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the Chrysler L head(flat head) seems to be the least modified engine out there. the lack of info surrounding modifications is astonishing.
lets keep what little info is left alive.
i know many of you will say "there's no point modifying a flat head they have rubber cranks and throw rods" "after ww2 the autobahn's were littered with flat heads with rods sticking out the side of the block" " "just put in a small block".....

if your like me and you like your flatty please share your knowledge before its lost to time.

my very rare stock cast manifold found on heavy dodge trucks .
m37 owners with stock military Lhead's regardless of having a 230 short block or the Canadian 251 long block are ahead in the modification game. our military blocks have the thickest castings (after the Chrysler Crown marine blocks). we also get a brass (not steel)water distribution tube, stelite seats, sodium valves, and bronze valve guides. however the stock 6.6:1 compression ratio, heavy 6 blade fan and restricted induction ties up many of our available ponies. so i ask how can we safely harness more power?
the most common mods i hear talked about are duel carbs, duel exhaust, high compression head and a four blade fan. it's hard to come by improved oiling and cooling methods for our motors. well except bumping up the oil pressure by adding an extra washer to the bypass. interesting to note that in the mid 50s Chrysler came out with the full flow oil block. can a non bypass block be modified to full flow oiling?

i have a standard bore(3 7/16th) 251 civilian dodge block that has some interesting mods to improve oiling and cooling
in the pic you can see that the previous owner drilled out bosses for extra oil passages (in red) and coolant passages (in blue). i have done my best to label what i know

i imagine he was converting this block to a full flow block but i cant understand all the plumbing any help would be appreciated .

hear are some graphs for net performance curves on the 251and 265 L head. first is a graph from 1947 when the 251 had a 6.6-1 compression ratio (like in the cnd m37)

i dont know when the change was made but the 251 was bumped up to 7.1-1. it is interesting to see the improvements in torque hp and specific fuel consumption by bumping the compression by .5
it would be interesting to see the net performance curves for the last years of the 251 when (to my understanding) went to 8-1 in some cars

i was under the assumption that bigger displacement equaled more fuel consumption but according to this graph the 265 has a better specific fuel consumption over the 251

can anyone provide graphs for 251/265 with dual carb/intake or with a four blade fan. any graphs on the 230

another interesting mod on the 251 civi block is the 3 angle grind and rotocaps

are chrome rings a good thing ?

i found a good site http://www.inliners.org lots of info. here is a good thread from their forum http://www.inliners.org/ubb/Forum8/HTML/000021.html "I've seen our 230 hit 6000 with the single carb"(

i made some revisions to my earlier posts and labeled the pics.

full flow oiling mods to the Chrysler flat heads are not as hard as they seamed and making this post help me work it out.
drill and tap two bosses. remove crossover pipe then plug the two holes. a couple of high pressure fittings, hose and a spin on oil filter assembly that uses a common filter. i like the ones for a ford 302(fram# PH8A) they also works on my Datsun L motors.

i want to take my Lhead from this: http://www.youtube.com/watch?v=4zWFIE0T ... creen&NR=1 to this http://www.youtube.com/watch?v=QfDw94-f ... ure=relmfu well maybe not so much cam

Thanks for those pictures RMS. My truck already has a four bladed fan, and I have thought about an Offenhauser dual carbed intake, but I can barely tune one carb as it is. I am better off with a more stock motor, although I would bolt on a higher compression head. Last time I checked I had good compression on all cylinders. I might be pulling the head off soon though. I just was checking my oil, and I noticed a butter like substance on my dipstick, and on my oil filler cap. Literally, it is butter colored and creamy. Is this a water/coolant emulsification? I am hoping it is head gasket related, and not a cracked block

sounds like a head gasket. i have never seen water in my oi all my hg failures came on quick. from noticing small white poofs of steam to total failure with coolant pumping out of the tail pipe. my local part stores only stock felpro's. i find that they blow between bores right at a water passage, quickly eroding the composite. this erosion usually happens over 50miles. i am told the old school double sided copper asbestos type would weep if not properly and constantly re torqued for the first 500miles. what type of gasket are you running? if you do, how often do you start your truck without allowing the motor to get to full temp? condensation is a killer.
here is a chart that shows how much meat can be planed off the head to increase compression
http://www.classiccar.com/forum/discuss ... ad-six-/p1

I am not sure about the gasket in there now. I was assuming any replacement would be copper. I will have to do some research on my options

Just went down to the closest napa, over 45 miles away. They ordered the exhaust and head gasket kit. From the pictures it looked like a copper gasket, but it was hard to tell.

Would deleting the heat riser be of any benefit? I ask because it seems that most newer engines, and the aftermarket intake/ exhaust manifolds for the L230, seem to try and use as cool an air/fuel charge as possible. I'm not sure though as the last engine I really worked on was 10+ yrs ago with my dad doing a fairly stock rebuild of a chevy 235 v8.

jimmy_stikx wrote:Would deleting the heat riser be of any benefit?

on a propane conversion it worked very well there was a very noticeable improvement on power and economy. link to thread: http://www.g741.org/PHPBB/viewtopic.php?f=3&t=4703
there seems to be mixed feeling when it comes to gasoline. one person will say "the colder the better, dragsters will often pack dry-ice around there fuel lines......". where on the other hand charles nelson pogue had other ideas.

hopefully someone will jump in and brake it down for us

I dont believe that they had more rod prblems than anything else in real world use. I have 100s of thousands of miles on 230s over 25 years and never thrown a rod. when the racers tried to run them at 5,ooo rpms over and over they throw rods becuase of the offset pin to big end. the 251s and other longer blocks dont have an offset wrist pin so wind up a littel better. the crankshafts are super strong forged steel. the best improvements i have made is cam shaft and shaving head. and jetting a one barrel or going to 2 barrel. never had the 2 one barrel set up. idealy having both the bypass AND a full flo would be best but if you change your oil lots bypass is fine.

Kaegi wrote:the best improvements i have made is cam shaft and shaving head

im with you on shaving the head. i have not tried a different cam, yet. whose cam are you running and what is the profile ? did you lose any of the lug-ability (low end torque)?

RMS wrote:

Kaegi wrote:the best improvements i have made is cam shaft and shaving head

im with you on shaving the head. i have not tried a different cam, yet. whose cam are you running and what is the profile ? did you lose any of the lug-ability (low end torque)?

it depends on the truck. I call Delta camsahfts in Tacoma WA and discuss what the weight is and what I am doing with it. on my command car I ran a different cam than in my Weapons carrier. Command car never hauls anything so wet for higher HP. WEapons Carrier I hauled stuff so wen with wider and longer torque band and that results n moe HP as well. and another for a PW I restored for a client that crossed the scales at 7k empty. Delta can grind it how ever you want. less expensive than buying a new cam and you have endless choices. they like to talk cams if you call. been sendng them my cams since the 80s. very knowlegeable guys.