How many skims and head thickness!

[Kingscott]

Hi everyone

I've got the head off today ready for checking at the local machine shop due to my ongoing water in oil issue.

comp test turned out OK and I cant see anything obvious yet with it all in bits!

Anyhow, does anyone know what is the minimum head measurement before it cant be skimmed again, looks like my head currently measures about 73mm thickness.

cheers all.

[GTphil]

That's about the minimum thinkness. Anything under 73mm will require some other mods to lower the compression ratio. That is of course if your using a lot of boost. I dare say that with standard boost or just slightly higher a short head with higher compression might make it a little more responsive.

Standard head thinkness Is 73.5mm

[Kingscott]

That's about the minimum thinkness. Anything under 73mm will require some other mods to lower the compression ratio. That is of course if your using a lot of boost. I dare say that with standard boost or just slightly higher a short head with higher compression might make it a little more responsive.

Standard head thinkness Is 73.5mm

Hi mate

Thanks for the answers, when I said 73, it's was more like 73.3 on adverage so I'm happy it's ok. Phew. Plus I also run low comp pistons, at about 19 psi boost to think I used to run 28 in my youth ha ha

Just got to see if this oil feed line is cracked. Such a tiny hole I've no idea how they will fix it if it's cracked? Apparently they can be drilled and lined with some resin sleeve. :confused:

[Kingscott]

Compression test was knocking out 125 130 ish psi across cylinders before I stripped it today.

[Trevhib]

You have OE pistons, OE cam and a 73mm head? I'd say those compression figures are a bit low then. With a standard head they should be 145ish IIRC. More evidence of an issue perhaps. :(

[GTphil]

Compression test results can vary due to quite a few factors, your cam timing can affect it as well as the obvious dished pistons or taking some of the squish area out from the head.

Your set up sounds fine for that sort of boost.

My old low comp motor would only do 125psi or so across all 4 pots, with spanking new boars and well run in rings. Low comp pistons and a retarded cam.

I wouldn't worry about those results as long as they are relatively even across all 4 pots.

[Kingscott]

It's fitted with a piper cam, I have no idea of the model anymore it's been so many years.

[Kingscott]

You have OE pistons, OE cam and a 73mm head? I'd say those compression figures are a bit low then. With a standard head they should be 145ish IIRC. More evidence of an issue perhaps. :(

No I've got a fancy cam, fancy low comp pistons. Sounds pathetic I know but I've no idea of the details. It's only done 10k on the engine in the last 7 years.

[Kingscott]

Compression test results can vary due to quite a few factors, your cam timing can affect it as well as the obvious dished pistons or taking some of the squish area out from the head.

Your set up sounds fine for that sort of boost.

My old low comp motor would only do 125psi or so across all 4 pots, with spanking new boars and well run in rings. Low comp pistons and a retarded cam.

I wouldn't worry about those results as long as they are relatively even across all 4 pots.

Sound :agree:

[GTphil]

Don't have any experience with the epoxy tube fix, however I remember reading that it does the job on a permanent basis of that's your issue. :agree:

[Trevhib]

No I've got a fancy cam, fancy low comp pistons. Sounds pathetic I know but I've no idea of the details. It's only done 10k on the engine in the last 7 years.

Ah, apols, I didn't realise (or had forgotten).

As Phil says then, your comp results could be a-ok.

Let us know what the machine shop says about your head :agree:

[Kingscott]

Ah, apols, I didn't realise (or had forgotten).

As Phil says then, your comp results could be a-ok.

Let us know what the machine shop says about your head :agree:


Will do mate :agree: