Ok guys. I'll probably ask a few questions for the machinists in the group, from time to time, as I'm going thru the S.A.M. school. Just things that might pop into my head if an instructor isn't around (like sitting at home going thru things in my head) or if I'd like another viewpoint. So, here's my first one:

I've learned to use the dial bore gauge to check the main caps for clearances. I've also been able to cut down the caps pretty good, on the face to get a straight, square reference and then the ends to obtain trueness. Also, I've been able to measure the rod cap ends, give them a reference cut and then trim the ends.

HOWEVER, is there anything one can do to reference cut the fork of the rod and then trim the ends of the fork? I've not seen anyone do it and frankly, I don't see how one could do a reference cut without screwing it up. The fork doesn't sit firmly enough in the fixture to achieve the results that would be needed.

You guys understand what I'm talking about? I was told that there would be no cut required on the fork (from another student....I was staying after school), so I'm curious if that's correct.

I would just think that if you can square the rod cap end, then you would also want the fork square as well. Maybe it's not possible?

Thanks!

Justin,
I hope they are teaching you better than that. You HAVE to cut both the cap and the end of the rod. You have to remove the rod bolts to do it properly. You would not believe how crooked some of the factory cuts are but if you understood the manufacturing process, you would see how it works ok. They cut the caps and rods first, then bolt them together, then machine the entire rod ... sides, bearing bore etc. So it does not matter if the end of the rod or the cap is crooked. But ... if you try to do the "lazy" mans recondition by only grinding the caps, there is no guarantee that the rod will be straight when its done. I dont care what anyone says ... you have to remove the bolts and grind both the cap and the rod ... PERIOD !

We only see a few sets of stock rods in a years time as we do mostly peformance work and we deal with Crower and Carillo type rods and when we resize them we only cut the cap or if the caps have dowels in caps we cut the rod ends and those have always been square.


And on the stock rods we see when we cut the caps we do a referance cut to see if they are square if there not we shim the cap with a feeler gauge to get the cap to cut as it was done at the factory as we only take just a couple of thousands off. Then we resize them, Square the sides up check them for alignment. This has worked for us for 29 years now with no problems.

Taking the extra time to only cut the caps to there original factory cut and keeping the center to center distance to blue print I don't feel that I"m doing the LAZY MANS WAY OF DOING IT.

Bill has a good point but to cut the cap and the rods square on some rods that we have seen you would end up honing out up to .010 (MAYBE MORE TO SQUARE THEM UP) out of the rod and also the shortens the rods about .005

I think its better to keep the center to center distance as close as you can on a set of rods thats why we have always cut the caps to there original factory cut and only take .002 of the cap as you are only change the center to center distance appox. .001 which is keeping them a lot closer to BLUE PRINT SPEC. And that way when putting them in a block that has been sqared and decked the pistons sould be all the same or very close. And so far no complaints using this method.

This is only my opinion on what works for us at our shop.

We only see a few sets of stock rods in a years time as we do mostly peformance work and we deal with Crower and Carillo type rods and when we resize them we only cut the cap or if the caps have dowels in caps we cut the rod ends and those have always been square.


And on the stock rods we see when we cut the caps we do a referance cut to see if they are square if there not we shim the cap with a feeler gauge to get the cap to cut as it was done at the factory as we only take just a couple of thousands off. Then we resize them, Square the sides up check them for alignment. This has worked for us for 29 years now with no problems.

Taking the extra time to only cut the caps to there original factory cut and keeping the center to center distance to blue print I don't feel that I"m doing the LAZY MANS WAY OF DOING IT.

Bill has a good point but to cut the cap and the rods square on some rods that we have seen you would end up honing out up to .010 (MAYBE MORE TO SQUARE THEM UP) out of the rod and also the shortens the rods about .005

I think its better to keep the center to center distance as close as you can on a set of rods thats why we have always cut the caps to there original factory cut and only take .002 of the cap as you are only change the center to center distance appox. .001 which is keeping them a lot closer to BLUE PRINT SPEC. And that way when putting them in a block that has been sqared and decked the pistons sould be all the same or very close. And so far no complaints using this method.

This is only my opinion on what works for us at our shop.



And that makes how much difference on the old HP meter????

There is more difference in the stroke of the crank from the factory to offset any difference in center to center, The damn pistons are all over the map in a stock engine, each hole at a different height because of small differences in stroke, rod length and center to center.

Justin,

I want to agree with Carl on the "good" rods, but I probably do 100 stock rods to each aftermarket rod and from what I have seen, I will not do them without grinding both the cap and the rod. I feel that having the cap bolted to the rod in a square position is much more important than even loosing .010" of rod length ... IN A STOCK ENGINE. If someone brought me a set of stock rods to do for a performance engine, to be honest with you I would tell them not to waste thier money. You can buy a set of Scat or Eagle rods for not much more than what it costs to redo the 30 year old OEM stuff. Its just not worth it.

