engine and drivetrain e12 versus 121 heads? opinions wanted...please?

[2761876]

I am running a 71 tii that has 40k on the rebuild. I have no idea what compression ratio pistons are in the car, only that the original 121 head has been replaced with an e12 and therefore assume the bathtub pistons are gone too.

I also have a complete, history unknown, 71 tii engine with the 121 head and 10-1 pistons, very clean and obviously rebuilt at one time.

I will be pulling the head on the car this winter to see what pistons are in there, if they are 10-1 pianos I will use that engine... if not I am thinking of swaping for the sake of performance and originality... though the numbers will no longer match:(

Whats going to give me the best breathing engine? e12/pianos or 121/bathtubs?

[JohnN]

1972 was the first model year.

Second off, the E12 head flows better than the 121/121Ti head and high compression Mahle pistons are easier to find.

The bottom end of the engine (low compression / high compression) is the same (except for the pistons of course). If the bore on your engine is not too worn to take the 10:1 121 pistons you have, I'd suggest using that. Otherwise you'll have a much easier time finding the 9.5:1 pistons for the E12 head.

The head does not have a serial number so if you wish to keep the numbers matching, just rebuild that block.

Make sense?

John N

[2761876]

both of the tii engines are early production year, euro-spec, cars.

I said 71 cause its quicker than writing early production run.... my bad.

[Jaycen_PNW2002]

Don't know when the transition occured (with respect to vin number) from 121 to E12 but it occured within production run for 72tiis.

Unless you go with custom pistons it will be easier to build around an E12 head because mahle high c/r pistons are still available. You can still get new E12 heads if need be too. -J

[02fanatic]

The old school of thought used to be "higher compression"...the ti 121 head was better (due to smaller head combustion area geometry on the early tii engines). But, I believe over the years most enthusiasts have gone with the E12 head as the better of the two. I remember my firend Michel Potheau telling me once that the E12 tii head was the best one to go with in a rebuild, and I believed "whatever" Michel told me! He wasn't wrong very often....

That being said, I have a long overdue engine project on an engine stand in the garage - VIN 2760081 and it has the original bathtub psitons...I have an early tii head off another early tii, and I will probably try to keep the 121 head on that engine for originality "if" the piston are salvagable. If not, I will switch to piano top pistons and go with an E12 head.

[2761876]

(nt)