[Kenth]

How can you check if the cylinder heads have been milled before?
Are there any reference points to measure against?
Are there any blueprint drawings for reference?

IMWTK

[Skip Fix]

Kenth I have used the distance from the deck to one of the end accessory bolts and compared to a known "virgin" head. If you have an identical virgin casting you can try measuring chamber depth but getting the exact same location can be difficult , even on the same head!

[Kenth]

Skip, thanks for your input!
I was thinking measure from deck surface to an intake bolt hole with a bolt mounted in the hole.
Wouldn´t all 1965-79 heads have the same distance?
Factory blueprints would tell if that´s the case.

[Formulabruce]

youll want to be sure the Intake side is equally milled so it all fits and you dont have to make it a 1 off engine.

[Kenth]

Absolutely, but if you bought used heads that you have no history on, how do you know how much is milled, if anything?

[Formulabruce]

Originally Posted by Kenth

Absolutely, but if you bought used heads that you have no history on, how do you know how much is milled, if anything?

probably need to bring to a shop that has experience with Pontiac heads, and or bring the specs, or a virgin head.
dry assembly "might" be able to tell if intake will be leak free too.

[PAUL K]

Originally Posted by Skip Fix

Kenth I have used the distance from the deck to one of the end accessory bolts and compared to a known "virgin" head. If you have an identical virgin casting you can try measuring chamber depth but getting the exact same location can be difficult , even on the same head!

This will give you an idea.

Looking at the depth on the countersink on the intake bolts that accept the gasket retainers will give you a good idea if the intake side of the head has been milled.

If the head was milled correctly the step for the valley pan to seal to will be the giveaway.

[grandam1979]

Could just cc the chamber’s.

[johnta1]

What heads are you working with?

The later heads with the stamped letter/digit would differ between each one.
The early ones like a 12 probably are the same, but different than a 13 head.

CC's would give you an idea if they are milled if one knows what they were stock.

[steve25]

In this area of any production iron head ( as in my first photo)I have always found to be .300” plus or minus .020” if the head(s) have not been milled .
If the heads have been run you should aways see minor rust pitting around the heads water passage holes in the deck, if not then that’s a sign that they have been milled.

The factory machining of the chamber is very
Accurate.
This means that if you CC one chamber in each head and then measure it’s depth as in my second photos, checking the depth of the other chambers in the same manor makes things easy.
If the depth of all the other chambers are .006” or less in variation then all of you chambers will be between 1 to 1.5 CC of each other.

[Joe's Garage]

Originally Posted by steve25

In this area of any production iron head ( as in my first photo)I have always found to be .300” plus or minus .020” if the head(s) have not been milled .

We've always used chamber depth, measured like you, as an indicator of milling.

Like you said, Pontiac heads are VERY consistent with chamber sizes/depths.

[Skip Fix]

Steve I will disagree with you. Here are similar measurments but to ne consistent at the edge of the intake vale to the deck on the heads I had at the house that day.

#614/SR 0.073

72cc E head 0.104

#16&62 0.137

#670 0.140

6X-4 0.225

6x-8 0.282

4X-1H 0.345

So all totally different.

Using the depth at intake bolt is assuming every casting is the same from the bottom and around the heat crossover. I would bet there are variables there. To keep accessorizes the same form head to head form deck(assuming not a 301) it should be the same

[Formulas]

to me anyways its pretty easy to tell by the pits near the coolant passages and overall look of gasket surface exactly how deep the mill is hard to tell but virgin vrs worked? no coolant pits or very shallow? dead giveway

[Pav8427]

Are Pontiacs broached like other GM heads from that era?
Not hard to mistake a virgin head if broach marks are present.

[Pav8427]

Are Pontiacs broached like other GM heads from that era?
Not hard to mistake a virgin head if broach marks are present.

[65 Lamnas]

The late Jim Taylor (Phillipsburg, NJ) at one point told me he had some Pontiac cylinder head blueprints. The length of the head bolt bosses was called out including the nominal along with the tolerance. It'd be nice to have access to those numbers.

[Kenth]

Here is what i have found on some of my heads measuring from a long intake bolt unthreaded upper surface to deck surface.
Seems like 1.665" is the magic number for an untouched head deck surface.

Pontiac-heads Date mm / inch

#191 L080 41,3 /1.626 Been on a racing engine
#191 L080 41,3 /1.626

#191 A081 42,3 / 1.665 Original single

#191 L080 42 / 1.653 Clean planed surface
#191 A081 42 / 1.653

#614 ?041 41,7 / 1.641 Been on a racing engine
#614 No date 41,7 / 1.641

#7F6 A052 42,3 / 1.665 Original pair

#64 I089 42,3 / 1.665 Original pair

I would still like the see the Pontiac blueprints on Pontiac heads dimensions. Can´t believe they are so hard to get!