John Collins
Well-Known Member
How can you tell if it’s been peened?
Under $4k budget build LA360 build
- Thread starter John Collins
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How can you tell if it’s been peened?
Generally on the non machined surfaces there are small pock marks.
Captainkirk
Old School Mopar Warrior
Shot peening compresses the grain structure of the metal, "pre-stresses" it and makes it more resistant to cracking.
A shot-peened crank will have tiny pock marks (as Rusty mentioned above) on the non-machined (counterweight) areas, just as if someone had pummeled it with thousands of tiny lead shot pellets...which is exactly what they did.
It appears the weakest crank of the 3 types (forged, cast and cast/shot peened) is the cast-only crank which apparently only left the factory in the '72 340 (now you know why I changed mine to forged). My sources list ALL 360 cranks from '71-'86 as cast/shot peened. Hope this answers your questions!
A shot-peened crank will have tiny pock marks (as Rusty mentioned above) on the non-machined (counterweight) areas, just as if someone had pummeled it with thousands of tiny lead shot pellets...which is exactly what they did.
It appears the weakest crank of the 3 types (forged, cast and cast/shot peened) is the cast-only crank which apparently only left the factory in the '72 340 (now you know why I changed mine to forged). My sources list ALL 360 cranks from '71-'86 as cast/shot peened. Hope this answers your questions!
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dartfreak75
Restore it, Dont part it!
I got mine from rock auto I just looked and they are out of stock now. But O'Reilly had them too.
Well now, that's debatable. Remember, there's a difference in "just cast iron". There's "just" cast iron and then "nodular" cast iron which is much stronger than plain cast iron. That's what made the 351 Cleveland cranks famous. They routinely spun to 9500 plus RPM on NASCAR tracks. Yes, of course they were professionally prepared, but nonetheless, they were indeed nodular cast iron. Very strong. If I am not mistaken, all the Chrysler cast cranks are also nodular iron. That's why, although it does happen, you seldom see broken factory Chrysler cast cranks. They really are that strong. That's exactly why I always give the advice to use what you have if you have a cast crank. The will last plenty long.
John Collins
Well-Known Member
The engine arrived today. To my surprise, the 974 heads already have 2.02 valves and what looks to possibly be a three angle valve job. The springs are 1 3/16th wide and 2 3/16th tall(without load ). It also looks like the engines been decked. The crankshaft is stock with casting numbers 3418640 with a Big “X” on one side and CFD(GM factory) on the other and stamped with M10 R10, which I believe is the stamp for it getting machined .10. One of the journals has a scratch that is very small, but kind of deep, but otherwise very smooth. It came with two cams, one is from the engine and the other is a BB cam, I believe. It also cam with what looks to be the stock stamped rocker assemblies and distributor.
I think it’s a score, overall. The scratch on the crankshaft gives me concern because it’s already been turned... Oh well, you can’t win them all. Now I need to get it all to a machine shop for a professional assessment.
I think it’s a score, overall. The scratch on the crankshaft gives me concern because it’s already been turned... Oh well, you can’t win them all. Now I need to get it all to a machine shop for a professional assessment.
moper
Well-Known Member
It’s already been rebuilt once from the sound of it.
John Collins
Well-Known Member
Yup. The PO had it prepped for a build and decided to buy a complete crate engine from Blueprint. The prep tape for paint on the heads is still there.
Captainkirk
Old School Mopar Warrior
Nice! Sounds like you're on your way. Now comes the really fun part...whip out your wallet!
John Collins
Well-Known Member
My wallet was extremely light and even lighter now since I just had a surprise $3000 vet bill... Basically my budget for the remainder of the build. All good though. My dogs are more important than a project engine. It’s not going to stop me, but I might have to switch gears and try a far more tightly budgeted build.
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Captainkirk
Old School Mopar Warrior
No surprise to me...I lived it, John. One step forward and six steps back. Keep your dreams, don't let life's booby traps discourage you. And it will try.
John Collins
Well-Known Member
Most definitely! I’m a scrappy guy who came from nothing and have no problem dealing with diversity. It does suck though. The great surprise was the 2.02 valves, which will save me a ton of money up front, by not having to buy aluminum heads if I failed doing the machine work myself.
John Collins
Well-Known Member
How does the block look to you? Does it look like a three angle valve job on the heads? Is the crank salvageable after it’s already been turned and has a scratch?
Captainkirk
Old School Mopar Warrior
Hard to say from the angle of the pic on the block. The crank will be salvageable...they can generally be turned .030 under if need be. The scratch may polish out...your machinist will have to be your guide. Valves look pretty good but if it were me, I'd have the shop check the angles on the valves and seats for true. Better to build it right first time around...it's usually cheaper that way. Whether or not you can reuse the valve springs will depend on your cam grind. I reused my springs last time around and they were shimmed a little. This time I'll likely go with matching springs to go with the cam.
John Collins
Well-Known Member
Awesome. I was worried about the crank since it’s already been turned... Hopefully I get good news from the machinist.
I’ll take better pics of the block. It’s in plastic cover and I was being lazy and only took the cover partially off for the pic... The machine marks don’t show on your end?
Captainkirk
Old School Mopar Warrior
No, can't really tell what the cylinder bores look like. When I blow them up they blur out.
John Collins
Well-Known Member
The cylinder bores seem great, smooth and without any imperfections in the metal. I was wondering if it looked like it had been decked.
Captainkirk
Old School Mopar Warrior
Decking is done on the topside. Can't see that in the photos, unless I'm missing something:
Captainkirk
Old School Mopar Warrior
You say this has been bored .040 over? If so, might want to have your machinist ultrasonic check the wall thickness while he's freshening things up.
Oh, and M10 R10 refers to mains 10 under, rods 10 under
Oh, and M10 R10 refers to mains 10 under, rods 10 under
John Collins
Well-Known Member
Ha! Apparently some of the photos didn’t upload and I missed it. To be honest though, I thought decking was a general word for machining material from the block. The top of the engine looks untouched, but the bottom and front have machine marks. Thank you for looking!
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Captainkirk
Old School Mopar Warrior
A decking mill can be used to true any flat surface, but generally in automotive machining it refers to machining the top of the block surface...and the more you have to machine off to true it, the more the pistons protrude out of the bore, hence "deck height". So, if decking is not needed, it's probably best not to.
If you're an exceptionally skilled welder.....Yeah, you can't really go 10 over when grinding a crank!
Shot peening involves shooting steel shot(Think BB's) at a freshly machined crank shaft at high speed. This beats down and hardens the surface. It's more dense, so it will withstand abuse better than a regular cast crank.
I don't think those are LA small block rocker arms. I think those are 1950s or early 60s bb pedestal mounts.
Decking the top of the block ensures that the top of the block(The Deck) is square, parallel, and the same stroke length to the centerline of the crank. I learned this the hard way many moons ago.......Sonic checking is worth the cost in the long run. I recommend it.
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