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Are 318 Magnum pistons different from 318 LA? #1071459 09/08/11 04:19 PM 09/08/11 04:19 PM
Joined: Apr 2007 Posts: 2,327 Glendale, AZ 6 69L78Nova OP Banned. Forever.
69L78Nova OP Banned. Forever. 6 Joined: Apr 2007 Posts: 2,327 Glendale, AZ	I'm in the middle of my little budget 318 build and I've hit a snag. The 95 Magnum 318 short block I picked up has a small crack in one of the cylinders. I already bought a new Mahle ring set for the Magnum pistons. I have a 75 318 in immaculate condition needing nothing more than rings, bearings and resealed. My question is, can I use the Magnum pistons in the LA block for a little compression bump, or are they basically the same except for the metric size rings. I was going to use the K6900 cam and Magnum heads from my current 360 in the 318 LA. I don't have the spare dough to have the Magnum block bored and buy new pistons, so I was looking to do it on the cheap. Or should I stick with the 75 318 pistons? 1969 Nova 454/M21/3.31 Mild mid-11 second weekend cruiser 1994 F150 XLT Super Cab 2WD 5.0/4R70W/3.55 (Daily driver)

Re: Are 318 Magnum pistons different from 318 LA? [Re: 69L78Nova] #1071460 09/08/11 05:15 PM 09/08/11 05:15 PM
Joined: Sep 2011 Posts: 31 Two Harbors, MN chrgr340 member
chrgr340 member Joined: Sep 2011 Posts: 31 Two Harbors, MN	I don't recall what the exact difference is, but I just read somewhere a day or two ago that LA and Magnum pistons are different. I'd probably stick with the LAs. 1972 Dodge Charger - F7, Rallye pkg, 340, A833 2007 Dodge Charger R/T R&T - 12sec daily beater 1999 Dodge Dakota R/T - M1, cam, heads, T56 swap 1997 Dodge Dakota - 318, NV3500, 3.92 Sure Grip

Re: Are 318 Magnum pistons different from 318 LA? [Re: chrgr340] #1071461 09/08/11 05:23 PM 09/08/11 05:23 PM
Joined: Mar 2007 Posts: 12,008 Finally a HUSKER again Moparnut426 I Live Here
Moparnut426 I Live Here Joined: Mar 2007 Posts: 12,008 Finally a HUSKER again	the width of the rod is it. the LA rod wont fit between the wrist pin bosses. If you run a scat I beam they fit. Pluss will be full floating. Kasey

Re: Are 318 Magnum pistons different from 318 LA? [Re: Moparnut426] #1071462 09/08/11 05:47 PM 09/08/11 05:47 PM
Joined: Jul 2003 Posts: 6,167 Maryland GO_Fish master
GO_Fish master Joined: Jul 2003 Posts: 6,167 Maryland	If the Magnum bore is the same size as the LA's bore(both virgin, both +.020,etc), you should be able to swap the magnum crank, balancer, rods and pistons over to the LA block and keep moving. Use the Magnum head bolts to bolt the Magnum heads on the LA also. Scott B. "I'm a self-made man... I started with nothing, and I still have most of it!" 68 360 rusty B'cuda 'vert (GO Fish)13.59@ 98.72 mph 69 340 GTS stock 14.18@ 95.60 mph 01 5.9L Ram 1500 Quad Cab 4x4 01 3.5L 300M 16.23@ 86.97 mph

Re: Are 318 Magnum pistons different from 318 LA? [Re: Moparnut426] #1071463 09/08/11 05:48 PM 09/08/11 05:48 PM
Joined: Apr 2007 Posts: 2,327 Glendale, AZ 6 69L78Nova OP Banned. Forever.
69L78Nova OP Banned. Forever. 6 Joined: Apr 2007 Posts: 2,327 Glendale, AZ	Whoops, I'm sorry. I should have been more clear. I mean I was thinking of using the Magnum pistons AND rods in the LA engine. Would that work, or is the rod different on the crank end as well? The only reason I ask is because the magnum engines are rated as being 9 to 1, and the LA is 8.5 to 1. I don't know if the magnum heads on an LA block would boost compression, or if the magnum chambers are around the same size as the old 70s 318 LA heads. 1969 Nova 454/M21/3.31 Mild mid-11 second weekend cruiser 1994 F150 XLT Super Cab 2WD 5.0/4R70W/3.55 (Daily driver)

