To stroke it or not that is the question

"Hello all gear heads-
I am a

"Hello all gear heads-
I am a fan of the longer stroke, I know, so is my wife. Anyway, the stroker kits available for the LM318 has me thinking...why not? Anybody done this yet and what do I do for the counter-rotating engine? I was think about using the stock camshaft and just going to a 1.6 ratio roller rocker and maybe a hydraulic roller lifter retrofit to free up some frictional losses. What do you think? Any ideas is appreciated and even the odd joke or two is cool by me. I have a thick skin and I did buy a fixer upper. So I think I want to soup it up too while I am at it. Thank you for your input."

"Hey Mark,
Welcome aboard.

"Hey Mark,
Welcome aboard.

I do know that reverse rotation can be achieved in the gearbox.
My neighbor has Velvet "V" drives, and its in the back box gives him the counter rotation.
Might be easier & cheaper. than trying to come up with custom, custom crank.

Fred 156-M"

"A 318 can grow to 400 cubes w

"A 318 can grow to 400 cubes with a longer arm, but going to a 360 instead would be a lot cheaper.

Jeff"

"The old saying is, "There

"The old saying is, "There ain't no replacement for displacement".
If it's a stoker crank, it's already custom. Custom pistons are also needed. There are a number of kits available with crank, rods, pistons, rings, & bearings. Make sure you machine shop checks everything - diameters, taper, indexing, balance. Most, if not all, kits are souced from China so expect to spend some $ to get it all corrected. More expensive kits will need less or no correction.
Since the aftermarket cranks do not have the knurling for the rear main, an OEM rope seal will not work, a neoprene real seal must be used. This allows the crank to run CW or CCW.
The 1.6 rocker will give a little more HP but it is not cost effective. A little pocket porting on the heads would give the greater gain for the same cost.
I've only stroked RB Chrysler motors. My first was in 1989, I used an old Mickey Thompson crank from the '60s! 4.35" bore, 4.25" stroke, makes a 505" motor. The RB block required a bit of rod clearance grinding, new RB kits are going with a BB Chevy rod journal size and clearancing is almost all but eliminated. The most common LM318 stroker crank will have a 4.00" stroke, punch the block +.030, you'll have a 390" motor!"

"I've heard that the 318 M

"I've heard that the 318 Marine versions have fairly restrictive airflow in the cylinder heads. For Example, smaller valves were used, specifically to de-rate the motor so that it lasted longer. (I've heard, anyway) Similar tricks were used on the Industrial versions. So there might be opportunity to use higher-performance heads, and it might be easier than re-stroking."

Correct. The heads are deliber

Correct. The heads are deliberately restrictive to improve mid-range torque. (Think truck engine.) Going to higher performance heads is the single greatest wake to improve hp on a marine 318.

Jeff

"Hey, after doing some more re

"Hey, after doing some more research...I found that the LA/LM (light Automotive/light marine) engines have allot in common. The marine versions were assembled by hand and of HD parts. The heads are restrictive to enhance torque and the camshafts were where the timing differences on the reverse rotation was accomodated. As far as I have read the crankshafts are the same. Same part no and so forth. The 360 heads with larger valves (J heads) are the low cost ticket to better flow without the torque suffering. As for the pistons, they need to be matched to the crank and the stock rods can be reused if 450 hp is not exceeded. I know what some of you are thinking...that is why I am staying with the stock camshaft and just using a ratio rocker to give it a little more lift and not affect the duration that much. Plus that make them in Stainless steel. Yeah! I wonder what this combo will dyno out at, hmmm.
v/r, Mark"

All smart moves--especially if

All smart moves--especially if this is a reverse rotator. Trying finding a hotter cam for one of those!

Jeff