Correct piston ring set for AE 21380

Hi Everyone,

I’m rebuilding a 4.2 XK engine from a S1 XJ6 that suffered from a very poor rebuild and only ran for a short time before failure (PO’s many, many mistakes). Because of this, most of it is in good shape including the standard size pistons that I intend to re-use.

The pistons I have are AE 21380 (low comp) short skirts. Obviously I need new rings and AE rings don’t seem to be readily available in the US.

The only ones that I’ve found that actually say in the spec sheet that they fit AE 21380 pistons are Deves 1256-B. I will probably wind up with these unless someone can suggest an alternative. The reason I’d like an alternative is because they would apparently have to be ordered and with the way things are going now who knows how long it will take.

Hastings lists Jag rings but there are 3 different part no’s and the fact that the Hastings spec sheet says the bore-diameter for some of them is 3.622 (instead of 3.625) doesn’t fill me with confidence.

So I guess I’m asking if someone can please give me the part number for a non-Deves piston ring set that they’ve successfully used with AE 21379/21380 short skirt pistons?


Check with Grant Piston Rings: got my cast iron set from them.

Hi Paul - I just checked the Grant catalog and they have em but I can’t find any in the US. SNG can get em but that’ll take a while. Interesting Grant uses the same part numbers for all 4.2’s - C1256 for Chrome and P1256 for iron. Same numeric part as Deves which is 1256B…

I’m wondering about Hastings again - The 2 that they list for 4.2 pistons are differentiated by Shallow Oil Groove Depth and Deep Oil Groove Depth. The Deep ones go farther back to earlier 4.2’s (1964) but they are listed all the way to 1991. Do you suppose they are referring to Deep Oil Groove Depth as the slot cut all the way into the piston behind the oil control ring that early, slotted-skirt pistons had? There’s no talking to Tech Support; I emailed them but we’ll see how long that takes.


Unless in new, Sunnen-honed bores, do not use chrome rings.

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Yup - I was intending to use plain, iron rings.

Amazingly Hastings got back to me pretty quick.
This is the info they gave me regarding their 2 piston ring set choices:

4625, 2C4625… Shallow groove … for the AE PISTON
Oil groove ring depth = .173” Max.

6800, 2C6800 …. Deeper groove… for the XK-6 PISTON
Oil groove depth = .182” Max.

The 2C prefix means chrome rings BTW.

I can’t find too much info about what the Deves rings are made of - Unlike Grant and Hastings there is only one part number.

I have short skirt AE"s 8.7 comp. pistons in my 69. I bought cast iron rings (per Wiggles suggestion) from Total Seal. Hand fit ring end gap to. 016".
Just took compression 15 years (12k miles) later 168 to 180psi.

A generous gap, Davey!

I used the 0.004"/inch of bore diameter for street engines.

As per Bill Terry, Paul. I figured he’s forgotten more than I’ll ever know. And a very strong possibility I am mis-remembering.
.004" × 3 is .012" (although I ran out of fingers). Maybe you’re right…15 yrs ago.

Thanks David - you don’t happen to know the Total Seal part number you used by any chance?

I did speak with Total Seal’s tech support and they have the same “Shallow Groove”/“Deep Groove” notations with the 2 part no’s of rings they carry. They however don’t seem to know that the Shallow Groove is for AE pistons (at least according to Hastings). The guy I talked to at Total Seal had no idea about what the applications were.

I wish there was a better spec than “Shallow” or “Deep” just for clarification purposes. After all this shopping around it might be safe to assume that Shallow Groove oil rings are for all short skirt pistons and Deep Grooves are for all long skirts but I wish I knew for sure - like maybe if Jaguar mentioned it somewhere. I can of course measure my AE piston oil ring groove depth but I don’t have an early 4.2 piston lying around to measure that one’s depth. I do have a 3.8 piston (original long skirt of course) I can measure just for kicks to see what the groove depth is.