Do I need to hone?

[scotts74birds]

A little off the normal mopar builds. I am doing a 2.7, v6 mopar engine. It spun a few rod bearings. But the cylinder bores are straight, with no scratches. As a matter of fact, the original cross-hatch of the cylinder hone is still visible. I dont have the measurement tools for this. So, does the appearance of the cross-hatch pattern mean that the cylinders are not worn enough to consider and machining, or overboring?

 

[Satellite65]

Judgement call. Is this a rebuild or a repair? Depends on how 'involved' you wanna get with this. If it's just a repair and the cylinders look as good as you say, just make sure it's clean and out it back together.

 

[HEMI-ITIS]

If your installing new rings,at least use a ball hone so the new rings will seat properly:grin:

 

[Meep-Meep]

I'd say if you put the pistons back exactly where they were, or never take them out to begin with, you should be OK. Just try to keep it as clean as possible. If you do the ball hone make sure you don't run it too fast and keep the proper cross hatch pattern.

 

[67 B-body]

If your installing new rings,at least use a ball hone so the new rings will seat properly:grin:

Agreed!!!!

 

[scotts74birds]

Thanks for the advice! I ran my nail across the bores and couldn't even feel a ridge at the top. I'm trying to start some biz on the side, so I thought I'd work on the most problematic motor out there. The Chrysler 2.7. Learned alot about these "potential grenades"! I'm open to questions from other members that have issues with this motor.
Best advice for now RUN SYNTHETIC! Feel free to IM me if you also have issues with this motor. I also have some good info for owners of 4.7 Dodge motors that are dropping rocker arms.

 

[67 B-body]

Speeking of "ridge", Some might not be aware, that you need to check for this BEFORE you diss-assemble the engine. With the piston down it its' bore, you need to use a ridge reamer to cut the ridge out first. Without doing this, you risk breaking a land on cast pistons during removal. The lower edge of a ridge within the cyl wall, is typically a square edge and does not provide gradual compression of the ring as it travels across this point during piston remomal. This can cause high amounts of stress placed on the ring land and create small and most of the time un-seen stress cracks. Failure will follow if pistons are re-used in this case.

I hope this helps someone,
My 2 cents.......

 

[Satellite65]

Good advice. Actually, you're less likely to find any kind of ridge on a modern, fuel injected engine than you would in some of our older carbureted stuff. The choke creates an overly rich condition that gas washes cylinder walls every time you cold start and causes a lot of wear. Back in the day, almost every engine I tore down had a ridge that needed to be cut first. Not so with most of this newer stuff. Still gotta check first.

 

[scotts74birds]

I agree with both of you. I've said this before, you just don't get the cylinder-washdown, and wear in the cylinders today, like we did in the carby days. I attribute this to FI. I popped a top ring off the #1 piston, and pushed it down all the other bores. The gap was the same, and in spec!

 

[green1]

If you have a ridge, the pistons are trash, as it needs boring.

 

[Cranky]

Good advice. Actually, you're less likely to find any kind of ridge on a modern, fuel injected engine than you would in some of our older carbureted stuff. The choke creates an overly rich condition that gas washes cylinder walls every time you cold start and causes a lot of wear. Back in the day, almost every engine I tore down had a ridge that needed to be cut first. Not so with most of this newer stuff. Still gotta check first.

I've done a lot of engine work too and didn't run into any bad ridges in Mopars but saw quite a few in GM's stuff. A car that got good maintenance usually avoided heavy wear because the carb was kept in good shape but the ones that didn't get any attention...that was a different story. Got a Chevy once that was so bad that the push rods were plugged so bad that I couldn't clean them. Don't think it ever had an oil change and it needed to be bored too. Even listen to the bore cutter on the different makes. I got to where I knew what make of engine was being machined just by the sound of the cutter!