Re: Are 318 Magnum pistons different from 318 LA? [Re: 69L78Nova] #1071464 09/08/11 05:50 PM 09/08/11 05:50 PM
Joined: Mar 2007 Posts: 12,008 Finally a HUSKER again Moparnut426 I Live Here
Moparnut426 I Live Here Joined: Mar 2007 Posts: 12,008 Finally a HUSKER again	They will go in, I recomend balancing the whole shebang though. Also you shouldnt have any piston to valve clearance issues, still way shy on compression to be worried about that. The chambers on the LA heads are bigger than the nice chambers on a magnum head. Kasey

Re: Are 318 Magnum pistons different from 318 LA? [Re: 69L78Nova] #1071465 09/08/11 05:53 PM 09/08/11 05:53 PM
Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska	360 piston ~584 grams pin 154.6 rings 56.6 comp height 1.590". Mag piston 470, pin 134, rings 40 grams CH 1.662". As said th LA rod small end is 2 wide but can b narrowed but that'd b $$$ plus then you'd need to weigh all the pieces 4 the balance factor & you're doing a budget build. Not sure what I'd do but that's what I could come up w live every 24 hour block of time like it's your last day on earth

Re: Are 318 Magnum pistons different from 318 LA? [Re: RapidRobert] #1071466 09/08/11 06:02 PM 09/08/11 06:02 PM
Joined: Apr 2007 Posts: 2,327 Glendale, AZ 6 69L78Nova OP Banned. Forever.
69L78Nova OP Banned. Forever. 6 Joined: Apr 2007 Posts: 2,327 Glendale, AZ	Could I use the whole 1995 rotating assembly in the 1975 block? Crank, rods, pistons, balanced and flexplate? I would just like to use the newer stuff if I can. I wasn't aware the old 70s 318 two barrel heads were open chamber. I guess ya learn something new every day! 1969 Nova 454/M21/3.31 Mild mid-11 second weekend cruiser 1994 F150 XLT Super Cab 2WD 5.0/4R70W/3.55 (Daily driver)

Re: Are 318 Magnum pistons different from 318 LA? [Re: RapidRobert] #1071467 09/08/11 06:10 PM 09/08/11 06:10 PM
Joined: Jan 2005 Posts: 3,344 Central TX roe master
roe master Joined: Jan 2005 Posts: 3,344 Central TX	wouldn't the magnum heads on his LA 318 give him a nice bump in compression, especially with a thinner head gasket. If the LA is in such nice condition why not re-ring, new bearings, magnum heads and go with the LA 318? 1971 Plymouth Satellite 408/904 8 3/4 3.23 SG

Re: Are 318 Magnum pistons different from 318 LA? [Re: roe] #1071468 09/08/11 06:13 PM 09/08/11 06:13 PM
Joined: Apr 2007 Posts: 2,327 Glendale, AZ 6 69L78Nova OP Banned. Forever.
69L78Nova OP Banned. Forever. 6 Joined: Apr 2007 Posts: 2,327 Glendale, AZ	That's what I planned to do. I wasn't sure if the compression height of the Magnum pistons was the same as the LA pistons. If the difference is minimal or not worth it, ill just run the LA stuff 1969 Nova 454/M21/3.31 Mild mid-11 second weekend cruiser 1994 F150 XLT Super Cab 2WD 5.0/4R70W/3.55 (Daily driver)

Re: Are 318 Magnum pistons different from 318 LA? [Re: 69L78Nova] #1071469 09/08/11 06:28 PM 09/08/11 06:28 PM
Joined: Jan 2005 Posts: 3,344 Central TX roe master
roe master Joined: Jan 2005 Posts: 3,344 Central TX	Im definately no expert on this. Somebody a few posts back said that you can swap over the entire rotating assembly. If that true what king of issues could he run into? Wouldn't that be like slightly stroking the 318 to about 349 or so? Would he have to start worrying about clearance issues with those pistons/heads in the 318? 1971 Plymouth Satellite 408/904 8 3/4 3.23 SG

Re: Are 318 Magnum pistons different from 318 LA? [Re: roe] #1071470 09/08/11 06:50 PM 09/08/11 06:50 PM
Joined: Apr 2007 Posts: 2,327 Glendale, AZ 6 69L78Nova OP Banned. Forever.
69L78Nova OP Banned. Forever. 6 Joined: Apr 2007 Posts: 2,327 Glendale, AZ	No, both are 318s. One Magnum, one LA 1969 Nova 454/M21/3.31 Mild mid-11 second weekend cruiser 1994 F150 XLT Super Cab 2WD 5.0/4R70W/3.55 (Daily driver)

