Thread: Did I buy a 428 and get a 390 Thunderbird?

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NO "A" after the dash mark, it is C6ME only. There seems to be an obvious grind mark after the dash though.

on the intake manifold and it says 390 66 6 6 b 357 S.

Originally Posted by afanoni

on the intake manifold and it says 390 66 6 6 b 357 S.

If you found the tag on the engine and it says 390 it sounds like you have a 390. On a side note it sounds like you have a 390 gt intake on the motor worth $50-75.

it seems there are too many things that point to the 390, but does anyone know why the machinist is not satisfied with anything other than a piston and/or a crank number? It seems obvious enough with the stroke measurement and his response to me was: A tape measure is a tool for carpenters and I ain't a carpenter" boo hoo.

I just talked to a person referred to me who is quite involved with T Birds and clubs and all. HE says the Engine block I have C6ME is a Mercury Block and could have a 428 crank in it. He referred to it as a 410. He also says to look for counterweights on the flywheel. And I do NOT like to get under the car because it wrecks my hair and my hands, but what do you think of the other ways of finding out about the block. I guess we are certain the intake manifolds etc.. are 390-ish, but are they built that way? Why would this happen?

Yes they did make 410's which are 390's with 428 cranks but i believe that engine tag would say 410. It seems odd that the car would be originally a 428 car, yet end up with a 410 in it and have a 390 engine tag on it. It could happen but i doubt it. Here is some good info on the flywheel, and they should also have some good crank identification info. The easiest/sure way to find out if its a 428 crank is to pull the pan. The crank is all you're after anyways.

The 428 has a added weight on the harmonic balancer also (external balance)

Ron

I tend to agree with some of the comments about "does it really matter?" So it isn't (maybe) a 428, big deal. Why are you so hung up on those extra 38 cubes? If you figure it diminishes the value of the car, I am not a purist, so that is only something you can know. But as far as the car being usable and just as much fun with the 390, I can't see where there is any difference.

Not to insult your car, but it is a '66 T bird, not something as rare and expensive as a Hemi Cuda or COPO car. It is still a great car, so just have the engine work done, drive it, and enjoy it. If you want it to be a 428, tell onlookers at shows and cruises that's what it is. They won't know the difference, and we all tell little fibs about our cars sometimes.


Don

Originally Posted by shoprat

The 428 has a added weight on the harmonic balancer also (external balance)

Ron

That's the SCJ only. It used the "cookie cutter" crank spacer to put the missing crank weight pad on the nose to balance the heavier LeMans rods. It also used a larger dia and thicker harmonic balancer from the 427. If you put a CJ and SCJ crank side by side you'll see the CJ unit has a extra weight on the cranks 7th counterweight. The SCJ does not. Also the CJ and SCJ flywheels have different weight pads but as mentioned both and the std 428 are all external balance. The CJ and std 428's used a FE stock balancer with another exception. The 428 PI's I believe used the larger dia 427/SCJ harmonic balancers. But it's been a few years and the mind ain't what it used to be. LOL. I'm pretty sure my old 67 Shel had one tho...

I'll agree with everyones train of thought....if the 390 is a good running engine enjoy it and leave well enough alone. The 66 bird is a wonderful ride so enjoy. If a 428 is what you must have you can shop and build a shortblock and change it in the future. It's next to impossible as mentioned to tell a 428 from a 390 from the outside anyway. But that is your decision.

G.