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#1
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318 poly to LA 360 swap
Hey guys, just a couple questions I wanna shoot to you all. I am looking at buying a fresh '75 360 to replace my aging '66 poly motor. Will my poly's trans bolt up to the 360? I was told it may be different, I already know the motor mounts are different. Also, the guy was wanting $700 for it, complete minus water pump, fuel pump, and carb. It is a fresh rebuild with new internals and everything was cleaned out. Heads are stock spec. Is that a good deal or should I maybe try to get it for a bit less? Any thoughts are greatly appreciated!
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#2
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I tried looking around for anything related to poly to 360 swaps and found a forum post (JalopyJournal).
I am worried that my 904 wouldn't be able to take a newer 360 torque converter because of the spline count. I have access to a 1970 904 out of a 318 coronet wagon so that solves the possible spline issue but I also read that a 360 T/C and a 318 T/C are not the same and so I would need a transmission from a 360 engine. |
#3
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If at all possible I'd find a "pull" with a matching transmission, but if you cannot, there are ways
First, I believe there is a minor problem with the old torque converter. I believe you will find that the newer engines have a larger crankshaft register where the torque converter snout fits. You used to be able to buy bushing rings to cure this, but it would not be hard to make. All you need is a simple steel ring to fit over the old torque converter, and inside the new crank Balance is not a problem. B&M markets a weighted flex plate to take care of the balance. Make sure you get one for a 360LA if that is the engine you get. Magnums are weighted differently. 700 sounds like a lot for a used engine. REALLY to easy to claim "new parts" etc, so why is he selling? I take a REAL jaundiced eye at used engines. Some comments on torqueflites: You want a long shaft, used in all pass cars, 2 wheel drive trucks and vans, and lighter motor homes. Heavy motorhomes and trucks used short shaft trans You probably want to stay away from "lock up" converter trans. These are easily id'd by a smooth section on the front of the input shaft, just like a pilot bushing snout on a stick gearbox. You can use either 904 or 727, but you'll have to change the driveshaft if you go with a 727, they are a tad longer, and use a different spline In 68? Ma went to a 3 terminal neutral safety switch which went to having the neutral safety and reverse light switch in one unit. No big deal, you just use the center pin. Make sure you get manifolds that work. I'm not sure on those bodies, but I'd bet pickup or A-Body manifolds won't work. EDIT suddenly realized I don't know what body style your car or truck is?? |
#4
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Its a 1966 belvedere. Do you think that the 904 I have that came from the 70 coronet wagon would work better than the stock 904 from my poly? Since i think it would have the newer spline? Someone told me that the 360 and 318 converters even from the same year (1975) were different which I am skeptical that of since the cranks should be the same as long as I get a newer converter like you said.
The 360 came from a dodge truck, forgot to mention. Still has the deep oil pan and everything. |
#5
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It is an old guy who has been building Chrysler and Chevy small blocks since he was 16. He's probably around his late 60s now. He is selling all of his Mopar stuff because his son, who is the owner of most of it, is going on his third or fourth tour overseas and doesn't have any use for any of it anymore.
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#6
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No, 360 / 318 cranks are different, 360 is really the oddball
273 / 318 "forged cranks" and 340 "forged cranks" were all internally balanced 318 / 340 "cast cranks" were externally balanced but don't use much weight 360s are LONGER STROKE and are all cast cranks, and use substantially more weights on the converter You'll have to scare up a 360 "car" (mid/front sump) pan, as the truck pan does you no good, and the 318 pan will not fit a 360. The half moon cutout around the seal in the rear of a 360 LA is smaller than a 318. I would lean towards the 70 transmission EDIT we may be confusing each other. The differences between early and late engine to converter mating is that the round snout on the converter was made larger about 68. You could used your early trans / converter by buying / making a simple bushing ring to take up the difference in diameter to the 360. The converters won't swap between transmissions because of changes in transmission input splines, and of course are different 904 to 727 if that's in the picture The WEIGHT problem. You either need a 360 weighted converter, or buy an aftermarket weighted flex plate from B&M. There used to be a kit and a template, you could weld weights for a 360 onto a "neutral" weighted converter yourself. Frankly I've never liked that idea. You might find a used BM flexplate if you look around. |
#7
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Just to cut out some interference, some people get confused about the Poly...
