Piston to Valve Clearance - I Head / Regular Eta Short block / Schrick 272

[e30sh]

Anybody run this combo and have any issues? Head is close to stock thickness, just a cleanup resurface.

[TobyB]

Use some modelling clay and find out for sure!

It's cheaP! All the KidZ are doing it now...

t

[jeffnhiscars]

Use some modelling clay and find out for sure!

It's cheaP! All the KidZ are doing it now...

t

Do you use the old HG and bolts when claying ?

[e30sh]

Do you use the old HG and bolts when claying ?

Yes.

A dial indicator with a soft valve spring is the best way.

I figured someone had run this combo to save me the trouble.

[TobyB]

I've even left the head bolts loose- if it doesn't jump the first time 'round,
tighten 'em finger tight, go 'round again.

What do you indicate? I just section and measure the clay...

t

[ThatOneEuroE30]

I've even left the head bolts loose- if it doesn't jump the first time 'round,
tighten 'em finger tight, go 'round again.

What do you indicate? I just section and measure the clay...

t

Clay method is useless above 6500rpm though. You need an actual measurement for high revving motors, with a dial indicator and a degree wheel on the crankshaft. For a street motor the clay method will do but for a motor that will spend its time up top its best to use the dial method.

[e30sh]

What do you indicate? I just section and measure the clay...

t

Old head gasket / used bolts @ ~20 ft-lbs. Motor timed as you are going to run it. Dial indicator set 90 deg to retainer. Rotate engine and look for the close spots. With a weak valve spring push valve down by hand. 0 the indicator when it hits the piston, let go and read the gauge.

[TobyB]

Clay method is useless above 6500rpm though.

Yeah, the clay flies off the tops of the pistons.

Otherwise, the 3 M10's I've built had no problems to 8k.
Yes, you leave .060" minimum (.080" if you're paranoid)
but if you have that much rod stretch or crank flex, your last problem
is the valve meeting the piston.
And if your valves float at all, then the rocker's already broken.

Ah, yes, I see- 'indicating with the valve'- I did that a couple of times
just to verify that the clay wasn't lying....

t

[digger]

there is nothing wrong with the clay method in fact it kind of tells you radial clearance to which is not something that should not be neglected especially with aftermarket pistons. sure you can only do it to within about 0.1-0.2mm accuracy but that close enough when youre targeting atleast 1.5mm.

if you have an issue at high rpm the valve springs are incorrectly chosen in which case you cant measure for that anyway