11 replies to this topic

[rae07]

So I recently had a slight leak at the head gasket area. Brought it to a shop and they did some measurement on the head flatness (with a true metal bar). The top block has a gap of about 5 thou and the engine block has a gap of 20 thou. Both measured diagonally.

Is this any cause for concern or I could tighten it up and hope the gasket do its work? Will be using GEG300 copper gasket from minspares.

[cal844]

Maximum tolerance (in my experience) for a copper gasket is 2 thou

[rae07]

Looks like I am screwed in this situation? Will those engine RTV help? Or I would need to skim the surfaces?

by the way, have checked the pressure in the cylinders prior. All seems ok.

Edited by rae07, 25 June 2021 - 03:33 PM.

[RooBoonix]

Spec we used to work to at work was 4 thou

 

 

20 thou is massive, needs a skim

 

5 thou across the head would probably be fine if the block itself was spot on, but in this situation I'd recommend getting both skimmed

[Cooperman]

You have to have both block deck and head skimmed.
I am surprised at the 20 thou figure and I wonder how such a warp could occur on a cast iron engine.

[bpirie1000]

What did the gasket actually look like and was the car run hot at any time? If you knkw all the history with the car and intend to keep the car long term i would try find another temporary engine and whip this one off to the machine shop for a skim...

Block and head..
They can also check valve seats and find a few bhp if your lucky..

[Spider]

If it's an early A+ Block, I could believe those numbers, if it's not, then I'd find another shop. Yes, the Head and Block Deck can distort, but 0.005" is quite a stretch, let alone 0.020".

 

If you have them there yourself, grab an Oil Stone, be sure the stone and the Machines faces are very clean, then run the Stone over them 3 - 4 times and that will show you where the high and low spots are, granted, it won't show you by how much but when you see how close the high spots are, and you'll soon see that the numbers are being quoted, you'd feel and see. 0.020" is very close to 1/2 a mm.

[Cooperman]

If it's an early A+ Block, I could believe those numbers, if it's not, then I'd find another shop. Yes, the Head and Block Deck can distort, but 0.005" is quite a stretch, let alone 0.020".

 

If you have them there yourself, grab an Oil Stone, be sure the stone and the Machines faces are very clean, then run the Stone over them 3 - 4 times and that will show you where the high and low spots are, granted, it won't show you by how much but when you see how close the high spots are, and you'll soon see that the numbers are being quoted, you'd feel and see. 0.020" is very close to 1/2 a mm.

I have seen a few slightly distored heads over the years, but I have never seen a warped block.I have seen uneven block decks where blown head gaskets have eroded the deck faces. but not so that more than a few thou has needed to be skimmed off. The main reason for skimming the block deck it to get the pistons to come right to the top of the bores.

Warped heads are common with alloy heads (think Hillman Imp!), but not on a cast iron A-series head. A slight uneveness may happen and require a small amount machined off. 

Personally I would check the measurements you have been given. I'm not saying you are definitely wrong, but just re-check. If it is that far out it MUST be machined to get it right. You cannot use any sort of sealant with head gaskets in view of the heat that is generated. If ity is as you say, a full strip and machining is necessary.

[Dusky]

I can only think they have the 20 thoi figure because somewhere their straight edge was resting on one of the head stud holes that pulled the threads up.

[rae07]

Thank you all for reply. Appreciate it.

I found out more and probably got misinformed about the warp.

20 thou refers to gap between cylinder 4 and 3. The 5 thou refers to gap between cylinder 2 and 3. I have attached the pics. (Pic 1 is the 20thou gap and Pic 2 is the 5 thou gap)


I think it is still of some concerns and some work is definitely required for the block?

Attached Files

•  IMG-20210627-WA0002.jpg   42.25K   9 downloads
•  IMG-20210627-WA0001.jpg   56.2K   10 downloads

Edited by rae07, 27 June 2021 - 01:53 PM.

[Dusky]

The ruler is resting on one of the stud holes. Are you (they) sure the hole is still chamfered?

[Spider]

I can't see the gauge properly to read it in your first photo, however, the second one, that looks like a metric gauge, in which case, that, just under 0.002".

 

Before you can get accurate measurements, rub an oil stone over the decks to knock off any silly highs or show up those over a bigger area. It will also show up frazes around the stud holes that Dusky is referring to.