I've finally found the source of a clicking/ puckering noise in my motor. But I don't know what I should do about it. It makes the noise because on the upstroke of #5 cylinder the rod moves ever so slightly on the wristpin of the piston. I don't know what this means and what/if kind of damage would it do to my motor if I were to put it together and just dismiss it????

 

dont think it will do anything. It should be just fine.

 

if you can see/feel any movement on the wristpin you have a problem , FIX IT .

 

About the only way that can happen, is if the cylinders aren't pointed straight at the crank, and perpendicular to it; specifically, they are tilted to the front or rear.

Typical 70s block quality control problem. I've had blocks that had it so bad that rods would hit the side of the piston at the pin boss and bind up the motor. Literally trying to bend the rod. If you run a motor that way, is usually wears that cyl QUICK, and makes a funny pattern on the rod bearing which also doesn't last too long. A piston that has a wider space for the small end of th erod between the 2 sides of the pin boss, will "cover up" the problem; but it'll still be there.

The cure is to "index bore" the motor. Set it up on the crank CL instead of the wear, which is all that the "rebuilder" types usually do when they bore a block (since the block might or might not get cleaned up by boring it in the RIGHT place if the wear is in the WRONG place) so that instead of following whatever the factory did, the cylinder is adjusted to be perfectly in the place it belongs.

Sounds like you need a trip to the machine shop and a larger set of pistons; or another block and start over. What block is this? Who did the machine work? How far is it bored over now?

 

Well its the factory block that came with the car lasted 200,000miles then finally spun # 1 and 2 bearings. Then I rebuilt the motor into a 383 stroker had it bored .030 over, honed, line bore, cleaned, balanced. Then a month and a half down the road it snaps the crank on me when I strenched it a hair over 6000 rpms. Now I am rebuilding it again and I had a small problem with the machine shop because he told me he'd have it rebuilt in 2 weeks. Took a month and a half just to tell me that it has this noise that he didn't know were it is coming from and that he doesn't want anything to do with it. But he wanted his #$%^ing money $450 later I have my block back and have gotten nowhere.

 

The factory's QC got better, starting in the early 80s; but still, for a factory motor, it only has to be just so good. Anything past that, to them, is a waste; costs money, but doesn't MAKE money. In manufacturing ANYTHING, there's a point where "good enough" is reached; and that can be VERY DIFFERENT from what we might consider "good enough" in a high-performance or competitive situation.

People throw around the word "blueprinted" about engines alot. To most people, that means Plastigaging the bearings, and anything beyond that is all just a vapor. But very little thought goes into what that might actually entail, to get a block really PERFECT. Keeping in mind of course, that there's A WHOLE LOT MORE to how an engine runs, than just the parts list it's built out of, and the basic maintenance on the core casting like vatting or even boring. What you have there, is one of those things. A short list:

Crank LC parallel to and centered on bottom of block
Decks parallel to and equidistant from crank LC
BH surface perpendicular to crank LC
BH dowel pins centered on crank LC
Cylinders perpendicular to crank LC
Cam bore parallel to crank LC
Head dowel pins in proper location wrt cylinders and crank LC
Lifter bores perpendicular to and pointed directly at cam LC
Starter bolt holes correct distance from crank LC

There's plenty more, of course; those are just a few of the typical dimensions that have LOTS of tolerance, and are FREQUENTLY off, that come immediately to mind. Note how many of them involve the crank LC. And all of this is just THE BLOCK: no crank, no rods, no heads, no NOTHING, not even assembly!!!! There's SO MANY things to check that can be made perfect and otherwise improved on, that it's no wonder how some motors are just better than others, for reasons you can't figure out.

And of course all THAT, is AFTER you've determined that there's no "casting shift" in the block; since blocks are cast in sections, with kind of like a panel at a time added to them, and there's tolerance in all THOSE too, you can have a block where the as-cast parts are far enough off that the machined parts can't even be properly installed, or will create other problems (porosity, thin/weak, etc.). Then there's other little details that can go awry; for example, the 3 passages that carry oil from the front to the rear of the block, are drilled halfway from the front and halfway from the rear; and like the Chunnel, they don't always exactly meet in the center.

This is why all that BS about finding a "high nickel" block is just that, BS. Besides the fact that in the casting plant they used the plates that have those numbers on them interchangeably without regard to the metal, there's simply SO MANY things that are FAR more important than that about a block, that it's down about #50 on the list of things to care about. All this other stuff is a big part of how you end up with those deals where the Engine Masters guys get 475 HP out of a parts list, but when yerbasic hobbyist puts the EXACT SAME parts list together, it comes out 50 HP shy of that. No, the EM isn't all BS; but that's not the same as saying that you or I could duplicate what they did.

A few shops can CNC a block. There is actually a base "datum" on a block: look on the bottom, at the oil pan surface, and note that there are 2 large holes (¾" or so) that don't seem to have any purpose. THAT'S the datum. Everything else is located off of those 2 holes.

If the cyls are pointed wrong front to rear, then the rod and/or wrist pin will have to move from front to rear as the piston moves up and down, to follow the piston. Obviously there's a certain amount of side clearance at the big end, typically .012 - .016" or so; which allows the rod bearing to take up part of that motion. I.e., the wrist pin could stay at a fixed point in the rod and piston, and the big end move along the rod, to take up that tolerance. But if the cyl is farther off than that, then the pin HAS TO move from front to rear in the small end and/or the rod, as well.

Keep those 2 dimensions in mind: .012" of side clearance, and .030" overbore. Half of .030", which is the nominal amount of metal taken off in boring the block that much, is about the same as that side clearance. In other words, if the boring bar wasn't set up perfect, it's entirely possible to produce a BEAUTIFUL looking new bore, that will use up EVERY BIT of that side clearance, and then some.

Sounds to me like the thing to do would be to either take your block to a real racing shop, and pay what they charge and/or wait however long it takes, for them to straighten out your block; or, just buy a block from such a shop, already prepped in the size you need; or, just live with it. Without seeing how bad it is, I can't tell you that you "have to" fix it, or "it's OK", for sure either way.

 

Dang, sofa! Good of you to take the time to type that......VERY good info.
Exactly why I don't trust any billybob shop to produce something even close to what the General does nowadays.

 

Well if any place would sell a block already clearanced for a decent price I'd go that route but everywhere I look nobody sells just the block.

 

Let your "will" power overpower your "can't" power.