Limits of a 318 cast crank

In general terms whats the limits of a 318 cast crank in a street setting, 9.1 comp at most a .528 solid, balanced oem rods and forged slugs just under oem weight and balanced.

Thanks.

I've seen them break near the center main on a stock setup.

Hard to say really.

Not what im wanting to hear but understandable.

Ive never heard how a lil 4.00 stroked 318 runs in a small bore but it is a option.

I can do one build for me currently and im trying to sort out options.

Guess you could have it magnafluxed to look for cracks.

Can't say I ever saw a 360 crank break the same way, might be why they went to bigger mains on them.

If you could find a cheap forged 273/318 crank it might be an option.

If you could find a cheap forged 273/318 crank it might be an option.

I have on not but six feet from me but its offset ground and im not really wanting to play that much.

I do have a nice oem 360 crank and block ect... maybe I should go that route, in the end I dont care 318/360 just needs to fit my budget so I can have a easy drive for a change.

I probably should just pop for the scat cast crank/scat I beams/forged icon kit for $1400 balanced for my 360 and be done with it and if I build the 318 just put stocker pistons back in it.

But id like to put the org.318 block back in the car just for kicks....

What to do what to do...

Well,

I prefer 360's myself and if I was gonna spring for a rotating kit I'd go for the cubic inches a stroker gives you.

But if I was gonna go for minimal fuss a mild 318 is the definition, I'd add a cam and a 4bbl and otherwise keep it stock.

I think you will be fine. I'd suggest a 360 with a 4" arm but if you are already together with what you have I'd go have fun.

Im thinking by time I fiddle faddle around with a oem crank, old heavy slugs, and still buying bearings and a BIG balance job my 360 is a good base and I should just order the dam kit.

And the 360 kit is internal balance and thats all I currently have is all neutral balance stuff.

The 360 stock crank will take a lot. We've run one to 850hp.
Doug

There is a member on here that built a 390 using a 4" crank in a 318 block. Flypaper? I can't remember.

Guess what they use in the 340s in stock class pushing 500 HP running mid to low 10s in the quarter. 440-383s use cast also

I used to run 318's with 360 heads,484 purple shaft, LD340, intake and a 750 holley with a 400 hp shot of nitrous. The rest was left stock. I used to get the motors cheap from junk yards and run them for one or two racing seasons in a Duster. I broke 2 cams due to bad bearings. I started replacing bearings after that. I had a crank get wobbly and lose oil out the front. I never broke a crank. If I had used one with badly worn bearings maybe the crank would have broke. I also ran a 727. The 833 is harder on cranks. Most 318 cranks won't take a pilot bushing. The way most people drive these cars today a stock 318 crank would never get hurt.

I'm putting a new Scat 4.0 inch stroke cast crank in a 340 now for a pump gas 4 speed 1966 Dart
I'll dyno it when it is done, I'm hoping for 450 + HP on pump gas using a set of Eddy RPM heads, Eddy Air Gap intake and 850 CFM carb. with around 10 to 10.5 to 1 compression

Twenty Years ago, Hot Rod Magazine (ie: David Frieburger) put a 150 shot of nitrous on a junkyard, cast crank 318. It survived until it had a piston failure. Don't think they hurt the bottom end any.

I got to stop being like a lady in a shoe store and make up my dang mind and just order the parts.

Back in high school when 340 and 318 A body cars were everywhere even the 318 with 340 heads ran good.

I overspend, overbuild and 90% of the time im racing a gps meter by myself, fun but not practical or cheap, not everything has to be a stroker and run 10s to have fun, but it is fun.... I just got to get it through my head.

Id really like to put the 318 block back in the car, a simple 76 duster and can do the 318 semi right for 1/2 the cost of the 318/370 stroker.

I have some wiseco PTS529AS pistons already and could do a nice near 9:1 318, I got a hughes girdle on the wall and a old 150 plate kit... see there I go.... why do I need the plate kit on a low po 318?

Ordered a nice kit for the 904 though today, so its a start.

Alot of good 318 builds on fabo on some nice "real" street cars.

Im gonna mag and test fit the crank tomorrow and see where im at on fitment and clearances.

So maybe a bore/hone and balance job is in order, if I use the 340 rods I think its gonna need metal in the crank, the scat I beams are light and $300 and might be better money spent then oem rods and $crank weight.

I just want one of my cars I can drive 500 miles in a day if I want and not worry it.

THANKS!

I know a guy in the Dakota community with a turbo 5.9. Stock bottom end and he's in the 10s with a 4K lb truck. It's all in the tune

Those stock rods are the same as 340 rods with out the floating pin, less hassle, different bore, big deal, you'll never know the difference. Keep the small valve head (360) good cam-intake-carb-ignition and have fun.

I whaled the living tar out of a lot of small block Mopars back in the 70s-90s. The only crank I ever broke was a forged 318 that was turned ,010/.010, it broke between the 1st rod throw and the 2nd main. I suspect it may have been cracked. Motor was a .030 over bore, 340 heads, big cam, big carb, headers, and 3 summers of abuse before hand. It was on the street, in a 70 Road Runner with a 4 speed, after a full night of hard thrashing and some serious high rpm 1/2 shifts. The next day it had what sounded like a lifter noise, and it suddenly started throwing the fan belt off, it had great oil pressure. About the 3rd time I put the belt back on, I saw the balancer lift up and knew I had a problem. I replaced it with a quickly rebuilt 340 short block, (rings & bearings), reused the heads & cam, and hammered on. Gene

Weights of stock connecting rod..."skinny" 273/318 rod - 717g
496 or 645 340/360 rod - 758g

The 645 was also used in 318s from early '70s til the Mag engines started. This is all IIRC. The 318s and 360s using the 645 rod were pressed pin, the 340 was bushed.

It is easy to find an aftermarket rod that is 100 grams lighter than a 645 rod. Most of the aftermarket rods are made of superior steel and have 7/16" rod bolts. In other words for your application they would be bulletproof.

The more reciprocating and rotating mass you can take out of the system, the fewer stresses on your crankshaft.

Later 318s were internally balanced, same as all other 318s. The later 318s had the 645 rod and a 591 gram piston. There is no way you should have to add Mallory metal to the crank if your piston weight is below 590 grams.

In a hypothetical situation where I had to buy Mallory metal to balance stock rods, I'd head straight to a lighter aftermarket rod instead.

R.

Thank you, I love the real world input, the scat I beams seem to be the way to go at $300 and what under 600 grams?

They're the ones I'd pick. Big bolts, low weight, best material. Look around there are more out there.
R.