which way do the pistons go in a isb/24 valve ctd?
most pistons have a slightly off set wrist pin to help get rid of piston slap.
i have looked every where, can not find the refferance material that says which direction they have to face
thanx in advance ...eeeven ,stage left said snagle tooth. :-

 

This copied from the Cummins Tech manual.

The number stamped on the rod and cap at the parting line must match and be installed on the oil cooler side of the engine.

--Justin

 

yes sir ,
but which way do the pistons face????

 

You will see an arrow on most of the ones I have seen. The arrow faces the front of the engine, toward the timing cover.

I just looked at my stocker 215HP 12 valvers and they have the word FRONT stamped on the top. I also checked my Marine replacements and they have an arrow pointing toward the front.

Since the ISB has a centered combustion bowl, I dont know for certain if they are or will be marked for FRONT.

Don~

 

Did some checking, with a project engine I have here.

I dont know where the assembly took place on this used set of pistons and rod assemblies I have.
But all numbers will be facing the front side of the engine.
Numbers on piston tops are also on the number side of the rod and cap assembly.

--Justin

 

Thumper, what is the latest on your engine? Sounds like you are rebuilding it yourself. Any engines I have rebuilt, the rule of thumb is for any numbers stamped on the head of the piston to face forward. Many pistons also have an arrow which must face forward. If the piston's came in a box, was there no info on any piece of paper? How about an 800 number for the piston manufacturer? Get them to fax or email the info to you. Or get the piston supplier to give you something IN WRITING. Don't accept verbal in this case.
Sure you know this already, but please do NOT forget to stagger the ring spacing by 180 degrees between each ring.
Please keep us posted on progress.

 

mexstan,
the latest? i have all the stuff laying in front of me finally,but as you see there is no evidence which way these pistons drop in... agan i'm up against the wall with sir cummins, its thir parts and they and thir book dose not say and nobody wants to sighn on the dotted line.
SO IF ANYBODY OUT THERE KNOWS THE ANS.TO this please try not to keep it a secret.

 

I just checked my '03 shop manual and all it says is "Make sure the front of the piston is oriented according to the markings on top of the piston and the numbers on the rod and cap are orientated as illustrated." There is only an illustration for the rods and caps. So my manual is of no use to you if your pistons have no markings on the head.
This must be very frustrating for you. Wish I could help more.

 

What justin was saying is true.

Keep the uniformity the same on the stamping numbers on the rod's in relation to the oil cooler. The piston part numbers can be orientated forward if you want but it's not necessary.

Cummins does not have a direction on the pistons for the ISB 24 Valve. They have a chart that tells you to check piston to deck height.

Call cummins and they can give it to you. When putting the pistons in the block take a measurement on how much the piston sticks up above the deck. Each cummins piston part number has a spec chart on the piston height to deck.

Like the ISB I just built had a spec of .014-.021 range on the piston part number. It does not matter on the direction of the 24 valve piston up to 2002 at all.

If your piston to deck number is out of range you can swap the bore it's in with a alternate cylinder and re-check it.

The block center line has variations to the crank journal in deck measurement due to the inline six being so long. This information i'm giving you is from experance and working with cummins.

I built Cummins engines that had piston to deck at .023 to .028 which seems to be alot but the gaskets also have a crush down number which only Cummins knows what that number is.

We played with this some on different Cummins pistons so I went through the same issues you did.

Never felt the changes however a good old time Cummins man will tell you that it can cause cylinder timing issues if the numbers are not within range to each other.

I know it works I have put some articles on the internet before on this issue some time back.

Hope this helps.

Don Ramer

 

Mexstan had reminded you about the ring gap spacing and that is also true.

It is also recommended to keep the piston ring gaps away from the wrist pin bore and the center of the thrust side of the skirts. So one ring at say 1:00 one at 7:00 one at 4:00 and 11:00 ect----- just 180 deg from each on the stack.

I can also email you a photo of a high HP Cummins 24 valve piston that has the #8465 stamped on the top and an arrow pointing to the front with the letter A.

It was Cummins recommendations with this piston to position it forward which is back to the stampings going forward if this also helps.

Some 24-valve pistons don't have this arrow or the letter A so it does not have a forward orientation on direction.

When it’s my money in building one I to wanted the facts on this since Cummins was not clear on this piston issue. Why they did not comment on this issue was a good question that we all have asked for. It really get fun when you start playing with other pistons, Cummins has very little info and you really have to know someone or dig hard to find the specs.

I can go further into this if needed. The oil lube holes are the same on both sides of the piston.

Hope this also helps

Don Ramer

 

Don Ramer.
thanx for the reply ,were all starting to get smarter here, but did you know if you get a over size piston there is NO grading gor it??? its all very fustrating dealing with cummins ,,,thir o.s. only comes in one deck ht!!
i thought this was nuts (or i am) considering how much time it takes to measire the deck ht. for stock, then as soon as you go o.s. there is no longer any reason to measure!!!
i spent a full day on the phone with 'them' and finally that was thir own conclusion...
makes me just thump. thump .thump.
p.s are ya sure they are symetrical (can be inslled in any direction???)

 

Yes this came from a very trusted cummins man that helped me out when I wanted to play with the 24 valves. It still is best to point the stamping forward. I was adding some info to the above post when you sent your reply. I will help you with what ever I can. I have to go out for an hour or so but will show this on a attachment give me a few hours to get it all together.

Don

 

Piston

 

thumper, what Don says makes sense to me. After making my post and then reading what Don said I thought about this and have come to the conclusion that if your pistons have NO markings on them and the oil holes are symetrical that the orientation of the pistons are of no consequence. Check inside the pistons carefully and see if there is anything not symetrical about them. If there is I would make sure that all the pistons are then installed with that non symetrical thingy facing in the same direction. Suggest forward.
Stagger your rings as Don said, make sure your rods and caps are orientated correctly, and assembly away.
Cannot advise you about the piston heights above the deck as I have no personal experience on that. However I can understand how this would be very important.
Please continue to keep us posted on progress. Hope to hear very soon that the engine is installed and purring smoothly.

 

So what's the procedure for measuring deck height? I never got into that with the gassers I built. I might need to know this if I have to replace my block myself. :


Chris