stock piston composition ?

[RMS]

is there a metallurgist in the house? how good are the stock pistons? can they take more heat? will the piston live if i turn 0.25 off the top to enable me to run the longer 251 rod on a 265 crank(i have yet to cut a piston in half). the book just says Aluminum alloy. are they just that aluminum alloy or are they hyper eutectic?


is anyone running fancy coatings on their pistons? I imagine the pc-9 dry lube on the skirts would extend cylinder wall life. what are your thoughts? http://swaintech.com/race-coatings/

[Kaegi]

cant answer the question but I have one. What will you gain by doing that? I have driven 265s and they are beasts compared to the smaller flatheads

[RMS]

im hoping to increase the rod ratio to get some gains out of my build. i have zero dollars invested and everything i need to complete the build including a fully machined block. i can afford to do a little extra. im looking to get 20% to 25% gains compared to my 40over 251 @ 8.2-1

I have driven 265s and they are beasts compared to the smaller flatheads

could you expand on this? I have only driven 251 powered m37s

[T. Highway]

RMS,

I think you want to call George in Penn state.

He has hot rodded flathead Dodges for ever. I won't post his number here but if you PM me I'll send it to you.

When I talked to him he was a wealth of information on cams and shaving heads. He stocked the needed parts.

Bert

[Kaegi]

im hoping to increase the rod ratio to get some gains out of my build. i have zero dollars invested and everything i need to complete the build including a fully machined block. i can afford to do a little extra. im looking to get 20% to 25% gains compared to my 40over 251 @ 8.2-1

I have driven 265s and they are beasts compared to the smaller flatheads

could you expand on this? I have only driven 251 powered m37s

is rod ratio another way to say lighter pistons? do you have the 265 rods? I would probably jus shave head and put in a cam.
The 265 has the longest stroke of all the light duty flatheads. the 230 is next longest. they all run WAAAY better and drive like a modern vehicle when you shave head and put in a cam designed for modern fuel. the stock cams in flatheads are designed to run on 70 octane! so when you rn 89 octane it is rocket fuel in comparison. upping compression and cam really works well. I have only built them that way. I have never built and supercharged highly modified flatheads but others have and there is lots of possibiities. But, with balancing, porting, cam and shaving you have the basics covered then other things could be added. here is head millling chart someone posted recently.

[RMS]

is rod ratio another way to say lighter pistons

I had never heard of rod ratios before reading a post @ http://www.inliners.org/ubb/Forum8/HTML/000021.html i will let hudson tell you :

we will pick up on the page were active inliner Hudson gets into rod ratio's
"hudson"
The rod lengths in these engines, both series, differs in length according to stroke. The longer the stroke, the shorter the rod. Its possible to increase your torque output at lower rpms by simply swapping rods with a shorter stroke engine and shaving off the piston head a smidge. A very good rod length/stroke ratio is around 1.75:1. If you check out the rod lengths vs. stroke in most flatties - you'll find something close to this number, that's why they seem to lug so smoothly at lower rpms than their bigger cid ohv cousins, who consequently run ratios around 1.55 with not much room to improve.

In the tractor world, Minneapolis Moline tractors built pre '55 all had stock rod ratios of 2:1, this is the ultimate rod ratio - my stock 40 hp Moline 4 cly. can show up a 66 hp IH 6 cly. on the pto any day of the week grinding corn @ 1000 rpm less at the

we pick back up with hudson farther down the page

"Hudson
The 1.75 is not ideal, but the reasoning behind calling it ideal is that the greatest increase in torque is attained at this ratio. In other words, if the torque increase due to rod length was represented in a curve, 1.75:1 would be a short plateau at the end of a steep rise. The apex would be at 2:1 with less relative rise than up to 1.75. Any increase beyond 2:1 being very small and impractical with most engines.

Why does this become so important? Its part mechanical physics in relation to rod flex and power transmission from reciprocating to rotating, part hydrodyamics in relation to cylinder filling and scavenging, and part pyrotechnics in using the combustion gases to their best potential.

The basic physics of the matter: the longer the rod in relation to stroke, a lesser angle is present between the centerline of the cylinder and the centerline of the rod beam at any point in its travel: as it deviates from vertical at TDC and BDC. This characteristic allows more direct transmission of power to the crankpin, via the longitudinal length of the rod. In shorter ratio engines, more of this transmission is transferred to the lateral section of the rod, using up power by attempting to force the rod to bend rather than push the crankpin around.

Another enormous benefit is the increase in piston dwell near TDC and BDC. As the ratio increases the amount of crank degrees that the piston dwells near the terminal ends of the reciprocating path will increase also. In mechanical perspective, this allows the crankpin to change the direction of the reciprocating mass under less resistance. The crank also rotates more degrees past tdc before piston direction changes and reduces the relative piston speed at these two points. Put these together and you have a rod acting more directly against a crank that is already past TDC by more degrees per unit of piston travel and moving the piston slower at critical points in its travel.

