it's not a L series its a L head and it seems to be the least modified motor out there, well some times you'll see a couple extra carbs and some zomies but nothing super wild, no EFI or forced induction and only on super rare occasions will you see them turning at 6000rpm. well 6000rpm is really fast for a motor with a 4 1/2 in stroke that is usually governed at 3400. after months of trying to gleam hot rodding tips out of others with the same motor to no avail i thought i would try here.
what im trying to do is make up for the power loss i got after changing the gears on my 52 dodge m37 from 5.83 to 4.89 about 20%.
the motor in my truck is a chrysler 251 L head also known as a flathead. in the stock configuration it makes 200 foot ponds of torque and 105hp @ 3400 with its 6.6to1 compression ratio. everyone i talk to says why bother just install a small block but being a datsun guy i love inline's and im always impressed with the power you guys get out of your L's and KA's.
I managed to get my hands on the holy grail of L heads. the chrysler crown marine 265. :

with its 4.75 stroke 3.436 bore stelite seats, sodium filled valves, bronze valve guides and huge barring surfaces it has a lot of good things going on. the block im working with has been decked and is a standard bore to give me lots of meat between the cylinders. it has been converted to full flow filtering. line bored on the mains, three angle grind, stainless sodium exhaust valves and a shadbolt cam(profile unknown) Im going to send the crank, rods and flywheel out to be balanced. I have some good quality chrome rings and some "roto caps" for the valves(not so good for gas but apparently good for propane?)i have spare rods from less stroked motors and can increase the rod length if i can find a piston that will work. here is a thread i made on another forum packed with all the info i could find along with pics of what i have:
http://www.g741.org/PHPBB/viewtopic.php?f=3&t=5180 even with running twin carbs and exhaust i dont think it will make up the 20% im looking for. even if I bump the compression to 9to1 i dont think i will see the gains im after.
So being a datsun guy my first thought was
lets add a turbo. I know what I'd like it to be like but don't know how to get it there. its in a 6000lb 4x4 that i bounce around in the bush i was thinking about propane to get away from float/vent problems on severe grades also with the long stroke it should run better on high octane with its slow burn and i wouldn't have to build a box for the carb. there is lots of room under the hood for plumbing and coolers. with that being said and knowing how i drive my truck the turbo has to work a certain way (i think). the turbo should kick in real fast like @ 800rpm to 1200rpm and run out of poke by 3400-3600rpm so im not tempted to keep spinning it up. then when i take my foot out of it it should dump really fast.
any help on this project would be greatly appreciated
cheers
Robyn