360 magnum to 408

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dustoff440

dustoff440

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Is it possible to put a 4 inch stroker crank in a bone stock 360 magnum without any more than grinding for clearance? Id like the extra cubes but don't need the custom pistons and rods as I probably won't turn it more than about 5700 rpm. I had heard that you can't do it on an LA but that you could on a magnum. If this will work which inexpensive crank is best??? Thanks
 
The crank and pistons have to be changed with any stroker engine. Otherwise the pistons will go through the head!
 
Whoa, it's not that easy buddy! Slow down. lol Think of what the extra stroke does, more piston travel right? So it is mandatory to have shorter pistons. I would suggest getting a complete stroker kit with crank, rods, pistons, bearings, and rings. Expect to spend a couple grand on the rebuild to a stroker...
 
mopardude318 said:
Whoa, it's not that easy buddy! Slow down. lol Think of what the extra stroke does, more piston travel right? So it is mandatory to have shorter pistons. I would suggest getting a complete stroker kit with crank, rods, pistons, bearings, and rings. Expect to spend a couple grand on the rebuild to a stroker...
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....Not including the machining on the block that will be necessary which in the best case could cost another 400-500 bucks minimum.

That's a bore/hone/cam bearings etc etc, and possibly a line hone if you need it.
 
dgc333 said:
A fully balanced kit from Hughes is $1700
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Shipping costs as much as a decent timing set too.
Hughes or IMM would be the place to go.

I personally prefer IMM since Brian will call you on his own accord to keep you updated and informed on everything as well as making sure you thought it all through and have everything you need.

This is not taking anything away from hughes though since my experiences with them have been good too.
 
plumcrazy704406 said:
magnum blocks are 89' and up?
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92 and up for the 5.2 and 93 and up for the 5.9. An 89 block would be an LA roller cam block, the difference being the 89 would still have provisions to pump oil to the shaft rocker system.
 
i just did the 408 on a 95 magnum block. When i was building the motor, i had to grind several areas because the rod bolts were hitting the block. Only thing i kept from the magnum motor was the block and the rods. i put arp rod bolts in.

you'll want to get new pistons since you'll probably bore the cylinders out to make sure they are true and round.

you'll definitely like the extra cubes. i've only put about 10 miles on my motor and haven't pushed it hard but i can't stop smiling.
 
71dustar said:
i just did the 408 on a 95 magnum block. When i was building the motor, i had to grind several areas because the rod bolts were hitting the block. Only thing i kept from the magnum motor was the block and the rods. i put arp rod bolts in.

you'll want to get new pistons since you'll probably bore the cylinders out to make sure they are true and round.

you'll definitely like the extra cubes. i've only put about 10 miles on my motor and haven't pushed it hard but i can't stop smiling.
Click to expand...

The nice thing about the SCAT I beam rods is you dont hae to do any clearancing. I had plenty of room to spare.:cheers:
 
I had an offer of 325 for an MP stroker crank new, and had some one else mention a set of KB pistons that would do the job which were under 300 and if i use the stock rods with arp bolts with machining and balancing around 600, rings, gaskets, bearings would bring it to about 1700 which is right around the price of a kit only. Also after much thought on this if the pistons would hang .120 out the hole with stock pistons then the crank is not really a full 4 inch stroke so part of the stroke is in the 1/8 inch raise in compression height so.. the crank is actually a 3 7/8 inch piece. Im not really suprised that you cant just buy the crank only and install it with out the "matching" pistons. If anyone knows of a crank that will just bolt in without having to buy pistons I'm all ears.
 
3 7/8 is 3.875....never seen a mp crank with that stroke...4 inch yes...3.79 inch yes..

as far as the pistons being out of the hole...it is in the math...

the 360 has a deck height of 9.600 approximately...

rods are 6.123

stock 360 pistons have a compression height of 1.66

the math.... 1/2 the stroke of 4 inch is 2 inches...plus the rod 6.123 plus the compression height 1.66....is 9,783

9.783 - 9.60= 1.83 ...the piston will be 1.83 inches out of the deck...it will be hammering the head...

you need pistons with a compression height around 1.45 for a 4 inch crank...

3.79 /2= 1.895 + 6.123 - 9.60 = 1.58 compression height pistons are needed for a 3.79...

stock 360s are 1.66....again...the pistons will stick out of the bore...
 
You can get a forged internally balanced kit for $1642 (or $1809 with all bearings included) from flatlanderracing.com
K1 forged stroker crank
K1 forged H Beams
Wiseco Pro-tru forged pistons

Seems like a killer deal for what you get

They seem to be supre cheap on the K1 stuff
 
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