318 stroker using Scat crank

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cudaracer

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Ok, so this is yet another 318 stroker combo thread, with a twist, as I thought it was a bit unique because I am now focused on a 3.58” Scat lightweight crank. I see it at Jegs for $378 (Link below). It appears about same price as a Mopar Performance crank, but claims lighter weight, holes in journals, etc. Any opinions on this matter? Is this not a better solution for quicker revs, etc?

My 318 stroker build would consist of this Scat crank, plus KB flat cast pistons with 1.658” CH, shaved down to 1.640”. This would also place these low surface-to-volume flat piston down in the bore about 0.40”, and still net me about 9.7:1 CR (66cc chamber). Perfecto!!! I get more stroke and volume to match my 360 heads (mildly ported with 1.88” valves) and DP Weiand intake & 600 carb. Cam is medium or so.

My goal?
Easy burnouts & low end torque & ultra low price.

But again, I really want to know more about that Scat crank, so opinions on all is welcome.


Crank link:
http://www.jegs.com/i/Scat/942/934010/10002/-1

Pistons link:
http://www.summitracing.com/parts/uem-1278-030/overview/
 
youre building an under-bored 360 at that point. are you attached to using the 318 block? if not you could likely build a 360 for at or less the cost of that "stroker" combo
 
As long as you understand you're going to spend more to get this together and running than a 360, that's cool. The combo you have will leave the piston sticking out above deck by .250" or so... You need to get a shorter 318 piston, or a custom piston (which would be my advice). Sure you don't want to just build a 4" stroke or get a 360?
 
moper said:
As long as you understand you're going to spend more to get this together and running than a 360, that's cool. The combo you have will leave the piston sticking out above deck by .250" or so... You need to get a shorter 318 piston, or a custom piston (which would be my advice). Sure you don't want to just build a 4" stroke or get a 360?
Click to expand...

Corrections are in order here:


New 360 block, plus oil pan, plus crank, plus pistons,
will cost more than,
crank & pistons. Even with mod cost to pistons, which is basically free for me.

As for calculations:

Stock 318:
9.64" block - 6.123" rod - 3.31"/2 stroke - 1.822" piston = 0.040" in the bore

Stroker 318:
9.64" block - 6.123" rod - 3.58"/2 stroke - 1.658" piston = 0.069" in the bore

or is my calculator broken????
 
AFAIK, the Scat crank is a good unit...I've used them before in SBFs...have it looked at all the same for diameters and such...and of course balancing.

Did you have your deck height measured @ 9.64"? Blueprint height is 9.6" and would put your 1.658" pistons .029" in the hole.
 
Also, please define medium cam...is it going to be an issue with flat top pistons?
 
yeah the 1.658 pistons used with the 3,58 crank would be a lot closer to the top of the bore as mentioned above about .029. you could then mill the block and have a "0" deck height if you wanted. what is the original application for the 1.658 piston?
 
FWIW my 410 was built with 4.00 inch Scat 9000 series crank and it has stood up to much more power than you will be making . I too have a numbers 318 sitting in the corner waiting to become something and go back into it;s car in place of the 410 so I will be watching your progress with great interest .
 
actually after looking at this I am thinking that this would be a good build and not too overly expensive. I could not tell from the picture but I believe the crank has the fillet radius on the journals which would be an improvement over the stock crank which was under cut. Also you would have the small journal of the 318 so that too is good for a reduction in friction etc. Then if you wanted to cut the block a bit you could have a quench setup with the right heads. I guesss the only thing you would have to watch would be the compression ratio which I'm sure would be up quite a bit. If you could get away with machining a D shaped dish in those pistons then you would have a reduction in the compression and the quench! not bad...cubic inch would be 349
 
cudaracer said:
Corrections are in order here:


New 360 block, plus oil pan, plus crank, plus pistons,
will cost more than,
crank & pistons. Even with mod cost to pistons, which is basically free for me.

As for calculations:

Stock 318:
9.64" block - 6.123" rod - 3.31"/2 stroke - 1.822" piston = 0.040" in the bore

Stroker 318:
9.64" block - 6.123" rod - 3.58"/2 stroke - 1.658" piston = 0.069" in the bore

or is my calculator broken????
Click to expand...

My math was off...lol. Sorry.
Scat crank is fine. Pistons suck IMO. You'll have to keep the cam relatively small (under .520 lift and depending on the lobe design under 225°@ .050 because of no valve reliefs but it will be torquey.
 
txstang84 said:
Also, please define medium cam...is it going to be an issue with flat top pistons?
Click to expand...


Yes - my math was off - sorry about that.
The crank's fine. The pistons are a problem if the cam's very big at all. I'd say kep it under .520 lift and under 225° @ .050 if it's a modern grind.
 
I don't understand stroker 318 the only reason I'll would build a 318 is cause I would want a short stroke engine the 318 is a poor man's 340. I wish they made a 3.31 crank for 360 blocks. When building a stroker the only factory part your using is the block and a 318 bore size ain't bad, but I'd try to fine a reasonable price 340 block but settle for a 360 block. Even with 3.58 stroke that's what my cousin run 340 block with 3.58 crank.
 
Sounds like a cool setup. Extra grunt,over a 3.31 stock stroke. As long as the machine work,is open access free to you,I see no negatives.
 
is this a preferred combo?
corvette LS 3.94 x 3.62 stroke
new hemi 3.94 x 3.58 stroke
i also have been considering this build ...
 
you opened the box ir3333...:)

this one has been brought up before. It's not typically preferred because of what bomber mentions above in regard to the cost of machine work (and I'll add lack of selection of high quality performance minded pistons). 360s have a different main journal diameter, so your choice for dropping a 360 crank in a 318 block are to either buy a new crank for $360+ or have the stock 360 crank machined down like .300"...which, that all depends on your local machining costs. And as moper mentioned, the pistons he's talking about using are basic cast flat tops with no valve reliefs, so unless you have them custom fly cut, you will run into a limitation of lift/duration for the cam you select.

It's not an intrinsically bad combo, but unless you have access to cheap or free machining, it's not optimal for most, and buying a running 360 is sometimes cheaper in the long run...but it's the beauty of the choices...you don't have to do what everyone else does...
 
ir3333 said:
is this a preferred combo?
corvette LS 3.94 x 3.62 stroke
new hemi 3.94 x 3.58 stroke
i also have been considering this build ...
Click to expand...

Smaller bore are better for emissions, more complete burn, and 318 bore size still offers great flow potential,
But will lose a few ponies to 4" plus bore especially when shooting north of 450hp
 
The Scat ones are supposed to be good. Wasn't it the Eagle cranks that were breakin?
 
Great info.
Thanks all.

As for the machining costs to the piston, it is still cheaper than getting custom forged pistons made. Or cheaper than existing non cast as well.
 
If the skirts on those pistons you plan to use are long, they might hit your counterweights.
 
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