Thread: 360 .040 over

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I got a 360 .040 over and i would like to know what i can do to make a 408 ill find out what heads and cam are in it but can you guys tell me what i need to make a 408 with this block already .040 over?

OOPS, too late to make a 408. That show was over when the bore exceeded 4.030". But at + 0.040", you can make a 410.

The main player is the Mopar 4" crank. Heavy duty cast, part #P5007258 for just under $400 or forged, part #P5007254 for just under $1000. You can use stock 6.123" rods or opt for aftermarket upgrades. Some piston manufacturers such as Keith Black will require narrowing the pin end of the rod to 1.000" to fit in their hyper pistons and will require machining of the piston squish pad to mate with your heads (see editors note below). Diamond Racing Pistons makes either flat-top or dished pistons for the 360 stroker...
http://www.diamondracing.net/MoParSection.pdf
http://kb-silvolite.com/performance....etails&P_id=23
This KB piston will generate a 10.3:1 static compression ratio with Edelbrock 58cc heads and +0.030" overbore. Slightly higher with a +0.040" or +0.060" overbore.

I ran across this verbage written by Bob Doty......
"The early 360 blocks (71 to 73) will accept an oversize of 0.080". This is due to the fact that the 340 and 360 shared the production tooling until the demise of the 340 in 1973. The standard bore size of the 340 was 4.040" and the 360 was 4.000". There have been successful bore jobs to 4.100" on the early blocks."

Editor's Note: Being basically cheap and with plenty of time on my hands as a result of being retired, I refuse to pay someone to do something for me that I can do myself. This "machining" operation of the squish pad on the KB piston would go something like this if it were my motor..... I'd chuck up one of the old wrist pins in my bench vise and work around it with a fine-tooth file to reduce the diameter by a couple of thousandths so that the pin would slide in and out of the pin end of the rod. You could do the same thing with a strip of emery cloth, using it in a "shine your shoes" fashion. I'd install the crank in the block on bearings and assemble one rod to one of the new pistons with the slide-through pin. I'd install the rod/piston (no piston rings installed) on the crankpin (pick one, making sure the rod chamfer is at the fillet for that crankpin) and rotate the crank so that the piston is at TDC. I'd use a sharp-point scribe to mark the squish pad at the deck, then remove the rod/piston and disassemble. I'd wrap the piston in a towel and chuck it up in my bench vise and go after the squish pad with a course-tooth flat file until I whittled it down to the scribe mark. Pay attention and keep the file perpendicular to the piston skirt as you make a stroke. Repeat on the other 7 pistons. This will put the squish pad at zero deck and your squish will be determined by the thickness of the head gasket you use. Squish will work anywhere from 0.035" to 0.050", so using a gasket such as the Fel-Pro 1008 would put the squish at 0.039 if the squish pad is at zero deck. If you take a little too much off the squish pad, it's OK. If the pad ends up down in the bore by as much as 0.011", you'll still have a 0.050" squish with this gasket.....Just make sure the pad isn't above the deck.....
http://store.summitracing.com/partde...8&autoview=sku

Same procedure for narrowing the pin end of the rods, be careful to keep the surfaces parallel and go after 'em with a file. Now the preceeding explanation is for the rodder who has ZERO machinery, no lathe, no mill, no drill press, etc. but might have a little coin to purchase a couple of top-quality Nicholson files and is using a head such as the Edelbrock with closed chambers. If my procedure scares you, then scribe the squish pads and take the pistons to a machine shop and lay down some green. Also, take all the rods and one piston so the shop can narrow the rods. But you should understand that fellows have taken off their belts, cut a piece off and used it for a rod bearing to limp home, so this stuff ain't rocket surgery. The KB's are fairly cheap, but if you're gonna have to spend money at a shop to make 'em work, you might be money ahead to pay a premium for pistons that will work without whittlin' on the pistons and rods. If you're using iron production heads with an open chamber, install the piston/rod the same way and bolt the head on without a head gasket. A couple of bolts closest to the cylinder you're checking is all you need. Turn the motor through a complete revolution. If the squish pad doesn't hit the head, you'll be good to go with a gasket in place. If it hits, remove the head and file the squish pad some. If you're careful, you can do this with the piston in the bore, but don't let the file touch the deck surface or you'll be taking the block in for a decking operation. Repeat until you have clearance through one rotation of the crank. The head gasket will provide the additional running clearance you'll need.


This is another motor that deserves to have a DynoSim run on it. I'll bolt on some Edelbrock aluminum heads and do that later today.

A guy might be better off just to use a stroker kit like this. I'm not advocating buying anything off ebay, but this seller has some history behind him and the price looks attractive....
http://cgi.ebay.com/ebaymotors/SB-MO...2em118Q2el1247