And that makes how much difference on the old HP meter????

There is more difference in the stroke of the crank from the factory to offset any difference in center to center, The damn pistons are all over the map in a stock engine, each hole at a different height because of small differences in stroke, rod length and center to center.

SO WHY MAKE THE PROBLEM WORSE.

I should of mentioned that the stock rods that we do in most cases are for a customer that building a street performance engine that we have machined a block for and are shooting for zero deck and the cranks are ground to the correct stroke and we sell alot of SRP pistons and when these engines are assembled the deck heights are not of as much as you think.

And on the cranks that we have seen the strokes not as bad as the phasing of the crank pins.

And I agree with Bill that the Scat rods are the way to go.

SO WHY MAKE THE PROBLEM WORSE.

And on the cranks that we have seen the strokes not as bad as the phasing of the crank pins.



How much would you say the phasing is off on a steel GM Crank???

By phasing I assume you are talking about what is known a degree??? One degree or more??

I found GM cranks, for that matter most cranks to be real close in this area so I'm interested in any observation that has real data tied to it.

A deviation of one degree is a big number.

As for making it worse, I agree with Bill, knock the bolts out and nip both the cap and the rod.

The only rods that are close on center to center are after market. I had access to a optical comparator to check this kind of thing and stock rods are all over the map, after market are real nice.

We just had a 427 big that was out of phase so bad it had to be ground .030 under on the rods.

And the stock rods aren't off that bad even after market have a tolerance of plus .001 and minus .001 which over all is .002 and we pay alot of money for some of our rods we buy such as the Carillo rod which we have checked and they seem to be the best overall.

We just had a 427 big that was out of phase so bad it had to be ground .030 under on the rods.

And the stock rods aren't off that bad even after market have a tolerance of plus .001 and minus .001 which over all is .002 and we pay alot of money for some of our rods we buy such as the Carillo rod which we have checked and they seem to be the best overall.

How much out of phase was the crank?? You need to answer the question and stop clouding up the issue.

First, THANKS for the wealth of responses! Discussing this stuff is even neater once you've actually done a bit of it hands-on.

Anyway, I'm rolling the responses around in my head and I'm thinking I may have clouded things a bit. Let me try it this way.......

As far as MAIN caps go, I understand to remove them and clean them up. Clean all mating surfaces for as true of a reading as possible. Bolt the caps back on (in the proper locations, ensure good register and use proper torque specs and sequence of course).

Then find the recommended main bore specs and tolerances. Using the dial bore gauge, measure the front and rear of each main. Record these measurements. If they are out of tolerance, then you would take the MAIN caps and give them a reference cut on each of their 2 faces (after measuring them with a dial indicator.....1/2 the main bore OD is how you might call it). Finally, with the reference done, you then cut approximately .002-.003" off the MAIN cap ends to get them square. Then they are bolted back on.............etc. etc. (Not glossing over what follows, but I'm trying to see if I'm doing the beginning procedures of an align-hone correctly).

NOW, moving onto the CONNECTING RODS, which was my original question (but somehow I threw main caps into the original question and I'm hoping that didn't mess anyone up.......).

Ok, clean them up and then measure the big end after it's been properly torqued. (hopefully already knowing what the proper specs and tolerance is). If it's out of round or out of spec, remove the rod bolts. Then measure the ROD cap with a dial indicator (1/2 the diameter I suppose). Give it a reference cut on each of the 2 faces. Then with it referenced, cut it square (hopefully), by removing .002-.003".

NOW, my original question....what the heck do you do with the rod fork? We were only introduced to the machines to get a feel for them. We haven't covered connecting rods in major depth or anything, so it is yet to come. However, in the brief explanation and introduction that I got to the machine, I don't remember seeing anything mentioned about cutting the ROD FORK. It wouldn't be difficult to put it in the fixture and cut the END of the fork (the 2 small places where it meets the ROD CAP).....but how do you get the proper reference cut for that? If I put the fork in the fixture and tighten it down, I can't get it stable enough. Also, I'm putting pressure on the big end, which gets it out of round (which I know I would be honing it later, but it still seems wrong) Do you put the beam in the fixture and then do it that way?.......naw, forget I said that.....still wouldn't work.

If the question was answered, I'm sorry, I guess I just didn't understand it. Common problem for me :) .

Anyway, with the orientation phase, they just gloss over a little bit of everything, so one can go out and practice on certain things with the machines to get a feel for it. Once I get to the section on connecting rods, I'm sure they'll really be taking me thru it from beginning to end.

