Cylinder cooling tins - can I get a ruling?
 

The patient is a 1979 turbo engine. Using 100mm LN Engineering jugs in place of the factory 1/2 finned Mahles. I'm uncertain of the fit of the factory cooling tins.
http://asbury.smugmug.com/By-Land/Po...97_nskHm-L.jpg

You can see the air gap near the "head" end of the cylinder is pretty large. The cooling fins on the factory jugs fit into the "steps" of the tin perfectly, but not with these. At the top of the piston, I couldn't get the spring clips in that hold the tins in place either...the slot at the top of the tin doesn't seem to protrude above the cylinder enough.

So I tried a little trimming on the tin...
http://asbury.smugmug.com/By-Land/Po...53_GS8nJ-L.jpg
Somewhat better fit near the "head" end, but now a large gap down at the base of the cylinder. Not sure if this is an improvment or not. I've gained some room at the top so I can install the spring clips.

This is the trimmed piece. Looks good from this angle to me, much closer to how they sit on the factory cylinders than before trimming:
http://asbury.smugmug.com/By-Land/Po...50_aKQsu-L.jpg

I am worred about the airgap down at the cylinder base. Is this ok to run, or should I be looking for a newer style tin?

Your input is appreciated:)

http://asbury.smugmug.com/By-Land/Po...21_jpAyS-L.jpg

My $0.02. My vote goes for the factory cut tin. My theory is the larger air gap closer to the cylinder head will allow more air to flow in that area where the greatest temperature is compared to the lower extremities of the cylinder.

I was in the same position last year when I converted to 3.4 fully finned cyls- I was going to squeeze the 3.3 tins on, but I sleep better at night since I bought the stock 3.2 fully finned tins. I got mine for $100 and had my friend sand blast them, then I painted them in high temp paint and now they are as new.
my 2 pennies

I go with the 3.0/3.2 cooling tins as they dont have the reinforcements at the bottom to close the air flow.
Bruce

I'd either try to get the modified tin to resemble the 3.0/3.2 fully finned tin as closely as possible or just get a new set of air deflectors. Definitely, you don't want to run unmodified 3.3 half finned air deflector tin with that huge gap.