Correct order for connecting rods on crank shaft?

[Adrock]

This is a bit of a 'duh' question... but I was about to put my crank with rods attached back into my case today, when I realised I'd completely stuffed up and put them on in the wrong order.
I have had the rod and pistons balanced, so they are all numbered. 1 - 6.
Stupidly I've been working off the theory that they all go on the crank in order eg, from the pulley end:

1
2
3
4
5
6

As I was about to install the crank, I realised my mistake.... ARGHH!!
Now, before I take the rods off and re-install them in the correct positions (ARP bolts), I want to make sure that I have the correct order for installation, from the pulley end, down to the flywheel end.

PULLEY
4
1
5
2
6
3
FLYWHEEL

Just hoping that you guys could please confirm that this is right or not? I have Wayne's book and Bentley and couldn't find the answer... I assume it's just the same as the staggered cylinders in the engine diagram?


Thanks!

[Flat6pac]

With the nose to the left and the small end facing you all the paring numbers face up
Bruce

[Adrock]

Originally Posted by Flat6pac

With the nose to the left and the small end facing you all the paring numbers face up
Bruce

I don't think you're understanding my question.
Basically I want to clarify which rod for which cylinder goes on which journal. Imagine crank is standing on a bench with flywheel as the base and number 8 bearing on top.
From top to bottom what would be the order of the cylinders?

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['78 SC]

#4 is closest to the crankshaft pulley, #3 is closest to the flywheel

[Catorce]

If all the rods have been newly balanced, and if the crank has been balanced and polished, and if you are using new bearings, the order you put them in doesn't much matter.

The problem you are describing only really matters if you are simply putting a NON RECONDITIONED rotating assembly back together.

[Mark Henry]

Originally Posted by Catorce

If all the rods have been newly balanced, and if the crank has been balanced and polished, and if you are using new bearings, the order you put them in doesn't much matter.

The problem you are describing only really matters if you are simply putting a NON RECONDITIONED rotating assembly back together.

^ This.
Doesn't matter, if you did do the rod big ends but no balancing it still does't matter. Still within stock balance spec.
If you want, weigh the rods and pistons and try matching up for the smallest +/- tolerance.

Rod orientation, I've always been told tangs down, but I believe it does't matter for stock rods as most Porsche rods have no offset.
Carrillo doesn't matter, tangs down or up still doesn't matter, no offset. (source: Carrillo)
Aircooled VW T1 have bumps on the rod beam that face up, the rods do have an offset.

Charles @LN told me "It's tangs down, just so you don't freak out the next builder."

[Adrock]

Originally Posted by '78 SC

#4 is closest to the crankshaft pulley, #3 is closest to the flywheel

Thanks for the replies guys.
So, my assumption is correct, that according to that diagram, the correct placement of the rods from top to bottom is:

[Adrock]

Originally Posted by Adrock

Thanks for the replies guys.
So, my assumption is correct, that according to that diagram, the correct placement of the rods from top to bottom is:

Thanks for the replies guys. So, my assumption is correct then? That the correct placement of rods from top to bottom is:

PULLEY
4
1
5
2
6
3
FLYWHEEL

?


My understanding of having my pistons and rods balanced is that the pistons, rods and pins are arranged so that they are matched to the closest matching weight opposing pistons, etc. My machine shop has gone through and numbered my parts 1 - 6.

I will call the machine shop today to confirm, but I believe that to setup the engine correctly - using the numbers on the parts, I should have the rods setup:

1 - 4
2 - 5
3 - 6

[Neil Harvey]

Originally Posted by Adrock

Thanks for the replies guys. So, my assumption is correct then? That the correct placement of rods from top to bottom is:

PULLEY
4
1
5
2
6
3
FLYWHEEL

?


My understanding of having my pistons and rods balanced is that the pistons, rods and pins are arranged so that they are matched to the closest matching weight opposing pistons, etc. My machine shop has gone through and numbered my parts 1 - 6.

