Is building a stroked 318 better than a stroked 340/360?

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since I have both 318/360 motors laying around, I’d choose 360 to stroke. You stroke a motor for more power. More cubes, easier it is to make power. Now if I found a deal on on a stroker 318 kit, I’d go with that.

Nicks garage dyno’d a stroker 318. Got some nice power.

 
I built a 318 stroker because I had a good 318 block. If starting from scratch 360 blocks are out there and an extra 18 cubic inches once stroked wont hurt and bigger bore 4.030 vs 3.94 also helps. if your putting money into the motor spend thr extra few hundred for a 360 vs 318…..
 
migsBIG said:
So I was planning to put a 440 in my 73’ Duster and decided to sell off all my small block stuff and did so over the weekend. At the same time, I was offered a deal on a torquestorm supercharger for a small block and think it might be a fun little combo for the duster instead of the RB engine I’m building. Now all I have left are a couple early 318 engines. Thinking cheap fun might be the way to go for now, contemplating building a 318 for the little huffer and running it in there.

So my question is, what benifits to stroking a 318 than a 340 or 360? Mind you, I’m just talking short blocks here, nothing to do with heads or intakes, just block wise. Now I know some 340’s came with forged cranks, but I don’t think anything really different between the LA blocks. So I’m asking if there is any difference between blocks strength and is it feasible? I could spend another $600-$1000 for a 340 block, $500+ for 360 or use that money towards the 318.
Like to hear some opinions on this.

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Using a blower is going to fill the cylinders. Yes more cubes = more torque, but you need to get a block. I would just build the 318 block. Yes you may get some valve shrouding but the blower works past that to a point. With a blower the need for large intake valves is negated, but bigger exhaust valves will aid breathing, along with porting. Use the cost of a block towards valves, exhaust porting and valve springs.
 
IMHO there is the possibility of sonic testing those early 318 blocks and boring one to 4". However a blower builds cylinder pressures quickly, so I would keep the overbore to 0.030" or 0.040" to have more stabile bores, which will aid ring seal.
 
chilsam said:
I'd B.B or GEN III it...
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Can’t afford the hemi, and was thinking big block, but the huffer showed up and would be a cheaper build plus headers on a big block duster with power steering gave me anxiety Just thinking about it.
 
moparlvr166 said:
Since you're pushing the air in, do a mild build 318 and get the combo to work then fix all the errors, then build with a larger engine combo, you will probably save money in the long run.
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X2 I have a fresh teen machine shop fresh, with some goodies 2.02 J heads, small cam, its a sacrificial lamb on my 6-71 build, find out what it will not take and then stick a really good forged engine under the 6-71.
 
Appreciate all the input from everyone. Just got a call and another 360 engine came into the recycling yard. Going tuesday to see if it's a good core.
 
I'd get rid of the hp expectation and just put mildish cam 4bbl exhaust tune, hopefully gears & stall etc.. Enjoy then if want more down the road then go next steps to that then, which generally means build a 2nd engine. Good thing is a stock 318 is very low powered and under cammed it's very underutilized doesn't take much to give it decent pep.
 
migsBIG said:
that's one of my concerns is that the 318 is weaker at some point than the other blocks. Thank you for bringing that up. maybe someone can chime in that that is a weak point that needs to be addressed.
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I had heard or read that the 273/318 block is weak around the drivers side motor mount ears and that the 340 360 has reinforcement in the block there, this is why the left motor mount brackets dont direct swap between 273/318 and 340/360. Im not 100% sure about that and I'm sure someone would say I'm wrong especially the "318 is a 340 " guys...either way it is something to read up on IMO. I seem to recall that it has to do with the crank journals and it is obvious the main caps are beefier in the 340 360. The 318 wasnt designed to rev as high as the 340. The guys that say a 318 is a 340 sort of miss the mark with that statement, Chrysler designed and cast a different block for a reason when they designed the 340.
 
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Dartswinger70 said:
I had heard or read that the 273/318 block is weak around the drivers side motor mount ears and that the 340 360 has reinforcement in the block there, this is why the left motor mount brackets dont direct swap between 273/318 and 340/360. Im not 100% sure about that and I'm sure someone would say I'm wrong especially the "318 is a 340 " guys...either way it is something to read up on IMO. I seem to recall that it has to do with the crank journals and it is obvious the main caps are beefier in the 340 360. The 318 wasnt designed to rev as high as the 340. The guys that say a 318 is a 340 sort of miss the mark with that statement, Chrysler designed and cast a different block for a reason when they designed the 340.
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That may be the truth. Now for a snappy street engine and especially with an automatic transmission, those concerns probably mean nothing. If regular drag strip weekends are in the plan, then finding as strong a block as possible is likely a good idea.
 
Remember the 340 claim in the sales brochures was "she'll rev at 6000 all day long..." or something similar :)
 
Well that was a bust. The yard said they had a 360 in and fresh, but guess they can’t tell a dodge 360 from an AMC 360 out of a jeep.
Guess I’ll just keep looking for more info on 318 builds. I do have an early date 1971 318 that would work for a good core block. Has less than 45k miles on it and has been garaged since 2000’s.
 
If this is going to be a street car, if you leave it close to the 318 bore size, you might can get pretty decent mileage out of it, even with the supercharger. The 4" bore engines seem to be more difficult to get good mileage from.
 
Since you’ll need custom pistons anyway, build a 3.79 stroker out of that 318 block, which will yield 365” with a .030 overbore.
That’ll give you a little taller piston and keep that pin away from your ring landing, which will be great for boost. Stay at 8-8.5 compression and spin that blower a little faster.

