Trouble Idling When Cold

[SumpBuster]

You adjust gap by changing shims? You can't just turn a nut onto of the valve and tighten it down? That's how my friend and I did it on his diesel marine generator. Do you have to pull the cam to adjust? Or is that something else, and I'm not connecting the dots here?

I had a Cosworth Vega with bucket tappets and shims in the recess, but Chevy had a 'fork', and you would rotate the cams so the tappet you are working on was pressed down and then the tool would hold it down while you removed the shim and put the correct amount back in.

 

[musselman]

Yes unfortunately the cams need to come out to change shims, this is new territory for me so it may take some time. I have attached the excel sheet I used to record all of my valve clearances for reference. I still need to update it with the current shims to figure out what new shims are required.

 

[steveg_nh]

So the shims just wear out over time? Too bad they just weren't adjustable.

 

[musselman]

No the shims don't really wear at all, the valve and seat wear causing the valve to protrude further into the head which reduces the clearance between the cam and bucket.

 

[SumpBuster]

No the shims don't really wear at all, the valve and seat wear causing the valve to protrude further into the head which reduces the clearance between the cam and bucket.

Yeah, the cosworth shims were pretty hard!

 

[steveg_nh]

Ah I see. Thanks for explaining that!

 

[musselman]

Got the cams out and removed the buckets and shims. Should I measure the shims that were in there or do they not wear? It's going to be tricky to get within spec on some valves since the replacement shims only come in 0.05mm increments.

 

[steveg_nh]

Holy crap that is surgery!

 

[SumpBuster]

Got the cams out and removed the buckets and shims. Should I measure the shims that were in there or do they not wear? It's going to be tricky to get within spec on some valves since the replacement shims only come in 0.05mm increments

Got the cams out and removed the buckets and shims. Should I measure the shims that were in there or do they not wear? It's going to be tricky to get within spec on some valves since the replacement shims only come in 0.05mm increments.

Absolutely mic them, especially where they made contact and adjust according to what you measured.

 

[SumpBuster]

Holy crap that is surgery!

A work of art!

 

[steveg_nh]

Very satisfying too!

 

[musselman]

Got my replacement shims last night and got the cams back in. The new measurements look good, just need to wait for my gaskets so I can reassemble. Measurements are in the spreadsheet below. I'm anxious to see how it will run

 

[musselman]

Added a picture to view the measurements easier.

 

[TBay Sledhead]

I'm having a little trouble interpreting your data. What are the no represent in the old shim new shim columns, is that standard or metric or some kind of part no.

 

[musselman]

The shim measurements are shown in hundredths of a mm, this is the format that is shown on the shim itself, for example a 175 shim will measure 1.75 mm.