340 / 318 Crank question - Moparts Forums

Register Log In Moparts Forums Unlawfl's Race & Engine Tech 340 / 318 Crank question

Print Thread

340 / 318 Crank question #1794102 04/01/15 09:48 AM 04/01/15 09:48 AM
Joined: Jan 2015 Posts: 20 Ontario B Budsworth OP member
Budsworth OP member B Joined: Jan 2015 Posts: 20 Ontario	I recently picked up a 69 340 with a "Noise" in the bottom end, When I tore it down I found this.. (See Image) Looks like a Castcrank in an early block. I have a "Steel Crank" from a 68 318 that has been ground .010/.010 would this be a good replacement for a mild street application. 8477341-IMG_0296.JPG (276 downloads) Last edited by Budsworth; 04/01/15 09:50 AM.

Re: 340 / 318 Crank question [Re: Budsworth] #1794103 04/01/15 09:51 AM 04/01/15 09:51 AM
Joined: Jun 2003 Posts: 52,972 Romeo MI MR_P_BODY Master
MR_P_BODY Master Joined: Jun 2003 Posts: 52,972 Romeo MI	Sure.. just check the balance on it EDIT What you have now is externally balanced with the conv and the front balancer so you need to get a internally balanced balancer and knock the weight off the conv but I would still have it balanced Last edited by MR_P_BODY; 04/01/15 09:57 AM.

Re: 340 / 318 Crank question [Re: MR_P_BODY] #1794104 04/01/15 10:55 AM 04/01/15 10:55 AM
Joined: Jan 2015 Posts: 20 Ontario B Budsworth OP member
Budsworth OP member B Joined: Jan 2015 Posts: 20 Ontario	Quote: Sure.. just check the balance on it EDIT What you have now is externally balanced with the conv and the front balancer so you need to get a internally balanced balancer and knock the weight off the conv but I would still have it balanced What do I need to know and what is involved in rebalancing this rotating assembly. I have New in the box Damper from Pro Systems, as well I will be ordering a new vert for the 3.23:1 gears I plan on running.

Re: 340 / 318 Crank question [Re: Budsworth] #1794105 04/01/15 11:14 AM 04/01/15 11:14 AM
Joined: Jun 2003 Posts: 52,972 Romeo MI MR_P_BODY Master
MR_P_BODY Master Joined: Jun 2003 Posts: 52,972 Romeo MI	Quote: Quote: Sure.. just check the balance on it EDIT What you have now is externally balanced with the conv and the front balancer so you need to get a internally balanced balancer and knock the weight off the conv but I would still have it balanced What do I need to know and what is involved in rebalancing this rotating assembly. I have New in the box Damper from Pro Systems, as well I will be ordering a new vert for the 3.23:1 gears I plan on running. You just want to have it zero balanced(internally balanced)... so it would be just a normal 68 340 balance job.. you would take the parts into the company thats doing the balance, pistons,rods, rings, bearings, crank and the balancer.. let them zero all the rods and pistons then figure the bob weight and correct the crank... when you get your conv you would order a 68 340 style conv with zero balance(like all the older 340 were)

Re: 340 / 318 Crank question [Re: MR_P_BODY] #1794106 04/01/15 11:23 AM 04/01/15 11:23 AM
Joined: Jan 2015 Posts: 20 Ontario B Budsworth OP member
Budsworth OP member B Joined: Jan 2015 Posts: 20 Ontario	Thank you Mr P you are a Gentleman, appreciate your input as always. Bud.

Re: 340 / 318 Crank question [Re: Budsworth] #1794107 04/01/15 02:06 PM 04/01/15 02:06 PM
Joined: Jan 2003 Posts: 16,376 D dogdays I Live Here
dogdays I Live Here D Joined: Jan 2003 Posts: 16,376	I don't agree. It's a forged crank. Cast cranks have sharp edges and squarish counterweights. This crank has rounded "kidney shaped" counterweights that to my eye look forged. R.

