Rebuild Question

[Robert O.]

Hi everyone,

Greetings! I am new to the group and am writing with a question about an Atomic 4 I might buy. The engine came out of a boat from the late 70s. The current owner/seller had it rebuilt via a professional shop but noted that the mechanic determined there was no need for the cylinders to be bored or even honed. I was wondering if someone could tell me if this is possible on such an old engine - that the cylinders would still be in good shape. The current owner/seller seems to have a lot of integrity and put a lot of work into the engine. He consulted Moyer at length for the rebuild which I like. This one point is sort of acting like a splinter in my brain😊. On a diesel, which I have lots of experience with – boring is really the primary task of a rebuild.

Thanks so much for any help or advice the group can give,
Robert

[thatch]

Hi Robert, and welcome to the forum. It is quite possible that the engine was in sound enough shape that boring the cylinders and replacing the pistons was not necessary. The A4 is a "long Rod, low compression" engine that is far less prone to cylinder wear than most engines. While rebuilding the engine the mechanic should have "de-glazed" the cylinders so that the new rings would seat properly. If you do decide to buy it two tests should be performed. First a compression test and secondly a low pressure water-jacket test to insure that the block and manifold are still in usable condition. Water jacket "rust-outs" are quite common in engines this old.
Good luck, Tom

[Robert O.]

Hi Tom,

Thanks for the fast reply and awesome information. I was also thinking about the water-jacket. This engine had a leaky water-jacket plate that was replaced as part of the rebuild. I think I read that this could be a sign of block rust-out but perhaps I am wrong. I will do both tests. I was wondering if you think it would be a big deal to ask the seller to crack open the plate so I can inspect the inside - or perhaps as you suggest a pressure test will provide the same information.

Thanks again!!
Robert
Cape Dory 25D
Alberg 30 (in-refit)

[thatch]

Robert, Before removing the water-jacket side plate, I would do the pressure tests and then proceed directly to things like the ignition and fuel system. The rebuilder should have cleaned the water-jackets during the re-build process. It should also be an easy matter to attach a garden hose to the system to check for flow, being careful "not" to apply too much water pressure.
The water-pump should be bypassed while doing this test.
Tom

[Robert O.]

Hi Tom,

Thanks again! Really great advice. I have been in contact with the guy and he agreed to the two tests - awesome. I am looking at the engine later this week and will follow-up to let you know how it goes for sure. I appriciate your help, it will make all the difference when it comes to the buy/no buy decision.

This is such a great group. I have been searching past posts which are just loaded with great information. I hope to be able to contribute myself when I become experienced with this engine. Thanks again!

Robert

[Al Schober]

Not needing a bore job is consistent with my experience with at least two engines. You'll likely find that there's not even a need to ream out a ridge at the top of the cylinders. Just a light hone and reassemble with new rings.
The A4 block is made of a high chromium alloy which resists corrosion and wear. You're likely to find that all that's needed is new rings.
Valve seats are another issue. Suspect you'll find that the intake seats aren't too bad. Exhaust seats are likely to need some work. Last engine I did the shop installed carbide inserts - no extra charge.
While the block is in the shop have them do the Kaminsky mod to the transmission casing. This is a drill/tap for a 3/4" pipe plug that allows the reverse shaft to be removed without removing the transmission casting. This is very handy if you ever have to replace the roller on the reverse shaft.

[Robert O.]

Hi Tom and Al,

Al, my apologies I did not see your reply some weeks ago! Thanks for the great advice. I was just posting about a different topic and realized I never circled back to say I purchased the engine, and it is great. Thanks guys, I really appreciate the help.

Robert