Progress Thread Cylinder Wall Marks - Too Bad Or Not

[65-Fstbk]

Hey Guys,

Haven't been on for quite a while due to Family stuff. Anyway getting a little more done here and there and am going to build the motor over the winter.

Block is an original bore 1987 5.0HO - history is not known other than that
It will be carbuerated when finished, not EFI. (Nostalgia)
Magnafluxed and was fine
Decks are good
It has the new cam bearings and freeze plugs in already.
Using Moly rings so I thought I'd hone the cylinders with a 400 grit flex hone first
Loos great except for some marks near the top of the cylinder #1 that will not hone out
#1 - piston seems fine.
Not like vertical scoring, almost like the marks are horizontal.
I need your opinions on how bad this is. Should it be a concern or not?
Just building a nice street motor, no NOS but have aluminum heads and a .512 lift Comp 281HR camshaft
Thanks for your thoughts on the scoring.
Chris

 

[robert912005]

it almost looks like pitting in the metal... almost like rust got to it, or it sat for a long time in one spot.... i would see if it could be bored out a little and see if they dissapear

 

[MustangIIMatt]

Personally, I'd be taking it to a machine shop to be bored out and shopping for a set of pistons, or shopping for another block. I only want to do the work once, so I don't take chances.

 

[65-Fstbk]

For anyone interested.
I have a neighbor up the street who is very experienced with engines. He's a Mopar guy that has raced blown alcohol dragsters and continues to build engines. He came down for a look and said if he was building an engine that had to be 100% perfect he would look at having it rebored but for a warmed up street motor the pitting is not likely to affect the engine with any noticeable difference. His advice is to pretend I didn't see it, the motor will run fine. Possibly get a little more plug fouling on #4 but that's easily dealt with.

FYI - He also told me I need to rehone the cylinders as my hatching angle is not steep enough. Going to rehone to get the steeper angle.

 

[horse sence]

We had a 302 with a noticeable drop in one cylinder ,when we removed the heads it had one cylinder just about like what you have pictured . It seems water had gotten into the cylinder when the engine compartment had been pressure washed ,and the motor wasn't started so it sat there for a few months and rusted the cylinder .I would bore it .

 

[65-Fstbk]

Broke down and caved as you all have me convinced.
Dropped the block off at the machine shop this morning. If they cannot hone the marks on #1 clean they are going to bore all cylinders 0.020 over for me and a new set of pistons and rings will be on the way.

 

[whisperer]

Definitely the right decision. As others have said that is pitting from rust. If you hone it to the point that the pits are removed the cylinder will be way oversized and will pump oil and loose compression. Bore it and use new pistons.

 

[tos]

Never ask a Mopar guy for advice on a Ford. They want to see you sittin on the side of the road with them. Ha Ha