I will call the machine shop today to confirm, but I believe that to setup the engine correctly - using the numbers on the parts, I should have the rods setup:

1 - 4
2 - 5
3 - 6

Somewhat of an old wife's tale here. You do have to go with what you are told, but a lot of that is similar to the flat earth society stuff.

The reciprocating parts (pistons, pins, clips and rings, and Rod SE) should be balanced equally to at least 0.5 grams of each other to a maximum and typically good balancing is to zero or 0.1gram.

So look at it this way, you match up the heaviest parts opposite each other on the crankshaft. If the parts were really heavy for example to make this point, what you are actually doing is inducing an in balance rocking motion along the length of the crank. In your case the parts are probably not that heavy and the difference slight, hopefully. An exaggerated example to explain the principle.

Have the parts balanced as close as possible and it should not matter. This is a dynamic balance and can be measured the same way any other crankshaft is balanced by adding bob weights. The bob weights if measured the same as the pistons weights etc., any in balance can be seen and the weights changed per journal to balance out the crank.

This is over the top but it is way of making sure. The point is, it is not required if the parts are balanced correctly. If the crank balance is checked at 350 RPM and is balanced and re checked up to 750 RPM, it will be dynamically balanced at 6000+ RPM. Same for the pistons etc.

With these engines, the crank can be balanced on its own without bob weights as it is expected that the parts attached to it are balanced equally. And Porsche cranks have 12 counter weights 2 per rod journal.

In some engines we change the weights on the crank to balance out any 2nd and higher order in balances, but this is done with V based engines.

[Adrock]

Originally Posted by Neil Harvey

Somewhat of an old wife's tale here. You do have to go with what you are told, but a lot of that is similar to the flat earth society stuff.

Thanks for taking the time to reply and for the explanation Neil.

Just to clarify - my parts have already been weighed and balanced. I just need to now assemble them in the correct order on the crank.

I just need to know if this is this correct, from top to bottom; if the crank is on a bench - standing on a flywheel as the base?

PULLEY
4
1
5
2
6
3
FLYWHEEL


Cheers,

[Alan L]

What they are explaining is - in your case it doesn't matter. You can leave them where they are and save some ARP bolts. But yes - if you were reassembling a non -refurbished engine , that is the order - as taken off originally.
They accept a weight differential of several gms at the factory, but would pair them up.
Alan

[Adrock]

Originally Posted by Alan L

What they are explaining is - in your case it doesn't matter. You can leave them where they are and save some ARP bolts. But yes - if you were reassembling a non -refurbished engine , that is the order - as taken off originally.
They accept a weight differential of several gms at the factory, but would pair them up.
Alan

Thanks Alan. Sounds like I'm missing what you guys are trying to get across. Sorry.

My thoughts are that if leave them as is, doesn't that defeat the purpose of me having paid to have them "balanced" and matched up with specific pistons and pins by my machine shop in the first place?
I agree that ideally I don't want to take it apart again. I know I can use ARP bolts of they haven't stretched beyond a certain point. I did take initial measurements with a micrometer but only used a torque wrench to lock them down because I didn't feel my micrometer was accurate enough without the pointy anvil.

Also if I leave it as is and i still have my numbered pistons, should I at least install them in the placement as the machine shop suggested?

Thanks again all.

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[Alan L]

The pistons were numbered as removed. Normal practice. As I explained earlier - the factory accepts a weight variation. And when assembling the engine, have a box of pistons to choose from (other dimensions also matching). They then match the weights in closest pairs - as long as the lightest and heaviest do not fall outside a certain range (8gms from memory). I think they go further and put the heaviest pair by the flywheel etc. So, if doing nothing else, they need to go back as numbered. But you have passed that point by balancing them (to 1gm or less hopefully). In which case it doesn't matter - they are all 'equal'.
Regards
Alan

[Adrock]

Just to clarify. They aren't numbered as they were removed. The original location numbers are still etched on the parts, however the rods, pistons and pins have all now been mixed and matched by the machine shop with new numbers for their new location.

