360 crank in 318 block

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gliderider06

gliderider06

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How hard is it? I know to have the mains cut to the 318 size and have rebalance. I have 2 sets of 318s that have the pistons way down in the hole one more than the other. Could I use those on the 3.58 crank? I can measure how far down they are tomorrow. I was thinking of this (already have a 360 crank that needs to be turned) and putting it in my 88 roller block for my Ramcharger. Thinking of doing things, and the squeaky wheels are turning in my head, while I'm recovering from my knee surgery.
Is it really hard to do?
 
That would turn your stock bore 318 into a 344. You will need special (shorter ) pistons to make it work.
 
The pistons would travel .135" higher and .135" lower in the bores, so it depends how far down they are at TDC with the OEM crank. Could mill the pistons a bit to keep from going above deck. (i.e.: Hoover's Mover 360 using low compression 340 pistons decades ago.) But then you might have issues with piston-to-valve clearance anyway and gotta check crank counterweight-to-piston clearance too. No valve notches. Custom work can get expensive quick. Tom Hoover did the 360 before 360's had many pistons to choose from.
 
Locomotion said:
The pistons would travel .135" higher and .135" lower in the bores, so it depends how far down they are at TDC with the OEM crank. Could mill the pistons a bit to keep from going above deck. (i.e.: Hoover's Mover 360 using low compression 340 pistons decades ago.) But then you might have issues with piston-to-valve clearance anyway and gotta check crank counterweight-to-piston clearance too. No valve notches. Custom work can get expensive quick. Tom Hoover did the 360 before 360's had many pistons to choose from.
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Trim some off the pistons and use extra thick head gaskets, no super high lift cam though??
 
Use the low compression truck piston (for example the UEM 1278 or the FM LC371P,has a small dish also at 3" x .040), these have a comp. dist. of 1.658". These will still end up with a below the deck height of 9.571" even in a Magnum block it's still below. Of course there's no valve reliefs so cam selection can't be radical. Now for the crank, .310" thou off the mains and reduce the slinger and oil seal surface size too. The counter weight remove .170" thou off in an off-set grind of .500" thou, vertically opposing each throw of the crank, this only removes the material in the portion of the counter weight where the underside of the piston would/ could come the closest to contacting the crank. This will need to be done on 6 of the counterweight to accomplish the necessary clearance. Chamfer the edge of the weight accordingly, and then balance.
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No need for custom pistons if you are not going to be super hard on this thing... Silvolite lists some cast low compression 318 truck pistons, PN 1278, that have a compression height of 1.658". With the 3.58" stroke, that puts the piston top at .029" below standard deck height at TDC, much better than the standard .070-.080" of the low compression LA aftermarket pistons.

No eyebrows as mentioned, so that needs either care and limits in cam selection or perhaps some machine work. I'd try to buy one and check the thickness of the crown. Being an older heavy design, it might be OK to mill some out of it.

Re-balance with the external 360 weighted parts (damper and flexplate/flywheel/TC) looks to be pretty easy: The standard bobweight of the 318 piston/rod's is in the mid 2100 range for the heavy 318 rods and the 360 is just a bit less: I have a 2162 grams (318) vs 2150 grams (360) in my data. That difference in within the reputed factory tolerances. I'd consider just drilling some extra holes in the damper and flexplate opposite to the weights to get that small of a change.
 
BTW, I'd trim the pistons before the counterweights as trimming the counterweights will make the balance move further off.
 
Been there, done that, Way too much butchery of the piston, It's getting balanced anyway, much cleaner with the slight arc of removed material off the counterweight.
 
gliderider06 said:
How hard is it? I know to have the mains cut to the 318 size and have rebalance. I have 2 sets of 318s that have the pistons way down in the hole one more than the other. Could I use those on the 3.58 crank? I can measure how far down they are tomorrow. I was thinking of this (already have a 360 crank that needs to be turned) and putting it in my 88 roller block for my Ramcharger. Thinking of doing things, and the squeaky wheels are turning in my head, while I'm recovering from my knee surgery.
Is it really hard to do?
Click to expand...

Here. Save the cost of machining and buy the 3.58 crank sized for the 318/340 mains.

Mopar Performance Cast Crankshaft
 
Why not just put a 360 crank into a 360 block and be done with it. Much less trouble
 
I think it could be a great combination. Stock pistons, normally .130 down the hole end up at .005 up.
If you can keep the block at .010 over max, you could source out a set of 66-69 (I think) pistons that have valve reliefs already cast in place.
Small bore would rock with a set of 1.88 360 heads.
 
You do that and you'll have the Generals' flagship....LS1
There is a reason why the GM engineers picked that bore stroke combination.
 
I say at its CID, give it 2.02-1.60 valves and let it rock. It’ll be good. Take note on the 5.7 HEMI bore and stroke...... look familiar?
 
Requires Narrow Bearings: Yes

Crank has radius fillet on journals requires narrowed rod and main bearing.....

Clevite MS-1266HG Engine Crankshaft Main
King Engine Bearings CR 805XPN Rod Bearing
Clevite H-Series Rod Bearings CB481HN
 
LOL, thanks! Can you expand on wide bearings then?!?!

:rofl:
 
rumblefish360 said:
It says requires narrow bearings. Can you shed light on that?
Click to expand...
Those are con rod bearings narrowed up on the 'heavy' side of the rod's big end; that is done to clear any large fillets on each edge of the journal. I just ordered a set of CB481HN con rod bearing to work with a stroker crank with generous fillets.
 
whitepunkonnitro said:
I think it could be a great combination. Stock pistons, normally .130 down the hole end up at .005 up.
If you can keep the block at .010 over max, you could source out a set of 66-69 (I think) pistons that have valve reliefs already cast in place.
Small bore would rock with a set of 1.88 360 heads.
Click to expand...
Which pistons are these?
 
Ok, so I have a really nice 88, roller cam 318, all std. Nice bores, no ridge and has nice cross hatch for an 88. #302 heads that I planned on cleaning up the ports some. I have a 73 318 sitting on the floor and those slugs are way down in the hole, (much more than the 88) so I start thinking and remembered MRL doing a 360 crank in a 318 and it made tons of torque.
Thought it would be a good idea, maybe if I could have my extra crank turned down, use those early 318 pistons (or new ones) and put it in my Ramcharger. I'm not planning for big hp at all, actually thinking of using the stock 318 roller cam, and cast EGR spreadbore intake. There is nothing wrong with the 88, 318 at all. I'm off on medical leave a few weeks and my mind starts wondering.
Kinda sounds like it will be more work than its worth. Butt... I do have a 340 that needs to go .020 and that 360 crank will fit nicely in it with .060 360 slugs...
Thanks!
 
Are there any issues with the rear main when the journal cut eliminates the mild serrations that assists the rear main seal do its job?
 
Locomotion said:
Are there any issues with the rear main when the journal cut eliminates the mild serrations that assists the rear main seal do its job?
Click to expand...

I "would think" with these modern seal materials, that would not be an issue. Course I've been wrong a time or two before. lol
 
Are you referring to the "directional pattern" on the seal surface of the crank, Think of a Chev 350 crank, never had this pattern and no problem.
 
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