[ajzride]

Greetings 5.0

I have a thread for my car going on in the classics section:

'65 Coupe 351w

But felt like the 5.0 forum was a better place to get into the nitty gritty of my engine details.

What I have is a 351w that was machined last October. I had the block boiled and bored 30 over, and had the crank turned 10, no other work was done.

The engine has less than 50 miles on it, and less than 5 hours of run time, and the crank looks like this:



Those grooves are as deep as a dime

So the engine is back apart, down to a bare block, and I'm trying to decide exactly what I need to do, specifically with regards to machine work.

I have two options that I am considering:

A) Order an Eagle Stroker Crank and some Probe Stroker pistons to use with my stock rods and make a 393w
B) Use a 1969 351w stock crank that I have, and just have it turned.

Either way I am buying all new main and rod bearings, gaskets, and head bolts.

Here are my two main questions:

1) I did not have the block decked last time it was apart, how important is this going to be? And by decked, I mean having the surfaces where the head gasket sits cleaned up and polished to ensure a good seal. What are the risks I'm running if I skip this, what are the probability of those nightmare scenarios coming true? Is it a waste of time to have this done to the block if I don't have the heads done as well?

2) Both the Eagle crank and stock crank are 28oz externally balanced, do I need to have a machine shop balance the rotating assembly? I am using a summit 28oz harmonic balancer. What are the risks I'm running if I skip this, what are the probability of those nightmare scenarios coming true?

If I have the motor balanced, won't the machine shop have to assemble the crank+rods+pistons. If they do this, will they go ahead and torque and plasti-gauge everything, so that all I have to do is finish the assembly, or will it still be disassembled?

I know the easy answer is buy a stroker kit with new rods, pistons, and crank, and have all the machine work done. But my project is crazy over budget, and I'm trying to get it back under control. At the same time, I don't want to cut corners, and wind up back where I am right now, tearing my motor apart before I have a 100 miles on it.

Thanks in advance for the advice.

Edit:

I forgot to state my goals. This is a weekend cruiser. I'm never racing it, never taking it to the strip. It will never see over 6500 RPM. I just want something with enough torque and hp to have some fun with.

[FastStang91Lx]

Decking the block is for 2 reasons that come to mind right away. One is ensuring a 'true' surface for head gasket sealing, and the other is to get your pistons TDC literally at the top of the block. Your pistons could be/probably are sitting lower than surface level which won't give you a true compression ratio either. How important to you? That's your decision.

Balancing the assembly is not done assembled. At least to my knowledge, lol. The pistons are weighed, and using the lightest one as the example, weight is taken out of the pads underneath for making them all weigh the same. Rods, same thing. Then the crank is spun with bobweights on it preferrable with your balancer and flywheel/flexplate on it too, and weight is removed where need be. How long, and how smooth you want this motor to run is up to you, but I wouldn't just throw anything in unbalanced unless you trust the company that it comes from and buy the harmonic balancer and flywheel/flexplate from them that was used for balancing to ensure it was done properly. Will it be close enough? That's the decision you have to make.

[93hatch]

cool machineshop

[ryanw]

do you have a theory on what caused the crank failure ? what signs were you seeing that made you tear the engine back down ? I'm assuming no oil pressure ?

[ajzride]

A picture (or vid) is worth a thousand words right?

YouTube - 351w Rod Knock

YouTube - 351w Rod Knock

As for what caused the damage... Maybe low oil flow. The crank was exposed to some drops o battery acid, and I'm sure that contributed to weakening the metal, but for it to have happened so quickly I think there must have been some other factors. I'm hoping the machine shop can spread some light on it for me.

[fogged306]

Definitely look into why that happened before anything else.

If you go with a 393 route, You should be able to use your rods, a 393 crank, and 302 pistons.

[ajzride]

Machinist says the problem was definitely oil flow. He is going to check the galley plugs while he is cleaning up the block and the first place I'm going to start at is my oil pickup. It didn't quiet clear the oil pan when I put it in, and I had to modify it a little bit. He also said there is a chance that my bearings were too large, and gave me quite a chastising for not plasti-gauging the mains and rods when I put the motor together.