Re: 340 / 318 Crank question [Re: dogdays] #1794108 04/01/15 02:37 PM 04/01/15 02:37 PM
Joined: May 2005 Posts: 1,995 Apollo, PA. B1MAXX top fuel
B1MAXX top fuel Joined: May 2005 Posts: 1,995 Apollo, PA.	1ST thing I thought too..... Balance job would be a mess with the heavier 340/360 rods. Lots of Mallory..$$ Last edited by B1MAXX; 04/01/15 02:42 PM.

Re: 340 / 318 Crank question [Re: dogdays] #1794109 04/01/15 02:57 PM 04/01/15 02:57 PM
Joined: Feb 2003 Posts: 12,675 Columbia, CT M moper I Live Here
moper I Live Here M Joined: Feb 2003 Posts: 12,675 Columbia, CT	Quote: I don't agree. It's a forged crank. Cast cranks have sharp edges and squarish counterweights. This crank has rounded "kidney shaped" counterweights that to my eye look forged. R. I agree. Do you have another pic of the counterweights? Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.

Re: 340 / 318 Crank question [Re: dogdays] #1794110 04/01/15 03:38 PM 04/01/15 03:38 PM
Joined: Jun 2003 Posts: 52,972 Romeo MI MR_P_BODY Master
MR_P_BODY Master Joined: Jun 2003 Posts: 52,972 Romeo MI	Quote: I don't agree. It's a forged crank. Cast cranks have sharp edges and squarish counterweights. This crank has rounded "kidney shaped" counterweights that to my eye look forged. R. A cast crank is usually smoother.. but I always look at the separation line on the counter weight.. a wide line is forged and a thin line is cast... I dont see any line on that pic... but he said cast..

Re: 340 / 318 Crank question [Re: moper] #1794111 04/01/15 03:41 PM 04/01/15 03:41 PM
Joined: Aug 2003 Posts: 43,223 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,223 Bend,OR USA	I know several drag racers of SB motors that looked for the forged steel crankshafts out of the 318-3 truck motors to use in there short stock stroke 340 motors, they had to have thin steel plates welded onto the counter weights to get them to balance correctly. This was before Mallory metal was used in balancing IHTHs Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

Re: 340 / 318 Crank question [Re: Cab_Burge] #1794112 04/01/15 05:50 PM 04/01/15 05:50 PM
Joined: May 2003 Posts: 6,566 Downtown Roebuck Ont Twostick Still wishing...
Twostick Still wishing... Joined: May 2003 Posts: 6,566 Downtown Roebuck Ont	Would a set of H-beams and a light forged piston/pin get you into the 318 balance ballpark? Kevin

Re: 340 / 318 Crank question [Re: Twostick] #1794113 04/01/15 06:09 PM 04/01/15 06:09 PM
Joined: Jan 2003 Posts: 16,376 D dogdays I Live Here
dogdays I Live Here D Joined: Jan 2003 Posts: 16,376	The big rod weighs 758 grams, the small rod weighs 726. 318s used the big rods from like 1973-on, and piston weight didn't change if one really weighs the items. The 318 cranks before and after this change point were the same old castings, no changes there. The 318 piston weighs 591 grams plus the pin. My 30 over replacement piston comes in at 600 grams exactly, no pin. Total weight is over 1500 grams with pin and rings.. It's mind-bogglingly heavy. The 340 piston adds another 130 grams. Small-block size with bigblock weight. No wonder taxi 318s ran forever. You can get a decent rod that weighs around 650 grams and a decent 340 lightweight forging should come in at 500 grams plus pin. There's no earthly reason to have to add weight to a 318 crankshaft to balance a modern rotating assembly. Well, I guess if you are building a 100% replica. Back to the crank, the absence of a parting line doesn't tell me as much as the shape of the counterweights. To the OP: Could you find the casting or forging number on the crankshaft and take a picture and post it? Let's put this issue to bed. R.

Re: 340 / 318 Crank question [Re: Twostick] #1794114 04/01/15 08:20 PM 04/01/15 08:20 PM
Joined: Dec 2006 Posts: 3,395 Pa Hot 340 master
Hot 340 master Joined: Dec 2006 Posts: 3,395 Pa	Fix the crank you have if possible. Its steel. Check to see if the crankpins are drilled, if they are, its not a steel truck crank.

