Cylinder wear ?

-
R

RedB.

Well-Known Member
Joined
Feb 19, 2019
Messages
289
Reaction score
155
Location
down south
I was wondering how much cylinder wear is too much before a new bore is necessary. We have a 5.9 magnum block that shows 5 thousands over and was wondering if we could get away with a fresh hone and new rings ?
 
If the bore was round and straight, and not tapered, you could; but that's only the half of it;
you still gotta deal with the ridge at the top of the bore, and
what do you do with the huge ring-gaps with grow by 3.1416 times the wear; which in this case is close to .016?
and finally,if the bore varies from top to bottom,(tapered) then the rings are gonna walk into and out of the grooves, accelerating the wear on those parts.

All in all, IMO, a bad deal.

Theoretically you could solve some of those problems, but it would probably be only a short term solution
 
AJ/FormS said:
If the bore was round and straight, and not tapered, you could; but that's only the half of it;
you still gotta deal with the ridge at the top of the bore, and
what do you do with the huge ring-gaps with grow by 3.1416 times the wear; which in this case is close to .016?
and finally,if the bore varies from top to bottom,(tapered) then the rings are gonna walk into and out of the grooves, accelerating the wear on those parts.

All in all, IMO, a bad deal.

Theoretically you could solve some of those problems, but it would probably be only a short term solution
Click to expand...


I was going to bring it to my machinist but he is out of town till next week, so just thought I would ask FABO members their opinion . I do want it to live for a while so I guess a fresh bore and hone on the CNC Rottler is in order.
Thanks AJ
 
Yep that is the right move if you are not just tossing it together. We had a block where the bores were exactly .005" over, no taper or out-of-roundness; it was a block machined for a drag race application. Even .005" perfectly straight bores were not acceptable to me for hyper pistons in street use, so we went to .020" overbores.
 
nm9stheham said:
Yep that is the right move if you are not just tossing it together. We had a block where the bores were exactly .005" over, no taper or out-of-roundness; it was a block machined for a drag race application. Even .005" perfectly straight bores were not acceptable to me for hyper pistons in street use, so we went to .020" overbores.
Click to expand...


Yes agreed, we will take .020 to keep max cyl. wall thickness. Thick, straight, round make power.
 
AJ/FormS said:
In that case, selecting the right compression pistons, for your cam is gonna be important
Click to expand...


For sure, when the time comes I will consult you and the other Motor Heads on FABO . I don't know what is available for the Magnum 360 vs la 360, iirc the magnum has a bit shorter deck ?
 
No brainer . The only answer is bore it. Why take the chance. Get new upgraded pistons. Remember make sure the shop has two torque plates installed. Also install and torque the main caps
 
RedB. said:
For sure, when the time comes I will consult you and the other Motor Heads on FABO . I don't know what is available for the Magnum 360 vs la 360, iirc the magnum has a bit shorter deck ?
Click to expand...
Yes the Magnum block is nominally .015" shorter.... 9.585" vs 9.599" or 9.600". Performance pistons will be the same pieces, ending up at a different deck height. One rod type is a bit wider at the small end, where the pins go through the small end and piston. So some rods have to get ground a bit thinner at the small end to fit between the pin bosses of certain pistons. Not a big deal.

Heads are different but interchangeable with some limitations, and the Magnum are all roller cams. IIRC, damper weights and flexplate/flywheel weights are different too. Probably more stuff that I can't think of right now.....
 
nm9stheham said:
Yes the Magnum block is nominally .015" shorter.... 9.585" vs 9.599" or 9.600". Performance pistons will be the same pieces, ending up at a different deck height. One rod type is a bit wider at the small end, where the pins go through the small end and piston. So some rods have to get ground a bit thinner at the small end to fit between the pin bosses of certain pistons. Not a big deal.

Heads are different but interchangeable with some limitations, and the Magnum are all roller cams. IIRC, damper weights and flexplate/flywheel weights are different too. Probably more stuff that I can't think of right now.....
Click to expand...


LOL....yep....”nominally” shorter. Most aren’t shorter.
 
You must log in or register to reply here.
-

Back
Top