Re: Are 318 Magnum pistons different from 318 LA? [Re: 69L78Nova] #1071471 09/08/11 09:59 PM 09/08/11 09:59 PM
Joined: Jul 2003 Posts: 6,167 Maryland GO_Fish master
GO_Fish master Joined: Jul 2003 Posts: 6,167 Maryland	Quote: Could I use the whole 1995 rotating assembly in the 1975 block? Crank, rods, pistons, balanced and flexplate? I would just like to use the newer stuff if I can. Yes, that is what I was saying in my earlier post. Use the whole 95 rotating assembly so you do not have to rebalance anything. You would still have a 318, but the compression should be the same as a Magnum. You would essentially have a magnum less the roller cam and lifters. You'd need hollow pushrods from Summit or other to finish the conversion. Scott B. "I'm a self-made man... I started with nothing, and I still have most of it!" 68 360 rusty B'cuda 'vert (GO Fish)13.59@ 98.72 mph 69 340 GTS stock 14.18@ 95.60 mph 01 5.9L Ram 1500 Quad Cab 4x4 01 3.5L 300M 16.23@ 86.97 mph

Re: Are 318 Magnum pistons different from 318 LA? [Re: GO_Fish] #1071472 09/09/11 01:06 AM 09/09/11 01:06 AM
Joined: Apr 2007 Posts: 2,327 Glendale, AZ 6 69L78Nova OP Banned. Forever.
69L78Nova OP Banned. Forever. 6 Joined: Apr 2007 Posts: 2,327 Glendale, AZ	Ok, good to know. I already have the complete Magnum top end on my 78 360, I would just transfer the heads, manifold, carb, and K6900 cam/lifters into the 318. Looks like that's what ill do. 1969 Nova 454/M21/3.31 Mild mid-11 second weekend cruiser 1994 F150 XLT Super Cab 2WD 5.0/4R70W/3.55 (Daily driver)

Re: Are 318 Magnum pistons different from 318 LA? [Re: 69L78Nova] #1071473 09/09/11 10:01 AM 09/09/11 10:01 AM
Joined: Jan 2003 Posts: 16,123 Grand Haven, MI patrick I Live Here
patrick I Live Here Joined: Jan 2003 Posts: 16,123 Grand Haven, MI	Quote: Could I use the whole 1995 rotating assembly in the 1975 block? Crank, rods, pistons, balanced and flexplate? I would just like to use the newer stuff if I can. I wasn't aware the old 70s 318 two barrel heads were open chamber. I guess ya learn something new every day! yes, and is what I'd do. compression height is marginally higher than the older pistons, and the metric ring packages are the big differences between LA and magnum 318. 1976 Spinnaker White Plymouth Duster, /6 A833OD 1986 Silver/Twilight Blue Chrysler 5th Ave HotRod SOLD!* 2011 Toxic Orange Dodge Charger R/T 2017 Grand Cherokee Overland 2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)

Re: Are 318 Magnum pistons different from 318 LA? [Re: patrick] #1071474 09/09/11 11:44 AM 09/09/11 11:44 AM
Joined: Mar 2007 Posts: 12,008 Finally a HUSKER again Moparnut426 I Live Here
Moparnut426 I Live Here Joined: Mar 2007 Posts: 12,008 Finally a HUSKER again	You might already know this, but make sure you match the lifters to the lobes. If not, the cam and lifters are certain junk. Kasey

Re: Are 318 Magnum pistons different from 318 LA? [Re: 69L78Nova] #1071475 09/09/11 05:13 PM 09/09/11 05:13 PM
Joined: Jan 2005 Posts: 3,344 Central TX roe master
roe master Joined: Jan 2005 Posts: 3,344 Central TX	Quote: No, both are 318s. One Magnum, one LA Silly me, not paying attention 1971 Plymouth Satellite 408/904 8 3/4 3.23 SG

Re: Are 318 Magnum pistons different from 318 LA? [Re: roe] #1071476 09/09/11 08:57 PM 09/09/11 08:57 PM
Joined: Mar 2005 Posts: 1,445 Sterling Heights, Michigan 483... daniel_depetro pro stock
daniel_depetro pro stock Joined: Mar 2005 Posts: 1,445 Sterling Heights, Michigan 483...	Supposedly the Magnum engines have a lighter rotating assembly weight too. 1969 Dodge Super Bee A12 (440 Six Pack, 4-speed, Dana 60 4.10) 1972 Plymouth Road Runner (400, 4-speed, 8.75" 3.23) 1974 Plymouth Duster 360 (360, 4-speed, 8.75" 3.23)

