LA 360 maximum overbore ??

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Brooks James

Brooks James

VET, CPT, Huey Medevac Pilot
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Yes I will have it sonic tested
First . Its already .040 over and has a gouge mark probably no more than a few thousands deep. How deep and wide would call for additional boring?
it’s like a little less than the size of upholstery thread and very uniform. I’m not interested in every ounce of hp. The motor is so fresh that the home marks are still in it. The owner claims 100 hours on it. Also what would be a reasonable price for a sleeve to be installed.?? I’m tempted to slap it back together with the basics, rings,gaskets , bearing sets and go for it
 
I wouldent sleeve it for that. Next oversize is probably .060" over. It all depends on the size pistons that are offered for your application. I have seen pistons in .020" .030" .040" .050" and .060" oversizes
 
Is your mark at the top or bottom of the cylinder? I would be more tempted to run it at the bottom.
Im probably running worse now in my engine. I have a .030 over now, with a gouge in the cylinder, about half way down. I know it needs boring, and i have .060 ross for it, but i just wanted it running so i slapped it together. Compession is down a bit in that cylinder.... but it still runs elevens.
If its not any worse that you describe, and its not at the top of the cylinder, I'd be tempted to fly it, rather than sleeve a hole, or buy pistons and bore it 060. But then.... I'm lazy.
 
33IMP said:
Is your mark at the top or bottom of the cylinder? I would be more tempted to run it at the bottom.
Im probably running worse now in my engine. I have a .030 over now, with a gouge in the cylinder, about half way down. I know it needs boring, and i have .060 ross for it, but i just wanted it running so i slapped it together. Compession is down a bit in that cylinder.... but it still runs elevens.
If its not any worse that you describe, and its not at the top of the cylinder, I'd be tempted to fly it, rather than sleeve a hole, or buy pistons and bore it 060. But then.... I'm lazy.
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Not sure yet? My friend has a boroscope with a camera. I’ll take pics Friday and post.
 
It's possible it's already at its max bore size. It's again possible it's not. It's also possible it's usable as is. Without pictures, we cannot tell here. Without a sonic test, you cannot tell there.
 
RustyRatRod said:
It's possible it's already at its max bore size. It's again possible it's not. It's also possible it's usable as is. Without pictures, we cannot tell here. Without a sonic test, you cannot tell there.
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After seeing the boroscope pics Friday if the gouge is near the bottom and fairly insignificant I will probably not go any larger. I’m not comfortable with anything past 30 thousandths.
 
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RustyRatRod said:
It's possible it's already at its max bore size. It's again possible it's not. It's also possible it's usable as is. Without pictures, we cannot tell here. Without a sonic test, you cannot tell there.
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It’s at 30 over now. If the gouges/scratches are insignificant and further down the wall I will probably not bore more. I am uncomfortable going to 40 or 60 over.
 
Brooks James said:
It’s at 30 over now. If the gouges/scratches are insignificant and further down the wall I will probably not bore more. I am uncomfortable going to 40 or 60 over.
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Some can go .060 or even .100. Have it sonic tested and you'll know.
 
Brooks James said:
It’s at 30 over now. If the gouges/scratches are insignificant and further down the wall I will probably not bore more. I am uncomfortable going to 40 or 60 over.
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Confused....first post you said it was already 40 over??? So is it 30 or 40 over now??
 
Brooks James said:
Yes I will have it sonic tested
First . Its already .040 over and has a gouge mark probably no more than a few thousands deep. How deep and wide would call for additional boring?
it’s like a little less than the size of upholstery thread and very uniform. I’m not interested in every ounce of hp. The motor is so fresh that the home marks are still in it. The owner claims 100 hours on it. Also what would be a reasonable price for a sleeve to be installed.?? I’m tempted to slap it back together with the basics, rings,gaskets , bearing sets and go for it
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There are a lot of opinions about how far to overbore. The LA engines are thinwall castings, so it is not recommended to go over .030-.040 though many have done it. Some who have gone big have heating problems too.
 
