him.

No mate, fair point you make but I think its down to the second builder, he told me they stripped the head and lapped the valves, there where other really hamfisted evidence in the form of hammer rash on the top of one the cylinder liners, I had to take a chance on it sealing when I reassembled the head when he had missed the o-rings out.



The issue is that the shop who installed the valve seats just set their heights willy-nilly, not taking into account that Alfa valve shims only come in a certain range of thicknesses. A competent Alfa head shop will know this and ensure that the valve-to-cam distance allows the use of common shim sizes.

Alfa head shops aren't on every street corner in the UK, tell the truth I wouldn't know where to take it if I were to get it done again.
As it happens when I took the engine to the second rebuilders I checked the clearances and they where all correct.



OK, so I think you are now saying that you don't need a shim < .050" because a damaged valve keeper was holding the cam follower too high. So the fix may be as simple as properly assembling that valve, and using shims within the normal range of thicknesses. You may need to pull the head again to re-attach the valve keepers. Set the valve clearances before re-installing the head to make sure that all is well.
I have pulled the head, there is a small amount of damage to the valve stem after the groove for the collet so this needs to be replaced, the collet was very damaged, it has a groove worn in the top of one collet half which is almost exactly the diameter of the shim cup (although I can see no damage to that) and a small amount of metal has broken off the bottom of the collet.

I will be replacing the valve with a new one, replacing the valve stem seal as I think the damaged valve will have ruined it when I removed it, I have a set of collets and a spring cup from another head I have for spares and I will lap all the valves and check the clearances before I resemble it, hopefully this will be the end of my woes.

Andy
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post #8 of 19 (permalink) Old 04-17-2017, 12:15 PM Thread Starter
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Originally Posted by Andrew View Post
Yes, valve keepers need to be pretty solidly in place. Sounds like the head might need to come back off. And maybe a different shop to evaluate? You are where?
I had the head off my MGA Twin Cam in the 90s, wrong valve keepers from a 60s rebuild, half moon ones in wedge slots of vice versa, I forgot, and it hadn't come apart and blown up, but it should have. Not something to take a risk on.

Andrew
Hi Andrew,

I'm in the UK.
I think the surprise was it getting back in where it had come out, what I did notice was was that all the grind marks on the valve top where straight and all the other valves had circular marks from spinning, which backs up that the collet was holding it up.
Anyway, I sort of got lucky that it didn't drop a valve and that I've now got the opportunity to sort it out.

Andy
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post #9 of 19 (permalink) Old 04-17-2017, 04:27 PM
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The way to grind a shim is put it on the end of a spare valve stem and present it to the side of a bench grinder. The shim will rotate as it is ground. It requires a light touch unless you are removing a lot of metal so stop frequently to measure the thickness. You will soon get the hang of it. Be careful when you are backing off from the grind stone as the shim may be launched across your workshop if one edge of it catches the stone.

Ed Prytherch
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A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #10 of 19 (permalink) Old 04-17-2017, 04:45 PM
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I did notice was was that all the grind marks on the valve top where straight and all the other valves had circular marks from spinning, which backs up that the collet was holding it up.
Here's one theory: The shop recognized that the "problem valve" was protruding too high for a standard valve shim to work. Instead of re-setting that valve's seat, they just used a die grinder to remove material from the top of the valve. The problem with that procedure is that the cup now bears on the valve keepers, rather than on the valve itself, and after a few revolutions will knock the keepers loose.

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Alfa head shops aren't on every street corner in the UK, tell the truth I wouldn't know where to take it if I were to get it done again.
No, and they're not on every street corner here in southern California either. I drive an hour each way to get to a shop that I am confident knows what they are doing with Alfa heads. And this is an Alfa-dense area; I have no idea what people in other locales do.

From my experience, a generic auto machine shop that works on overhead cam Toyota/Nissan/Honda can do an adequate job on Alfa blocks/cranks/rods/pistons. But they can't seem to grasp what it takes to properly set up Alfa heads.
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'65 Guilia Sprint GT
'67 Duetto
'91 164L

Last edited by Alfajay; 04-17-2017 at 04:52 PM.
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post #11 of 19 (permalink) Old 04-17-2017, 06:54 PM
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I have no idea what people in other locales do.
Ship it to someone you trust , probably in another part of the country.

Ed Prytherch
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85 GTV6 3L
76 Suzuki GT500

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #12 of 19 (permalink) Old 04-17-2017, 09:50 PM
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Ship it to someone you trust , probably in another part of the country.
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post #13 of 19 (permalink) Old 04-19-2017, 01:05 PM Thread Starter
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Here's one theory: The shop recognized that the "problem valve" was protruding too high for a standard valve shim to work. Instead of re-setting that valve's seat, they just used a die grinder to remove material from the top of the valve. The problem with that procedure is that the cup now bears on the valve keepers, rather than on the valve itself, and after a few revolutions will knock the keepers loose.



Definitely had all new valve seats, you can't imagine how damaged the head was when they started on it.
The job they did on the head was very nice, I know nice when I see it I own a machine shop and employ 24 skilled machine men in it.
I'll post a picture of the collet at some point as it is a genuine mystery, I thought about whether it had been rubbing on the cup as you say and this had knocked the keepers loose as you say but there are no marks on the cup (not that much of a surprise as I guess its very hard) but also other than damage to the side of the keeper there aren't any running grinding marks round the top of the keepers so I don't think its done that.
My only othere theory is that somehow the damage was done by a hamfisted fitter just putting a damaged collet in, I don't think this is the case, for the minute its a mystery.
I'll build it again at the weekend and hopefully all will be well, I have to try and check and set the valve timing with the engine in the car which I really wanted to avoid.
I'll put photos up when clear the decks a bit.
Thanks for the help and advise.

Andy
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post #14 of 19 (permalink) Old 04-19-2017, 01:12 PM Thread Starter
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The way to grind a shim is put it on the end of a spare valve stem and present it to the side of a bench grinder. The shim will rotate as it is ground. It requires a light touch unless you are removing a lot of metal so stop frequently to measure the thickness. You will soon get the hang of it. Be careful when you are backing off from the grind stone as the shim may be launched across your workshop if one edge of it catches the stone.
Really, I'm guessing dressing the wheel nicely first?#
Any idea how thick the case hardening on the shims is? (or are they through hard)

Andy
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post #15 of 19 (permalink) Old 04-19-2017, 01:37 PM
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I'm pretty sure that there are two types of shims floating in the market, hard shiny steel type and copper or softer type... I was told to get the hard steel type and not the copper type during my adventures in $3 parts sourcing... another thing I was told was that the engine will tolerate .25 differences (the standard increment change in shim sizes).

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