Engine Unit Numbers Explained

[Tom Klemme]

Sadly, I have to replace my blown 1957 engine (365 ci)

Im looking, of course, for an exact replacement.

My limo engine unit number begins 77K, but the closest I can find are blocks with Engine Unit numbers beginning 76K.

I know the first number signifies the year (1957)

I believe the K is the important part , because it designates all air conditioned , single carburettor models for 1957.  

Im not sure about the middle number, the book says 76K is for all series 60 and 62 cars with A/C and single carb, and the 77K was for limos and commercial chassis cars with A/C and single carb.  Whats the difference?

My assumption is if Cadillac give different numbers, there must be a reason. Im hoping that any difference is internal and not significant or obvious.  

Perhaps someone out there knows the difference(s) and can explain exactly what these numbers mean. Thanks.

Tom Klemme

[Philippe M. Ruel]

The only difference between 57 Series 75 engines and Series 60/62 engines seems to be generator output - and therefore voltage/current regulator. But front damper and crankshaft pulley are identical - no difference in diameter, same part #.

Hydramatic transmissions are not strictly identical (different unit #) but starter, flywheel and transmission cooling systems are the same.

There are much more differences between 57 Brougham engines and multi-carb engines optional on other Series.

[Tom Klemme]

Phillipe,

Thanks for your advice. Im learning more as I go along.  A couple of years ago I did rebuild my generator and learned at that time that the the 75s and 86s with air came equiped with the heaviest duty generator. Maybe generator capacity is the only difference between engines with 76K and 77k EUNs.

I wonder if anyone out there can confirm this?

I have a 76K long block to rebuild and replace my blown 77k.  

I trying to determine if the 76K and 77K long blocks are completely interchangeable. Any comments on this will be appreciated!

Alot of vendors say all the 365 ci engines are the same. so when someone tries to sell me a 58 block, I say, Not true! The dip-stick is on the other side!  Originality, at least looks-wise, is everything to me.

I dont really show the car but I do strive to keep it sbsolutely correct and original; its sort of a family thing, having mostly sat around the garage for most of its life. So, Im truly embarassed that just cruising down the highawy at 65 mph, I somehow let my beautiful and pampered 60,000 mile Cadillac to blow its engine.

Tom Klemme