Straightening Harley VL rods

[Buster]

I am ready to install cylinders on rebuilt bottom end of my 1931 VL motor. This motor was built from parts and most of the parts have never been run together. I have checked straightness of OEM rods to crank case base for cylinders with the S & S connecting rod bushing dowel and found dowel to be approx .004 higher on one side of cylinder base area of crankcase showing non alignment with cylinder base of crankcase. When I match up dowel to cylinder studs mounted in case, the rods appear to have about a 1/16" twist in them. I have made a tool as S & S described on their web page which grabs the rod beam to twist the rods back in alignment with cylinder base mounting area of cases, but rods flex and go right back to were they were. Am I not twisting it far enough. Just trying not to twist too far and mess up this fresh bottom end. I know people are going to say I cannot straighten rods this way when already installed in crankcase, however I cannot see how to get them in alignment with cylinder bases with the rods outside the cases. Any help,appreciated.

[aumick10]

Buster,
First of, the cylinder studs are not relevant in the alignment of the rods, they only need to be square to the case deck (Where the cylinders bolt on) I am not sure on this one but unless the cylinder studs are a perfect square, you cannot use them as an indication of twist. It won't affect the engine operation on a flat head motor.
You don't mention which rod has the 0.004" clearance. The forked rod will have less rock than the male rod, assuming the races have been honed parallel.
The measurement is taken by pushing a rod to one side, measure this, then push it to the opposite side and measure. The average measurement is the square/out of square measurement. The average reading is what the piston wrist pin will see. If it is too much offset from the case deck, the wrist pin retainers are usually pushed out and the wrist pin gouges the cylinder wall.
If both rods out by the same amount. This would indicate that the main bearings were line reamed out of square with the case decks.
Using the S&S rod bending tool can take some effort. I have done maybe 50 bottom ends and only had to bend/ align the rods twice.
Take it slow and try to feel when the rod moves, if you have to do it.
Cheers,
Mick

[Steve Slocombe]

The military Harley 45 manual, available on the Virtual Library, has a very clear procedure for straightening bent rods.

[kitabel]

Don't some instructions say to insert a long bar through the piston pin bushing? Eek!

I've read the factory method, and referred this process to a friend in the bearing industry.
He made some rude remarks about the wisdom of using a lever to press hardened rollers into a hardened crank-pin - unless you take it part, how would you know if the surfaces "disagreed"?
It apparently works, none the less.

[aumick10]

If you try and hold the rods at the crankcase face, you will never be able to tweak the rods, you need the full length of the rod to get some leaverage.

I don't like the bar through the piston pin method that harley recommends. The wrist pin bushing is bronze and would probably distort.
Harley have another tool they described to grab the rods on the Ibeam section to tweak rods. They provide details on how to make this tool. I have been through all my manuals, but cannot find the correct one. I think from memory that is was published in one of the Shovelhead service manuals.
It is a 2' bar with two blocks welded onto it that snugly fit across the web of the rods to tweak them sideways. This sounds like the S&S one that Buster mentioned.

The rod bearings are designed to take the pounding of the gas explosions. They seem to be able to take the pressure of tweaking rods. Just take it easy and do not pound the bar or rods.
They rods will flex before they take a new set, just sneak up on it.
Once again you do not specify where the 0.004" play is measured.
The rods will rock as they have clearance in the lower bearings. You need to tweak the rods so the clearances are the same when you push the rod to one side or the other.
I agree that this process seems primitive, but this is the official Harley repair procedure since the thirties.
Cheers,
Mick

[T. Cotten]

HD no longer recommends it either, Mick!

Or at least my "schooled" associates tell me so.

Tweaking the female rod while assembled skews the races, especially when there isn't a reinforcing "oil scoop" web like later models.

Rods can only be accurately gauged, straightened and aligned 'on the bench', with proper equipment of course.
Anything else is a "field repair".
(A brief discussion can be found at http://virtualindian.org/1techflywheel3.htm)

Do we want rods square and aligned to the crank, or to the case decks?

....Cotten

[aumick10]

Cotton,
I am not surprised the tweaking bar is no longer recommended.

We must consider that misaligned rods usually point to a more serious underlying problem.
Any lapping or line reaming must be done so that everything is square.

If the main bearing races are not line reamed square to the cases, you will have rod misalignment.
If the rod races are not hones square to the rods, you will have misalignment.
Harley bottom end races typically wear in an oval shape, due to the power stroke pushing down on the races.

It all comes back to proper rebuilding procedures.
Cheers,
Mick

[T. Cotten]

I agree of course Mick!

I guess my point would be that re-fitting either end of the rod introduces error, so straightening and alignment comes afterward, before assembly.
(Better de-magnetize, too. I suspect the Sunnen does it.)

They don't really wear that much oval; they stretch.
Once upon a time I pressed out a male Chief rod race, and re-installed it ninety degrees off so it could be honed to match the female that didn't stretch as much.

Still running I believe. With a hack at that.

...Cotten

[Buster]

I went back and got better measurements. From S&S measuring dowel to cylinder deck on crankcase, the rear rod is pretty good when measured at front and rear of deck. The front is .004 high at front position and .0015 high a rear position. I will try to align the front rod and I believe I am going to leave rear rod alone. I have metal ordered to make the S&S tool. Manual says to correct rod first for sideways alignment and then for twisted alignment. I know this is a very controversial subject and I appreciate all advice.

[T. Cotten]

I've gotten away with it, Buster!

Good luck of course.

...Cotten
PS: Measuring bend side to side is easy, like my first attachment.
But how do you measure 'twist'?

[Buster]

Cotton, Good question on twist. Steve Solcombe pointed me to the military "45" Engine Overhaul Manual". Page 31, section 14, part 1 describes how to identify twist and section f at bottom of the page describes how to straighten a twisted rod. Unless any better ideas come up, looks like that is the way I will attempt to remove twist if I have any after removing bend.