Rod Cap Alignment

[tvd]

Hello,

I have a question about rod cap alignment when re-assembling a 1996 V4 looper, E120TLERK.

I am wondering about the "feel" of the crack where the rod and cap come together. I have searched and read posts on this question, but I haven't seen an answer to the specific thing I am experiencing.

I am doing this rod cap alignment as a dry fit for practice with the rod in a vise. I align the rod cap, and I can immediately feel when it is aligned correctly. Any mis-alignment is instantly noticible by a ridge on the outside of the rod that can be easily felt. So, I get it aligned, and lightly hand tighten the bolts, check again for sure, and then torque to spec.

Here is the problem: When the outside crack line is checked, no ridge or edge is noticible. But on the INSIDE of the rod where the bearing rides, there is a noticible edge, something that would not be acceptable if it was felt on the outside surface.

I have tried nine different rods, all with the same result, a "feelable" edge inside when dry fit and torqued.

I don't know if this is OK or not. Anyone have ideas or suggestions?

 

[tvd]

Re: Rod Cap Alignment

Anybody? Bump up....

 

[jonesg]

Re: Rod Cap Alignment

Why are you assembling it if its not on the crankshaft?

 

[tvd]

Re: Rod Cap Alignment

Why are you assembling it if its not on the crankshaft?

Well, for practice, to get the feel of how to align the rod caps. That's the only way I would have found out that the inside surface was "feelable" while the outside parting lines were smooth.

There is a noticible edge. Using the pencil method, you would feel it on the inside, but not on the outside.

 

[Mas]

Re: Rod Cap Alignment

On a matched rod/cap set...if the outside is perfectly even so should the inside...but if you torque the caps without the rod journals and bearings (which I would not advise) you may be seeing distortion that may not otherwise be there if installed on the crank.

Are you certain the cap/rod is a matched set?

I do not know, but that's my thinking.

Mas

 

[CharlieB]

Re: Rod Cap Alignment

The bearing surface is ground AFTER the rod is fractured, then bolted to torque spec's.

NO, there should NOT be any noticable 'feel' on the bearing surface, same as on the ground surface outside.

Something is amiss.

Either rod caps have been switched, or the caps have stretched, either case, they are out of spec and should be discarded.

 

[mikesea]

Re: Rod Cap Alignment

I have done alot of powerheads,I have only come across MAYBE a half doz.situations where the rod and cap had issues.You say you have 9 problems.that is suspecious.Are you CERTAIN they are matched properly?however,most rod cap sets are so different that a miss match is usually very obvious.Is it possible your being a little overly cautious"i say that with total respect.Anytime you have a seperation in a material ,if you look hard enough ,you will find the seam.Having 9 is just too much,the odds are against it.I suggest you get your best 4 and bring them to a mechanic knowledgeable of outboard rebuilds and ask for an opinion.Again ,Id bet your being cautious ,perhaps over cautious,get another Professional opinion.

 

[tvd]

Re: Rod Cap Alignment

Well, this is interesting.
I will describe a similar matching task. Lets say you break a china plate into two pieces (oops, not you, the wife breaks the china). The plate can be fit back together only one way, if it is off a very little bit, you will see the broken seam. If it is just right, you will barely be able to see the crack.
That is the accuracy level I am going for when aligning these caps.

I am getting the feeling that maybe you guys think I am just doing it wrong, or that I may be "too cautious" as mikesea suggests. Believe me, I value each opinion very much, and am considering all possibilities.

I can assure you, I understand what has to be accomplished, but I am really questioning the feelable edge when torqued down. Torqueing to 43 ft-lbs as specified on page 4-23 in my OMC manual in three increments. The beveled outside edges are so smooth you cannot feel them. The inside bearing surface has a definite feelable parting line.
The rods were removed by me, and matched with their caps immediately after each rod/piston was removed. There is no mixup of caps and rods.

Mikesea, will you PM me with your phone number? I am going to KW in a few weeks and wonder if you would look at these rods.

Maybe I am being too critical and overcautious.

 

[jonesg]

Re: Rod Cap Alignment

Look at it like this, what you're doing isn't in the service book.

 

[clanton]

Re: Rod Cap Alignment

There was a poster here or other site that worked in plant that made these rods. He spoke of going to OMC plant more then once during the time OMC was going broke. He could probley tell you anything you need to know about these rods. Not in the manuals about the rods, except which side up. I would want to know the size and out of round of the rod, with the cap torqued.

 

[clifton63]

Re: Rod Cap Alignment

I have searched this forum up and down for an answer and found this post as being the closest, but not exactly answering my problem. I am experiencing the same problem as this original poster. I am bench assembling the rod caps (not torqued all the way) with the outside seams in perfect alignment. I then feel the inside and it seems there is always one side that has a "feel" to it and would not pass the pencil test. I have a couple rods that have both sides passing pencil test. but the rest are ever so slightly off on one side (inside). My question is if the outside is perfectly aligned, why not the inside? I assure you that I have not mismatched the caps. Another question is: when I assemble on the crank with the bearings in place and the outside seam aligned perfectly, is this all I need to do and worry about?

 

[boobie]

Re: Rod Cap Alignment

Are you using an alignment gauge or a good sharp lead pensil ? Normally if the rod alignment is perfect when fully torqued and assembled all will be okay.