Leakdown on a never fired rebuild

[SoCal_Lynch]

This is a cross post with the engine building forum but didn't get a response there so hoping this more active forum can help.

Have a '78 ROW large port 3.0L engine I am looking at that was supposedly professionally rebuild 10+ years ago then stored since. Asking price on the engine is attractive, seller is a good guy but engine condition is all word of mouth since it has changed hands a couple times. It has been stored inside in with the plugs in and fuel injection system installed.

The seller offered to do a leakdown prior to my purchasing it this weekend. He said the engine rotates freely but is stiff with plugs in. When the leakdown test was started the PSI never got to 90 and there was 50%+ leakdown via the crankcase. Apparently you could clearly hear it hissing.

I would expect an engine that hasn't been fired and run-in to not have the rings sealed yet. I am hoping to get some coaching on this leakdown behavior and how concerned I should be about the ability to service it and then carefully fire it up and use it?

Any thoughts or experiences to share here? I don't want an attractive price to lure me into an engine that needs to be re-rebuild, at the same time I don't want to be unfair to seller and let a lack of knowledge have me miss out on a good engine.

Sorry again for the cross post but I need to make a decision and want to be fair to the seller. Thank you.

[yelcab1]

Pump some oil into the cylinders via the spark plug holes. Redo the leak down test. If it is still more than 20% leak down via the rings, pass on the engine.

[Solamar]

Here's my experience with leakdown numbers after a top end (valves and rings) -

Chasing leak down after valve job

An important bit that I don't see mentioned often, is different leakdown tools can give vastly different results. I had an old Snap-On LD tester that was calibrated so 50% was considered good.

Might be worth buying your own LD tester if there is doubt. There not expensive. This is the one I own -

Lang LD Tester

[SoCal_Lynch]

Thank you both for the responses. @yelcab1 - Doing a wet test is a good idea, will give that a go.

That was a good thread @Solamar, looks like you have a very healthy 3.2 engine there.

[Robman]

Thanks for the post. I’m the seller of the motor and completely understand the concern. I bought an OTC kit new off Amazon and it seems to work fine. The plugs are clean as is the rotor and no a drop on the engine. Not fired, not broken in.

I bought it very reasonably and knew the word of mouth builder as a fellow PCA AX racer up here.

I have 3 options: 1) sell it as is, 2) do a wet leak down, or 3) take it to a shop and break it in. Since it might be fun to take it in, I’m leaning towards 3).

I appreciate the feedback!

[SoCal_Lynch]

@Robman - I think #3 would be a good approach even it is prices me out, if it is healthy you should get full market value for it.

[john walker's workshop]

You really have to get it running and up to temp before doing a leakdown. Even then, it may need 1000 miles on it before you can get a true reading. Things need to wear in, ya know.

[Robman]

Originally Posted by john walker's workshop

You really have to get it running and up to temp before doing a leakdown. Even then, it may need 1000 miles on it before you can get a true reading. Things need to wear in, ya know.

Good point. It won’t be broken in on a test bench... Thanks!