Posted by Brian in Oregon on Tuesday, January 29, 2002 at 1:36AM :
In Reply to: 340 V8 conversion posted by Gordon Maney on Tuesday, January 29, 2002 at 0:33AM :
Some thoughts off the top of my head...
The 340 is a great HOT ROD engine (especially the TA version, which I'm not botering to compare here). It makes it's power at higher RPM than the 318 or 360, mainly due to larger ports and valves in comparison to its size. (The 360 uses the same basic head as some 340's, but 20 more cubies utilize the difference better for lower RPM HP & torque.) The 340 costs a lot more to boot. My feeling is that the 340 is best left for cars or street rod pickups, while the 318 and 360 are best for trucks needing torque, especially the 360.
My 318 has a 67 318 forged steel crank. This crank is balanced for the 67-72 rods. It is basically the same as the 340 crank, but the 340 crank has hollow rod journals to compensate for the heavier 340 rods.
Interestingly, a .060 over 318 (max overbore) is a 327, only 13 cubies from a 340. Considering how cheap 318 blocks are, and that the 318 and 340 have the same stroke, that's a mighty big argument for punching out a 318 from a cost savings standpoint.
Don't overlook that the compression on a 340 is higher, and no doubt is not going to run on regular. This is also a cost factor, when premium runs from 10 cents to 25 cents or more per gallon.
The 360 is more of a torque motor, though it makes more HP than a 318 as well. It's longer stroke than the 340 with the same size ports and valves means more torque at a lower RPM range. This is the range most useful to a truck.
My M37 is running the stock tranny, 5.83 gears and stock 900x16t tires. 55 MPH cruise should be 3200 RPM. I prefer the shorter stroke of the 318 for that, especially since I did not balance the motor. (This is probably a moot point for a balanced 360.) I also felt the lower torque of the 318 was more suitable to the stock M37 components. I think a 360 would be more useful in a truck running taller tires and/or gears, and particulqarly one with an automatic, given the losses inherent with an automatic.
One person on the Big Electric M37 board stroked a 340 to, if I recall right, a 414. The 340 would make a nice stroker motor, using the big valves and ports to advantage, since it would shift the power range downward. It would also be a lighter engine for its size than a big block. On the other hand, often these 'big-block-ized' small blocks have reliability problems when compared to a true big block of about the same size. For example, when punched to around 400 cubies, the Ford 351 Windsor will not last as long as a Ford 390 big block. But you do save a few hundred pounds in weight.
BTW, out of all the small blocks out there, the Ford is the lightest, the Chevy is the cheapest for everything plus it has fantastic options, but I think the Chysler and particularly the 318 are the most reliable, and a couple of friends who maintain large fleets back this up. Asthetically for a hot rod, the Ford and Chevy are more eye pleasing than the Mopar.