thoughts on head straightening

[Dave WM]

the head has between .003 and .0025 gap in the middle (presuming the straight edge is flat). I was thinking of bolting to a block with .001 spacers on the ends, then torqueing down. Perhaps figure a way to heat to say 300f, bake it for a few hours and check again.

[Dave WM]

hmm found this

 

[Dave WM]

more interesting tooling

http://www.bhjproducts.com/bhj_content/products/cylinderhdtooling/hsp.php

I guess machine shops are all over this. All I seem to hear about is milling the surfaces flat.

[Dave WM]

and some more interesting reading

https://www.enginebuildermag.com/2007/06/common-mistakes-to-avoid-when-resurfacing-cylinder-heads-blocks/

[madkaw]

I attempted this with a head that was .035 warped. My problem was having the correct fixture to bolt the head down . Since I was just playing around I used a cut up L24 block as the fixture . The block surface was also warped in the opposite direction, so it worked well for this instead of shimming a flat surface . I heated all this is a pottery kiln. 350 degrees for 2 hours worked well. There was rebound effect that made it difficult to predict . The next try my buddy forgot the head was in the kiln and cooked the head . That was my last attempt. 

With what little you are doing I would shave it . Hell, I could have shaved the .035 and been alright , but I wanted to play with trying to bending the head. Make sure you slow cool it and don’t bang on it until it is fully cooled. Don’t want to loosen any seats . The head I was trying was a e31 that was a head I didn’t care about . Some guys here said I was crazy for thinking this would work, but it’s right there in the How to Modify book.

[Dave WM]

I wonder if its SOP at shops to attempt some degree of straightening before the machining process are started?

I think one of the test should be a trial spin of the cam shaft (all rockers out of course) before starting anything. install it on the block, test spin, perhaps measure the torque required, remove it, do the same, just to see if there is a difference. Then if any machine work is done do the same, in reverse order. Would be some interesting data points.

[Dave WM]

sounds like I need to get that book! I have the rebuild book, maybe its in there, I just don't recall.

Edited August 2, 2019 by Dave WM

[madkaw]

1 minute ago, Dave WM said:

sounds like I need to get that book! I have the rebuild book, maybe its in there, I just don't recall.

This was all part of the welding process to close the chambers on some of the heads . Again, I would only consider this process if I had a head that I had a lot of money and mods in and was trying to salvage it after it was warped by overheating .

Shaving is the a better alternative if you have the room for P2V clearance - IMHO. Heads are plenty enough still, so unless you can straighten heads yourself, the expense of straightening is not worth it.

[David F]

Brooks Elliot straightens cylinder heads, located in Austin, TX

https://austincylinderhead.com/

On overhead cam engines, I would prefer to straighten the head as much as possible prior to machining so the camshaft is running as true as possible.

[Patcon]

53 minutes ago, David F said:

Brooks Elliot straightens cylinder heads, located in Austin, TX

https://austincylinderhead.com/

On overhead cam engines, I would prefer to straighten the head as much as possible prior to machining so the camshaft is running as true as possible.

I believe, that most of the machine shops I know of true both sides of the head when they flatten them. So that the towers are straight and true

[madkaw]

1 hour ago, Patcon said:

I believe, that most of the machine shops I know of true both sides of the head when they flatten them. So that the towers are straight and true

Do you mean to say - machine both sides- Charles?

[Patcon]

16 minutes ago, madkaw said:

Do you mean to say - machine both sides- Charles?

Yes, that is my understanding. The heads I have seen done are stripped clean of all the valve train and dressed on both sides. you end up with two flat perfectly true and parallel sides. Otherwise you add distortion to the cam. Also I haven't ever seen a milling machine that could mount a head with the valve train installed or a situation where you would want all the milling chips strewn throughout the valve train. I might be mistaken on this but this is how I believe it is done.