I think that there is such a thing as a 318-III crank that was for Motorhomes, I think it was forged and not cast. In the old days, we had to make sure the small block crank was drilled for input shaft IF you had a standard transmission (manual) (with a clutch).

340 crank will also FIT, but balancing issues at that point. They are forged 68-71, IIRC.

 

            A 318 crank is pretty common, cast. Is that $300.00 with bearings or
        without? If it's $300.00 for a cast 0.10-0.10 crank and no bearings that's
        a little steep.

 

lots of 318 cranks are forged, look for one out of an early 70s engine. they should all fit. i would rather have an old crank in good shape than a cheap after market one.

 

walk into any NAPA and get a new one with bearings for $230 bucks

http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Crankshaft-Kit-Remfd/_/R-CRA13570_0434569492

 

core is only worth 11 dollars and change?

 

Not only are most 318 cranks the same- the 340 cast cranks weren't different either. There's a few different PNs but they're the same throughout a vast number of applications and years. There were "HD" cast and forged cranks, and prior to '68 all were forged after '77 I don't believe any SBs were.

My '72 340 and '85 318 had the same crankshaft PN.

$300 isn't reasonable for a refurbed stock 318 crank, a new 4" crank's probably a touch cheaper than that. Mine was $250. I imagine he's actually talking about  new crank but if you're replacing the crank and pistons it's no more expensive to stroke it. If you're having this rebuilt you are improving the heads right? (or is it a factory 4bbl?)

 

The 318-3 engines were also used as industrial engines and fitted with a belt driven govenor.  Both 318 and 225 industrial engines have forged cranks.  Been a long time since I've had one apart and I can't remember for sure, but I believe the industrial versions have a different bolt pattern on the end of the crank. 

 

318s went to a cast crank in '72, as did 340s. The 340 crank has been said to be a better forged crank, but I have not seen a significant difference between a forged 318 crank, and a forged 340 crank. Your engine came with a cast crank. Both forged and cast cranks are internally balanced, but the dampers are different. You MUST use the correct damper for the crank. If you're not planning on wringing a bunch of horsepower out of that engine (like 500), I wouldn't hesitate to use a cast crank. All the magnum cranks are cast. All 360 cranks are cast (except for aftermarket hi po stuff). Fear not. FWIW, a 273 crank is the same as a forged 318 crank, if you happen to find one of those and a damper.

And one more thing: if you swap to a forged crank with a factory damper, the timing marks on your timing cover will be in the wrong place. When they went to cast, they also changed the inlet of the water pump and moved the timing marks on the timing cover and balancer. You could correct this with a timing tape, while degreeing in your cam.

 

wow guys thank you for all the information.  I don't plan on trying to get huge power out of this engine.  I want to put it back to "as stock" as possible but with some mild performance mods.  I'm new to the old school engine game, I've built plenty of high compression forced induction VW's and Audi's in the 2000-2009 range, but I've never really done anything with something this old haha. 

Just to be clear, the only performance upgrades I am doing are just the standard: Holley carb, Edelbrock intake manifold, headers, and a full MSD ignition system.  I did not cam it, bore it, or otherwise change the displacement of the engine.  My intentions are to have a reliable daily driver that I don't have to worry about, and can pull a boat when needed.  It is a 4wd, standard transmission.

Thanks for all the advice, I'll probably just get the one from NAPA.

Also I should add that I'm doing away with the original fan blade on the truck and going with an Electric one to try and squeeze a little extra MPG out of this old tank.  I noticed that the factory fan blades were in a weird asymmetric position, is this because they were balanced with the factory crank? Or was there another reason the blades would be in an odd arrangement?  Also when going with the new crank and electric fan, will I need to have the crank rebalanced because of no longer using the original fan?  Thanks again for the help

 

Also I should add that I'm doing away with the original fan blade on the truck and going with an Electric one to try and squeeze a little extra MPG out of this old tank. I noticed that the factory fan blades were in a weird asymmetric position, is this because they were balanced with the factory crank? Or was there another reason the blades would be in an odd arrangement? Also when going with the new crank and electric fan, will I need to have the crank rebalanced because of no longer using the original fan? Thanks again for the help

That's not something I'd ever do. It'll run cooler on the road with a mechanical fan, though an electric can be a nice low-speed cooling upgrade.

The fan's not on the crank, it's on the end of the water pump. The balance of the crank is irrelevant to the fan and vice versa.

 

The staggered 5-6 blades on the fans were to make them run quieter.  My '74 D300 had a 4 blade fan and when I still had bias mud tires on it, it sounded like a B17 bomber when running 50-60 mph, having the same harmonic resonance that came from the 4 propeller engines.

 

Just to be clear, the only performance upgrades I am doing are just the standard: Holley carb, Edelbrock intake manifold, headers, and a full MSD ignition system. I did not cam it, bore it, or otherwise change the displacement of the engine. My intentions are to have a reliable daily driver that I don't have to worry about, and can pull a boat when needed. It is a 4wd, standard transmission.

Thanks for all the advice, I'll probably just get the one from NAPA.

Also I should add that I'm doing away with the original fan blade on the truck and going with an Electric one to try and squeeze a little extra MPG out of this old tank. I noticed that the factory fan blades were in a weird asymmetric position, is this because they were balanced with the factory crank? Or was there another reason the blades would be in an odd arrangement? Also when going with the new crank and electric fan, will I need to have the crank rebalanced because of no longer using the original fan? Thanks again for the help

should have put some sort of towing/RV cam in it if you wanted better fuel mileage and a bit better performance. stock cams are not really that great.

also the best fuel mileage i have ever got was with the mechanical fan on the truck. even with electric fans or no fans at all i have never matched the fuel mileage that i had got with the mechanical fan on the engine.