Rod resizing, who to send to?
 

With rod resizing, do most on here find a local shop or ship to a known expert on this board and ship?

Also read dozens of threads on this back to 2004 and have a nice headache...

Best I can tell, if you go to arp 95% on here recommend resizing.

Where it gets hazy, is with standard bolts... Assume you measure and it's not out of round...

If you reuse your old bearings and new bolts, do you resize?

New bearings, new bolts, resize?

My understanding is you don't need to resize if using the standard bolts... Is that right?

The 944 guys seem to be changing bearings often due to a high risk of oil starvation and spun bearings. Seems it's just done in the car, dropping the oil pan, and back to racing. No resizing needed...

I totally get the slippery slope thing... :)

It's pretty easy actually.

If the rods come off the crank because you did a tear down, you send them to your shop. They are checked for out of round, and at the very MINIMUM, balanced.

I think you said "if you reuse your bearings" . First of all, NEVER do that. Just throw them away, they are cheap.

After your rods are resized and balanced or otherwise reconditioned (they should be reconditioned during every build IMHO), then you pick your bolt based on your application and how radical your build will be. A 120HP T won't need ARP bolts....

Good advice.

Bolts should be chosen based upon application as suggested. If you change bolts the BE must be re remeasured and typically will need to be resized, as suggested.

Bolts should be stretched not torqued. CCl lengths equalized and sometimes you can get away with only the cap that needs dressing. If the beam needs dressing then the CCL lengths will change.

Folks, still trying to find someone local to resize rods...

Is this procedure so straightforward that any machine shop can do it, or, does it have to be a Porsche specific machine shop??? Will a nonporsche shop have the measurements/sizing/info needed?

Some shops are asking if I want the small bushing replaced...

Some are asking about balancing. Optional? Recommended? Mandatory?

Is that optional on a low mile motor?

Suspect I will just mail it to Ollies to get done. Somewhat surprised I can't find anything local... The Chicago/Milwaukee area ain't exactly small...

Rod resizing can be done anywhere a decent auto/diesel machine shop is.

They grind the cap down a tad, then hone it to size. Really fast procedure.

I'd say if your wrist pin is very 'snuggish' in the small end, you are fine. If it wobbles AT ALL, they are worn.

When you replace the bushing, you hone the wrist pin to probably a 0.0005" (<-- don't quote me on the actual fit clearance!) fit.

At this clearance I posted, you virtually cannot wobble the wrist pin.

If I can give some advice from someone who does this work to someone asking what to do.

There is proper and "just getting way with it" repair work.

Anytime you have the rods out of an engine, you should do everything possible to ensure they are in perfect working condition. Missing steps is often a cost thing or the shop doing this cannot be bothered.

Not replacing the bolts or changing the bolts, factory or ARP, the BE should be measured. Most often the new bolt will clamp the BE differently and require the BE to be re sized. Many times the shop will automatically cut the cap and or beam and do this regardless. However it is done the BE should be measured before any other work is done to know how much the bore is out of round. This changes the CCL so all rods need to be machined the same amount.

Pin bushings typically need replacing as they are a soft material. They need to be measured also. 0.0005" is too tight. What you are adding with clearance is an oil film. Common is 0.0015- 0.002". The more the engine is used for high performance use the more you would move towards the 0.002" clearance. You have to give the shop doing this two pins, but should ask then to measure all the pins as these wear also. Clearance is to the pin.

Any good machine shop can do this work. There is nothing special about Porsche Rods. Ask them what they do when reconditioning Rods. Any good shop will do the following.

finished spec's/sizes found/known
Cleaned and inspected for inclusions/damage
assembled and straight checked
CCL checked to ensure all are the same
magnuflux crack checked
bolts replaced, if required, stretched and bores checked.
Pin bushings replaced if required
cap/beam dressed
both ends re sized
CCL re checked
balance checked and adjusted if required
BE split and rods cleaned.

Appreciate the info guys...

Will any local machine shop know what size to hone to, and have the right size bushings? Or, do I need to provide the sizing (I assume a Porsche shop would of course know)?

Trying to balance mailing these parts cross country, vs having someone local do it and do a less than optimal job...

The BE bore is different on some engines. If you tell me the engine they are out of I can give you the sizes. If they are 911 here are the most common spec's.

Early rods
BE diameter is 56.00mm - 56.019mm
SE pin bushing 22.02mm- 22.033mm The specs show the clearances tighter than we run them. We run them on the wider side at 0.0015" Tighter as per spec will not hurt you. Typically they will aim for the middle.
CCL is 127.80mm

Later Rods
BE diameter 58.00mm - 58.019mm
SE diameter 23.020mm - 23.033mm
CCL 127.00mm

The host here sells the pin bushings and fasteners. Have faith in your local shop. Just ask questions and check out the shop when you drop them off. This is always a good indication of the level of work done.

Never seen any machine shop do this, they expect a matched factory set, maybe they'll check to see if the whole rod is within factory weight spec, but that's it.
Balancing rods (end to end) is a separate job you ask and pay extra for, usually done with a full engine balance.

