Small block stroker

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Josh owen

Josh owen

Bang em till it breaks
Joined
Dec 8, 2019
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Bay city wisconsin
Hey guys im looking to build another small block for my 71 duster, this ones going to be different than my others this ones kind of a crazy no F given kinda build, it's a 318 .060 over speedmaster aluminum heads, big mutha thumpr cam, air gap dual plain intake. my question is what stroker crank and rods would everyone recommend it Is a 4 speed car as well 3.55 rear gear again this is not to be serious like my other cars, this is looking to be high revving fun looking for multiple opinions and why
 
scat cast racing crank they are a good strong piece . jmo . for the money .
 
SCAT would be my choice also, forged or cast crankshaft take your choice! 65'
 
Depends on what kind of power you want to make....also depends on what your definition of "high revving" is. Strokers make max HP at lower RPM than standard stroke engines. My car for example makes max HP somewhere around 6500-6800, if it were a stock stroke it would make max HP about 500 RPM higher.

For my stroker, I used a Scat forged kit (forged crank, forged pistons, and Scat I-beams)...but I race almost every weekend, so I wanted it strong....the car also runs low 10's. If it is just a street car making ~ 450hp (which is what your other parts suggest), you would be fine with the Scat cast crank (note: I would use the Scat I-beam rods regardless due to their strength, light weight, and low price).
 
It's just a play car nothing crazy I have others for "business" this one I'd be fine with 6500rpm take to like a cleetus and cara type event and just burn the tires off not scared to scatter parts on the ground
 
Guess I should add it has cheapo stock type cast pistons again .060 and a 750 holley brawler series carb
I have a couple wild built 340s but just wanna hear other variations of stroked 318s obviously i know the big mutha thumpr isnt the cam to make big power but like I said it's purely a play toy at this point something that sounds just nasty but will also pull pretty hard to near that 6500 range we have alot of LS folks around here that would just love a 318 to come to the party in a clapped put looking duster
 
Your going to need pistons, your stock stuff wont work because of the stroke difference
 
stroker pistons are a must as they have shorter pin heights to compensate for the taller stroke of the crank. dont want to shove a stock 318 piston that is >.120 higher up into the combustion chamber! I fyour not cared of scattering parts, the Eagle cast cranks are cheap and the amount of breakage reported on these divided by the amount sold is probably in line with the rest of the cast cranks out there. Gonna PM you.
 
Josh owen said:
Wasnt sure on that since they have valve reliefs
Click to expand...

it is not the valve reliefs....it is the compression height on the piston that must be changed..

the 4 inch stroke usually want compression height around 1.46 ish.....and the 3.31 stroke CH is around 1.82....
shorter piston is needed to keep the piston from hitting the head....plus they come out alot lighter too
 
Im not scared to alot i don't know it all that's for sure thank you everyone keep the Intel coming and build ideas
 
Hey I have a stroker motor too. It's a 408. :)

20210704_210216.jpg
 
Josh owen said:
Hey guys im looking to build another small block for my 71 duster, this ones going to be different than my others this ones kind of a crazy no F given kinda build, it's a 318 .060 over speedmaster aluminum heads, big mutha thumpr cam, air gap dual plain intake. my question is what stroker crank and rods would everyone recommend it Is a 4 speed car as well 3.55 rear gear again this is not to be serious like my other cars, this is looking to be high revving fun looking for multiple opinions and why
Click to expand...

High revving + stroker = high piston speeds = +++$$$+++ parts.

Talk to the piston, rod, pin, and ring manufacturers about piston speeds.

Use clay on the piston-valve clearance checking.

Just my thoughts on the matter.
 
Don't know how far you're wanting to cheap out, but, along the lines of the old Speed-O-Motive 350 LA Mopar.... They used a 318 block .030 over with 360 crank with the mains ground to 318 size and the old TRW forgings and milled the tops to zero deck, being they had .300 inch of crown material. But, with cast pistons one could use Sealed power 285AP cast pistons (1.72 compression height) for a .033 out of the hole dimension factoring in a 9.6 deck height. So with selection of the proper head gasket thickness (Felpro 540 SD Magnum gasket with a 4.06 bore would work well at .055 thick compressed as long as the fire ring doesn't hang out into the chamber) you could come out with piston to head clearance close to a pre '72 340. Balancing involves taking weight out of the crank. Now, I'm not saying it's going to make the same power as a 3.79 or 4 inch crank stroker does but you would probably have enough compression for race gas and it would still rev pretty happily. I imagine it would certainly good enough for a "showing out / tire show type of car".
 
Now that is a heck of an answer, they are cheap sealed power pistons from an ebay 318 truck full engine kit from ebay like I said it's all low budget minded junk incase i make junk with it its the new trend and I wanted to jump on board and try it to. I have not even started on the block yet the parts I listed above is what I have laying around right now for it so shooting for the budget aspect I'm going to he using what I have left over i am leery on the .060 on the 318 BUT we shall see what happens i would like to pump 75 or 100 shot of laughing gas to it just for fun as well in the future
 
Also, even though those sealed power pistons are cast, they are surprisingly strong. Certainly strong enough for a 75hp shot of spray if you provide adequate ring gap and piston to wall clearance, and as always with nitrous, avoiding detonation is paramount. What are the cc's of your J heads you have around, and what do the chambers measure across at the narrowest point? I'll go ahead and figure out which head gasket you need and the compression on the 3.58 stroke engine if you can get that information for me. If you were closer, I would have you in 318 hydraulic roller cam block that the stock bores would torque plate hone back to round in and a 360 crank that needs turned before you could blink.
 
Okay, thanks! I remember where you mentioned that now, don't know how I got that mixed up with J heads. That makes things a little more difficult on the head gasket but not impossible. Going to have to run a thick MLS gasket and get the decks finished to a fine RA to run them with the pistons out of the hole that much. So the head gasket cost or availability may make it impractical at the moment. This Cometic would afford .053 piston to head clearance at a 9.6 deck, though.
DODGE Cometic C5622-086 Cometic MLS Head Gaskets | Summit Racing
 
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