I was wanting to know if the crankshaft can be interchanged into different year blocks as long as the appropriate flexplates and front crank spacers are used?

Say install a 79 externally balanced crank into a 77 internal balance engine block and use the front crank weight for the 79 and the balanced flexplate for the 79 crank.

 

NO! You must keep all rotating parts together. An externally
ballanced block, (or crankshaft assembly) has a certain counter balance depending on the year model of the parts.
A motor that has been internally ballanced will be, as they say (0) ballanced. This means that an externally ballanced rotating assembly will not have the correct offset on the end of the crank.

You will have a huge vibration if you mix these parts up.

Of course these blocks must be the same engine type and cubic inch. There is more to it than just what I have told you. You must do some reserch of give us more info on what you have and are trying to do.,,,,,,,,,,

 

The crank dimentions are the same, the difference as you stated is the reciprocating assembly. Although blocks do vary in deck height, as long as the bore is the same it can be done. Been there, done that.

 

So you are saying you can not, for instance, use a 79 crank and the 79 externally balanced flexplate and the appropriate 79 weighted front crankshaft spacer and install them in an older block.

I am not meaning mix and match components. Keep the appropriate fixtures on each end of the crank, that apply to the year of the crankshaft.

When I rebuilt my 79 460 it had D6xx rods in it.

 

As long as you use the correct damper, spacer, & flex plate, yes you can. You just can't use an external balance flex plate on an internal balance engine & not expect to be rattled out of the truck

 

I don't see any balance issues with what you're talking about Superdave. The block doesn't know the difference if you have an internally balanced assembly versus an externally balanced assembly.

Rods are irrelevant. Harmonic balancing (the issue at hand) and reciprocating balancing are two different subjects and really don't relate to each other as far as your question is concerned.

 

77'F-150Mudder

Yeh, I know the rod issue is not relevant, just pointing out that my 79 block uses rods with a 76 casting number on them, as in, it did not know what year they were because the proper balancing parts were on the crank.

What you said is what I was thinking. The block does not know whats in it as long as the appropriate parts are on the crank relevant to the year of the crank, for balancing.

This is just one of those things thats good to know for future reference.

Thanks,

 

Superdave, I wasn't trying to be a smart *** or condescending. Sometimes I have a tendancy to make very direct and to the point statements sometimes and I think it comes off wrong.

 

77'F-150Mudder

No offense taken.

I just was just clarifying what I was trying to say and appreciate your response.

You know how sometimes its hard to put to words, what you are thinking and then present it in a manner where someone can understand what it is your trying to say.

I suffer from that on occasion.

 

I can tell you from experience that you can not put a 429 or early 460 crank into an externally balanced block. Only because the counterweights hit the block. I know this first hand because I tried it. But I see no reason you couldn't go the other way. The block itself has no balance issues


Bushman

 

Chris, I have not forgotten about the 460 sitting under your bench.....My wife is cramming for Finals, and I of course am assembling and typing EVERY ONE of her end of term papers....let me know if you need any professional typing done, I think I am up to 40 words per minute.....lol.
A Pox on college professors who like to receive assignments back in essay form....