nichoulas91rs

i broke down the 454 i bought from a co-worker this past weekend and discovered that one of the cyliners is scarred up pretty bad on one side. it lookes like a piston ring from the position it is located.

the scarring is pretty deep.

im optimistic that a .060 overbore will remove the wear. but im a little nervous that it might not.

i know that it is recommended that certain small blocks should not be bored past the .060 mark. but what about a big block?

and, since this is the only cylinder that has any wear or scarring, how much would it effect the engines balance if a .60 overbore didnt remove all of the scar?

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92 CAMARO RS 25TH ANNIVERSARY LO3
91 CAMARO RS V6
83 CAMARO Z28 (new project!) 700r4, 3.73 posi, 4 wheel discs, 454 in the works...

godsmakz28

I have and have seen many 454's .120 over (482ci). I ran mine for half a season in my bracket car without any problems. .060 doesn't seem like a problem but you might want to have the block checked before you spend the money on boring it.

Dr. Pepper

Are you talking about that '73 RV block? Earlier blocks have thicker walls than the later blocks. Early blocks have little difficulty going .125" over. I haven't seen anyone try it, but I would feel ok with an early block that has been tested to go to .150". This would be a race only block, which is probably not what you are after. .070" over is a somewhat common overbore after .060", but that depends on the amount of wear. What is the block's current bore size? If you are at like .030" over .060" will probably clean it up, if not .070" will have a better chance. Pistons larger than .060" are not as easy to get as a normal off the shelf piston. Without looking at the damage it is hard to say how much overbore you will need to clean it up, and how much damage is acceptable. You will want it cleaned up to where it is nothing more than a few minor scratches. Vertical damage is easier to withstand than horizontal. Rings collide with horizontal damage, while the piston and rings will slide right over a vertical cut. Also keep in mind they can resleeve blocks. This is not a real popular procedure with different opinions as to its quality, but it is an option I would keep open. A machine shop should be able to tell you what they can do. A good machine shop will be able to eye it for you and tell you how much bore they can save, and how much is gone.

And for your mention of balance, I am not sure in what manner you are saying this but all the pistons will need to be .060" over. You don't take one cylinder to an overbore. At best you can resleeve it back to standard and keep the rest at standard if they are still very clean and straight. If you are worried about the piston weight difference, for $100-$250 you can get the entire engine balanced after the work is done and you have all the new parts. Then it will run nice and smooth with all the new parts.


[This message has been edited by Dr. Pepper (edited July 25, 2000).]

nichoulas91rs

yes i am referring to the 73' rv motor.

i know i need to have every cylinder bored, but when i was talking about balance i meant this:

in my opinion, none of the other cylinders (just eyeballing it for right now) look like the need to be bored over. no scratches, no wear. its just this one cylinder that is scared up on one side.

if a .60 bore does not remove all of the scratch, say it leaves just a little scarring left over, how badly would this effect the compression on that cylinder, and would having a cylinder who's compression was a little off effect the engines balance significantly?

thanks for the info... i thought a .125 bore was safe on big blocks myself but just wanted to see for sure.

ive never seen pistons or rings for engines for .070 or .120 in catalogs and stuff. would these be a custom order kinda deal? and would they be much more expensive?

and since all the other cylinders look great, my opinion, should sleeving this bad cylinder be my best option? how much would this cost?

------------------
92 CAMARO RS 25TH ANNIVERSARY LO3
91 CAMARO RS V6
83 CAMARO Z28 (new project!) 700r4, 3.73 posi, 4 wheel discs, 454 in the works...

nichoulas91rs

oh yeah, the engine currently has a standard bore and the damage is vertical in the cylinder. ill post pics of it later... itll be hard to judge the depth of it but i estimate its .035 to .040... this was guestimated with a feeler gauge.

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92 CAMARO RS 25TH ANNIVERSARY LO3
91 CAMARO RS V6
83 CAMARO Z28 (new project!) 700r4, 3.73 posi, 4 wheel discs, 454 in the works...

9.0L Firebird

Nearly every BBC will take a .060 overbore with no problems. Most will go .100. The 512 series blocks will go .125 most of the time. One consideration is that you do not always need to use the existing bore as the center guide. If the scratch/gouge is facing the intake valley or the exhaust side you can offset bore the block to save it. You will still bore .060 over, but how much you take off from which side of the cylinder bore is up to the machinist. If the gouge is on the face nearest the adjacent cylinder(s), you have limited flexibilty to re-center the bore. (crank clearances become a problem). When a hard core race block (non DRCE or specialty block) is being machined (CNC or old school) the bores are arranged on a 4.84" bore spacing regardless of the existing bore location. Because of core shift or seasoning, the old bores can be as much as .020 off center from each other. Just some food for thought.

Dr. Pepper

I know I have seen a few .070" listings, look at the Keith Black piston offerings. By no means do I recommend their pistons, but the overbore options are pretty good and give you an idea of what is out there. The .070" bore is the same as the Mopar 440 bore. That is why the odd size, it gives an application that is easy to get piston rings for. I have been shocked a few times myself at what scratches would come out. I have had a few times where I would swear .060" over would not clear all the scracthes up but .030" cleaned it nicely. If you just have a few scratches the cylinder will not be affected. Oil carried through will help make the seal, not that it is that air tight of a seal to begin with. If you take it to a good machine shop they should help you get it ironed out. They will have more experience on what is acceptable and will actually have their eyes on your block. Pictures are good but nothing can beat having the part in your hands. Also, wasn't the RV engine running to where you could hear it? If it was still running ok then the damage may not be as bad as it looks. For resleeving, I think it runs about $80 a hole but I have never had it done myself. It depends on what it takes to clean up that one bore and how good the others are. You really need a bore gauge to determine the wear on the other cylinders. Usually I try to start with a fresh bore when rebuilding. Any wear is just that much less life your engine will have, and even on great looking bores I have always found .002"-.003" wear and taper. Considering a tight clearance of .003"-.004" that is a big variance. Unless you are building a race engine where you can hone the cylinders true and take on .008"-.010" clearance I would try some overbore, maybe .020" if you can find the pistons. If you can take the entire block to .030" over then I would just go with it. If you start talking .060" or larger I probably would resleeve that cylinder and try for as small of an overbore as possible. It will save you money on resleeving the entire block if you keep ahold of it long enough to rebuild it a time or two more.

[This message has been edited by Dr. Pepper (edited July 25, 2000).]