240 Might get new rings, hone or not to hone?

I'm doing a full rebuild using the the original piston heads. I've never burned oil and my motor was at 230xxx miles when pulled. Is it necessary to hone if I'm going to install new rings? Should I install new rings?

jstblz said:

I'm doing a full rebuild using the the original piston heads. I've never burned oil and my motor was at 230xxx miles when pulled. Is it necessary to hone if I'm going to install new rings? Should I install new rings?

Click to expand...

Then you aren't doing a full rebuild. You're just "freshening up" the thing..
Before I go further, please, carefully and in detail tell me everything you did to the pistons and bores.

ABSOLUTELY NOTHING as of yet. I have just lined up a new crank/rods (oem) and will be reassembling soon. Just trying to decide if I should do the hone/rings or just bolt it back together.

I'm a sponge for your knowledge.

Sorry, double post.

What is the intended purpose this engine will see? DD service? DD/Auto cross? Track car?

Summer DD/Infrequent track days - Mostly autocross, some drag and road course.

I would think that new rings would require a fresh honing to seat properly.

jstblz said:

ABSOLUTELY NOTHING as of yet. I have just lined up a new crank/rods (oem) and will be reassembling soon. Just trying to decide if I should do the hone/rings or just bolt it back together.

I'm a sponge for your knowledge.

Click to expand...

It's kinda heartbreaking to see guys all thrilled and excited to be assembling things but now--2013---know that crap we could do 20 years ago just barely--like pop open motors and freshen---we almost never can do anymore..

So that said..
You need to clean the ring grooves out absolutely spotlessly but you cannot be brutal to them. The finish and especially the fit is one of the absolute most critical things in the whole engine right up there with the con-rod big and and mainline ID sizing.
A LOT of things you can "get away with"--like cylinder wall clearence.

But "ring side clearance" is something that has to be right and you cannot fake it..

With a NEW ring in the germ-free all minty fresh groove the MAX side clearance is .004"

More than that and the ring face will not be held square against the cylinder wall.
If the ring face is not square, combustion pressure will go in the little wedge created and it WILL push the ring back into the groove and you'll have blow-by..

And hate life.

So, have the machine shop in your presence dial bore gauge the cylinders to check for size, roundness and taper.

I use gallon cans of Carb-n-Choke cleaner and dip the pistons in for a 3-4 days--soemtimes more.. A B21T we're building now had maybe 300k miles and they were so full of baked on carbon it took 10 days...
Use a section of your old rings , the finished end---to clean the goop out. then measure with a NEW RING...

When you find ONE piston that the side clearance is over .004, the set is fuxxored, and you need new pistons--and then need to budget to bore it..

Sucks on one hand but hey NOW you'll have a rebuilt motor and expect long happy life from it..

Rosta ruck finding stock new cast pistons..Again, 20 years ago it was easy.
Now, custom forged is the answer..lucky for you you know somebody who supplies custom forged pistons that are the best available...me!

And if you are gonna reuse the old pigeons and not rebore then absolutely you must hone.
If the bore Is nice and straight and in really good nick you can get away with those bottle brush deglazers but for best results a proper three stone hone is the minimum.
WIthout deglazing the bores the New rings will probably never seat properly.

John V said:

It's kinda heartbreaking to see guys all thrilled and excited to be assembling things but now--2013---know that crap we could do 20 years ago just barely--like pop open motors and freshen---we almost never can do anymore..

Click to expand...

I'm always late to the game so no worries.

John V said:

So that said..
You need to clean the ring grooves out absolutely spotlessly but you cannot be brutal to them. The finish and especially the fit is one of the absolute most critical things in the whole engine right up there with the con-rod big and and mainline ID sizing.
A LOT of things you can "get away with"--like cylinder wall clearance.

But "ring side clearance" is something that has to be right and you cannot fake it..

With a NEW ring in the germ-free all minty fresh groove the MAX side clearance is .004"

More than that and the ring face will not be held square against the cylinder wall.
If the ring face is not square, combustion pressure will go in the little wedge created and it WILL push the ring back into the groove and you'll have blow-by..

And hate life.

So, have the machine shop in your presence dial bore gauge the cylinders to check for size, roundness and taper.

I use gallon cans of Carb-n-Choke cleaner and dip the pistons in for a 3-4 days--soemtimes more.. A B21T we're building now had maybe 300k miles and they were so full of baked on carbon it took 10 days...
Use a section of your old rings , the finished end---to clean the goop out. then measure with a NEW RING...

Click to expand...

After some reading and youtube videos, I understand. So you definitely believe I should put new rings in?

John V said:

When you find ONE piston that the side clearance is over .004, the set is fuxxored, and you need new pistons--and then need to budget to bore it..

Click to expand...

Is that for each ring groove? Can I mix and match sets?

John V said:

Rosta ruck finding stock new cast pistons..Again, 20 years ago it was easy.
Now, custom forged is the answer..lucky for you you know somebody who supplies custom forged pistons that are the best available...me!

Click to expand...

If I need them I will let you know!

carnut1100 said:

And if you are gonna reuse the old pigeons and not rebore then absolutely you must hone.
If the bore Is nice and straight and in really good nick you can get away with those bottle brush deglazers but for best results a proper three stone hone is the minimum.
WIthout deglazing the bores the New rings will probably never seat properly.

Click to expand...

pigeons = pistons?

Bloody auto correct on my phone...;didn't notice before I hit send!

carnut1100 said:

And if you are gonna reuse the old pigeons and not rebore then absolutely you must hone.
If the bore Is nice and straight and in really good nick you can get away with those bottle brush deglazers but for best results a proper three stone hone is the minimum.
WIthout deglazing the bores the New rings will probably never seat properly.

Click to expand...

Carnut, those three stone things are vile and brutal....haven't touched one in over 25+ years.
The so called dingle-ball hones are a seriously good tool. They'll give you the surface finish you want, and, unless you let it sit and run for a a half hour or so, it won't take off measurable material.. Serious crazy shops do final honing with ball hones cause they will "follow the hole"..

the bar things are bad. Unless the stones are the right grit---and they never are---and the pressure on the spring is correct---and nobody has any idea of that, and barrels of lube used, there are high chances of wrecking a bore, so stay away... (I do this crap for a living for 30 years)

Jstblzz,, 004 for the top ring, that's the most critical for compression.

mix and match, sure if they are same weight.
Problem is EVERYTHING for a B21 is 30 years old...the next ones are going to be dead too.
Ring groove wear is a function of material, ring weight, and how many hundred million cycles the thing has done--slamming the ring into the top of the groove every time it goes to the top and starts down and every time it goes to the bottom and starts up--two whams a rev..
Simple cycles.. Not lube like on the crank..rotating like the crank can do a bazziollion miles with correct lube.

Not saying you should put new rings in, saying when checking the side clearance, you check that with new rings..And that's a bitch cause the near certainty is you'll find 1-2 that the grooves are .0055 or .006 and that means new pistons---and that means bore the block. Whaddya gonna do with the new wrong sized rings?

I will check them tonight. Wish me luck and thanks for all of the info.