All Small Six 68 small log head porting

[clochard68]

I am considering the copper gasket, with Hylomar spray. Maybe I can make it work.

And I ran the numbers on dynamic compression (here is the calculator link if anybody is interested: https://www.pcengines.com.au/calculators/calculate-dynamic-compression-ratio/ )

With my setup, the stock cam (Duration 240° and 106.5° LSA, these are the measurements I got when I degreed the cam) installed with 4.5° advance, I would get a dynamic compression ratio of 8.47:1 with a 0.020" copper gasket and the head shaved to a chamber of 52cc.
It is interesting that with the stock cam the static compression ratio would only be 9.22:1, but the dynamic is quite high.
Also with that gasket the quench distance would be 0.039" and I would be under 8.5 dynamic compression ratio, like from classicinlines.com recommended (I put their chart in the picture attached below) :





I will order the gasket, since the machine shop hasn't machined the head yet, and the reduced quench is worth a try I guess!

 

[drag-200stang]

AK Miller said that you could reuse the factory shim gasket...I would use a good carefully cleaned up used gasket with Hylomar or KW copper coat before using a copper gasket for what you are doing.

 

[clochard68]

Thanks for the advice. I will get a used gasket from powerband and use that one instead of the copper one

 

[gb500]

Close up of original 144 steel shim gasket showing the embossed detail

 

[clochard68]

AK Miller said that you could reuse the factory shim gasket...I would use a good carefully cleaned up used gasket with Hylomar or KW copper coat before using a copper gasket for what you are doing.

Can I soda blast the gasket, or is it better to just use chemicals (acetone, gasket remover?) and a scotch brite pad?
Or just chemicals and a soft cloth?

 

[gb500]

US 250's with a 3.68+ bore or an AU 250, there can be a big difference there, in fitting some AU 250's head gaskets to a US 250.

Just to be clear here for future tha australian log heads gaskets are same as US. Its the australian crossflow head that has a different gasket.

 

[drag-200stang]

Can I soda blast the gasket, or is it better to just use chemicals (acetone, gasket remover?) and a scotch brite pad?
Or just chemicals and a soft cloth?

Not sure, I know that sand blasting will warp thin sheet metal, maybe fine..Try the brake, carb cleaner and gasket remover with finer scotch brite first.
Funny now that I am older with more patients, I find that I can do things that I could not when younger.

 

[clochard68]

The steel shim head gasket is on the way (thanks to powerband!), so one last thing I need to do is tell the machine shop how much to shave off the head...

Will the compressed thickness of the (used) steel shim gasket (D7XX...) be 0.022" or will it be 0.025"?

 

[bubba22349]

I always though the steel shims were .022 but maybe I am wrong. How much Compression do you want? Are you using a stock camshaft or an aftermarket performance cam?

 

[gb500]

I reused my shim gasket. Cleaned up with steel wool, gave a clean with prepsol an gave a spray with hylomar -both sides.

 

[drag-200stang]

It depends, there is thinner and thicker oem shims.. I cannot remember exactly what they were. If you have to know exactly you may need to wait until you get it, or split the difference and call it good.

 

[clochard68]

Further conversation @ steel shims - HELP appreciated:

The Compressed thickness of the Steel D7xx gaskets is probably closer to .025-.027" although that is only an assumption.

I can't find any empirical evidence of the later 200/250 shim gasket compressed thickness and I never did the math..

I assume the later (250) D3xx and D7xx steel shim gaskets are more similar to later Ford OEM service replacement steel shim gasket( C9DE 6051C ):

Anecdotally, the very early C0xx (144/170 bore) gaskets were purportedly @ .018 - .022" compressed. But later Ford OEM replacement steel shim - 200 - C9DE 6051C - was purportedly .027" compressed.

AFAIH ...

have fun

Might be up to 0.27". I will measure when it arrives...

 

[clochard68]

One more question for the community:
The wear pattern on my valves dtems with the 1.65 RAU shaft rockers. The pattern is not centered, leaning more to the shaft side.

Can I leave it as it is, or should it be corrected (shimming under shaft mounts/milling shaft mounts)?
The rockers have a roller tip...

 

[pmuller9]

Can I leave it as it is, or should it be corrected (shimming under shaft mounts/milling shaft mounts)?
The rockers have a roller tip...

I would shim the shaft mounts.
A centered pattern will decrease side loading on the valve stem, and it will also decrease the roller tip travel on the valve stem.

 

[clochard68]

Are there any shaft-rocker-shim-kits available, or fabricate them myself (brass?, steel?)?

I think I will try hardened washers first to figure the shim height out.
In the "horsing around" article AK Miller installed hardened washers to make up for the head milling, so would it be ok to just leave the washers in petmanently if they fit?

 

[drag-200stang]

The bolt torque spec is 34-36 do not exceed this, the stands or pedestals are cast aluminum and are not very strong. And also, for this reason I would make the permanent shim, just like the base of the stand, larger outside shape better, but no less, the hole should be no larger than the stand base hole, note that the rear is square for oil flow the others could be round. Give the weak stand all the back up support you can, the higher ratio rocker will increase the load on the stands. I think that any of the higher strength al. alloys would be fine or mild steel. Of course, it needs to be flat and consistent.
Washers would be fine to test., keeping the above in mind. You can get shims to test but I do not think that they would give proper support to run.

 

[clochard68]

Might be up to 0.27". I will measure when it arrives...

I just cleaned the head steal shim gasket at work today (thanks again to powerband for the D7BE gasket!).
After cleaning (before and after picture) I measured it on a few spots directly on the bead. With the caliper I measured between 0.8mm - 0.85mm, that would be 0.031" - 0.033" thickness of the used head gasket not installed.
I am curious how much the compressed thickness finally installed will be, maybe I'll never know (don't know how I could possibly measure that...).







For the shimming of the rocker shaft I was planning on laser cutting some sheet metall like that:


Any thoughts about that (good/bad idea) or things I have to take into account?
If it fits, I will post the dxf-file in the CAD forum.

 

[drag-200stang]

There should be a place that you can get a feeler gage between the block and head, when installed and torqued down.
That does not at all look like what I described for a shim. That has a lot of material where it is not needed, and no material where needed. The rocker will teeter back and forth without full stand, base support.

 

[clochard68]

There should be a place that you can get a feeler gage between the block and head, when installed and torqued down.
That does not at all look like what I described for a shim. That has a lot of material where it is not needed, and no material where needed. The rocker will teeter back and forth without full stand, base support.

So I would need a gap between the head and the block that is not filled by the head gasket and accessable ftom the outside, right?

Regarding the shim, it is just a schematic yet, so the proprtions may not be 100% correct. I understand that the base surface (red circle) has to be fully covered. I connected the individual shims to align them, is there a disadvantage in doing so? Do you mean that 6 separate shims would be better?

 

[pmuller9]

Regarding the shim, it is just a schematic yet, so the proprtions may not be 100% correct. I understand that the base surface (red circle) has to be fully covered. I connected the individual shims to align them, is there a disadvantage in doing so? Do you mean that 6 separate shims would be better?

Once you figure out what thickness you need for a shim, you can use one long piece of sheet metal that covers all six pedestal mounts as a shim.
You may have to clearance the long shim for the pushrods.