http://cgi.ebay.com/ws/eBayISAPI.dll...m=221660739717

Seller is advertising block and caps separately

When questioned, he says:

"Ever since 1974 working on engines I never heard BS about MATCHED components (parts) that you talk about.

That's what they make micrometers for if you know how to use one.

- sciotospeed"

So, what say all y'all?

I have always heard, and it has been my experience that, the main caps should always stay with their block. While you certainly CAN machine another set of caps to fit a block, that takes time and money.

 

I accidentally mismatched a set of main caps and found that the difference in clearances literally seized up the rotating assembly. Luckily I had the correct set for the block. Things like this happen when you have 4 spare engines lying around lol.

 

Well in my case, when I bought my car, the disassembled original motor was in the trunk and of coarse....there were no main caps. So I had to buy caps on ebay and my machine shop guy had to carefully line bore the unmatched caps to my block and it worked Yes , he should keep them with block, but then he would get 0$ for them....I paid $50 for mine....fair to me....hard to find.......just my thoughts
Eric

 

I dont think a block always needs to be align honed, but if you change up the caps it certainly would need it. Same as buying Aluminum or bilit caps. I would think a very high performance motor may also need it to be sure everything is in good order, but not a street motor if ORIGINAL caps and no spun main bearings. JMO
And if he has the caps, why wouldnt he include them? thats crazy

 

The guy sounds like an idiot with a response like that.

 

x2

 

Well, at least he can read a mic, right?
:-)

has to stop chewing the gum first.

 

There is a guy locally here that is selling a Bbo bare block for cheap as it's missing the caps I have been tempted to pick it up as I have a cracked block that has a recent rebuild on it that froze ( marine motor ) and use the caps a rotating assembly maybe

Story short he has been trying to sell it for years now with no luck

 

If you have a block with mismatched caps it will need to be align honed, worst case it will need the register for the caps done as well. its really not too big a deal.

 

Back in my training program, I did a rotation at the WV powertrain plant. We receive our castings, machine them, then assemble the bolt on parts into engines and transmissions. The first thing on the short block sub line was the cap cracker. The block would be picked up, sat on the line, and run under a machine that would back the 4 bolts of each cap out. An end effector would pull the bolts, then a pneumatic cylinder device would lever the caps loose and you could sit them, and the bolts, in order on the tray next to the block, which would then go into the parts washer for catching the last bit of machining debris.

After the bearings and crank had been installed, the caps and bolts would be put back on in the exact same order, along with a bolt coming into each side of each main cap, making them 6 bolt mains, I suppose. They were machined with just 4 bolts though.

So, in my experience, it still matters a lot.

 

GM and Ford (UK) and I dare say other makes sometimes had the main bearing housings machined oversize.
Certainly I came across an Oldsmobile diesel that had oversize mains, and many British Ford engines. It must have been a fairly common practice, I was able to get the right bearings with little trouble.
I would put a big bet on any caps other than the ones that came with the engine locking up the crankshaft. maybe a line bore will work if the replacement caps are too far out for simply honing.

Roger.

 

So are you saying that you don't think the wrong caps will result in a misalignment?

 

Any mechanical engineer understands the fact that main bearing bores MUST be line bored with all the caps in place to take out production manufacturing tolerances. This is called "match machining" and once you do it, the main caps can only be put back in the original location. The alternative of making the block production and machining tolerances tight enough to allow the parts to be interchangeable is an economic non-starter.

 

Isn't it pretty much standard procedure during any build while in the machining process to line bore the mains?

I know I would insist it be done...

 

At the start of this thread is the e-bay post. I checked his other items he is selling, he has no bids on any of his items, that should say something! He needs to put all oldsmobile parts in one lot, if he hopes to sale.

 

no, but it should be done whenever the crankshaft has to be reworked

 

It's good practice but not typically done or required for a stock rebuild. The downside is that a line bore requires the main cap mating surfaces to be milled slightly, so the new crank centerline ends up slightly higher in the block. This can cause slack in the timing chain if the new centerline moves excessively.

 

When I had my first 67 442 forty years ago, I spun some main bearings while on the highway. Pedal to the metal for too long... LOL. It had to be align bored, I had to get an undersized timing chain. It was the first motor/engine I ever rebuilt, but all was good, also the only engine I ever rebuilt that started first crank.

 

Well, you'd get a little more compression, at least.

 

I just asked this question on Rop
Line bore required
Line hone required
In my area I would be looking $600.00 for both to be done.
I would pass unless the block was rare or numbers matching.

 

"I would put a big bet on any caps other than the one that came with the engine locking up the crankshaft".

I'm saying the wrong caps will result in misalignment.

I mean that if you put different caps on it will almost certainly need some machining. I would say definitely, but there is a multiple lotto winning odds chance that two sets of caps are interchangeable.

Roger.

 

I just thought it was crazy to sell the two things separately instead of keeping the caps that belong with the block, with that block.

Maybe it CAN be fixed with enough $, but why MAKE trouble that needs fixin'?

 

the caps were not select fit but the factory bearings were in various sizes