So how do you check piston to valve clearance

[86T-Top]

Like the title says. I have a good idea on how to do it but a few questions.
- What do I use, is play doh cool? If not what can I use.
- How much do I put in there to start? Just lay it over the valve reliefs?
- Finally how much clearance do I need?

Combo - 351W, flat top pistons with valve reliefs, AFR 185 heads, lift is .523"
with 1.6 rockers.

Think I will have a problem with this cam and head?

Mario
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[Glen's 1965 5.0]

Info

I used play-Doh to do mine and it worked fine.

I am not up to speed on the clearances.

On a side note I did build a piston relief notcher from a magazine article that allows you to notch the pistons while in the block. Worked great!!!! Bad news is I only had to use it once when I install my World Product heads with 2.02 intake valves.

 

[meanroy]

I've always used regular kids modeling clay.

It is claimed by one major piston manufacturer that the optimum "quench" distance is .040. It depends on piston design though.
Here's a pretty good article from Silvolite.
Speedomotive says "if you are building an engine with steel rods, tight bearings, tight pistons, modest RPM and automatic transmission, a .035" quench is the minimum practical to run without engine damage."
The Speedomotive article referenced is pretty comprehensive, BTW.

(.035 is approximately what a "regular" head gasket compresses to when torqued down.)

There's a bunch of good info around, use Google.
Roy.

 

[12sec67]

I've always used regular kids modeling clay.

It is claimed by one major piston manufacturer that the optimum "quench" distance is .040. It depends on piston design though.

.035" quench is the minimum practical to run without engine damage."


(.035 is approximately what a "regular" head gasket compresses to when torqued down.)

so if you clay the piston while not using a head gasket and it clears or depresses the clay without topping off on the valve - then you would be fine?

 

[brianj5600]

Quench is piston to head. Piston to valve is different. Soft checking springs and a dial indicator for me. Clay is ok for checking radial clearance, but ptv should be done with a dial indicator. That cam will not even be close to hitting.