Re: 340 / 318 Crank question [Re: Hot 340] #1794115 04/01/15 08:53 PM 04/01/15 08:53 PM
Joined: Jan 2004 Posts: 8,290 fredericksburg,va C cudaman1969 master
cudaman1969 master C Joined: Jan 2004 Posts: 8,290 fredericksburg,va	The stocker guys actually use the cast crank because it is lighter. Using stock 318(lighter) rods and NHRA approved pistons of stock weight, they are not adding metal back to these cranks, which would defeat the purpose of using lighter cranks. These engines are buzzing 7500 or more all day. My buddy's 74 g- stock Duster low comp 340 with cast intake and J heads runs 7.0 eigth and 10.9 quarter with a cast crank. You will never hurt a cast crank on the street imo if you indeed have one.

Re: 340 / 318 Crank question [Re: cudaman1969] #1794116 04/02/15 06:06 PM 04/02/15 06:06 PM
Joined: Jan 2015 Posts: 20 Ontario B Budsworth OP member
Budsworth OP member B Joined: Jan 2015 Posts: 20 Ontario	I picked up this crank today for $125.00 bucks, it's a 340 "cast" crank. Turns out the crank in the block is a Steel crank according to the machinist. Going to send it out for repair. The local machine shop has had this crank on the rack since 1985. Last edited by Budsworth; 04/02/15 07:03 PM.

Re: 340 / 318 Crank question [Re: Budsworth] #1794117 04/03/15 02:35 PM 04/03/15 02:35 PM
Joined: May 2005 Posts: 1,995 Apollo, PA. B1MAXX top fuel
B1MAXX top fuel Joined: May 2005 Posts: 1,995 Apollo, PA.	Are you going to try to use the cast crank? I had cast crank 360 internally balanced it took 2-3 slugs of Mallory as I recall and cost me over 350$ 15 years ago. I won't do that again. Just my

Re: 340 / 318 Crank question [Re: B1MAXX] #1794118 04/04/15 01:38 PM 04/04/15 01:38 PM
Joined: Jan 2003 Posts: 16,376 D dogdays I Live Here
dogdays I Live Here D Joined: Jan 2003 Posts: 16,376	First - on the forged crank, I told you so way back there. Second, disregard any scare stories about 360 cranks because they don't apply. In your case, the crank would neutral balance if built as a 318, so any replacement piston that weighs 591 grams or less will balance up fine with no additional weight in the crank. Look at the Number 1 and Number 4 crank throws. Are they bored out with a hole around 1" in diameter? 340 crank. Are they not bored out or a little hole like 3/8"? 318 crank. The 318 and 340 used the same casting, so they will have the same casting number. R.

Re: 340 / 318 Crank question DELETED [Re: dogdays] #1794119 04/05/15 09:57 AM 04/05/15 09:57 AM
Joined: Jan 2015 Posts: 20 Ontario B Budsworth OP member
Budsworth OP member B Joined: Jan 2015 Posts: 20 Ontario	Post deleted by Budsworth Last edited by Budsworth; 04/05/15 10:04 AM.

Re: 340 / 318 Crank question [Re: Budsworth] #1794120 04/05/15 10:08 AM 04/05/15 10:08 AM
Joined: Jan 2015 Posts: 20 Ontario B Budsworth OP member
Budsworth OP member B Joined: Jan 2015 Posts: 20 Ontario	Quote: Ask and you shall receive, as they say. Thank your for your input Dogdays. In the original post I stated "Looks like" well I have learned quite a bit in regards to Mopar factory small block crankshafts this week. Yesterday I went searching on the local classifieds, I found and purchased a standard/standard Forged Steel crankshaft out of 1967 273. I checked the rear register with a digital caliper and it has the larger 1.8 vs the smaller 1.5 now I have a second option. And for $80.00 bucks.. That's cheaper than a slug of Mallory.

Moderated by Al_Alguire, Hotwheelsjr, moparts, not_a_charger, RangerDan440, tboomer

Hop To

Powered by UBB.threads™ PHP Forum Software 7.7.1