Guys,

I recently acquired a 66 model 425 (non toro from what I can tell). The engine had a stock 2 barrel intake. I have popped the intake and heads off. From my understanding there was a low and high compression version (9.0:1 and 10.25:1 maybe?). Anyway to tell from these photos of the pictures if it is high compression or low? They have a 'recess' but not sure if they are 'dish' pistons. Engine has 'B' heads.

thanks!
Warren..

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1964-67 V-8 Engine:
Code is stamped on the right cylinder head. Unfortunately, this only applies to what was originally the driver's side head. This code consists of a prefix letter (330 V-8=T (1964-65) or W (1966-67), 400 V-8 = V), then a production sequence number, followed by a suffix code letter (L = Low compression, E = 2-bbl export, G = High compression, H = 4-bbl export). A 2-letter code on the oil filler tube identified the engine.This should apply to the 425. Most likely a low compression 425 2 -barrel I recall it being 310HP.

 

B heads indicate a 66

 

Those are high compression pistons. 10.25:1. The notch is a V instead of a U.

- Eric

 

HC 2-bbls are not uncommon in that era
usually the HC air cleaner is red, so black 2-bbl = LC, Red 2-bbl = HC
of course if you don't have the air cleaner then go by the piston notch, head stamp, and maybe even measure the dish and calculate its volume.

 

Nothing I can find on drivers side head. Pass side front has an 'M' and then a sequence of numbers

 

Front of the passenger side head is the correct location.

The number will be Myxxxxx (with y= 5, 6, 7, 8, or 9 and x=any digit).

Mxxxxxx with no suffix letter signifies a 1966 10.25:1, 2bbl 425.

- Eric

 

Thanks.. that is what I was hoping for..

 

Look like HC to me....

 

All this info is great if your not going to rebuilding it. Once you change pistons and cam all that info is negated. Unless your doing a numbers match vehicle, but I don't think in this case.

Gene

 

I understand. Appreciate all the information.