318 Magnum pistons and rods in an LA motor

[392Mopar]

Hey guys, can you use magnum pistons and rods in an LA 318? Looking into buying a set of used 390 stroker pistons and rods for a magnum engine to use with a 4" crank in my late 70's 318 block. Thanks

Butch

 

[rumblefish360]

Rebalance the rotating assembley with the "LA" balancer and flywheel/flex plate unless you get everything from the Magnum engine. That is it.

 

[392Mopar]

Thanks, thats what I thought. I'd be getting a new 4" stroker crank anyway so it will be basically all new. So just use the ballancer on my 318 and the neutral ballanced flywheel that I'm running , ballance and I'll be all set?

Thanks!!!

 

[rumblefish360]

Maybe. Are the pistons and rods balanced? Check them.
Then once that is done, have the crank checked, proper bearings purchased after the crank is checked and then your balancer and flywheel with the above all at once to be balanced.

 

[392Mopar]

Yeah the piston/rods are ballanced I was told, I'll check anyways though. Would I need to ballance using the flywheel and dampener, arnt 318s internally ballanced and use neutral flywheels and dampeners ?


Thanks again

Butch

 

[rumblefish360]

All 318's are internally balanced, a different balance is used between "LA" and Magnum engines. If you can, use the Magnum balancer and flex plate/flywheel so it is a drop in. If you can't use the Magnum's damper and flywheel/flex plate, then you'll need to have it checked and balanced.

 

[volaredon]

the 3751841 crank was used for MANY years, from at least the 80s thru the end of Magnums; I have used "LA" cranks in Magnums and "Magnum" cranks in LAs;
at one point I had an 88 D-100 w/a 318 and I went to Car Quest and priced a crank kit; IIRC the interchange was like '68-97; (this was back in like 1998) so as long as you used the whole set yes, Magnum or LA rods CAN be interchanged, on 318s.

the "different balance" on LA vs Magnum referenced above is primarily related to 360s which were external balanced. ALL 318s were internal balanced (from the factory anyhow)

 

[392Mopar]

Ok, well when the time comes I am going to be taking the 4" stroker crank, rods and pistons to get ballanced so, my questions is, are the flywheel and dampener neutral ballanced or do they need to go to the shop for the ballancing, I always thought they were neutral on the 318.

I just picked up a set of Diamond forged 390 stroker pistons on Eagle SIR rods, so I'm starting to peice together a 390 build.

Butch

 

[moper]

If it's a stick car, have the flywheel balanced with the assembly. IMO that's the easy way to use what you have. If you dont have a flywheel yet, have the rotating assembly neutral balanced and get a nuetral flywheel. If it's and sutomatic, just balance the rotating assembly and use the neutral flexplate and caonvertor.

 

[volaredon]

yeah the FW and damper are neutral on a 318 but with all new "other parts" in the mix it definitely would not hurt to have them checked along with the parts that yuo plan on using. I'm puttin together a 318 Mag as we speak that I hope to get an honest 300HP from, and I have another 318 Mag block here that I hope to turn into a 390 down the road.