Itinerant Air-Cooled

Do I use the thin little paper gaskets under the cylinders?


neal

Permatex 3h only I do believe. Check Wilson to be sure.

Use 'em if you got 'em apparently. Oil was leaking at my stacks of barrel shims. They are gone, now to see what the deck height is. Should I let the Permatex set up a bit before torquing to spec? I certainly saw none that was applied between the shims. Maybe a more generous application? Is there a way to not overthink this kind of stuff?


neal

ruckman101 wrote:Do I use the thin little paper gaskets under the cylinders?


neal

I like them! Applied with Permatex Aviation.
ColinClean-Engine-R-Us

Done. Well, one side. Torqued the head on to spec last night without letting the Permatex Aviation dry any longer than it took me to get the cylinders and head on. Now going to do the same for cylinders 3/4, then will loosen up and remove my 1/2 head and check the deck height. I used Permatex on the shims but saw virtually none between them when I took them off. A stack of two with the paper gasket underneath. My compression ratio was 7.3 to 1. Subtracting the values of the shims, my compression ratio went to 7.8 to 1.

neal

Good to hear, maybe see you in the woods this summer. Big plans.

7.8 to 1.

neal

Okeydoakie.

Deck height on cylinders 1/2 is .043 inches. Deck height on cylinders 3/4 is .040 inches. Using actual metric conversions of those values, and not rounding off to fit the deck volume numbers on the AircooledTech page gives me a compression ration of 7.91:1 for cylinders 1/2 and 7.96:1 for cylinders 3/4.

It certainly is above the ideal of 7.5:1. Is it an issue to address or am I being overly anal.


neal.

I'm not sure if you would notice a difference. What are the size(s) of your current base shims? I wouldn't want two down there, since that's two extra surfaces to leak, but I'm not sure if it is as critical as I imagine it to be.

Robbie

My stack of two shims was compensating for shaved, lower volume heads and were 1.6 mm on the 3/4 side and 2 mm on the 1/2 side. I had deck heights of 2.5 mm on 1/2 side and 2.6 on the 3/4 side. Rough measure. It gave me a compression ratio of 7.4:1. I used feeler gauges to measure without shims. I suspect they were leaking because the heads had loosened after my initial install. I had put 1,321 miles on them without a re-torque.

neal

Why oh why, when everything is measured metric, do we deal with deck height measurements in inches?

neal

ruckman101 wrote:Why oh why, when everything is measured metric, do we deal with deck height measurements in inches?

neal

It is a horrendous legacy of the arrogance of the British Empire Era of Wigged White Men. Now then, I do strongly recommend that you find your compression ratio down to 7.5. Nothing wrong with a .010 base shim or two of them, with a slathering Permatex Aviation.
Colin

I suspect you may be right. That engine is working much harder from the get-go moving a bus about. It isn't a beetle or ghia. The higher the compression ratio, the greater the heat generated. I gave a guestimate on the compression ratio of my first engine, with no consideration, just 87mm slip in piston/cylinders with stock heads, and got essentially close to just under 8:1 compression ratio, and pre-ignition was an issue. Slather Permatex I will. Well, maybe not slather, but healthy application. Although I'm going to try to avoid double shimming.


neal.

Has anyone used nylon lock nuts on the single port manifold to head connection? Would it get too hot? Apparently they nylon is good up to temperatures of 250 degrees. Or maybe just a nut taller than the lip of the manifold to make it easier to get a wrench on them?

neal

Some aftermarket exhaust manufacturers use "long" 11mm or 12mm nuts for easer wrenching on larger manifolds that are close the the header pipes like our intake manifolds are. A deep offset box wrench has always worked for me, though it's tough to get at in the car. I'll check with my local fastener drawer tomorrow. In the mean time, could you use two or three washers beneath the nut, one of them being wavy?

Robbie