Idea for a cheap 318 stroker. (opinions?)

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omahamoparguy

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Late one night last week I was surfing over the Summit Racing web site in the wee hours (you know how it is, you lose track of time). I was looking over the 318 pistons and I noticed there was a piston that had a compression distance of 1.658. Now that is way low down there in a stock 318. Like 7:1 territory. It is a cast piston made by silvolite, $239 a set.
I got to thinking that the piston would be so low down there that maybe you could utilize a 360 stroke in the 318. Yep, sure can. Do the math youself. Even with a .015 shave off the deck you would still have about .014~ of deck clearance. But then I thought, well you still gotta turn down a 360 crank and that could get pricey. So. I scanned over to the ceankshaft section and sure enough, there was a cast 3.58 stroke crank with the 318 size of main journals, all for the price of $366 dollars. So I ran some compression ratio calc on the web and I came up with this.
The cubic inches with a .040 over bore would be 350~ and the compression ratio would be 9.6 approximately with a set of 360 heads with 72 cc chambers. I don't know how much of a cam this would accept cause the pistons a perfectly flat tops. Has anybody done this yet?
Anybody know how much abuse the silvolite pistons would take? If anything, sounds like a great motor for a truck.
 
Yes. Been hased over bedfore. I think if you search for it you'll find it under "budget 318 stroker" or "349" or something...
 
That's gettin pretty high up in the bore for a true flat top and wantin to use a performance cam. You might end up needin to cut some valve reliefs.
 
yeah, thats why I was thinkin it be ok for a truck with a small cam. Or if anybody knows how much meat is in the top of the silvolites?? notches might work. There is also a piston with a 1.72 and a dish. you would have to mill about .030 off the top of the piston or use thick gaskets but the dish would probably take care of the valve clearance.
Milling the top of a dished piston would be easy and should not have any bad side effects. compression would be approx 8.8 or ~. Pistons way cheap too. (like $13 each)
jus thinkin out of the box I guess.
 
I built a 3.55" stroke 318 using the MP 8 bolt 4340 race crank and a set of 6" MP aluminum rods combined with the kb 318 high compression slugs....right at 10:1 and zero deck.

Made for one sweet motor but I'm pulling it just to make way for a 414" 340 deal that fell into my lap...hate to pull out a perfectly good motor though...it's a roller block too which makes it extra hard.
 
Just pick up a junkyard 360 it can be had for cheap. Same stroke and cheap Hypereutectic pistons with streetable compression..unless you just 'want' to stroke the 318 and that is good too, but I believe the 360 would end up costing less and have more punch too. JMHO.

Terry
 
That is allways my advice too, but, if a 318 is what he wants to do, then a 318 it will be.
 
rumblefish360 said:
Stroker and cheap do not go together, however, .... This guy did a weird build that I wouldn't do myself or rcomend; http://www.forabodiesonly.com/mopar/showthread.php?t=19556
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Was not Bobby exposed as being incompetent? I'm sure it was him that some bloke on here was crying about making a complete abortion of his brand new heads/motor.
I read that entire thread and bared in mind what iI'd read about the work he'd carried out on the motor of the guy who was complaining about him. Needless to say I wasn't too suprised to read that the motor had such dubious longevity.
 
Valvebounce said:
Was not Bobby exposed as being incompetent? I'm sure it was him that some bloke on here was crying about making a complete abortion of his brand new heads/motor.
I read that entire thread and bared in mind what iI'd read about the work he'd carried out on the motor of the guy who was complaining about him. Needless to say I wasn't too suprised to read that the motor had such dubious longevity.
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I believe he screwed up someones heads...

As for the original poster start with a 360 more cubes right off the bat to start with...
 
Valvebounce said:
Was not Bobby exposed as being incompetent? I'm sure it was him that some bloke on here was crying about making a complete abortion of his brand new heads/motor.
I read that entire thread and bared in mind what iI'd read about the work he'd carried out on the motor of the guy who was complaining about him. Needless to say I wasn't too suprised to read that the motor had such dubious longevity.
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I ditto the reply below. Also, the stroker he did was nothing more than a beat on build on the extra cheap without concern for long life. The build is actually doable, just not how he did it.

stroked 340 said:
I believe he screwed up someones heads...
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Yes, indeed he did and he didn't do right afterwards ethier.

As for the original poster start with a 360 more cubes right off the bat to start with...
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Absoultely!

