Rod caps have cross hatch?

[jahjahSQC]

I'm a novice engine builder. I've assembeled a few motors... and i'm confused by what i see on this rod cap that i've pulled from my 97 gst.

I'm pretty sure the rod was cut, and i'll spec it to be sure when i pull the motor out, but I've never seen rods with a crosshatch on them. I dunno if maybe this is how its typically done after cutting a rod... but this is a new look to me. I can post a pic of the rod cap, but it looks identical to this. Definiately was machined/cut this way and not from wear.

Looks exactly like cross hatched engine walls.

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any ideas?

 

[99gst_racer]

You would need to machine/hone the big end if you ever changed out the bolts. That's probably the #1 reason for machining them, so that could explain it.

 

[delta448]

Honing marks.

Edit:
Beaten by seconds Paul...

 

[BoredDSM]

Yep, rods will come with cross hatching because they have to machine the small and big end to specific tolerances.

 

[jahjahSQC]

okay, cool. Yeah, the motor had some ACL .25 bearings in it.

you say "if i replace the bolts"...

my rods had studs/nuts. is that how they come from mitsu? or is this aftermarket hardware?

 

[BoredDSM]

From factory they come with studs and nuts. You can tell if the hardware says ARP on it or not.

 

[99gst_racer]

Yeah, .25 is .25mm oversized, which equals .010".

The factory fastener is a pressed-in bolt and a nut. ARP uses a similar style bolt and nut, but theirs should be a black oxide finish, and will say ARP on the head of the bolt.

 

[jahjahSQC]

Yeah, .25 is .25mm oversized, which equals .010".

The factory fastener is a pressed-in bolt and a nut. ARP uses a similar style bolt and nut, but theirs should be a black oxide finish, and will say ARP on the head of the bolt.

Excellent. thanks guys.

 

[bastarddsm]

They will have the cross hatch from the factory too! Also, the bearing size has nothing to do with the rod, it only affects the crank. When a rod is rebuilt, a small amount (~ .001") is ground off the mating surfaces of the rod and cap. The the hole is honed to the original size, making it perfectly round again. Mitsu did basically the same thing when they were first made.

 

[99gst_racer]

^^Correct.


Definitely wasn't my first brain fart today.

 

[jahjahSQC]

They will have the cross hatch from the factory too! Also, the bearing size has nothing to do with the rod, it only affects the crank. When a rod is rebuilt, a small amount (~ .001") is ground off the mating surfaces of the rod and cap. The the hole is honed to the original size, making it perfectly round again. Mitsu did basically the same thing when they were first made.

if the crank end of the rod was out of round, couldnt someone have cut the rod in order to round the hole?

 

[donniekak]

You will need to have the bolts replaced in the rods, and the big end resized again, if they are from the engine in a 97 gst. The . The 92.5 and up engines use torque to yield, one time use rod, and headbolts. The 010" bearings are from your crank being cut before.

 

[bastarddsm]

if the crank end of the rod was out of round, couldnt someone have cut the rod in order to round the hole?

Thats exactly what I was describing. Generally the big end is only a few thousands out of round at most. So you take a couple thousands of the mating faces of the rod and cap. This makes the big end small, its then honed back to the original size. As donnit put it, its call "resizing the rods".