14 replies to this topic

[Spackaveli32]

I made the rookie mistake of not tracking the order of which my pistons and rods came out before taking my block to get machined.

How do I determine what order to put them in? Additionally, I am looking to change the pistons, what’s the best way to disconnect the rod from the piston?

Thank you in advance.  BB704136-35B1-4909-8F4F-958508A992FE.jpeg   46.65K   4 downloads

Edited by Spackaveli32, 20 June 2019 - 06:19 AM.

[unburntfuelinthemorning]

What are you having machined on the block?  When reboring it is normal practice to measure the pistons that are going to be used to determine the correct size for boring/honing.

 

If you are having new big end bearing shells and new pistons then the conrod order won't matter but do check that the con rod side clearance on the crank is within tolerance.

 

A good machine shop will be able to fit your new pistons.  The pins need pressing out and back in.  Special tools are needed for this but the con rods shouldn't be heated.  There needs to be a certain amount of interference fit to ensure the pins don't move once installed.

 

There are others on here far more knowledgeable than I am on this subject who will be able to advice further.

[gazza82]

Check for small dots in the sides of the rods and caps .. they may show you the order if they are there, plus which cap matches which rod.

[Rorf]

Just do not mix up the rod caps ever! Mark them now with punch dots. Engine rebuild : 1st crankshaft measure and regrind if necessary, trail build fit to see if crank turns without tight spots, check thrust clearance. If a problem you might need main journal alignment bore. Once pistons purchased then bore cylinders and hone to spec. Then trial build again with new pistons with out rings to check block height. Pistons to be level with deck. Hopefully all oil gallery plugs and water jacket plugs were removed right at the beginning - have the block cleaned perfectly inside and out.

 

Now the rebuild should be done under hospital theater clean conditions and you should have a beaut of an engine.

[Spackaveli32]

I intend to used the original rods. I purchase +40 pistons. If I understand correctly, it’s okay to mix the order of the rods and caps if I am using new pistons and bearings?

It seems that my new pistons utilize a clip to secure them to the rods.

Edited by Spackaveli32, 20 June 2019 - 08:10 AM.

[nicklouse]

I intend to used the original rods. I purchase +40 pistons. If I understand correctly, it’s okay to mix the order of the rods and caps if I am using new pistons and bearings?

It seems that my new pistons utilize a clip to secure them to the rods.

No the caps are matched to the rods. You can not mix them up.

As to which rod Assy. goes into which hole then there is only one way they will actually fit and work but it does not matter which goes where.

And it seems your pistons are not the same fitting as the old ones.

Some reading http://www.reizendem...l/engine/13.htm

Edited by nicklouse, 20 June 2019 - 11:34 AM.

[timmy850]

Small bore rods like these come in 2 pairs. The rods on 2 & 4 are the same and 1 & 3 are the same.

They are offset from the crank in opposite directions so you need to install them in the right order.

The pistons are also marked with an arrow toward the front of the engine (water pump end) so you need to make sure you’ve got them all sorted before installation in the block

[Cooperman]

If you have mixed up the caps then you have a big problem. Each rod and cap represents a single matched component.
Once mixed up there are two options. Buy another set of correctly matched rods or take yours to a machine shop where they can have a few thou machined from the mating face of each cap followed by line-boring/honing to make each cap and rod concentric. It might well be cheaper to buy new rods.

[Spider]

Usually if the caps haven't been referenced to it's rod, you can work out which goes with which.

 

Remove the bearing shells and then fit each cap in turn to each rod, fit the bolts and tighten them up. IF at ANY point while doing this part, of this exersize a Cap or bolt is too tight to fit by hand, don't force it, as it's likely they are not matched.

 

After tightening them up, visually check the alignment of the tunnel and also the thrust faces for alignment. The thrust faces though, are occasionally off from the factory but they'll only be out a thou or maybe two. If the Tunnel looks right, usually a torch from the back helps here, run a 1 thou feeler strip on edge over the parting line. If may hang up slightly on them, but will usually glide right over them. You need to check, where possible, every cap, on every rod, even if you think you have the right match.

 

If there's any doubt on any of them, then best off having them closed and honed, but be sure to mark them prior to doing this.

[Spackaveli32]

Thanks all for the guidance and support.

[DeadSquare]

Usually if the caps haven't been referenced to it's rod, you can work out which goes with which.

 

Remove the bearing shells and then fit each cap in turn to each rod, fit the bolts and tighten them up. IF at ANY point while doing this part, of this exersize a Cap or bolt is too tight to fit by hand, don't force it, as it's likely they are not matched.

 

After tightening them up, visually check the alignment of the tunnel and also the thrust faces for alignment. The thrust faces though, are occasionally off from the factory but they'll only be out a thou or maybe two. If the Tunnel looks right, usually a torch from the back helps here, run a 1 thou feeler strip on edge over the parting line. If may hang up slightly on them, but will usually glide right over them. You need to check, where possible, every cap, on every rod, even if you think you have the right match.

 

If there's any doubt on any of them, then best off having them closed and honed, but be sure to mark them prior to doing this.

 

BEFORE removing the shells, examine them very closely.

 

There are usually score marks in the surface of the shells that if you are lucky, sometimes enable caps and rods to be re-matched.

[Spackaveli32]

DeadSquare, thank you! Your idea worked out great.

[DeadSquare]

DeadSquare, thank you! Your idea worked out great.

 

Glad to help, but if I ever get to Honolulu..................you owe me a pint !

[DeadSquare]

Have you managed to remove the rod from the pistons ?

 

If you haven't got the correct tool, I'm sure that your machine shop would do it for you, and fit the new pistons.

[Spackaveli32]

DeadSquare, anytime my brother! I haven’t had a chance to take them in. Hopefully, today I will be able to get them removed. Thanks again for all the help.