Yes and no. There is a special rear main insert needed to make it happen, the rear main is a different size, smaller than a 318. Next issue you have is the longer stroke makes the pistons pop out the top of the block, so pistons to work would be needed. So, if going to all this work, and if you are willing to spend a little bit of money, one of two ways to go. Either get a 5.9 or 360, or, Hughes Engines (one location I know of) has a 318 Stroker kit that includes the pistons, rods, crank, to make a 396 (or thereabouts) . Either solution is going to cost, your money.
The 318 can be built to make plenty of power, it just never had any factory support, which I to this day cannot figure out why. You can get good power out of the engines with a mild cam, ported heads, and higher compression. Half that battle has been done with the Magnum heads (pushrods and lifter changes required as you know), and the larger 1.92 intake valves and smaller combustion chamber right off the bat. You can gain a giant amount of power by removing the ridge that transitions from the valve pocket to the quench pad of the head, it blocks flow a ton, and also remove those ridges right around the valves, intake and exhaust, those steps cause curls as the valves open and slow the flow out (both intake and exhaust). Uou may also find a shark fin on the intake ports as it comes to the valve guide/bowl area, reduces flow by a lot, my 3.9 Magnum heads had it, big improvement when it was removed and significantly improved low end torque (and the top end is pretty good, too, for all stock).
318 and 340 share the same crank and rods, but the pistons have to have the pins moved according to the stroke of the crank. And to add, there were some beefier rods for some of the 340s the 318s never saw.
I’m also planning a 318 rebuild. I’ve read a lot of the posts here and have been very impressed with the amount of knowledge and willingness to help. I’d appreciate any feedback. This will be my first mopar build and only my second engine rebuild ever, so I have a lot to learn. J This is a daily driver but I do tow occasionally, so I don’t want to lose too much low end torque.
2001 Dodge 5.2 Magnum bored 30 over
Cloyes Double row timing chain
Harland Sharp 1:6 rockers
Melling High volume oil pump
EQ Monster heads (stronger springs and better flow characteristics from what I understand) 64cc , 2.02 intake 1.62 exhaust with mild porting (port matching and cleaning up the castings from what I’ve read od DANA-44’s work)
Cam (Hughes Engines regrind HER0814AL Intake lift .512, exhaust lift .520, intake duration at .050 208, exhaust duration at .050 214, lobe separation 114, intake centerline 111,)
KB Hypereut flat top piston KBP KB167-030 (with 64cc should give me a compression ratio of 9.6)
New stock roller lifters (current ones have 260000 miles on them so replacing them just seems like good common sense.
Torn between M1 intake and Edelbrock Air Gap FI intake. Conflicting user reports and such
Modified throttle body (hughes engine HUG 5502 – reported 1015 CFM
Appropriate SCT tune to make sure the computer likes everything
Long tube headers into 3 inch single exhaust with apppropriate y-pipe and high flow cat.
I’ve also read a bit about cam degreeing. Is it necessary, worth it, etc?
This will be a very strong engine, cam lift may sound a little excessive, but the short duration will offset that and be streetable without any issues. Good on the head work, removing those sharp edges in the combustion chamber and port matching (along with the intake manfold), is all great. At this point, because you are sticking with the EFI setup, which is a good thing these days, port injection does not need a dual plane design, M1 works, but the air gap would keep the air a little cooler, as long as it is a single plane intake, so I have to match your thought, it is a hard decision, once the heads are ported both will work just fine for bottom end torque on the street and towing, the injection on the port opening fixes this, and on a carbureted engine, works on the street. At this point I would then say, since they will both work properly and give you bottom end power you will need (the edging in the chamber does a majority of this for your towing needs), go with the cool looks factor, it is a six, one half dozen decision for functionality. Again, as with the heads, match the manifold ports, they are always off on one side, leave the carbide burr cutting surface, keeps everything cleaner and promotes fuel atomization in the ports, less carbon and fuel coking inside, which is a plus, the chamber edgine stops the pinging and allows your compression without batting an eye, and you can run the cheapest gas you can find, I was able to run 13.3:1 compression on 75 octane without a problem.
Thanks! One other question just came to mind. Since this is an internally balanced engine, and I'm keeping the original crank, connecting rods, etc. will I need to have a shop rebalance the rotating assembly considering the new pistons?
Just picked-up on this topic (since I am always weeks or months out of touch). I do not know how many of the readers are aware that the 318 has much smaller main bearings than the 360 - 2.50" versus 2.81". (trivia that the 360 has largest of ANY modern-era Mopar). I do not have the text in my hand to back this up but logic would have it that there is no feasible or cost-effective way to enlarge the 273/318/340 main (counter-bores) to accept the much larger 360 size. I have both blocks with caps under my porch but haven't looked at them since October. Also, the early LA 318's had skinnier connecting rods than the later ('72+) versions. In fact, these later ones were identical to the 340 and 360, including size, weight and casting numbers. Only the 340 used 'full-floating' pins. I suppose one direction to take would indeed be a 'stroker' crank but why not stroke the 360 vs the 318? I wouldn't mess with the 340 anyway for such a project (unless) the vehicle has it as OEM and you wish to keep matching numbers.
Well, there are a couple of advantages to using the 340 over the 360. First, apparently the metallurgy changed over time and the engines of the early seventies are of a slightly more desirable alloy than the mid to late seventies and eighties. Also, the 340 started out with a larger cylinder bore and apparently with a larger cylinder wall casting, so one can bore it further without as much concern for overdoing it.
There were a couple of years in which the 360 and 340 were both made, and apparently for those years, the 360 is very desirable, from what I've read the cylinders were cast with the same rough dimensions as the 340, which would mean that one could overbore those 360s as far as one could overbore a 340, plus they have the better alloy quality, and they have the large crank journals. But, those are rare blocks and difficult to find as there aren't many trucks and vans from those first years of the 360 left, most have been crushed.
My stroker is from a late seventies 360, and since I didn't go more than .030" overbore it wasn't an issue, but if someone wanted to start out with a 340, If I remember right, they instantly end up at 416 cubes with a clean-up grade .030" overbore, and can push 422ci with a .060" overbore while still only stroking the engine to 4". If one can get .080" overbore out of a block that started out 4.040", with a 4" stroke one can reach 426ci, which would make the badging much easier... *grin*