I’m checking the ring gap on my 3.8 before assembling the engine.
The compression rings are perfectly gapped at .015 - .017
The oil control rings should be .011 - .016, however they are .025
My thought is to buy new oil control rings, but I thought I would ask for an opinion first.
Your input is much appreciated.
To me, this is the wine and cheese part of restoration.
Alan.
“[quote=“absmgb, post:1, topic:360834”]
To me, this is the wine and cheese part of restoration.”
[/quote]
Which follows the earlier “Whine and Jeeze!” phase, where you discover exactly how much really needs doing…
1 Like
Yes, but by the time the “Whine and Jeeze!” is realized it’s too late to turn back.
And here I am wondering if my ring gap of .025 on the oil control rings is going to work.
Looking for advice.
What type are they? One-piece cast iron or 3.or 4-piece spring type, where you can stagger the two rail gaps at least? I think 0.025” is fine for oil control. Spec is 0.015-0.045”
They are the 3 pc spring type, two rings with the staggered spring spacer in between.
I’m using Mahle pistons and rings
In the manual it says the oil control rings should be .011 – .016
I’m not sure though though if the new ones differ from the old.
(The upper 2 compression rings are cast iron). Just to be clear.
Thanks.
Alan.
Typical multipart spec is minimum 4 thou per inch bore, which would mean at least 14-15 thou gap. I always get slightly nervous with Mahle’s tight clearsnces but haven’t actually used their stuff yet.
if the workshop manual allows up to 0.045 for probably for slotted AE cast iron style(?) then why buy new when existing new are mid range out of the box?
remember this post, Pete? I was nervous about trusting Mahle’s pre-gapped, pre-installed rings. The recommendation I’d received from the supplier was not to remove the rings from the pistons for measuring lest I break one in the process, but rather to verify the bore against the number stamped into the top of the piston and install as-is.
I remember the topic of Mahle tight bore clearances but don’t see the relevance. Here we have clearances in the middle of the expected range.
It seems to me (not a seasoned engine builder) the disagreement is from reading different Service Manuals. The 3.8 spec from the Jaguar Service Manual is 0.011" - 0.016" as Alan states. The 4.2 spec from the Jaguar Service Manual is 0.015" - 0.033". Peter is quoting a Spec of 0.015" - 0.045". Alan’s engine is a 3.8. Does that help clarify at all?
-David
For some reason I thought it was a V12 and that’s the spec I looked at last night 
The relevance is trusting Mahle’s preset ring gaps or not, which I think was the point you were making at the time.
I was impressed at how the upper two compression rings were gapped at .015 - .017
In my repair manual by Robert Bentley it gives a tolerance of .015 - .020
I suspect the manual was referring to an older style cast iron bottom ring, with a tolerance of .011 - .016
I’m inclined to believe Mahle made all the rings correctly.
Barring anything to the contrary, I will put the pistons in place.this afternoon.
Wish me luck!