I just want to make sure I have this right:

5.565" rods will require no clearance in the block where the 5.7" rods will require some grinding of the block in order to have sufficient clearance.

Is this a true statement?

How much of the block needs to be cleared? Ive done some porting work but am no means an expert so should it be tried at home or leave it to a machine shop?

 

That is not necessarily correct. It depends greatly on the rods themselves, the rod bolts, and the individual block.

Clearancing the block is an easy thing to do. You just put the crank in, and stuff one rod & piston; rotate the crank and see if the rod hits anything anywhere; and grind accordingly. You want to remove as little material as you can to get the job done, but make sure there's .030" or so of clearance. A die grinder is best. Install each rod & piston (you don't have to have the rings on the piston) and clearance them individually. Fairly time-consuming (= expensive if you pay a shop to do it) but not difficult or technical. Thorough clean-up is required afterwards.

There can be an issue with the cam too; it's best to do a trial fit of each rod with the cam in place after you get the block all done. Sometimes you have no trouble; if you do, but it will usually be the corner of the head of the rod bolt. Sometimes you can just touch the bolt with the die grinder and fix it. It depends on the cam and all the other factors listed above. You can also get small-base-circle cams for this situation in some grinds; if you do that you'll usually need longer pushrods.

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"So many Mustangs, so little time..."

 

Though putting shorter rods in may eliminate some machining that will need to be done, that's the last thing you want to do as far as a performance/durability standpoint.

The reason for using 6" rods in a 383 is that going to the longer stroke makes it that much harder on your engine and brings your rod to stroke ratio way down, which leads to the engine reving much slower and the cylinder bores getting out of round much sooner. Going from a 5.7" rod to a 6" makes that ratio better, but it's still worse than a stock 350. You want to run the longest rods possible in the engine without making your piston crown too thin.

So going to a 383 makes the situation worse with the longer stroke and the same length rod. Going with a shorter rod makes it much worse and would not make for a very well-designed or thought out engine. Regarless of saving a little clearancing.

That make sense?
Todd

 

I agree with everything RB said with one exception. Now this is just me, but I would not run with under AT LEAST .050" clearance between the rods and block / cam / cylinders.

I'll mock up a piston / rod and check with a .050" drill bit. If it will pass between, your okay, if not, grind some more. I shoot for .075" and live with .050".

It's best to grind the cylinder prior to the final hone. If that little sucker slips, it'll make a mess of the hone in a hurry.

When building a stroker or useing longer rods than OEM, I'll go ahead and get a cam cut on a small base circle. If you end up with clearences too tight to the cam, your screwed unless you've got enough metal to grind away from the rod bolt.

If my damn flash path adapter would ever show up, I could send you some shots of the block I just finished working over for 6" rods. It's a simple proccess. Just takes patience and an assortment of burs for the die grinder. Piece of cake, don't sweat it.