Re: Are 318 Magnum pistons different from 318 LA? [Re: daniel_depetro] #1071477 09/09/11 10:22 PM 09/09/11 10:22 PM
Joined: Jul 2003 Posts: 6,167 Maryland GO_Fish master
GO_Fish master Joined: Jul 2003 Posts: 6,167 Maryland	That is true (lighter Magnum rods and pistons). That is why the whole Magnum rotating assembly needs to move to the LA block to maintain correct balance without a trip to the machine shop for custom balancing. Scott B. "I'm a self-made man... I started with nothing, and I still have most of it!" 68 360 rusty B'cuda 'vert (GO Fish)13.59@ 98.72 mph 69 340 GTS stock 14.18@ 95.60 mph 01 5.9L Ram 1500 Quad Cab 4x4 01 3.5L 300M 16.23@ 86.97 mph

Re: Are 318 Magnum pistons different from 318 LA? [Re: GO_Fish] #1071478 09/10/11 12:13 AM 09/10/11 12:13 AM
Joined: Jan 2005 Posts: 12,419 Kalispell Mt. H HotRodDave I Live Here
HotRodDave I Live Here H Joined: Jan 2005 Posts: 12,419 Kalispell Mt.	The differance in piston height is about .080 witch will make a nice bump in compression. However just swapping magnum heads onto a 318 LA with magnum heads will not yield you as much compression as a factory 318 magnum because the 318 magnum had a lower deck height also by about .015. I am not causing global warming, I am just trying to hold off a impending Ice Age!

Re: Are 318 Magnum pistons different from 318 LA? [Re: HotRodDave] #1071479 09/10/11 12:18 AM 09/10/11 12:18 AM
Joined: Apr 2007 Posts: 2,327 Glendale, AZ 6 69L78Nova OP Banned. Forever.
69L78Nova OP Banned. Forever. 6 Joined: Apr 2007 Posts: 2,327 Glendale, AZ	Yeah I'm just going to swap the whole magnum rotating assembly into the LA block. Plus, I already bought the rings and they weren't cheap. Does it matter what year bearings I use since the cranks interchange? Every listing I've seen lists pre-80, and 80-newer for rod/main bearings 1969 Nova 454/M21/3.31 Mild mid-11 second weekend cruiser 1994 F150 XLT Super Cab 2WD 5.0/4R70W/3.55 (Daily driver)

Re: Are 318 Magnum pistons different from 318 LA? [Re: HotRodDave] #1071480 09/10/11 12:20 AM 09/10/11 12:20 AM
Joined: Jan 2004 Posts: 27,347 Today? Who Knows? 1_WILD_RT Management Trainee
1_WILD_RT Management Trainee Joined: Jan 2004 Posts: 27,347 Today? Who Knows?	I know nothing about the differences but I'll throw this out... Most late model engines have gone to a one piece full circle rear main seal... For that to work the back of the crankshaft is different from an earlier style engine... "The Armies of our ancestors were lucky, in that they were not trailed by a second army of pencil pushers."

Re: Are 318 Magnum pistons different from 318 LA? [Re: 1_WILD_RT] #1071481 09/10/11 12:21 AM 09/10/11 12:21 AM
Joined: Apr 2007 Posts: 2,327 Glendale, AZ 6 69L78Nova OP Banned. Forever.
69L78Nova OP Banned. Forever. 6 Joined: Apr 2007 Posts: 2,327 Glendale, AZ	They are both 2-piece seal blocks 1969 Nova 454/M21/3.31 Mild mid-11 second weekend cruiser 1994 F150 XLT Super Cab 2WD 5.0/4R70W/3.55 (Daily driver)

Re: Are 318 Magnum pistons different from 318 LA? [Re: 69L78Nova] #1071482 09/10/11 12:25 AM 09/10/11 12:25 AM
Joined: Jan 2004 Posts: 27,347 Today? Who Knows? 1_WILD_RT Management Trainee
1_WILD_RT Management Trainee Joined: Jan 2004 Posts: 27,347 Today? Who Knows?	Cool.. Just a thought... "The Armies of our ancestors were lucky, in that they were not trailed by a second army of pencil pushers."

Re: Are 318 Magnum pistons different from 318 LA? [Re: 1_WILD_RT] #1071483 09/10/11 11:23 AM 09/10/11 11:23 AM
Joined: Jan 2005 Posts: 12,419 Kalispell Mt. H HotRodDave I Live Here
HotRodDave I Live Here H Joined: Jan 2005 Posts: 12,419 Kalispell Mt.	The only bearings that may make a differance is the thrust bearing, or the rear main bearing, the flange on the thrust bearing may be different (bigger diameter)and I think one bearing fits all but the other will not fit in the other block so if your thrust bearing goes in your block it is good. The rear main bearing one was wider than the other and again I don't remember the year break or witch one is universal. I am not causing global warming, I am just trying to hold off a impending Ice Age!