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[Alan L]

Well you could always ask the shop why they numbered them.
Regards
Alan

[NICE 69 S]

The parts were probably numbered just so they could keep track of them as they were balanced, which has nothing to do with what position the occupy in the engine as assembled.
Normally the rods are balance end to end, which means the small or big ends would hang from a fixed point and the other end would sit on a scale. This assures that all the big ends, which rotate with the crankshaft, weigh as close to each other as possible. Then they would do the same with the small ends. At this point the whole rod would be weighed and adjusted for total weight to hopefully within .1 or .2 grams.
Then the pistons and pins would be weighed separately and the lightest pin would be matched with the heaviest piston, and so on. Then the pairs would be balanced so they all matched. Again, they would be numbered just to keep track of which assembly you were dealing with during the grinding to achieve overall balance.
So what I think everyone is trying to say is that rod #1 does not have to be matched with piston #1, and so on. And rod and piston #1 do not necessarily have to go into position #1 in the engine.
Bob B

[Adrock]

Originally Posted by NICE 69 S

The parts were probably numbered just so they could keep track of them as they were balanced, which has nothing to do with what position the occupy in the engine as assembled.
Normally the rods are balance end to end, which means the small or big ends would hang from a fixed point and the other end would sit on a scale. This assures that all the big ends, which rotate with the crankshaft, weigh as close to each other as possible. Then they would do the same with the small ends. At this point the whole rod would be weighed and adjusted for total weight to hopefully within .1 or .2 grams.
Then the pistons and pins would be weighed separately and the lightest pin would be matched with the heaviest piston, and so on. Then the pairs would be balanced so they all matched. Again, they would be numbered just to keep track of which assembly you were dealing with during the grinding to achieve overall balance.
So what I think everyone is trying to say is that rod #1 does not have to be matched with piston #1, and so on. And rod and piston #1 do not necessarily have to go into position #1 in the engine.
Bob B

Thanks Bob. I spoke to the machine shop today - and what you said is exactly spot on. I had completely misunderstood what engine balancing entailed - so thanks to everybody for attempting to explain.

What I THOUGHT was that the pieces all varied in weight and the machine shop put the closest matching pistons, rods, pins, etc on opposing sides to each other.

As Bob said above - what ACTUALLY is the case is that the machine shop mixed and matched each piston, rod and pin up so that in the end, all of them were as close as possible in weight to each other.

Which of course means - as everybody was trying to get through to me above, that it doesn't matter where on the crank they go - as they are all a similar weight. As long as I keep number 1 piston and pin with number 1 rod, etc, then all should be good!

Thanks again to everybody who attempted to explain this or something similar to me. It took hearing it in person to change my train of thought.

Cheers,
Adam

[Alan L]

The Pelican site and its forums are worth their weight in gold. So much experience shared. When you get guys like Neil Harvey and Flatpac and often J Walker and other pros and experienced shed mechanics chipping in, you have to take notice. I could never have resurrected my 930 (bought sight unseen) from the unexpected mess it was, without the help of the Pelican guys.
This Pelican family is gold plated.
More power to your Porsche.
Alan

[speedo]

Originally Posted by NICE 69 S

Then they would do the same with the small ends. At this point the whole rod would be weighed and adjusted for total weight to hopefully within .1 or .2 grams.
Then the pistons and pins would be weighed separately and the lightest pin would be matched with the heaviest piston, and so on. Then the pairs would be balanced so they all matched. Again, they would be numbered just to keep track of which assembly you were dealing with during the grinding to achieve overall balance.
Bob B

My spec book for the 2.2 -2.4 stroke I am doing ...says the factory rods need to be within 9 grams of each other. I was working to get my rods within 1 gram...considering they came to me with 5 grams difference. Same with my pistons and pins. Now I see this...within .1 grams? Seriously, for a street engine?

[Trakrat]

I've never heard that it matters WHERE the rods are attached on the crank, as everything should already have been balanced properly. I think the ONLY case that this would matter is if your rods have different weights... as I've read that there is a certain placement for heavier rods vs. lighter rods. I know not all my of rods are the same weight.. only 3 of them weight the same.