I dunno, maybe I’m all wrong on my thoughts.
 
migsBIG said:
Well that was a bust. The yard said they had a 360 in and fresh, but guess they can’t tell a dodge 360 from an AMC 360 out of a jeep.
Guess I’ll just keep looking for more info on 318 builds. I do have an early date 1971 318 that would work for a good core block. Has less than 45k miles on it and has been garaged since 2000’s.
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I would not look back. Build the 318 block with maybe the 3.58 stroker crank or 3.75. Bore only enough to get the bores straight and round with a modern finish. I would talk to TotalSeal about piston rings with the blower. Then select pistons for the ring width they recommend. 1/16" should be maximum these days. This will cost a bit more but you should get better results. Others on here can recommend the heads to look for. Intake valve size is not as big a concern on a supercharged engine as the exhaust valves and ports. You can give up intake valve area to increase the exhaust valve area to get the much larger volume of exhaust gases out.
I would consider contacting David Vizard for a cam recommendation. He will charge for his service, but the information should be well worth the money.
That blower is much smaller than the 4l71 and 6l71 blowers commonly used, so a mild cam with fairly high lift is what you should be looking to, IMHO. Keep overlap down by using a shorter duration cam. For mainly street use and Cars and Coffee events, torque is king.
 
The 5.7 G3 is basically a 318 with a 360 crank. Often wondered if the factory found a bit of a sweet spot with that combination and what led to the factory settling on those numbers.

Interestingly, the LS1 5.7 uses similar bore and stroke numbers (3.898 in × 3.622 in).

They both went bigger from there, but just makes me wonder if there isn't something about those bore and stoke numbers that seems to work well. Long enough stoke to give the crank some leverage but not oversquare? I know a smaller bore is easier to make emissions compliant so that was probably part of it, too. I don't know, just makes me wonder.

Comparatively, GM's 5.7 was their performance offering for many years, but Mopar's 5.7 was never offered as a "performance" motor regardless of the fact that it came in "R/T" offerings. In many ways the 318 and 5.7 G3 are similar in that they showed up almost across the board, in both trucks and cars and pretty much unchanged. But the 318 got a 4bbl option later and the 5.7 never did.

Either way, I wouldn't stroke the 318 unless I had the parts laying around. I think a stock stroke 318 is more than enough for a fun street car, even more so with boost.
 
My guess maybe a bore around 3.91 is decent balance between power and emissions maybe fuel mileage too. Small bores multiple valves become more necessary like Ford did.
 
DionR said:
The 5.7 G3 is basically a 318 with a 360 crank. Often wondered if the factory found a bit of a sweet spot with that combination and what led to the factory settling on those numbers.

Interestingly, the LS1 5.7 uses similar bore and stroke numbers (3.898 in × 3.622 in).

They both went bigger from there, but just makes me wonder if there isn't something about those bore and stoke numbers that seems to work well. Long enough stoke to give the crank some leverage but not oversquare? I know a smaller bore is easier to make emissions compliant so that was probably part of it, too. I don't know, just makes me wonder.

Comparatively, GM's 5.7 was their performance offering for many years, but Mopar's 5.7 was never offered as a "performance" motor regardless of the fact that it came in "R/T" offerings. In many ways the 318 and 5.7 G3 are similar in that they showed up almost across the board, in both trucks and cars and pretty much unchanged. But the 318 got a 4bbl option later and the 5.7 never did.

Either way, I wouldn't stroke the 318 unless I had the parts laying around. I think a stock stroke 318 is more than enough for a fun street car, even more so with boost.
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There is something about square engines for torque and power with fuel economy.
 
Mopar44134 said:
since I have both 318/360 motors laying around, I’d choose 360 to stroke. You stroke a motor for more power. More cubes, easier it is to make power. Now if I found a deal on on a stroker 318 kit, I’d go with that.

Nicks garage dyno’d a stroker 318. Got some nice power.

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400+hp / 442 tq. Those are good numbers. And through manifolds too.
 
The 340 X Block you had was the one to build. Even took common 318 mounts. Was a heavy high nickel block with weight added in all the right places. Only the R Blocks were better. I would try and buy it back.
 
Nah dog, that block was for someone wanting to push four digits with little worry. I’m contempt with enough horsies to have fun and be dumb and just do my thing. Not trying to be number one at every stop light, expressway merger or Even if I see a random mustang owner. 318 might be worth stroking because nobody wants to do it.
 
migsBIG said:
Nah dog, that block was for someone wanting to push four digits with little worry. I’m contempt with enough horsies to have fun and be dumb and just do my thing. Not trying to be number one at every stop light, expressway merger or Even if I see a random mustang owner. 318 might be worth stroking because nobody wants to do it.
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Cores to build are plentiful. That is a plus. Most parts that would fit on a 340 or 360 will bolt onto the 318.
As Nick's Garage showed, a stroked 318 putting out over 400HP and pound feet of torque is no slouch.
Like the Chev 305 and Ford 302, the 318 emissions engines got cams with reduced intake lift and retarded timing. The reduced lift choked airflow into the cylinders. A retarded cam timing should benefit higher RPM power, but the intake valves restricted flow so no power. Gave the all a bad rep as crappy engines. Stuff the 360 cube cams in and they wake up.
 
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migsBIG said:
Appreciate all the input from everyone. Just got a call and another 360 engine came into the recycling yard. Going tuesday to see if it's a good core.
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whats the diff in price between the 360 n say a 5.7 GEN III from a ram ?
 
chilsam said:
whats the diff in price between the 360 n say a 5.7 GEN III from a ram ?
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Good thought. 5.7's are more common now as the older trucks get junked, wrecked, and rusted out. The question is, how much to hook one up and make it run?
 
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