cylinder machining question
Thread Starter
Drifting
Joined: Sep 2004
Posts: 1,270
Likes: 4
From: Celeste Texas
cylinder machining question
Here's a long winded story to get to a question. I'm working on a 72 project. The original block came with the car but has been redone at some point. When I opened it up it I found enough rust in the back three cylinders to prevent the motor from tuning over. It took a week and a whole can of PB Blaster to soak all the rust out and spin the motor. Once I could turn the motor and inspect all the cylinder walls I found a couple of very small divots in the back cylinder wall. They are about the size of a grain of rice but only half the thickness of one.
Here's my question. When I get this block to the machine shop should I expect him to tell me it needs to be a perfectly smooth wall or are there allowable dips?
Bill
Here's my question. When I get this block to the machine shop should I expect him to tell me it needs to be a perfectly smooth wall or are there allowable dips?
Bill
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,117
From: Crossville TN
They can't be in the 'working' area of the piston rings. It might have been better to just disassemble the engine, rather than trying to turn it over with that much debris/rust in it. It's possible to 'stitch' the damaged areas; I don't know how successful welding would be to fill them before machining. Your machine shop should research possible ways to salvage that block, but you need to consider how much expense is reasonable to save that block [over dropping in a crate engine].
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
If necessary, I'd sleeve it before welding. Have had very good success with the former, even in drag racing mills, while IMOE the latter could crack it thru to the deck if the planets aren't perfectly aligned.
Thread Starter
Drifting
Joined: Sep 2004
Posts: 1,270
Likes: 4
From: Celeste Texas
Here's what it looked like when I started. It's the correct block for the car so I figured if I could reuse it without spending crazy money on machine work it was worth it. If this block can't be reused there's a big block in my future.
Bill
Bill
Le Mans Master
Joined: Dec 2006
Posts: 5,557
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From: Oquirrh Mountains
St. Jude Donor '09
Just because there's rust in the cylinder walls doesn't necessarily mean the block is crap. Get it apart and magnaflux it. If it checks out, bore it and you're good to go.
Pro
Joined: Oct 2004
Posts: 573
Likes: 0
From: Stafford VA
The cylinders can be bored oversize to make the walls smooth again. You will need to buy oversized pistons to match. If the block has been rebuilt once already, there is a good chance you have enough material left in the cylinder walls for another bore job.
Blocks can also be sleeved by boring that cylinder way oversized and installing a cast iron sleeve. They work extremely well if the shop that installs them knows what they are doing.
Neither option is terribly expensive, much cheaper to fix that block than replace it.
Blocks can also be sleeved by boring that cylinder way oversized and installing a cast iron sleeve. They work extremely well if the shop that installs them knows what they are doing.
Neither option is terribly expensive, much cheaper to fix that block than replace it.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
typical piston oversizes for sbc are +20, +30, +40 or +60 (No +50).
From the info offered, it's Not likely it'll clean up at +40 ... +60 is limit and even then the walls Might become too thin ... only your machinist can tell.
Prepare to sleeve this block.
also, this block likely requires decking ... that usually machines away the engine ID characters on pad... suggest verify shop can deck without cutting away ID pad ... some can, some cannot.
From the info offered, it's Not likely it'll clean up at +40 ... +60 is limit and even then the walls Might become too thin ... only your machinist can tell.
Prepare to sleeve this block.
also, this block likely requires decking ... that usually machines away the engine ID characters on pad... suggest verify shop can deck without cutting away ID pad ... some can, some cannot.
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Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
Absolutely!! If you go to the trouble and expense of saving this block because of the ID pad numbers, you don't want some 'yayhoo' milling them off. Put a clause in the work order agreement that the pad is not to be milled...and if it is, by mistake, the shop will suffer a $3000 penalty. {That's about what you will lose on a future sale if you can't prove the block is correct for that car.} With that clause in the contract, there is no way the shop owner will allow that pad to be machined.
Team Owner
Joined: Jun 2000
Posts: 38,923
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From: Southbound
Cruise-In II Veteran
Your block might cleanup with nothing more than cylinder honing. It may not need to be decked.
Let your rebuilder take a look and discuss things with you before any real work begins.
Let your rebuilder take a look and discuss things with you before any real work begins.
Race Director
Joined: May 2003
Posts: 10,956
Likes: 409
From: California
Thread Starter
Drifting
Joined: Sep 2004
Posts: 1,270
Likes: 4
From: Celeste Texas
Thanks guys.
I talked to the machine shop. For a couple hundred he is going to clean, magnaflux and measure everything. I kinda want him to find something bad so I can drop a 454 in. From what you guys are saying I should be prepared for him to tell me it needs to be sleeved and that runs a risk of needing to be flat decked which can remove the numbers. We'll see.
Bill
I talked to the machine shop. For a couple hundred he is going to clean, magnaflux and measure everything. I kinda want him to find something bad so I can drop a 454 in. From what you guys are saying I should be prepared for him to tell me it needs to be sleeved and that runs a risk of needing to be flat decked which can remove the numbers. We'll see.
Bill