However, if stroking the 318 with a 360 crank is what you want, proceed carefuly and think before you start machining parts into a expensive mess. Look for pistons first and then move onto what it will cost between the pistons and crank work to have it all fit and work.

Better off stroking the 318 w/a 4.00 crank IMO.
 
The only real problem I have with this are once you get a piston in there, the cheapo pistons have no valve reliefs. So you can't really put a decent cam into it. Normally those pistons would be way down away from the valves but you're doing all this just to get them up closer, then you can't run a cam in it. I think you could get more overall power and a better shaped power curve just by doing a 318 with performance parts over giving up a lot just for the stroke. JMO, but it didnt seem like a lot of sense to me to do even back then.
 
I've been kicking this idea around too. Seems like as long as you go with a mild cam, or have reliefs cut, it's doable. How much would it be to cut a 360 crank down for 318 mains? I have a block and crank, so if the pistons are that cheap, and it's not too expensive to turn down the crank, it would be a cheap, mild little stroker.
 
moper said:
The only real problem I have with this are once you get a piston in there, the cheapo pistons have no valve reliefs. So you can't really put a decent cam into it.
JMO, but it didnt seem like a lot of sense to me to do even back then.
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Double yep.

64physhy said:
I've been kicking this idea around too. Seems like as long as you go with a mild cam, or have reliefs cut, it's doable.
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That's the half of it. Once you spend....whatever it is to turn down a crank in your area to fit the block, then order the stock pistons with no valve relief and then a tool to cut reliefs into the piston... and on and on and on and on....

At this rate, unless your doing it yourself, why not start with a 360 OR pep up the 318 like moper said. It's not like the 318 can't make 400 HP easy or anyting.

I just see a 4.00 stroker kit for this alot easier and quicker with more power.

Why go to a 349 when 390 is near a drop in deal?

But then again.... Whatever floats your boat!
 
rumblefish360 said:
Double yep.



That's the half of it. Once you spend....whatever it is to turn down a crank in your area to fit the block, then order the stock pistons with no valve relief and then a tool to cut reliefs into the piston... and on and on and on and on....

At this rate, unless your doing it yourself, why not start with a 360 OR pep up the 318 like moper said. It's not like the 318 can't make 400 HP easy or anyting.

I just see a 4.00 stroker kit for this alot easier and quicker with more power.

Why go to a 349 when 390 is near a drop in deal?

But then again.... Whatever floats your boat!
Click to expand...

I have a 360 based stroker already. I was just thinking of using the 318 I pulled out and the stock 360 crank that I have laying around and putting them to use. With a mild cam, like a Comp 268H (.454 lift) or XE268H (.477/.480), there should be enough clearance to not need to notch the pistons. So if there was enough clearance without cutting, I'd be paying for pistons/rings, machining the crank and deck (if needed), the cam kit, gaskets, and nickel & dime crap. I have a set of 302 heads too. The 318 has either the 262H or XE262H in it now (the P.O. couldn't remember for sure, he even said it might be the XE268H, but I don't think it is). So if I really wanted to go cheap, I could reuse the cam. Just something I've been kicking around in my head, and if it does happen, won't be anytime soon.
 
THe only way to make it cheap (for me) is the $366 crank from summit. Yes, the 360 crank can be turned down but it is not so easy (lots of material removal and then there is the oils seal area to deals with.) (but if you could find someone who could do this cheap...?) Also, I was thinking if you didnt have to cut the block any, the piston would be down about .028. 1/2 stroke 1.79+ rod 6.123 + piston 1.658 = 9.571. That leaves
.028 clearance! (according to a 9.599 deck height). I was putting in a .015 shave on the block with my calcs. I was thinkin smallcam ~ .454 lift and ~ 262 duration and 110 LSA. I think the valves would clear with maybe a small notch (done with a "sawed" head used as a fixture for a Iskenderian valve notch cutter or something similar). That would be not too bad of a compromise. The thing I like about it is the small bearing size of the mains which would free up friction and therefore improve mpg. And would be very near to the 360 which are not known for fuel mileage. BTW, I asked my machinist about cutting a 360 crank and he said that he does not have the proper equipment, if he tried it, it would take too long. I think I will look and see if I can find someone to turn the mains, heck a buddy of mine has a lathe. Oh well, just call me cheap! HAHA
Merry christmas!!
 
so, I am kinda agree ing with 64physhy. Just call us the mad scientists of the bunch.
 
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