Hi i have a question about mounting the rods; i mounting a 928 stroker engine and i have je pistons and k1 rods.
Je says that the piston clearance with the rod is 0.050" or 1.27mm.
my question is if i can turn the rod on one way or other to get more distance with the piston.
The rod is assimetrical, one side have more distance with the centre.
can i mounted in one direcction some rods an others in other direction?

 

I don't know what a K1 rod is but assuming it's a modern Chevy rod, it's symetyrical and what you are seeing is the difference between the cylinder bank offset and rod width. The rod would be offset in the piston by about .5mm which looks to be about what you have going on there.

Why do you say it's asymetrical?

 

This is what I've been talking about. Look at how that piston is centered on the rod.

This is what the incorrect offset looks like. When this engine is running, the piston will not "push down" on this rod equally. Every combustion event will be trying to "twist" the piston in the bore. The
twisting" loads transfered to the rod and the rod bearings are huge. Even though the piston is supported by the bore of the engine, the loading on the rod and the piston are exactly the same, as if the cylinder was oval and the piston could shift that far in the bore.

Why did anyone ever think that a Chevy rod was proper in a 928 engine, in the first place?

 

Wow, that's a nice visual.

It might be the photo, doesn't look like there is much gap between the rods and the cranks - with regards to the side clearance.

 

Because the "beam" of the rod is not "centered" on the "cap" piece of the rod. You can see this, in his picture. This "offset" varies from engine to engine, depending on design. Move the left hand bores and the right hand bores .065" towards each other and those rods will be centered....as if they were in a Chevy engine.

The other option is to move the "beam" of the rod more towards the center of the rod "cap"....like a 928 engine requires.

 

Common "rookie" mistake.

You are trying to use a Chevy rod in a 928 engine. The offset is wrong. This has ruined many stroker engines. Many.

You need a rod with 928 offset. I have Carrillo rods, with the correct offset, in stock.

 

With the combination that he has, the connecting rod is actually touching the inside of the pin boss. This particular combination of pieces will not allow the rod to ever get perpendicular to the crank....the pin boss will not allow it to move far enough. The rods are actually "twisted" on the journal, so it appears that there is not enough side clearance.

This engine, if he doesn't change something, will join the long line of "failed" stroker engines, very quickly.

 

If you are using Chevy small block rods, do turn them 180 degrees around (the side of the rod normally facing the crank shall face the other rod) and you will end up with zero offset. Do change place of the bearing inserts, the insert marked upper in the lower rod half and vice versa. The protrusions on the inserts and the notches in the rods are located differently on the upper vs the lower part. You will end up with the inserts being located more in the middle of the rod. Some machining (chamfering) of the rods and inserts will be necessary to get sufficient clearance at the radius fillet of the crank throw. Do not forget to machine a 360 degree oil groove in all main bearings, especially the third trust bearing. Also do make more oil slots around the circumference of all main bearings (a total of six slots in the main bearings no. 1 and no. 3 each and two slots in each lower half of the other main bearings).
If you have a modern Chevy LS1 rod, the rod is centered (no offset) and the above cannot be carried out.
The offset of left and right cylinder bank on the 928 engine block is exactly 25mm (.984"). The left cylinder bank is located 25mm to the rear of the right cylinder bank. When both rods are installed on the crank throw, the C-C distance between the rods at the small end shall be exactly 25mm in order to have zero rod offset.

Ake

 

Turning the rod 180 degrees doesn't solve the offset problem...it just changes it, the other direction. In the study that Carrillo did, any "offset" that exceeds .020" has virtually the same effect as being off .060" or more. Additionally, cutting an additonal champher in the connecting rod and bearing, to clear the radius on the crankshaft, is going to reduce bearing and connecting rod "surface area".

Please note although a "zero" offset LS1 rod might not allow the connecting rod to touch the piston pin boss, it is certainly not centered, on the pin....and the "offset" problem is certainly more than .020". The forces on the rod and the bore are almost identical to the forces that would occur at .060"....as Carrillo proved, in their study.

I don't understand why people keep insisting that the wrong pieces are correct.

Why not just use a proper rod for a 928 engine and be done with it?

 

It is interesting how this topic of stroker builds has come up all of a sudden in two seperate threads. It is also interesting how this OP has started right off with a great picture which clearly shows the perameters that appear to relate, at least as they relate to his particular project.

In the picture shown, it is obvious to me, but missed by most others, that there is in fact clearance between the small end of the rod, on the left, and the piston's wrist pin boss, because I can clearly see the wrist pin in the gap. Look at the tiny bright spot in the picture and see if you don't agree with me.

It is also pretty obvious, too, that there is a really large gap between the small end of the rod on the other side and the wrist pin boss on that side of the piston. I am pretty sure that it is the significant difference in these two gaps that is stimulating the apparent concern about Chevy rod offset. I suppose it is natural for all of us to think in terms of equality, balance, and symetry, but in reality asymetry does not automatically spell failure or some other disaster or tragedy.

