Not sure my machine shop knows the correct info on my 318............

[bandit67]

  Guys, I just tore down a 318 I removed from my 72. For many things I saw during the tear down , I beleive it was the first time it has been into.  It has the full floating pistons and rods. The crank is cast iron. Two of the mains were .012 to .013 under the standard size of 2.5. The rest of the mains and all the rods were .001 to .003 under. I beleive the two mains were .010 under from the factory. My machinist said no, that those two were just worn badly. I said no, all the bearing looked very good. All the main and rod bearings had  4   72   stamped on the underside.  He then pulled a book from under the counter and showed where it said all 318 cranks from 67 to 78 were steel.  I did not agree with that either.  Did I not read somewhere that Mopar had a stamp or sign that was to indicate undersized journals or am I just having a brain fart. The engine is in extremely good shape internally for it's age and miliage and I was concerned about changing the crank would change the factory balancing. His statement was that it would not, that all 318 cast cranks were balanced the same. So I came home with a crank kit, .010 and .010, could this be a problem because the cast number is different from the one I had?  Any comments or opinons on this would appreceiated............John

[Challenger340]

A318 with full floating Pistons & Pins ?  I thought that stopped by '69 ? Shows ya what I know besides "diddle-squat" !

Any more relevant information, ie; (actual crank numbers you took in and got back), might help you get some good answers on here, some very smart guys will read.

I'm still stuck on the '72 318 having floating Pins ?

All 318's were cast cranks, EXCEPT, the 318 Heavy truck engines, which had the "infamous" 318-3 Forged steel Cranks. They were usually .001 undersize factory sizing on the rod journals, and all those engines had floating pins.

INFAMOUS, because as far as I understand, they had actual "radius" filets, as opposed, to even the 340 Forged steel units having the cheaper "rolled" filets. I had heard a few made it into '72 date engines, but don't know myself for sure.

318-3 Forged cranks were widely sought after for racing ! Very strong pieces. Why didn't you get the original crank you took in, ground, and returned to you. Are you SURE, the one you took in was CAST ?

Is it possible this 318 wasn't original to your car ? or, came from a heavy truck ?

Does the engine serial # match the car # ?

Sorry, I don't have a clue on this one. I'm better at pictures.

[bandit67]

The original crank was for sure cast. Being a Chevy guy for the last 35 years I have many of each.  The only other motor I have with floating pins is a 302 from a Z28, so I was quite surprised myself.  The original crank numbers are 2658278, which in the  How to rebuild small block Mopars , by HP books, says that is a heavy duty crank. Will have to go get the crank numbers from the new crank. I could have gotten the original crank reground , but would have to wait a week or so before it would be ready.  Also, 340, the HP book shows the floating pins being used in all 273, 318 from 64 thru 73, even with the standard low compression pistons.  The block is the matching numbers block , as is the transmission.  As I stated , I do not think ANYONE  has  been in the engine before me. All the little clips, brackets, were there. The head gaskets were the original thinner ones, and all the bearing were of 1972.   I shall look for more on this......thanks ...J

[bandit67]

Ok, Guys, I just got my machine shop guy really upset with me, can anybody help . He looked at my crank, number 265827 and gave me a crank, number 3751841 and said they are the same as far as factory balancing is concerned. I cannot find that number in my book, so I called him back and ask him to regrind my original.  How can I be sure that this crank was balanced at the factory for my heavy duty rods and not the lighter duty standard 318 rods. Am I being as anal as he thinks I am....hmmmmmmmmm........J

[Challenger340]

I don't think you're being anal at all, you're trying to be prudent, as you indicated, you may have a different set of rods(heavier) than what this crank may be balanced for.
And, the best way to insure that it balances OK, is to either pay for balancing, or, re-install the same crank "reground".

If not, and he's so sure of the same balance, ask him if he'll warranty against a vibration when it's re-assembled ?

PS; Geez, I didn't know 1973 318's had floating Pins !

[John_Kunkel]

'72 was the last year for the 318 floating pin, '73 and later are press fit.

Here's the SB crank info I have:

62-67 318 and 64-67 273 forged 2128278, 2128869, 2205700

68-69 273 cast 2658268, 2658393

67-73 318 cast 2658278, 2658393

74-86 318 cast 2658278, 2658393, 3462387
2658391

68-72 340 forged 2532457, 2843868

73 340 cast 3462387

71-86 360 cast 3418640, 3418641, 3418642

[bandit67]

Thanks , John, I did a google on 3751841 and came up with some sites that showed that crank number on into late eighties and I think nineties. What I was hoping to find was a way the tie that crank to a motor that COULD have been produced with the heavy duty rods.........and have not. The HP book stated that the heavy rod could be a much as a 100 grams heavier. I have no idea what the total floating rod / piston combo would weight compared the a pressed set, but would a 100 gram plus difference be a problem in a street motor that might see 1000 to 5000 rpm .................I am sure somebody out there has walked this way before........thanks again ,..........J

[Nacho-RT74]

Being a Chevy guy for the last 35 years I have many of each. 

Don't worry, we take care of you without prob. Is just a destiny bad joke.

[TylerCharger69]

I dunno...but it seems that this machinist isn't giving you concrete answers to your questions.  Those measurements you gave at the top of this post are very erratic.  Usually....when a crank is turned and re-balanced  ALL  of the journals  are either 10 under, 20 under...and so fourth.   Not just one or two.   Now...You can have  Standard main journals   with 10 under rod journals  and vice-versa,  but I've never heard of just one or two of the journals being cut  and the rest std....Unless  I misunderstood the way you explained it.   I'd put a caliper on it myself  on every journal  and see what it says  and compare it with the specs it should be.  If there was extensive wear....You'd see it...especially that much!!!

[Chryco Psycho]

I agre e, the last year for full floating pins was 72
the front of the service manula has the stampings for under size from the factory