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bearing and piston questions

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Skip & Lynne

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Hey does anyone know if the A/H pistons were ever coated? Mine had what appear to have a teflon coating on the skirts. It might just be some blowby since the wristpin side was bright aluminum where they had been rocking in the bore. Also there are no markings on the pistons or bearings indicating size. Judging from the bore and journal dimensions I think my engine has stock crank journals and bore. Anyone know anything. thanks Skip
 
[ QUOTE ]
Hey does anyone know if the A/H pistons were ever coated? Also there are no markings on the pistons or bearings indicating size. Judging from the bore and journal dimensions I think my engine has stock crank journals and bore.

[/ QUOTE ]
Hi Skip,
To my knowledge, Healey piston skirts were never coated. Original factory pistons might have a small <1>, <2>, or <3> stamped into the tops. this denotes a slight difference in piston size to allow for selective fit to the particular block bore during factory assembly. There were usually corresponding marks stamped into the top block surface.

Standard bearing shells will havo no size marking on the backs. Thicker bearing shells will be marked with the undersize such as .010, .020, or .030 on the back of the shells.

It is not uncommon for Healey engines to have original bore & crank sizes after high mileage & still have nearly perfect bearing surfaces. Those that had some kind of disaster such as loss of oil pressure excepted. Sounds like you have a very original engine.

An aside: On a new engine that I was building, I would consider having the piston tops coated with a high tech ceramic thermal barrier. This increases thermal efficiency of the engine & reduces operating temperatures somewhat, just rambling.
D
 
Following along with Dave (ever notice how often that happens...?):

About the last ten engines that I have built (MGBs, Spridgets, TR's and a couple of Buick 3.8s) I have done the whole enchilada of engine coatings; thermal barrier, thermal dispersant and dry film lubrication. I used all Techline products.

While a bit labor intensive, adding about a week to the build time of each engine, I doubt I will ever build another engine without doing this process. Unfortunately, the Healey was last gone through before I discovered metalic/ceramic & polymer coatings.

Give this some thought, I feel it is well worth the trouble. Perhaps not so much from a performance standpoint as a reliability one. The rotating/reciprocating parts are better protected from a momentary loss of oil pressure; the water jackets have less heat being radiated to them for a reduced load on the cooling system (I proved this to myself with a previously hot running 3.8 in an MGBGT).

techline
 
Randy,
To go a little far out, a light coating of carbon on piston tops & chambers will perform somewhat of a thermal barrier function also. In a well setup & tuned engine the carbon never builds up much beyond a minimum beneficial level.
D
 
[ QUOTE ]
Randy,
To go a little far out, a light coating of carbon on piston tops & chambers will perform somewhat of a thermal barrier function also. In a well setup & tuned engine the carbon never builds up much beyond a minimum beneficial level.
D

[/ QUOTE ]

I KNOW that to be true! Being in the boiler business, nothing ruins the effiency of a boiler like sooting up the tubes. Scale on the waterside (of the tubes) is another detriment. And it doesn't take that much (of either) for the performance to fall off.
 
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