Head/Block Flatness Check within .001"

[Larry Brumfield]

Head/Block Flatness Check within .001"

When a head or block is significantly warped or not flat, thicker feeler gauges and a straight-edge placed directly on the gasket surface are all that's necessary to determine the degree of flatness. However, if the surface is closer to flat, thinner gauges have to be used.

Feeler gauges for most of you do-it-yourself Model A 'ers get as thin as .0015" and that's it. Gauges in this area (.0015, .002) bend and damage easily and are difficult for some people to use even when they don't bend while poking them at the base of a straight edge trying to measure flatness. Here's a better way which will give you closer to machine shop accuracy using thicker feeler gauges that won't bend so easily and are easier to work with:

Instead of laying the straight-edge directly on the head or block surface like most of you do, lay the straight-edge directly on top of a couple of feeler gauges...... Yes, you heard correctly.

Obtain two feeler gauges of the same thickness, say .006" for example. (You can choose whatever thickness you want as long as it's considerably thicker than the ones mentioned above.) Place one of the .006" gauges at the very end of the head or block on the gasket surface near the head or block's edge with the gauge laying flat. Place another .006" gauge at the opposite end of the head or block in the same manner. In other words, one at the front and one at the back right at the edge.

Place the straight-edge over the head or block surface and allow its edge to come down and rest directly on top of the feeler gauges.

The feeler gauge at either end is now supporting the straight-edge. In the center of the head or block there is now a gap between the gasket surface and the straight-edge.

Obtain another .006" feeler gauge and attempt to slide it under the straight-edge in the center of the head or block. If it slides under the straight-edge then go up to the next size, .007", and try again.

If the .007" feeler gauge won't slide beneath the straight-edge ...... then you know that the head or block gasket surface is flat within a .001 of an inch!

Perform the measurements again diagonally.

If the 006" won't go then try the next size down, i.e., .005". If the .005" slides then the surface is high in the center as compared to the ends within a .001 of an inch.

Make sure the surface is clean and smooth where you place the feeler gauges. Also make sure there are no burs or nicks on the straight-edge.


Larry B.

 

[Ron/IA]

Larry - There's always another way. Thank you for a different procedure that gets the same results. Sometimes we "rookies" can't see the forest for the trees.

 

[kevinmac/toledo]

hi larry; machine shop wher e i used to work, we would use .002, or .003 as a determining gauge to find out if the heads we were doing were warped.... ,.001 ,a little too tight??? the gaskets take up some, and it aint a drag car

 

[Larry Brumfield]

hi larry; machine shop wher e i used to work, we would use .002, or .003 as a determining gauge to find out if the heads we were doing were warped.... ,.001 ,a little too tight??? the gaskets take up some, and it aint a drag car

It's @#@!% ridiculous to have to re-explain every post a person makes.

The purpose of my post was to demonstrate a simple method of measurement for those who desire closer tolerances than the typical work done by some run-of-the-mill jockey at some half-*** machine shop.

Moreover, I made no mention of it but .003 of an inch on a Model A with a high compression head can be a significant amount of clearance when combined with a block that's out .002 to .003. The Model A's size and number of the studs and nuts were not designed for high compression heads. Consequently, flatter surfaces and higher torque amounts help assure longer lasting gaskets.

 

[glenn in camino]

Thanks Larry. Good method for us newby mechanics.

 

[George Miller]

Head/Block Flatness Check within .001"

When a head or block is significantly warped or not flat, thicker feeler gauges and a straight-edge placed directly on the gasket surface are all that's necessary to determine the degree of flatness. However, if the surface is closer to flat, thinner gauges have to be used.

Feeler gauges for most of you do-it-yourself Model A 'ers get as thin as .0015" and that's it. Gauges in this area (.0015, .002) bend and damage easily and are difficult for some people to use even when they don't bend while poking them at the base of a straight edge trying to measure flatness. Here's a better way which will give you closer to machine shop accuracy using thicker feeler gauges that won't bend so easily and are easier to work with:

Instead of laying the straight-edge directly on the head or block surface like most of you do, lay the straight-edge directly on top of a couple of feeler gauges...... Yes, you heard correctly.

Obtain two feeler gauges of the same thickness, say .006" for example. (You can choose whatever thickness you want as long as it's considerably thicker than the ones mentioned above.) Place one of the .006" gauges at the very end of the head or block on the gasket surface near the head or block's edge with the gauge laying flat. Place another .006" gauge at the opposite end of the head or block in the same manner. In other words, one at the front and one at the back right at the edge.

Place the straight-edge over the head or block surface and allow its edge to come down and rest directly on top of the feeler gauges.

The feeler gauge at either end is now supporting the straight-edge. In the center of the head or block there is now a gap between the gasket surface and the straight-edge.

Obtain another .006" feeler gauge and attempt to slide it under the straight-edge in the center of the head or block. If it slides under the straight-edge then go up to the next size, .007", and try again.

If the .007" feeler gauge won't slide beneath the straight-edge ...... then you know that the head or block gasket surface is flat within a .001 of an inch!

Perform the measurements again diagonally.

If the 006" won't go then try the next size down, i.e., .005". If the .005" slides then the surface is high in the center as compared to the ends within a .001 of an inch.

Make sure the surface is clean and smooth where you place the feeler gauges. Also make sure there are no burs or nicks on the straight-edge.

Larry you did good a lot of good information. I also like .001 or less. Country Boy George


Larry B.

Larry you did good a lot of good information. I also like .001 or less. Country Boy George