Steel VS Cast Crank

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Demon_Jeff_71

Demon_Jeff_71

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I am building up a 318 and I am going to be aiming for around 400 to 450 HP and I am wanting to have a decent lumpyness to the cam and it will have an auto 904 with an 8.75 rear. My question is will I be okay with a cast crank or will I have troubles and should I really spend that much more money on the steel crank.


Jeff
 
Demon_Jeff_71 said:
I am building up a 318 and I am going to be aiming for around 400 to 450 HP and I am wanting to have a decent lumpyness to the cam and it will have an auto 904 with an 8.75 rear. My question is will I be okay with a cast crank or will I have troubles and should I really spend that much more money on the steel crank.


Jeff
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yah the cam gonna sound very lumpy in a 318 if your looking for 400-450hp. get your crank magnufluxed and thoroughly checked and speced. if it passes, then no problem using it.
cheers
 
With the RPMS needed to get your 400+ hp from that 318. I would explore your options on getting a steel crank. As you will be winding it pretty tight. Not to mention you have added peice of mind during your rebuild.
 
eaglesguy1981j said:
With the RPMS needed to get your 400+ hp from that 318. I would explore your options on getting a steel crank. As you will be winding it pretty tight. Not to mention you have added peice of mind during your rebuild.
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what does rpm have to do with anything? i know cast cranks are much lighter then steel, therefore can turn rpms more easily. just curious.
cheers.
 
I am not going to be taking it much higher then 6200 or 6500 RPM's. My 318 is the stock block from my late 70 production 71 Demon. I am assuming it would have a cast crank in it. I have no idea how to check for that. I am not going to be racing it on a constant basis and it will mostly be for terrorizing imports on the streets and some track time here and there. But I am not going to be taching the crap out of it all the time.


Jeff
 
70 or 71 318 would be a steel crank.And you can turn a small block alot harder than 6200-6500.You might want to check out 440source.com they have a 390 stroker kit for your 318 if I remember right.
Jim
 
68383GTS said:
70 or 71 318 would be a steel crank.And you can turn a small block alot harder than 6200-6500.You might want to check out 440source.com they have a 390 stroker kit for your 318 if I remember right.
Jim
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I appreciate the help. Like I said I am not going to be going crazy with the car but I want to get some power out of it. Thanks for the advice on the stroker crank. I am not sure if it is something I am going to do because I dont want to start having to grind down the block to make sure it fits and everything.
 
Demon_Jeff_71 said:
I appreciate the help. Like I said I am not going to be going crazy with the car but I want to get some power out of it. Thanks for the advice on the stroker crank. I am not sure if it is something I am going to do because I dont want to start having to grind down the block to make sure it fits and everything.
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If you dont have a forged crank i wouldnt worry about getting one personally,a cast crank should hold up fine.There are alot of cast crank 360s out there turning 7k and making 450 h.p. with no problem.The best thing to do is have it machined well and use good rod bolts and lighter pistons.
 
68383GTS said:
70 or 71 318 would be a steel crank.And you can turn a small block alot harder than 6200-6500.You might want to check out 440source.com they have a 390 stroker kit for your 318 if I remember right.
Jim
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My 318 was made in August 1970 and it's a cast crank. I'm pretty sure all 318's were cast crank except for the special heavy-duty truck versions. Engine Masters had an article a couple years ago that had a hot 415-hp 318 build and they used a junkyard steel crank from a 273. However, they said a cast crank would've worked fine with no problems unless you were going much higher in the RPM's or HP.
 
360Z28 said:
what does rpm have to do with anything? i know cast cranks are much lighter then steel, therefore can turn rpms more easily. just curious.
cheers.
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What was ment was that small blocks generally make there HP in higher rpm ranges. Which puts more stress on the engine. Also if he was rebuilding it anyways and was able to find a good priced steel crank it might be worth looking in to.
 
I pulled a steel crank out of a 67 Fury with a 318 once. If the crank he has is good-striaght, no cracks and bearing surfaces good , and thrust surfaces not worn out I would not hesitate on using it.
 
