sldwys

How to determine if engine is true high compression or low compression. 67 olds cutlass supreme convertible. Member on here is selling and neither of us are sure what engine.

Any help would be appreciated. I want the engine if it checks out.



Pic of engine.

joe_padavano

The cowl tag unfortunately won't tell you anything about the engine. If the heads have not been touched, the engine unit number stamped on the front of the passenger side head will indicate high or low compression. The foolproof way is to use an inspection camera in one of the spark plug holes to look at the size of the piston dish.

sldwys

I gotcha. Can you atleast confirm from the cowl plate it’s a cutlass supreme?

joe_padavano

The engine unit number will look like the lower photo. A 1967 330 engine unit number will start with "W", followed by six digits. A low compression 330 will have no suffix. A high compression 330 will have a "G" suffix. While unlikely on a US car, an "E" or "H" suffix would indicate a low compression export motor.

joe_padavano

33867 is a Cutlass Supreme convertible.
Trim 980-C is a black vinyl bench seat with arm rest
Paint T-2 is Cameo Ivory (T) lower body color with Black (2) convertible top

ACC Codes
Group 1
E = tinted glass
X = power windows

Group 2
E = firewall piercing for A/C

Group 4
F = outside remote mirror

Sugar Bear

ID the pistons as suggested or test compression on a cylinder. A forum member will know the pressure expected for LC vs. HC. If it is high compression # you know it is an HC engine but if a low # it could be due to leakage.

Does it have a Premium Fuel Only gas cap?
That is another indicator of HC; but, obviously it could have been changed.

ID the pistons if you can, it is the most conclusive way.

Good luck!!!

Oldsmaniac

If original air cleaner and paint its a low compression engine. Black was used on the air cleaners if it was a LC engine. The HC engines got the orange air cleaner paint.

brianbeez67

Here is a pic of the pistons, to me would be hard to tell the diff if not in your hand?

joe_padavano

HC has a dish about 1/16" deep. LC is about 1/4" deep. It's pretty obvious.

joe_padavano

oldcutlass

I've always believed that if it came with a 4v it was hi comp and a 2v was low.

joe_padavano

Unfortunately that is not correct for the 1967 330 motors.

sldwys

Thanks for all the info. I never got the engine and wasn’t driving 4 hours since it was assumed to be low compression.