which 318 to use

[lvlrlvlopar]

i have 2 318's to choose from to swap into my car one is a '70 truck motor with the truck 3 crank. its not quite finished yet still need the 4 deg. cam key and valve srpings, or a '81 318 that was rebuilt in my schools auto tech program i got for $250. I am wondering if the 81 has a cast crank and if so will it vibrate too much if i dont chang the harmonic balancer and torque converter. if so could i put the truck crank in the 81 engine then then switch the heads and cam over when i get the key and valve springs. i think i would rather use the 81 motor beause it has over $1100 into it for parts and in the 70 i just put new rings and berrings in it. i have a set of headers and an alumnium edilbrock 4bbl intake, the .474 280 cam and the 360 heads that would be put on the motor that i use.

[rumblefish360]

The '81 has a cast crank. It will create a rolling vibrater machine if you don't use the correct parts. Swaping out the "3" crank into it will require the balancer and proper torque converter.
Did you rebuild the 70 engine or just the ring and bearing deal?
The 70 shold be a thicker wall unit. Save that one.
I myself would leave the 81 engine alone and slide in the hi-po parts. Not the crank parts. Mill the heads to bump compression.

[Billydelrio]

Please fill me in on what the "3" crank is. I am not familiar with big truck 318s

Billy

[lvlrlvlopar]

the 318-3 truck crank is suposed to be better than the 340 cranks. it is hardened. Part #2668810 . I have read about it in a couple engine building books that i have.

(Swaping out the "3" crank into it will require the balancer and proper torque converter. )

Which balancer and torque converter would i need to use,
yes just a ring and berring job (limited funds)

[rumblefish360]

Use the balancer and torque converter from the 3 crank on the 3 crank. The 3 crank is fordged. Right. The other cranks is cast. Right? If you mix up the balancers or t-verters, you'll get a vibration.

[pishta]

I would use the one with the matching balancer and convertor. Balancing a motor is a pain, all the rotating has to be removed and sent out along with a few Jacksons. Then you are talking about new rod bolts because the old ones have already been stretched, and a bunch of other little things. Cast or forged wont matter with that cam. As long as the one you use has been checked. Rings and bearings sounds like a shade tree rebuild, good enough for a driver. 1100 bucks into a 318 sounds like new pistons, cam.....block...resell it! You put the 3 crank in the 81 block and youll have to balance the whole thing anyway, (new pistons)