Mk3 Compression ratio following skim

[Sandy Gibson]

Pete

I would like to think you are correct, but I can’t see how that could be the case.  Studs were the  correct way in, I used new flanged nuts and I checked the torque wrench against another one just to make sure.

Could it have been a faulty gasket or something else I may or may not have done?

I’m sure you’ve forgotten more about these engines than I’ll ever know!  so all help hugely appreciated 

Sandy

[Pete Lewis]

sorry cant suggest anything youve done the studs /clean threads  new flanged nuts just cant get my head round that gasket 

i would expect some deformation around the coolant passages etc  

even just on a few minutes fitting   it should have a good squash  down 

are the fire rings flush with the gasket or raised  a bit ????   Rob suggested it may not have the tab but they look more for recessed  fire  rings 

that would explain a gusher  its happened before rathe rthan dive into cracked heads and bore which is more unlikely 

Ive forgotten a lot but stick to basics and  not go myth hunting   Ha !

 

[Sandy Gibson]

The rings are very slightly raised. Getting 001 to 002 above the gasket face. Overall ring thickness .040 to .042.

Broadly about 2 to 3 thou thicker than the old Payen that came of the engine before the rebuild.

Bear in mind the engine only ran for about 5 minutes before I discovered the mayo and obviously the head was never re-torqued so I would have expected the gasket to look pretty new.

Anyway, the project continues!!

Sandy

[JohnD]

Sandy, was the block face skimmed at all?    I'm just trying to think of reasons for your problem.

If the block is skimmed, then the stud holes should be countersunk, slightly, just to take out the first turn of thread.    Without that, the stud can raise the edge of the hole, enough to stop the gasket seating.

John

[Sandy Gibson]

John

No the block face is original

Thanks

Sandy

[Sandy Gibson]

As it came back from the shop!

[Chilliman]

Quote

I am going to get my head skimmed following blown gasket issues.

Going back to your original post - I don't see any sign of the head gasket having 'blown' in fact as Peter has rightly said it looks as good as new & with very limited compression marks. What torque is the head set at and do you use a sealant?

I ask that simply because I only work on the four pot TR 'tractor' engines & I always use a coat of Wellseal on my copper shim gaskets, I appreciate they are completely different engines, just curious.

[KevinR]

Is it possible that you have a calibration problem with your torque wrench ?

Even expensive high quality ones are notoriously inaccurate and should be checked on a calibrator before every use.

[Sandy Gibson]

Used a Payen gasket without any sealant. Most advice seems to say that is correct.

Torqued to 45 ft/lb and wrench checked against another one so am sure it was done correctly.

[Josef]

Could (one of) your studs be not quite the right dimensions perhaps? Or washers too thin or something like that. So you’re tightening against the stud threads not the head?

[Sandy Gibson]

Studs all ok and the right way in with plenty thread. New flanged nuts used.

I am sure the gasket has not failed between the coolant ports and the combustion chambers but possibly between the coolant and push rod ports.   This would fit with the symptoms I had.  i.e water getting into the sump but no significant air coming up through the rad header.

Thanks

[JohnD]

12 hours ago, Sandy Gibson said:

Torqued to 45 ft/lb and wrench checked against another one so am sure it was done correctly.

Better than nothing, but not 'calibration'!     If you have somewhere to fix the drive bar, a bench vice or even a "Workmate", the hang a known weight from the handle.   Torque at drive bar = weight x distance of weight from bar.

EG: 24lbs (12.5kgs) x 1.5 feet = 36ft.lbs torque

Set the wrench to 36 and move the weight out until it clicks.  Measure the distance to the strap.    Add more weight, or extend the handle with a pipe to check whole range.

[Sandy Gibson]

Just an update on progress!

Sealed up all the water channels and did a compressed air pressure test on the block.

Went to 20psi and no drop in pressure after an hour.

Still doesn’t tell me what’s wrong but it eliminates a few possibilities such as accidentally drilling into water jacket etc.

[johny]

can I ask how you sealed the water ways?

[Sandy Gibson]

Bit of Vaseline on the top of the block then some soft plastic sheet on top of that then replaced the head and torqued it up lightly. 
Connected air line through the drain valve.

[Colin Lindsay]

If I wasn’t on my mobile and miles from home I could show you an almost identical photo to yours, same water marks round the push rod tubes. It’s on my Herald restoration thread. In my case the water was leaking out along the side of the head near the engine number tab. No idea why, I could see no reason but went for a different head gasket which cured it immediately.

[Sandy Gibson]

Finally traced the leak. Lots of compressed air and soapy water!

Head back on and water pump etc sealed off 
20 psi in the coolant system and air leaking mainly through the head side of the gasket to push rod 4/5 port.

Took the head off again, sealed round the water channels on the head side of the gasket, put head on and re-pressurised.   Very slight leak from under the gasket (soapy water down push rod port!)

