Moparts
340 crank in a 318 from factory?
Posted By: 68GTS383
340 crank in a 318 from factory? - 01/21/11 07:54 PM
I just pulled the oil pan off of my 318 to install an oil pump and noticed that the front and rear rod journals were drilled like the early 340s.It is definately a forged crank.The block was cast in ?/14/72 the month casting was omitted.Front of block JM 318R 40773161.This eng was in a 68 Dart Post project car that I bought..The engine came out of a 72 or 73 Scamp. The K frame from the Scamp was LBP with disc brakes.It also had a front sway bar. I know that Mopar sometimes cleaned the parts shelves from the previous years. Any input?
Posted By: MoparforLife
Re: 340 crank in a 318 from factory? - 01/21/11 09:04 PM
Sounds to me like the engine has had major surgery at some point. Been many 340/318 shaft transfusions over the years.
and some definitely came with a steel shaft.
Posted By: babarracuda
Re: 340 crank in a 318 from factory? - 01/21/11 10:12 PM
Some 318's came with a steel crank!
Posted By: dennismopar73
Re: 340 crank in a 318 from factory? - 01/21/11 11:56 PM
ive owne to date 2 68 318 with steel cranks ,
and bushed rods,,!!
right out of fact
Posted By: Supercuda
Re: 340 crank in a 318 from factory? - 01/22/11 01:17 AM
318's of that era were cast crank in a Scamp. Nice find, but not stock.
Posted By: rattler
Re: 340 crank in a 318 from factory? - 01/22/11 01:31 AM
I did just the opposite. I put a truck 318 steel crank in place of the cast crank in a 340 i had.
Posted By: 68GTS383
Re: 340 crank in a 318 from factory? - 01/22/11 02:34 AM
Were any 318s drilled or is it a 340 crank?
Posted By: dodgefarmer
Re: 340 crank in a 318 from factory? - 01/22/11 04:52 AM
Might be 273
Randy
Posted By: Gabmando
Re: 340 crank in a 318 from factory? - 01/22/11 04:01 PM
I've never had 318 and 340 cranks side by side. What is the difference exactly between a 340 steel crank and a 318 steel crank? Are the harmonic balancers similar?
Posted By: Supercuda
Re: 340 crank in a 318 from factory? - 01/22/11 04:09 PM
biggest difference is balance, 340 rod and piston combo is more than the 318's in weight.
Posted By: ozz383
Re: 340 crank in a 318 from factory? - 01/22/11 04:25 PM
Aren't the balancers and rods the same between steel crank 318s and 340s? I,ve never seen a diff. ozz
Posted By: Supercuda
Re: 340 crank in a 318 from factory? - 01/22/11 05:56 PM
Early teens had lighter rods, later on they commonized to the heavier rods. Piston wieght is different too, 318 is lighter.
As for balancer, not 100% what, if any, difference there is. I don't have a parts book handy to see if they are the same number or not.
Posted By: 68GTS383
Re: 340 crank in a 318 from factory? - 01/22/11 06:33 PM
No one has answered my main question:Were 340 cranks the only SB cranks that were drilled?
Posted By: dodgefarmer
Re: 340 crank in a 318 from factory? - 01/22/11 07:17 PM
Quote:
No one has answered my main question:Were 340 cranks the only SB cranks that were drilled?
No, 273's were drilled.
Randy
Posted By: JohnRR
Re: 340 crank in a 318 from factory? - 01/22/11 07:34 PM
Quote:
No one has answered my main question:Were 340 cranks the only SB cranks that were drilled?
What do you nmean by DRILLED ??? All cranks are drilled to balance them, even the lowly 318.
Posted By: Supercuda
Re: 340 crank in a 318 from factory? - 01/22/11 08:17 PM
Quote:
Quote:
No one has answered my main question:Were 340 cranks the only SB cranks that were drilled?
What do you nmean by DRILLED ??? All cranks are drilled to balance them, even the lowly 318.
GO READ THE VERY FIRST POST
Posted By: JohnRR
Re: 340 crank in a 318 from factory? - 01/22/11 09:51 PM
Stop yelling .... francis I can here you just fine
looks like something to sell on ebay , must be a 340 crank
Posted By: Dakota_Don
Re: 340 crank in a 318 from factory? - 01/23/11 03:10 AM
Quote:
ive owne to date 2 68 318 with steel cranks ,
and bushed rods,,!!
right out of fact
both my 68s have steel cranks..