Any LA that is going to be over bored more than .040 SHOULD be sonic tested for core shift. All of my strokers, 408 & 416 blocks were sonic tested to be SURE that the cylinders would stand the .060 bore that I require & I full filled the blocks with Hard Blok to help keep the main caps from walking. I DO NOT suggest .060 over bore on a street engine because of over heating problems, some have done it with success. My street engines usually turned into race engines, but that's what I enjoy. I have a friend who has some early 67-69 cast date LA 340 blocks that were bored 4.125, most of them ended up as door stops.
 
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I had my 1998 5.9 Magnum sonic checked for a .030 over bore. The block has 113K miles on it, still had some cross hatching visible in the bore. For $90, I found it has plenty of thickness for .060, if I wanted to go that far. I think it's worth the money, especially if you're going to put a couple thousand dollars into a nice street/strip motor.
 
I’m not wanting to frig with a 60 over block which is actually what is. Going a different direction all forged 408 kit, 30 over.
 
mygasser said:
neither it's 60 over now, apparently:BangHead:
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Yes the bore cam pics were grainy but it’s definitely 60 over.
Between procuring parts, working on an idea for an almost hear me almost self sustaining car with a small power source to put it in motion, we both know there is no such thing as perpetual motion. Working on the car, full time job, my wife’s demand I’m scattered all over the place. I have to take sedatives to sleep because I can’t shut my mind down. I’m bipolar 1 mostly manic and I haven’t taken meds for a while.
With all that is goingon it makes me miss details, also I’m a big picture guy who doesn’t like details. Sorry for the confusion.
Love the emoji banging his head against a brick wall , it’s absolutely perfect.
Brooks/ Dustoff
 
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Brooks James said:
Yes the bore cam pics were grainy but it’s definitely 60 over.
Between procuring parts, working on an idea for an almost hear me almost self sustaining car with a small power source to put it in motion, we both know there is no such thing as perpetual motion. Working on the car, full time job, my wife’s demand I’m scattered all over the place. I have to take sedatives to sleep because I can’t shut my mind down. I’m bipolar 1 mostly manic and I haven’t taken meds for a while.
With all that is goingon it makes me miss details, also I’m a big picture guy who doesn’t like details. Sorry for the confusion.
Love the emoji banging his head against a brick wall , it’s absolutely perfect.
Brooks/ Dustoff
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I thought you said you were retired?? Not sleeping is a HUGE issue and is a big cause of dementia, Alzheimer’s and other disorders on that spectrum.
 
I'm retired, and suffering from insomnia, and can find you a 5.9 Magnum in central Florida for $700. I'll help if you want. I'm not exactly sure where Fruitland Park is, But I was born in central Florida in 1958. I still have plenty of friends and family that would help you out. PM me if you need help finding a core engine.
 
I don't mean to butt in, but my 1998 5.9 Magnum has been sonic checked , and sonic checked good. I'll send you a PM so the snow flakes aren't upset. I want your balls out, true opinion. Paul
 
If the block is 60 over I'd sleeve the damn thing if i were running it on the street just to be safe , sleeved my old 340 that was stolen , i drove it for 8 years as far as i know it is still going strong . 60 over on an LA is pushing it IMO, BUT iI'm no mechanic .
Good luck whatever you decide
 
Brooks James said:
Yes I will have it sonic tested
First . Its already .040 over and has a gouge mark probably no more than a few thousands deep. How deep and wide would call for additional boring?
it’s like a little less than the size of upholstery thread and very uniform. I’m not interested in every ounce of hp. The motor is so fresh that the home marks are still in it. The owner claims 100 hours on it. Also what would be a reasonable price for a sleeve to be installed.?? I’m tempted to slap it back together with the basics, rings,gaskets , bearing sets and go for it
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I would just run the dang thing! You ought to see what some of the dirt track and mud bog guys run, no money to bore, just hone and go... You said your not worried about every ounce of hp. Again, RUN IT!
 
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