Conclusion - both head and block need refaced.

Does that seem reasonable?

[Chilliman]

Well done Sandy, that was worth the effort if it's identified the problem, I would personally go for a head skim first as the head is the most likely unit to have changed shape...that doesn't  mean to say the block doesn't need doing but given the cost & effort involved I'd get the head skimmed & pressure tested first - it's the most likely offender - Your machine shop should be able to give you some idea as to the quality or otherwise of the head face. Of all the engines I've built I have only had to deck a block once.....

[Sandy Gibson]

Thanks John

That’s exactly what I intend to do and pressure test before it goes back into the car.

Hopefully a head skim and a new Payen gasket will sort it.

Toying with the idea of a smear of Hyolomar blue round the block coolant ports when I rebuild.  Any thoughts on that?

Sandy

[Chilliman]

i think when the original workshop manual's were produced the recommendations were entirely appropriate but we are now 50 - 60 years down the road and I personally would have no issue with the use of a gasket sealer. I'm not a great fan of the silicon sealers (RTV) which I have seen destroy engines due to over use causing blocked oilways but a a smear of something like Wellseal  would provide some significant reassurance without risk...I remember Hylomar blue from the old days but no recent experience so I am l cannot comment. as to how appropriate it would be but either way I think you are on the right course.....

[Pete Lewis]

in general head gasket are not sealed  and fitted dry  they have to grip you dont want any slippery stuff in the joint 

the head does pant under the firing and sealer will allow head movements   

the only one triumph say seal  is the staeel shim gasket on the1600  

wellseal is a good old fasioned semisetting compound if you must that would be my choice     any silicon type just a light smear around the rocker oil feed 

but pressures within the coolant is very likely to end up tracking through the sealer  so  as designed   fit it DRY

Pete

[PeteH]

For Information. The Triumph 1200 owner manual, (1962) In the Special Accessories section, "Twin carburator conversion" In recomending raising the compression ratio (8.0:1 to 8.5:1). It states "Machine aproximately 0.030" from Cylinder head joint face".  Which would imply that, on the 4 cylinder at least, There is sufficient material to cope with a 30thou. "Skim".

Could one Infer from that that on the 6 Cyl a similar amount could be safely removed IF necessary?.

Pete

[JohnD]

"Machine aproximately 0.030" from Cylinder head joint face"

that assumes that nothing else is done to the chambers, even in the interests of improving flit and mixing.   Such work will increase the chamber volume and make a deeper skim desirable for that same increase in CR.    

Anyway, raising compression by 0.5 is a piffling change with no real world benefits!   The max CR with modern fuel can be 10.5, on 99 octane, say Shell V-Power.

The only way to reliably increase CR is to MEASURE the chamber volume And do the maths.   It's not quantum chromodynamics, and easier than rocket science! See my article at: https://sideways-technologies.co.uk/forums/index.php?/topic/7551-how-to-raise-the-compression-ratio-safely-and-effectively/#comment-99739

[PeteH]

3 minutes ago, JohnD said:

"Machine aproximately 0.030" from Cylinder head joint face"

that assumes that nothing else is done to the chambers, even in the interests of improving flit and mixing.   Such work will increase the chamber volume and make a deeper skim desirable for that same increase in CR.    

Anyway, raising compression by 0.5 is a piffling change with no real world benefits!   The max CR with modern fuel can be 10.5, on 99 octane, say Shell V-Power.

The only way to reliably increase CR is to MEASURE the chamber volume And do the maths.   It's not quantum chromodynamics, and easier than rocket science! See my article at: https://sideways-technologies.co.uk/forums/index.php?/topic/7551-how-to-raise-the-compression-ratio-safely-and-effectively/#comment-99739

John, In general I concur. Whatever the O-P wanted to achieve, lot more work would be required to make a Benefit worth having.

His query was would it be SAFE to remove 40thou without risk. I was merely posing the question as to if the possibilty of taking 40thou off the head would or not compromise the structure of the head. As would appear that back in 1962, Triumph where "happy" to recomend removing 30thou from the 4 Cyl head. In that context measuring the CR`s was not an issue.

The "old glass/pipette/burette" "trick" is even older than I am, and well used back when "blueprinting" engines, for Stock car racing or in our case rally work, where actually MODIFYING engines was not allowed, they had to be technically "Stock".

Cheers, Pete.

[Iain T]

13 hours ago, PeteH said:

His query was would it be SAFE to remove 40thou without risk.

I've just looked at the invoice from CTM who did my head and have done hundreds over the years. It only says head skimmed to acheive chamber volume of 30.5cc for 10.5:1 CR. According to the spreadsheet I previously posted that requires at least 30 thou skim but does depend on reworked chamber and valve heights. As John said and CTM obviously did measuring the chamber volume is the only sure way to achieve a specific goal. 

Iain