Posted By: dodgefarmer
Re: 340 crank in a 318 from factory? - 01/23/11 04:09 AM
I believe he is refering to the through drill on the front and back crank throws (1+"). The 273 and 340 steel cranks were drilled. The 318 steel crank was not.
Randy
Posted By: mopar_man
Re: 340 crank in a 318 from factory? - 01/23/11 04:57 AM
Its been a few years(20+) since i had the two cranks side by side , but I seem to recall something about the 340 cranks being radiused and the 318 not or very little . Been a while so I could be wrong.
Posted By: 500ciDuster
Re: 340 crank in a 318 from factory? - 01/23/11 06:24 PM
I had a steel crank from a 318 that had a 1971 340 number on it but it wasn't drilled through the front & rear rod throws, the 273 steel cranks were that way too. One more tidbit I took a 1970 318 apart that was from a manual tranny Duster and it had the 1973 cast shot peen numbered crank.
Mitch
Posted By: Supercuda
Re: 340 crank in a 318 from factory? - 01/23/11 07:27 PM
Quote:
I had a steel crank from a 318 that had a 1971 340 number on it but it wasn't drilled through the front & rear rod throws, the 273 steel cranks were that way too. One more tidbit I took a 1970 318 apart that was from a manual tranny Duster and it had the 1973 cast shot peen numbered crank.
Mitch
I wasn't aware that they put part numbers on cranks, casting numbers yes, but those are different animals than part numbers.
Posted By: HotRodDave
Re: 340 crank in a 318 from factory? - 01/23/11 08:14 PM
273 and 318 used the same cranks, the forged cranks used in them were NOT drilled in the journals. They both were balanced for the same bob weights and used the same rods and the 273 had a heavier wrist pin to make up for the lighter pistons so they could use the same balance factor. The 340 used a much heavier piston and rod so it required a lighter rod journal to balance it internally even with the forged crank, that is the reason the crank pins had lightening holes drilled in them ONLY in the 340. The balancers for all 3 of those motors was the same any given year until the 340 went cast crank, the cast crank just was not heavy enough to balance internally useing the stock heavy pistons and rods even though the cast crank 273 and 318 could still be balanced internally with the cast crank, they just started drilling holes in the cast crank pin so the 273 and 318 could internally balance.
Bottom line, if it is forged and has holes in the crank pin it is from a 340, if there are not lightening holes in the crank pin than it is from a 273-318. All cast crank had the lightening holes in the crank pins weather 273 318 or 340.
Posted By: 68GTS383
Re: 340 crank in a 318 from factory? - 01/23/11 08:48 PM
Thanks Dave!That is what I thought!It is amazing how many people will respond to a post when they have no knowledge of the subject!
Posted By: 500ciDuster
Re: 340 crank in a 318 from factory? - 01/23/11 09:29 PM
Some forged cranks do have numbers,when I sold it that was the reason the guy bought it.I have a set off those heavy wrist pins from a 273, they are really thick.
Posted By: dodgefarmer
Re: 340 crank in a 318 from factory? - 01/24/11 01:25 AM
Quote:
273 and 318 used the same cranks, the forged cranks used in them were NOT drilled in the journals. They both were balanced for the same bob weights and used the same rods and the 273 had a heavier wrist pin to make up for the lighter pistons so they could use the same balance factor. The 340 used a much heavier piston and rod so it required a lighter rod journal to balance it internally even with the forged crank, that is the reason the crank pins had lightening holes drilled in them ONLY in the 340. The balancers for all 3 of those motors was the same any given year until the 340 went cast crank, the cast crank just was not heavy enough to balance internally useing the stock heavy pistons and rods even though the cast crank 273 and 318 could still be balanced internally with the cast crank, they just started drilling holes in the cast crank pin so the 273 and 318 could internally balance.
Bottom line, if it is forged and has holes in the crank pin it is from a 340, if there are not lightening holes in the crank pin than it is from a 273-318. All cast crank had the lightening holes in the crank pins weather 273 318 or 340.
I have a 1969 273 (marine engine supposedly) crank that is through drilled, and extensively drilled on the counterweights to achieve balance.
Randy
Posted By: Dean_Kuzluzski
Re: 340 crank in a 318 from factory? - 01/24/11 01:46 AM
Correct me if I'm wrong..........
A casting number is the raw piece, unmachined..........
The p/n is then assigned when the part is modified/machined to the required spec'd per the application that the engineer created it for.
I'm saying this to inform some that haven't seen the distinction.
So, a given crank casting number could apply to either a 318/273 or 340 depending on how it was machined and the p/n assigned.
At, that's how it went when I worked for a competitor.