Good afternoon all,
I'm trying to determine if my 65 Jetstar1 does in fact have the ultra high compression motor. Searching the forum I have found that the engine casting number in my car (386525A) is the 65 block, but not sure how to figure if it is the higher compression motor. From what I have read in the forum search, the heads are what makes the difference? I'm not real up on new cars, as I have mostly done 20's to early 50's at work, lol!


The engine looks virtually untouched, I.E., all the correct looking bolts and ground straps, and misc. brackets and clips that tend to not get put back on after a motor swap.


When I go to sell it, I would like to be able to state with confidence that the engine is at the very least, what should be in the car, since I cannot prove it is original to the car, not being the original owner. Any help appreciated.

 

Pistons, not heads.

Low compression pistons have a deep dish, high compression pistons have a shallow dish, ultra-high pistons have a shallower dish (or none, I can't remember offhand).

For what it's worth (probably not much), that casting number is the same as the engine I've got from a 65 Delta 88, low-compression.

What carb is on the engine?

 

It's the bigger 4GC 4 barrel.

 

ALL 1965 425 motors used the same block and head castings. Compression ratio was varied by using pistons with different size dishes. The only way to know for sure is to pull one head and measure the dish on the piston. You might be able to use a borescope through the spark plug hole to get an idea of the size of the piston dish. The engine unit number stamped in the end of the passenger side head should have a letter "G" suffix for a high compression motor, but that really just proves that the head left the factory on a high compression motor.

 

Thanks, Joe.


I guess one of the things I'm trying to figure out, is whether the Jetstar 1 came with only the Starfire engine, or if the 370 horse engine had to be ordered. Mine was pretty heavily optioned in my opinion, with air, PS, PB, seat belts, and tinted windshield. The fuel cap says "premium fuel only", and is referenced in the owners manual as well. If I understand correctly, they could have got a Starfire for just a little bit more.


It's a pretty neat old car to me, and just enjoy learning a little more about it. Thanks for your input.


Jim

 

for sure- measure piston

next best thing - Engine Unit Number on front end of RH head. If undisturbed original engine, that will suffice.

PFO gas cap is a good indicator of High Compression

 

Oh, why didn't you say so?

Per the SPECS booklet for 1965, the Jetstar I came standard with the 370 HP motor:

 

Thanks a million, Joe! All kinds of useful information there. When I get a chance I'm going to try to figure the cost of the car as optioned when new.