Up to '61 they did have a different bolt and dowel pattern on the back of the block as well as a longer crank tail and an 8-bolt fixing for the flywheel or torque converter. But from '62 they are identical to the 318 LA. |
#8
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Ok I think I am starting to understand now. So basically I either want to use my trans/converter and buy a weighted flex plate or use the 70 904 and do the same thing. If I cannot find the weighted flex plate then I need to find a weighted converter but most likely it will only fit on the 70 trans, not mine, since the input spline count is different. Am I correct so far?
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#9
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Pretty much, except, if you do use the early converter / trans, you'll have to build / find a bushing for the converter snout. I'm sure there are specialty people who sell 'em
I mentioned I'd lean towards the 70 There were internal changes, and if you ever need to overhaul the trans, might be easier to replace some parts. Finding a weighted flex should not be difficult. Ebay and the various Mopar forums "for sale sections" and of course you can buy them new. Check Summit, Jegs |
#10
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If the transmission in your '66 Belvedere is original it isn't a 904, a '66 318 would have come with a 727...prior to '67 only the 273 got the 904.
The '66 727 is the last year of the 19-spline input shaft which won't mate to any later 360 externally-balanced converter, the best way to go is the B&M #10236 flexplate and use the stock '66 converter. I've been told that there is one bolt (lower left) that is located differently on the poly and the LA, requires elongating that bolt hole in the bellhousing. |
#11
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I've not seen any difference there, John...
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#12
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Wow, I had no idea, well the fact I have a 727 really changes things then.
My options are either one or the other if I do decide to go with this 360. I either need to A) Keep my trans and buy that flex plate and bushing....or B) Find a newer 727 with converter and get the flex plate as well. I haven't looked into which way is cheaper and/or easier to locate the required part(s). I also have thrown around the idea of keeping the poly and having it rebuilt. It needs a full gasket kit, a new water pump, all new hoses, a choke(which I have yet to find after 8 months of looking), a new thermostat housing, a dual brake cylinder, and my 2bbl carb needs redone. Otherwise it has run great and it has gone on two 200 mile+ trips since I bought it in 2012. The only issue is I have no garage and little time to put into even that stuff. The guy that has the 360 (on top of a BUNCH of other mopar stuff) said he would throw the idea around of rebuilding my engine since he has nothing right now to keep him busy since he is a retired grandfather. I am very grateful for all of the excellent information I have gotten here!! I am also glad I know that 727 and 904 converters won't interchange or else I would have tried to use my dad's weighted converter that he has laying around.....would have been a mistake |
#13
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What ever you do dont just throw that poly away,There is a forged crank in there.
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#14
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That's no biggie, really...
LAs, including the 273s, had forged cranks for years. |
#15
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Quote:
Quote:
If you mean the factory flexplate, there's no advantage; the factory put the weights on the converter not the flexplate, only the aftermarket offers externally balanced flexplates to avoid having to weld weight on the converter. |
#16
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Quote:
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#17
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So , not to bring this post back but, did the op do the swap and how well did the flex plate work ? I'm getting ready to do the same swap in my 64 polara 318 poly 727 push button combo.
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#18
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Don't think he's been back to update us, so unless he chimes back in we may never know. Personally for a street motor I'd strongly consider building the poly and keeping everything numbers matching ( can't believe I just said that cause I'm the one that wants to change everything). In this case I just don't see enough of an advantage to warrant the PIA issues sure to turn up. Poly's can be respectful performers.
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#19
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no activity for 2 yrs
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#20
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A bit of a shame...
I think we'd all like to know how he got on. |
#21
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Quote:
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#22
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I've got a older 904 was hooked to a 318 so I might could get a flex plate and use the 904 on my 360 and keep my same tc.
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#23
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The tc.that was for the 318
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#24
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yes to use the torque converter for the 318 you need to have a flexplate weighted for a LA 360.
B&M has one #10239 Chrysler SFI Flexplate 6 Bolt Crank for TF A904 1971 to 1992 Chrysler, Dodge, Plymouth w 360 CID - B&M Transmissions, Shifters, Torque Converters, Diff Covers, Coolers |
#25
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When I get a chance I'll post some pics of two 904s both pulled from 318s but with different im put shafts maybe one is a lockup don't know ? But I will post some pics and well see
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