Balanced assembly installed in Incorrect Order

[rhinosoft]

Hi All,

my 390 with roller cam etc and Edelbrock heads and manifold has always 'shaken' if that's the right word at idle after rebuild and not very pleasant to live with. I found metal filings in the filter the last two oil changes so pulled the engine this weekend.

What I found was 2 rod bearings were heavily loaded and had a lot of material worn away while the others while worn were not too bad. This is with less than 2000 miles since rebuild. The thing that had me concerned/annoyed was the entire rotating assembly was balanced but my engine builder may have put the wrong rod/piston in the incorrect locations.

- if the rod has a marking from 1-8 (which they do), should #1 go in #1 in the block etc etc?

- if the engine runs out of balance like this for a long time will the bearings be loaded up eventually fail?

Thanks for your insights - the bores are good, some minor scuffing so might have dodged a bullet?

Graeme
 

[My427stang]

Balancing consists of making sure all the parts match, then calculating a bobweight value which is then bolted to the crank during balancing.

With all the parts matching, you can move all the parts around without changing the balance. 

Now, as far as the shaking, you'll have to figure out what was happening.  If a bad balance, that'd do it, but it could as easily be a bent crank, twisted rod(s), wrong flywheel, etc.  FWIW, they can be pretty lopsided before they shake where you can feel it, something is definitely wrong

[fekbmax]

Were the two rod bearings side by side ?

[cjshaker]

The thing that had me concerned/annoyed was the entire rotating assembly was balanced but my engine builder may have put the wrong rod/piston in the incorrect locations.

- if the rod has a marking from 1-8 (which they do), should #1 go in #1 in the block etc etc?

Why do you think the rods/pistons may have been in the wrong locations? Can you expand on that statement?

While the rods are typically marked to go in their respective cylinder, 1-8, as you mentioned, it really depends on WHO marked the rods, WHEN they were marked, and what engine they were marked FOR. And it's always wise to double check on anything and not just assume that it's correct. Also, the bearing chamfer must go towards the outside of each journal, or it will chew at the bearing and radius of the journal.

Either way, even the 'good' rods should not be worn with only 2000 miles. Sounds like something bad is happening if there was a bad shake going on. Time to do a slow diagnosis and double/triple check everything and find out why it was shaking in the first place. Lots of things to check, but some of them should have been checked while it was running.

[rhinosoft]

Balancing consists of making sure all the parts match, then calculating a bobweight value which is then bolted to the crank during balancing.

With all the parts matching, you can move all the parts around without changing the balance. 

Now, as far as the shaking, you'll have to figure out what was happening.  If a bad balance, that'd do it, but it could as easily be a bent crank, twisted rod(s), wrong flywheel, etc.  FWIW, they can be pretty lopsided before they shake where you can feel it, something is definitely wrong

Thanks for all the responses - yes, the badly worn bearings were next to each other.

I do not know how the rods were setup - the engine builder back then (first build) bored the block to 60 thou, had everything balanced and I cracked the bore in #3 in short order, block has gone to God. Has since gone out of business so not sure about the numbering sequence and how everything was setup! But as you say it should not matter.

Now has Sealed Power pistons which were not balanced - those things are pretty rough too!

Graeme

[jayb]

Graeme, pictures would help.  Do you have pictures you can post of the rods and rod markings, and the worn bearings?  And which rods were on which journals?

[rhinosoft]

Will do Jay - won't have time until the weekend so stand by for those images.

Edit:: so many people here in Australia keep telling me the Fe is dead, whack in a Cleveland or 460 and that will be the end. But I want to stick with the FE in the old Thunderbird, spent enough that I can't throw it away now! I want a stroker kit actually and that will put me deeper in the hole - but not planning on selling it any time soon so it can only appreciate in value!!

Thanks for the interest.

Graeme

[rhinosoft]

Ok, I have the images - hopefully you can see them ok here. Straight out of photobucket.

EDIT :: oops forgot the rod markings - not all rods have markings and some are copper coloured...what's that about??!

Left bearing in each image is the top shell (closest to rod end) and right was in the lower shell - all in order here from #1 to #8.

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[jayb]

So, #2 and #6 are the ones with excessive wear?  Hard to tell for sure in the pictures, and none of them look all that bad (not scored down to the copper or anything).  With all the scoring on the bearings it looks to me like there was a bunch of trash in the motor when it was assembled, kind of like the oil passages weren't properly cleaned out prior to assembly, or there was some trash in the oil pump, something like that. 

That has nothing to do with the vibration issue, of course.  The rods are all marked with a number?  And the #1 rod is in the #1 cylinder, #2 rod in the #2 cylinder, etc.?  How about the position of the markings, were they to the outside of the engine for each rod?  Just trying to confirm that the pistons and rods were assembled correctly...

[Heo]

I'm with jay on the dirt in the engine. Especially that bearing
that's scored where the oil hole is in the crank
Check my build tread, what you can find in a used
oil pickup whe you take it apart
Then you have some not uniform wear pattern on some
bearings. Is the conrods round and straight or was there
some dirt under the bearing when they assembled the engine

But nothing of that explains the vibrations

[cjshaker]

I'd also agree about dirt being the culprit for the majority of the bearing wear, and that they don't look all that bad otherwise.

The vibration issue could be many things; a bad harmonic balancer, a miss or uneven cylinder loading, a bad/mismatched or out of balance flywheel/flexplate, a bad motor mount or transmission mount or just bad tuning for idle. Obviously you'd want to eliminate the flywheel being bad or cracked and that the balancer coincided with TDC, because those can cause serious and bad issues. And don't overlook the possibility of the WRONG flywheel/flexplate, because 428's and 410's used an offset balance on them, and if this wasn't determined before and during the balance job, a bad vibration would be the result. As for a bad balance job, that can only be determined by a rebalance.

[fekbmax]

Are they over sized bearings/ crank been turned ? I'm wondering if one of those rods were put in backwards. Normally with a factory crank or one that has been turned properly if you put a factory rod (or 2) in backwards it would tighten up enough that it would be quite noticeable when turning by hand but it's possible that a not so great crank turning job could take away some of the radius away allowing  a rod (or 2) to be put in backwards and not be noticed when turning by hand. I would think this could certainly cause a vibration. 

[rhinosoft]

Thanks for the feedback - you know, I have a gut feeling too the block was not cleaned out properly when it was machined twice. I have the invoice from the machine shop but it does not say anything about being washed & cleaned when I just checked - my fault.  The guy before that I doubt if he did anything at all and I could not get an invoice or anything out of him.

Assembly was possibly incorrect as well based on previous history. For example the first guy did not use rod protectors on the bolts and EVERY crank bearing surface had to be linished due to large scratches and bumps!

Ok - better go to plan C now, I am over this!

• Pull everything apart and have block checked and fully cleaned
• Check balancer and flex plate
• Hope the cam is not damaged - check that out
• Update with stroker kit and have it all balanced
• Have engine assembled properly
• Enjoy!

[fekbmax]

Sounds like a good plan, keep us posted..

[WConley]

The copper-colored rod is a factory fix to correct a slightly oversized bore in either end.  Rods that checked oversize on the line were sent in batches to be plated, then re-machined to spec. 

This isn't a bad thing, so don't worry about it.  The discrepancy would have been very small - tenths of a thousandth.

- Bill