Jeff, If Your On A Budget Use The Parts You Have .just Get Them Checked Like Some Of The Guys Are Telling You .
If You Have A Money Tree In The Back Yard Then Go Crazy And Buy The Best.
One Phone Call To Summit Could Cost You $3000.00
 
Some 318's Had Forged Cranks, Not Many, Most People Are Thrown Off By The Balancer, Just Because It Was The Thin Type Balancer Does Not Mean It Has A Forged Crank As Mopar Balanced Their Cast 318 Cranks And Put On Thin Neutral Balancers That Appear To Be Like The 273-340 Balancers, So Assume Most 318's Are Cast Cranks, And They Will Take A Lot Of Punishment, If You Seek A Forged Crank Look For A 273 Donor Motor Or 340 Motor And Some Trk 318's-some Marine Motors Also Had Forged Cranks, Not All Of These Listed Are For Sure Finds For F-crank But Good Likelyhoods--for More Info And A Better Understanding Get Mopars Small Block A-engines Book Part#p4876826 Its Like The Smblk Bible-----400-450 Hp On A Cast Crank Is Not Really A Problem
 
According to the Mopar Performance "A" engine book. 318 's from 1967 have forged crankshafts (as well as the 318 poly engines) , but 318's from 1968 to 1989 have cast crankshafts.

I would not worry about using a cast crank in a street/strip engine.

Bob
 
A few years back i had a factory 318 steel crank motor,it came from a pick-up truck...As far as a cast crank when properly preped they'll hold up fine,i have a 4" one in my 416 pushing 520 h.p....
 
Cast iron 70,000-80,000 psi -------------OE engines
Nodular iron 95,000 psi ------------------OE engines
Cast steel 105,000 psi -------------------strongest of the cast cranks
1010/1045/1053 100,000-110,000 psi ----high carbon factory grade forging
5140 steel 115,000 psi ------------------sportsman grade forging
4130 steel 120,000-125,000 psi ----------premium alloy
4340 steel 140,000-145,000 psi ----------strongest alloy for cranks and rods
 
Demon_Jeff_71 said:
I am building up a 318 and I am going to be aiming for around 400 to 450 HP and I am wanting to have a decent lumpyness to the cam and it will have an auto 904 with an 8.75 rear. My question is will I be okay with a cast crank or will I have troubles and should I really spend that much more money on the steel crank.


Jeff
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Hi Jeff, I built a low-buck 318 for my 68 cuda drag car that runs 11.50's at 115 on unleaded gas. 400 hp is a snap. Use a pre-71 core engine with a steel crank, so all the internals should be forged. I bored mine +.030, stock 9.2:1 flat top pistons, cast iron rings, clevite bearings, stoick oil pump with the high pressure relief spring kit installed. The cam and heads are the key to the combination ( and getting the power to the ground) I used the DC 4120653 cam/lifter pkg (284/.528") and a set of home ported 587 non-smog 360 heads with 2.02/1.60 valves and the DC dual springs. The 360 heads were milled .040 on the compression face and .020 on the intake face. This gave me .100" clearance on the valves. The intake is a port matched Victor 340 with a 750 Holley annular discharge carb. 4200 stall Hughes converter, JW wheel flex plate and a roller bearing 904 trans with reverse pattern manual valve body. Rear gears are 4.86 with 12x29 slicks. I have over 2000 passes on this combo with no problems.

Good luck!
 
Have the crank checked and get the best machinework you can. A cast LA crank will go past 450hp pretty reliably.
 
Well thanks for all the help guys. I am looking for going with a pretty high lift cam. The one I was looking at is like a 530 lift and 237 duration so that is the idea. I have a set of 340 J heads with the 1.88 1.60 Valves so I was thinking it would be better to just go with stock 1.88's. Someone was telling me that putting chevy 1.94 valves would be better and almost cheaper in the end. I am planning on going with a 300 stall convertor and 3.55 gears in the back. I will just keep my crank that I have and make sure everything is good on that end.


Thanks

Jeff
 
1.94s are cool, but you need to replcea all the guides with 11/32" guides. Mopar are 3/8. Personally, I'd stick 2.02s in them. You won't feel any drop in power.
 
Save yourself the money and just use a cast crank and have it internally balanced for that horsepower range in your street car. If you're going to race it every weekend and become a serious racer then go for the forged unit. I've been running a 415sb in my street car with a cast crank that's internally balanced for 4 years with over 100 passes on it running mid 11's. No problems. jysnflem
 
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