Hope I didn't cloud the issue more. Thanks one more time!

How much out of phase was the crank?? You need to answer the question and stop clouding up the issue.

YOU MUST NOT OF READ MY ANSER AS I SAID THE CRANK HAD TO BE GROUND .030 ON THE RODS TO PHASE OR INDEX THE CRANK PINS IN TO SPEC. PM ME IF THATS NOT CLEAR ENOUGH.

First, THANKS for the wealth of responses! Discussing this stuff is even neater once you've actually done a bit of it hands-on.

Anyway, I'm rolling the responses around in my head and I'm thinking I may have clouded things a bit. Let me try it this way.......

As far as MAIN caps go, I understand to remove them and clean them up. Clean all mating surfaces for as true of a reading as possible. Bolt the caps back on (in the proper locations, ensure good register and use proper torque specs and sequence of course).

Then find the recommended main bore specs and tolerances. Using the dial bore gauge, measure the front and rear of each main. Record these measurements. If they are out of tolerance, then you would take the MAIN caps and give them a reference cut on each of their 2 faces (after measuring them with a dial indicator.....1/2 the main bore OD is how you might call it). Finally, with the reference done, you then cut approximately .002-.003" off the MAIN cap ends to get them square. Then they are bolted back on.............etc. etc. (Not glossing over what follows, but I'm trying to see if I'm doing the beginning procedures of an align-hone correctly).

NOW, moving onto the CONNECTING RODS, which was my original question (but somehow I threw main caps into the original question and I'm hoping that didn't mess anyone up.......).

Ok, clean them up and then measure the big end after it's been properly torqued. (hopefully already knowing what the proper specs and tolerance is). If it's out of round or out of spec, remove the rod bolts. Then measure the ROD cap with a dial indicator (1/2 the diameter I suppose). Give it a reference cut on each of the 2 faces. Then with it referenced, cut it square (hopefully), by removing .002-.003".

NOW, my original question....what the heck do you do with the rod fork? We were only introduced to the machines to get a feel for them. We haven't covered connecting rods in major depth or anything, so it is yet to come. However, in the brief explanation and introduction that I got to the machine, I don't remember seeing anything mentioned about cutting the ROD FORK. It wouldn't be difficult to put it in the fixture and cut the END of the fork (the 2 small places where it meets the ROD CAP).....but how do you get the proper reference cut for that? If I put the fork in the fixture and tighten it down, I can't get it stable enough. Also, I'm putting pressure on the big end, which gets it out of round (which I know I would be honing it later, but it still seems wrong) Do you put the beam in the fixture and then do it that way?.......naw, forget I said that.....still wouldn't work.

If the question was answered, I'm sorry, I guess I just didn't understand it. Common problem for me :) .

Anyway, with the orientation phase, they just gloss over a little bit of everything, so one can go out and practice on certain things with the machines to get a feel for it. Once I get to the section on connecting rods, I'm sure they'll really be taking me thru it from beginning to end.

Hope I didn't cloud the issue more. Thanks one more time!


PM me your phone number and I will see if I can help you out on both matters.

Justin,
I have to wonder what type of rod cap grinder you have at school ? With the Sunnen cap grinder that most machine shops use, it holds the rod and the cap by the flat sides, not the side that you are describing. In no way would you be forcing the cap or the rod out of round. I think you either need to ask your instructors to show you how to use the machine. You are making me start to wonder about your school :confused: I will try to remember to bring the digital camera to the shop tommorrow and take some pics, especially since I still owe Carl a shot of the bent up PM rod that I have there :) If you are serious about learning this stuff, you might want to buy Sunnen's book on engine rebuilding too. It covers a lot of the basics such as this.

If you are serious about learning this stuff, you might want to buy Sunnen's book on engine rebuilding too. It covers a lot of the basics such as this.

I second this......as a n00b to engine building, it gives SOO much info on how to check, machine, do whatever to every part of the long block. Well worth it.

Actually we have a Sunnen rod machine and my textbook is the Sunnen one as well. I'm going to check in the book, as I may have overlooked it.

As I said, I'm just in the beginning stages of the class. We have actually just been going over pistons and rings lately, so rods is yet to come.

I checked the Sunnen book and my Rick Voegelin book on Engine Blueprinting. There is no mention of a reference cut on the sides of the rod fork, before you cut the fork mating surfaces.

I'm befuddled. Maybe there is no reference cut on the fork as there is on the rod cap?

Wait a minute. Is there even a reference cut on the rod end? If you cut it down too much, wouldn't this change the rod side clearances? Maybe I never actually saw a reference cut on a rod cap, but simply confused it with the main cap in my head. Hmmmmm.

Lord knows I'm paying attention, but the amount of information that's being presented to me here can be overwhelming.