Oddly enough, when I put my dial caliper on the picture on my computer screen, it measures out to be almost exactly true to scale with the small end of the standard 5.85 Chevy rod(s) that I have to work with which look very much like the ones in the picture. If I assume that the actual width of the small end pictured is the same width as mine, then by measuring the gap of the wrist pin on the right in the picture it suggests that in order to center the rod end exactly between the pin bosses will require moving the rod about 80 to 90 thousandths of an inch. If so, that is the offset in this particular case.

AKE and I have been discussing this topic by PM and he suggests that the Chevy rod offset is actually .039 inches or almost exactly one millimeter. In addition, at the suggestion in the other thread, I contacted Carillo and was informed that the offset put into their rods to supposedly center them in the 928 piston is .050 inch. That is really a wide range of offsets; so I wonder how Carillo decided to settle of .050. Perhaps that is just an average they came up with. If so, I wonder just how far from the average one can deviate in their perspective?

Going back to the JE piston in the picture, I have to ask why the gap itself between the pin bosses is so very much wider than probably the width of any applicable rod small end? I suspect that the answer to that is that the piston is designed to be used with any connecting rod that will in fact fit within the gap provided, without offset being any kind of issue, so long as it does fit and does not bind. I think that says that the piston designer has already decided, as I have, that the offset, at least within the gap provided, is no problem.

Personally, I have formed more metal objects in hydraulic presses from 25 to 75 tons than just about anyone on this forum, and I can tell that although theoretically pushing in the exact middle of the form with the middle of the hydraulic ram might be ideal, in fact I have found that being even more than a little off-center make no difference. It still forms straight without cocking the form.

More specifically, what I have learned about pushing various metal forms into other metal in order to change its shape is that with the nose of the hydraulic ram in any of the presses I have used, which range from about 1 1/2 inch to 4 inches in diameter, is that the ram can be off-center, or less than perfectly centered, with the center of the form at least to the point where the center of the form is anywhere within the "footprint" of the ram itself. In any of those cases there is NO--ZERO--tendency for the form to "rock" or cant in any way; and, since the force is being directed within the ram there is no tendency for the ram to bend, at least any that can be measured without something akin to whatever it might take to measure the deflection of something like a steel beam when a fly lands on it.

Now, it might be a little different if the nose of my hydraulic ram was a point rather than a flat circular surface, in which case the form might very well want to rock or cant if it is not perfectly centered; and I think that is the root of the myth about a problem related to the offset. I think that those touting a problem, and likely their supposed supporting engineer, are assuming that the force of combustion is being transferred into the connecting rod at a finite point rather than being spread all across the width of the small end of the rod the way it actually is. On the other hand, if the nose of my Hydraulic ram were a point, but a point not in the center of the ram, it might still need to be on the center of the form, but being off-cener on the ram is still not going to try to bend the ram.

So, if I can locate my hydraulic ram anywhere on my forms so long as the center of the form is within the footprint of the ram, so can the OP and anyone else who is not terrified into the purchase of $2500 rods, locate the small end of their standard Chevy rods essentially anywhere on the wrist pin between the pin bosses so long as the center of the piston is located within the "footprint" of the small end of the rod. There will be no rocking motion, and, so long as the centerline or plane down through the piston is also located within the beam or shaft of the rod there will be no discernible tendency for the rod to bend.

In response to AKE about reversing the rods and champhering the other side of the big end of the rod and the bearing also, it occurs to me that if the slightly off-center of the small end were really a problem, why not simply mill off one side of the small end so that the resulting narrower small end is now in the center with even gaps on each side of it. Even then the center of thrust will be well within the body of the beam or shaft of the rod so there would be essentially a direct thrust of the force into the bearing in the big end.

Really, what this all says is that the alleged problem with the Chevy rod offset is a total myth. Why not just leave the small end the way it is for the additional bearing surface as was intended. There is no reason that the additional bearing surface must be exactly on each side of the small end.

My advise to the OP and to the previous OP is that with this configuration I am very sure that you are good to go. The offset issue is a myth. There are just way too many 928 strokers running very well and for long periods out there to support the myth as fact.

Jerry Feather

 

KEEP THIS ON POINT GUYS.........IF YOU HAVE SOMETHING CONSTRUCTIVE TO ADD OR A QUESTION ON THE TOPIC.

-Hacker-Pschorr

 

What he said.

 

Heinrich, What he said! JF

 

Can those of us who have any engine building experience, please answer technical engine building questions. And can those who are here only to sell plastic wheel covers, PLEASE PLEASE stop giving people the world's very worst advice on engine building, a topic of which they clearly know zip zero nada? PLEASE!

That picture looks to me like a perfect example of what GB has been saying.

 

I know nothing about engine building... I assume that piston was not intended for the 928 since there is a large gap one one side of the wrist pin?