shim question

[wengr]

so I'm trying to straighten out my clearances before putting my head back together. I checked clearances before I took it apart. I've miced the current shims, done the calculations, and it seems that none of the sizes I need are offered by vendors. most vendors shims start at around 2.5mm and thicker, but what I need are more like 2mm + -. So what is most likely going on here:

1 I see in a manual now that the cam lobe should be at a right angle to the valve when checked? I did not do this, I had the lobe pointing up in line with the valve stem. did I get bad readings?

2 cheapo harbor freight digital micrometer is inacurate? there was no reference piece included.

3 overzealous valve lapping by PO's mechanic? seat and valves did not look odd in any way

4 ? any advice appreciated

[engineerted]

What? We need some more information. So you took your head apart and re-assembled, did you have the seats re-cut? or what? What were the clearances before stripped it down?

If your clearance are too tight because of the re-cut seats you have a couple of options,
1. grind down the valve stems to bring back the clearances
2. install two cam box gaskets. Guy Croft's book makes reference to this, you can stack up to three.

Ted

[ventura ace]

Don't use any shims thinner than the height of the lip of the shim bucket, or else the cam will hit the shim bucket and you will have a mess. That's why the vendors don't offer and thinner than XXX dimenesion.

[wengr]

What? We need some more information. So you took your head apart and re-assembled, did you have the seats re-cut? or what? What were the clearances before stripped it down?

If your clearance are too tight because of the re-cut seats you have a couple of options,
1. grind down the valve stems to bring back the clearances
2. install two cam box gaskets. Guy Croft's book makes reference to this, you can stack up to three.

Ted

I removed and stripped the head for an overheating issue, and figured I would check and adjust the clearances while it's off. there was no prior problems with the valve train. the clrearance I measured before I took it apart were:

intake .011 to .015

exhaust .011 to .015

there has been no modification to the seats or valves at this time. I want to even out and open up the clearances to .015 intake, and .018 exhaust. So I would need shims thinner than what's there now, however no one is listing any as thin as mine, no less thinner - they use mm, mine are all around 2mm and the vendors seem to start at 2.5mm. Alvon, my 2mm shims are sitting higher than the buckets by at least 25% or so iirc. I suspect I've made a simple error somewhere but can't find it yet.

[wengr]

I should add that the car is new to me so I do not know the extent of any previous head work. the valve seats could certainly have been cut before. I can't tell. I can say however that if this is the case, whoever did it somehow found some shims in the correct size range, as I have 8 shims all around 2mm.

[ventura ace]

I should add that the car is new to me so I do not know the extent of any previous head work. the valve seats could certainly have been cut before. I can't tell. I can say however that if this is the case, whoever did it somehow found some shims in the correct size range, as I have 8 shims all around 2mm.

This all sounds very odd to me, unless Pinninfarina (83 - 85) did something different with the shim buckets than all the earlier years productions of spiders. All the shim buckets that I've seen have an edge of roughly .120" (about 3mm), and the thinnest shims that I've seen are slightly over 3mm. I wonder if somebody ground the shim bucket edges down, or was able to use shim buckets from a similar engine (Volvo??) that has different buckets. In any event, Fiat shims are not normally stocked that thin. You may want to check with Volvo.

Alvon

[joelbert2k]

I admit that I'm not the most experienced on these engines but those shims seem awfully thin to me. Is that normal?
I just did my valves this weekend and they ranged from 3.55mm to 4.30mm. Are you measuring these or reading the numbers off the shims?
Joel

[wengr]

I admit that I'm not the most experienced on these engines but those shims seem awfully thin to me. Is that normal?
I just did my valves this weekend and they ranged from 3.55mm to 4.30mm. Are you measuring these or reading the numbers off the shims?
Joel

Joel, thanks for the reply. I am measuring them, albiet with a harbor freight micrometer. I'm measuring in inches and multiplying the results by 25.4 in order to obtain mm that the vendors require. all my shims calculate out to about 2mm.

[wengr]

I should add that the car is new to me so I do not know the extent of any previous head work. the valve seats could certainly have been cut before. I can't tell. I can say however that if this is the case, whoever did it somehow found some shims in the correct size range, as I have 8 shims all around 2mm.

This all sounds very odd to me, unless Pinninfarina (83 - 85) did something different with the shim buckets than all the earlier years productions of spiders. All the shim buckets that I've seen have an edge of roughly .120" (about 3mm), and the thinnest shims that I've seen are slightly over 3mm. I wonder if somebody ground the shim bucket edges down, or was able to use shim buckets from a similar engine (Volvo??) that has different buckets. In any event, Fiat shims are not normally stocked that thin. You may want to check with Volvo.

Alvon

that's a good idea Alvon, maybe someone cut the seats, then unable to find proper shims, ground down the bucket tops and the original shims to fit? the shims however don't look overly thin to me. I did some 1300 and 1500 sohc fiats many years ago and don't recall the shims being dramatically thicker. also the valves did not really look like they are really seated down in excessively. for example you could not resurface the head with the valves installed, as the shave would hit the edge of the valves, which actually protrude below the head surface. I could have an error in my methods or math, or I could have a bad micrometer. if I can't figure it out soon I try to get some pics up.

[pope]

how about a pic to solve everything

[Europa]

Wengr, I just rebuilt the head on my '83. I don't recall the shims being that thin either. The thinnest one I used was 0.130in or 3.30mm.

I second Pope, please post pictures of the valve train and if possible close up pics of the tappet.

Here's a shim conversion chart from IAP.
http://www.international-auto.com/fiat- ... rsions.cfm

Here's the information from IAP for the tappets.
http://www.international-auto.com/index ... sid=895494

[ventura ace]

I could have an error in my methods or math, or I could have a bad micrometer. if I can't figure it out soon I try to get some pics up.

To eliminate math error or bad reading with your micrometer, if you stack a US quarter and dime together, the thickness is about .125", or slightly more than 3mm. That's about the thinnest shim that would be used for a normal Fiat shim bucket.

A

[mbouse]

2 cheapo harbor freight digital micrometer is inacurate

any advice appreciated

sorry, i tried. but i could not resist. tried for a couple of days in fact.

as many times as i have warned.... serves you right. Those Chinese rice paddy farmers are laughing at you now.

[wengr]

ok here are some pics.



hope that worked, as you can see guys the shims are thicker than a quarter and a dime, and do stand out of the buckets some. I see no machining to the buckets. While I had this out again, in a momentary flash of common sense, I closed the mic all the way and it shows -3.78mm as opposed to zero. the largest I can get the quarter and dime to measure is .978mm I guess I'll be revisiting harbor freight. many thanks for all the helpful replies, at least it's the mic screwed up and not my seats.

[kilrwail]

Isn't there a "zero" button on the micrometer?