Unless the nuts and bolts are ARP (etc) they must be replaced, single use only.

If you are going to use OE bolts, send the old ones with the rods to be machined.

If you will be using ARP bolts, send those with the rods to the machine shop.

Also, the bushing needs to be replaced anytime the big end is resized. That will ensure all the rods are the same center to center length.

We have found, not all sets are matched very well. Often you find the overall weights to be close but the ends are different. Sometimes we see rods that have been repaired poorly and the weights and CCL's all over the place. Jeff's "home built" rods as an example. All 6 rods from different sets.

It depends how close you want the weights to be. Steel rods are easier to match but Ti rods pose a completely different issue.

It is always hoped that the 6 rods are matched, but if not you need to adjust. As for the CCL , lengths, this is critical otherwise the Piston deck heights are different as is the static compression. The pin bushing typically sold do not give any material to bore offset to adjust the CCL. If the beams are lapped and not dressed this helps, but if any beams need skimming, all must be done the same amount. Same for the caps then the BE center line remains the same.

The bushings do not need to be replaced just because the BE is resized, if they measure in spec. But the CCL's need to be checked before any work is done. This way to know what needs to be done. If they are all different, regardless of the BE sizes, the beam lengths needs to be matched. But with the stock pin bushing the CCL will shorten as there is no material in the bushing to adjust the CCL. Now, the customer should be told the new CCL, and the deck heights adjusted on assembly with less shims under the cylinders, for example. Or custom bushings fitted that can be bored offset, but this would typically require you to go down in pin diameter size. This changes the Piston as well.

In fact, these early NA engines have a pin size that is overkill. The new Piston we designed for Jeff's project engine uses pin a lot smaller in diameter. This has allowed us to offset bore the Rods, make the CCL longer and shorten the compression height of the piston quite a lot. This lowers the pivot mass over the pin which along with the longer rod, helps keep the piston more square in the Cylinder bore. If we keep the Cylinder straighter, we can go down to narrower rings and lower the friction.

Oh oh... Hopefully this thread will no go the same way as this one!!! http://forums.pelicanparts.com/porsche-911-technical-forum/968113-ignition-options-efi-itbs.html

Curious... why do rods need to be balanced?
Assuming that the engine was in decent running condition, and that no major failures occured, if you were rebuilding just to address oil leaks and then change bearings "while you are there", what would cause the rods to go out of balance?

Me too. Remember there are Jokers in every pack!!!

I'm just trying to help and offer how we do this type of work. Never think of one minute we know it all. If I can help and its free, you cant beat that.

As for why the need to balance the rods? You don't if you don't want to. Same for measuring the bearing clearances or piston to wall clearances. Its the assemblers call.

As a professional engine building business we have to hold ourselves to a high standard and cannot overlook the basic stuff. If you don't check you will never know. For the DIY at home, if it goes wrong you get lots of sympathy here. For a pro shop to do the same screw up, you get hammered.

I guess it called risk management. If you check you know, if you don't, you won't.

Thanks Neil.

Just spent hours perusing the pelican rebuild specs...

Looks like clearance for the crank bearings is .0005 to .0035...

Clearance for rods, BE, is about .001 to .003

That's a helluva range... Is see folks on here mention that their crank clearance is .004 and folks suggest that's too loose, and appropriate for a dragster... But .0035 is ok?!

Confused...

My crank has 60k miles on it, looks great, no scoring, and crank bearings look like new. Crank is in spec, but on the low end... It seems they were cut that way...

Bought a sample valve, see my other thread, and NEW that's at the low end of spec.

Rod ends also in spec, but on the low end...

If your crank rod shaft is at the low end of spec, do you ask your machinist to cut the rod ends at the tight end of spec??? If they are cut at the loose end of spec, your clearance will be higher, though in spec...

When you say the clearances are, 0.0005" - 0.0035" are these the measured numbers? Same for the rods??

You can mix the shells around to see if that makes it better. If not, you can polish the backside of the bearing shells to help gain clearances. Take 1/2 of the small size and fit it with 1/2 of the big bore. If you get my drift.

This should only be done if both the case housing bore is in spec and straight. Also, are the bore sizes measured across the parting line or vertical. Rods may differ across the parting line as they pinch inwards and the case often gets wider.

Those aren't my measured clearances. I haven't measured yet.
What I listed was the calculated clearances at spec but loose.

Only suggest I can make at this stage is to measure. If you do not have bore gauges you can use plastic gauge, but expect a higher level of error. Unfortunately plastic gauge will only measure the fitted clearances, not the housing bore sizes.

Trust you local shop. You can ask them to measure everything and give you the sizes. In the case(excuse the pun) of the Porsche engine, the main housing bore and bearing ID sizes require the case to be assembled twice. This could cost $$. My suggestion would be to take the case to a shop and have them measure the housing bore, then go home, split the case fit the bearings and take it back to measure. Measuring should take around 15-30 mins each time. Do the same for the crank and rods. Then you know for sure.