Re: Are 318 Magnum pistons different from 318 LA? [Re: HotRodDave] #1071484 09/10/11 11:37 AM 09/10/11 11:37 AM
Joined: Mar 2005 Posts: 1,445 Sterling Heights, Michigan 483... daniel_depetro pro stock
daniel_depetro pro stock Joined: Mar 2005 Posts: 1,445 Sterling Heights, Michigan 483...	Quote: The differance in piston height is about .080 witch will make a nice bump in compression. However just swapping magnum heads onto a 318 LA with magnum heads will not yield you as much compression as a factory 318 magnum because the 318 magnum had a lower deck height also by about .015. Interesting... Is there a difference in deck heights between: 1971-88 LA360 1989-92 roller camshaft LA360 1993-2002 5.9l Magnum ?!?!?! 1969 Dodge Super Bee A12 (440 Six Pack, 4-speed, Dana 60 4.10) 1972 Plymouth Road Runner (400, 4-speed, 8.75" 3.23) 1974 Plymouth Duster 360 (360, 4-speed, 8.75" 3.23)

Re: Are 318 Magnum pistons different from 318 LA? [Re: HotRodDave] #1071485 09/10/11 11:57 AM 09/10/11 11:57 AM
Joined: May 2003 Posts: 15,487 Florida S scratchnfotraction I Live Here
scratchnfotraction I Live Here S Joined: May 2003 Posts: 15,487 Florida	Quote: The only bearings that may make a differance is the thrust bearing, or the rear main bearing, the flange on the thrust bearing may be different (bigger diameter)and I think one bearing fits all but the other will not fit in the other block so if your thrust bearing goes in your block it is good. The rear main bearing one was wider than the other and again I don't remember the year break or witch one is universal. I didnt think of the thrust bearing..but IIRc all the magnum engine used the 360 size rear main bearing or main cap size and 360 oil pan. not sure if the bearing would have changed or the main cap size for the pan seal something you might want to look at before the swap starts

Re: Are 318 Magnum pistons different from 318 LA? [Re: daniel_depetro] #1071486 09/10/11 12:05 PM 09/10/11 12:05 PM
Joined: Aug 2011 Posts: 1,083 SE PA Yellow Fever super stock
Yellow Fever super stock Joined: Aug 2011 Posts: 1,083 SE PA	Don't forget that you'll have to balance your flywheel or torque converter for the magnum balance unless you neutral balance the assy, which is the route I would take.

Re: Are 318 Magnum pistons different from 318 LA? [Re: Yellow Fever] #1071487 09/10/11 12:25 PM 09/10/11 12:25 PM
Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska	Quote: neutral balance the assy, which is the route I would take. X2 live every 24 hour block of time like it's your last day on earth

Re: Are 318 Magnum pistons different from 318 LA? [Re: scratchnfotraction] #1071488 09/11/11 02:36 PM 09/11/11 02:36 PM
Joined: Jan 2005 Posts: 12,419 Kalispell Mt. H HotRodDave I Live Here
HotRodDave I Live Here H Joined: Jan 2005 Posts: 12,419 Kalispell Mt.	The 318 and 360 magnums both have slightly shorter deck heights than the LAs did. TBI and carb had one deck height and the MPI magnum had the shorter one, I am not sure why they made one ity bity change like that Main bearing diameter on ALL 318 polys, LA, and magnums are the same includeing the rear main. The differance in the magnum and earlier ones is the thickness of the cap, it was changed so you could use one pan for both motors. I am not causing global warming, I am just trying to hold off a impending Ice Age!

Re: Are 318 Magnum pistons different from 318 LA? [Re: HotRodDave] #1071489 09/16/11 02:19 PM 09/16/11 02:19 PM
Joined: Jan 2003 Posts: 16,376 D dogdays I Live Here
dogdays I Live Here D Joined: Jan 2003 Posts: 16,376	To recap: Use the whole rotating assembly AND the Magnum heads on the LA block, this will give the best results. As you're swapping a neutral balance 5.2 assembly for a neutral balance 318 assembly you don't have to do anything babout torque converter or flywheel balance. ALL 3.91 x 3.31 V8 engines are neutral balance. OR, you could spend $100 and have the 5.2 block sleeved and finished to your existing piston size. Then it would be all 5.2 and you'd have the roller cam to boot. R.

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