Will a 318 be ok to punch out to a 4.0" bore, cut a 360 crank to 340 mains, and build a stroker for a late model dirt car and hold 7K pluss RPM.

It could be done with the right 318 block. You need to have it sonic tested. Early blocks will be the thickest, I think they ended in 030 casting number and were produced from 67-71 or so. Another option if you wanted that bore stroke and main combo would be a poly 318 block with LA heads, they were very thick and have seen a few guys run them to 4.040 bore sucessfully, again get it sonic tested. Or another option would be a 360 with the crank turned down and spacers in the mains, but it would need very good bores to run at standard size. A 360 magnum block would be good for this purpose. A few years ago I had a bunch of 318s tested and only the early ones were any good, .030 wa about all I would have felt safe on the mid 70s and up blocks.

What we are planning on doing is running a chevy piston as there are a large variety of chevy pistons with all kinds of pin heights, and we can run a mopar rod with the small chevy pin size. Or we could even run a chevy 6.125 rod combo.

Just wondering??

Kasey

how many cubes are you looking for? how much $$ do you want to spend? some other thoughts, .060 over 283 pistons are .025" over 318 bore. 6" rods, 283 pistons and a 360 crank make a near or 0 deck stroker 318 that would be 348 CID (352 if you found .080 over pistons)....

or use some low comp cast 318 pistons, 318 rods, and 360 crank for a similar displacement.

Youhit it on the head, I figured a 348" stroker. Im glad you have the piston sizes now I dont have to work as hard figuring out the math.

Thanks

Kasey

well if you bore it to 4.0" and use a 360 crank you would have a 360,just use 360 pistons.

My concern is will an earlie 318 take a 4.0" bore, I dont want a weak thin block thats going to heat up all the time.

again, what's the budget, displacement limit, and what kind of RPM are we talking?

I'm not a fan of spinning a cast 360 crank to 7500 let alone for long periods.

W2s are the head alowwed, and we arent supposed to port, but :acid flowing" will be done. Oiling mods are going to be the normal trick mods, resizing oil holes, etc...

anyone make a 3.79" stroke crank anymore? .030 over 318 w/a 3.79" is 370CID.....

with KB forged pistons for a 4" crank and 6.25" rods, you have a short block with the pistons .010 out of the hole, diamond forged will be .002 OOTH....

or on the cheap, using .060 over jeep 4L pistons (3.935", 1.58-1.592 CH and .931" pin) and 6.125" chev rods will net you a 0-.012 out of the hole short block....but they have a 13-18cc dish in them....

The CI limit is a limit, we dont want to build right to that incase of a huge problem, so we would like to keep the 348-355CI range.

Kasey

I had a 4inch stroke 4 inch bore 68 318 ran real nice.

There is a guy on here with an even bigger bore bigger stroke 318 in his aspen.

If I was you I would just buy a steel crank for a 360 and put it in a 360, even .060 over will not be too many cubes. This will make more power because you valves will be less shrouded.

We dont want a 360 due to the large main bearings, We want a nice little buzzer, nothing with a crazy rod bore ratio, and no larger stroke than a 3.58 is allowed. W2 heads are it, 3.58 is it, and we can only run 1 intake, and it has to be a holley 2 bbl and make 450+hp to compete well.

Kasey

i have a brand new in the box mopar 3.51" forged crank,i'll take $350.00 plus shipping

I agree with dave, if you're limited to 3.58" stroke, you're better off using a 360. less valve shrouding....and if you only need 450-500 HP to be competitive, why do you need to buzz it to 7k+ RPM? why not build it for midrange power with a torque peak in the 4-4500 RPM range and a HP peak in the 5500-6000 range?