I am building a 2056 for a friend and it is mounted on my run up stand and fires right up as expected but has a serious oil leak on the 3/4 side . Not the filter ,not the oil cooler, not the pressure switch. I replaced the push rod tubes and installed Vuton O rings. Oil is coming from above the air diverter plate above the pushrod tubes . The diverter plate is filling it's pockets with oil. I removed the plate and see no Leake.I removed the spark plugs and turned over with the starter motor and got 25PSI {I have a direct reading guage installed) can see no leaks . When running I'm pumping over 50PSI . NOW I NEED SOME HELP .Can the small "freeze plug in the main oil passage be leaking? I have NEVER had a plug leak and with checking some other builders including my Son who has built many T4 s for his own race car and many others . If this is a problem can I repair with "JB" weld? Please help, I hate to have to take this apart and start over. AL

With that quantity of oil leaking (filling the guides) I would say it’s probably coming out under pressure (i.e a loose galley plug) or you have a massive leak at the base of a cylinder. Were the cylinder spigots checked to ensure they were all level?

FWIW - a leak that large won’t be solved with JB weld.

Part of building an engine is being willing to unbuild it if necessary to troubleshoot and fix an issue. It’s never fun but it’s how we learn.

When you say your running 50 psi - at what RPM and what temperature? 50 psi is high unless your spinning 4k-5k rpms or right at a cold start before oil and the case warm up.

Check inside spark plug holes - is tin oil coated up top?

Borescope above tin if you have one.

Believe me , I've learned plenty over the years and dozens of rebuild , but I have never had this issue . 20 / 50 Valvoline racing = 80PSi at idle cold . I use it or DRIVEN 20/50 on my own T 4 s no problem. No other leaks , I've eyeballed the cylinders ...dry.

There are a multitude of galley plugs on the 3/4 side.

The main one above the guide tin is the pressure relief valve. That one should be removable and should have a crush washer.
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Can you remove some of the tin/accessories and run the engine? Could be a galley plug, hate to suggest, cracked case?

Oil pressure switch?
Oops. Missed it!

I think we found the oil leak problem . One of the cylinders is seeping oil out between the bottom (case side)two fins . Not the sealing gasket to case . Anyone ever seen this . AA cylinders. seems like the cylinder is cracked on the bottom because we removed the tin and the top and sides of that cylinder are dry.

If the cylinder is cracked, that's going to suck!

talked to me Son who has been building Ty4 for years and he has seen AA cast cylinders with a leak several times. . not a crack but pores . I'm taking that side apart now and will report back.

I have a set of 96mm AA P&C’s sitting on sideline - guess they will get extra close eye when they get used.

Hopefully AA Pistons will stand behind them if porosity or crack is found, documented, and brought to their attention.

In the same boat. I have a set on the shelf waiting to go. My recent build incorporated 96 P&C's from AA and are working perfectly. Seated just about instantly. I suppose anything is possible, curious as to a bad casting? Please report back and good luck with AA