Hydrodynamics? Gases and fluids share the same phyical properties with the exception of compressability. We express fluid/gas flow in CFM. We often catch on to the volume, but overlook the function of time in this expression of measure. To increase the amount of piston dwell at BDC during the intake stroke, is to allow a more complete filling of the cylinder at peak demand by allowing more "time" for the cylinder to fill at its maximum volume. In addition, to increase piston dwell at TDC during the exhaust stroke, is to maintain the cylinder's minimum volume longer for a more complete expulsion of gases through the exhaust valve. Although these properties do not change the cfm capacity of a group of cylinders, they definately change how effective an engine employs its theoretical capacity. This will effect the VE% in the classic formula ((CIDxRPM)/3456)VE%=CFM.

Now, we have exhausted the spent gases more completely, taken a denser charge into the cylinder - lets examine the pyro part of longer ratios. Again, we are dwelling at TDC longer with the wider ratio. This allows the combusting gases to reach more of their potential in a smaller space over a greater amount of time, and crank degrees. This really conserves the maximum force of the combustion at is most advantageous point against the piston head. Power is really only transmitted at its maximum at this point as the change in cylinder volume during the power stroke takes up the potential of the explosion rapidly.

The benefits of this are enormous, just ask the sbc builders how much improvement they get from just .300" of rod length. The first measurement I take on any engine is deck height above the mains' centerline. The stroke is then determined based on available rod length and piston combos to effectively use the available height.

Offsetting the wrist pin center in the direction of crank rotation will accomplish the TDC effects of the rod ratio, but speeds up the BDC end of things. In high compression and forced induction engines, the increase in lateral force on the rod, due to the exaggerated angle during its upward stroke, can bite you on the touche'. But, all things considered, if I had to build and engine with a ratio less than 1.55 - I would seriously consider offsetting the wrist pin. Offsetting the wrist pin makes it important to degree your cam closely, as the crank position at TDC will change - altering everything from cam phase to timing marks by a smidge.

You fellas have a good day!

Hudson"
Active Inliner
excerpt from http://www.inliners.org/ubb/Forum8/HTML/000021.html ( hope I quoted that right )

I know its a lot to take in.

having three choices of rods at my disposal 265, 251 and 218 i thought i would give it a try. assuming i can find a piston that will work and at the same time give me better rings. assuming that rings on a modern piston will seal better and wear better in this application. a slow spinning torque master.

the stock cams in flatheads are designed to run on 70 octane!

I had never considered that cam profiles changed as did gas. very interesting, now i know why new grinds offered for the 37 increase power and torque @ the same rpm. i have a shadbolt cam with an unknown profile i should take it in and have him tell me if its right for the job.

But, with balancing, porting, cam and shaving you have the basics covered then other things could be added. here is head millling chart someone posted recently.

im the op

if my cam has a better profile i will only have to shell out for balancing. i have a selection of heads to chose from. one is even freshly planed and covered in cosmoline. i have yet to cc them.

[Kaegi]

that is intersting educational stuff. thanks for posting it. But I think the point of all that is to gain more torque. I personally dont think you need to look for torque gains on a 265! they have a 4 3/4 inch stroke as it is. they are torque monsters. They idle smoothly at 325 rpms. I would run stock 265 cranks and rods, balance evrything. I dont think modern pistons an rings will seal any better than stock unlss you splurged on custom racing type parts.

did you calculate the rod ratio of a stock 265?

I saw a youtube video of early power wagon with 265 and it won its class in the sled pull up against big block chevies and a bunch of other V8 trucks. wasnt even close! even a218 crankshaft is a huge mass of weight swinging around making torque at very low rpms.

[RMS]

did you calculate the rod ratio of a stock 265?

stroke X rod length = R

i have not checked the rod lengths my self. the info i have is from the internet
265 stroke is 4.750 the numbers i can find say the rod length is 7.75 giving a 1.63to1 ratio. the 7.875 rod = 1.66to1 a 8.0 rod =1.68to1
251 stroke is 4.50 the numbers i can find say the rod length is 7.875 giving a 1.75to1 ratio

the stock piston pin height that i can find is 1.978 so to run the 7,875 rod i need to take 0.125 off the piston if there is not enough meat. if I need a different piston i will go with the 8.0 rod and a piston with a pin height of 1.728

[Kaegi]

you could just run it stock for now and then if you come up with the parts switch them with engine in the frame and see if there is any difference. The big crankshafts in these engines are always making torque. the crank in a mopar flathead six weeighs more than a straight pontiac crank. I would guess the rod change wouldn't be noticable. I think you would be impresssed by the performance with stock rods and pistons and modern cam, higher compression, balancing, porting. but let s know what you do will be interesting to read about.

[Monkey Man]

Bolt a 251 straight in, a gear better on the road, keeps the look and is a bolt for bolt changeover bar the filler tube and distributor plus I think the front mounts may need tweaking a bit as it's a whisker longer, OR, whack a 273, 318 or 360 CUI V8 in there but new axles are recommended for this mod. The only thing that limits mods to your truck mods is your imagination and budget, I have seen 251 CUI engines set up for drag racing, mega $ put into them and spectacular fails when they do go bur awesome output when they are going, another less thought of option for an M37 is a slant 6, almost bulletproof, shouldn't be too hard to get and it should be an easy mate to the origonal drivetrain (an auto would be nice though).
Maybe I am off track with the thread but the basic 230, although reliable may not be the best option for tweaking, it would also be a good move to contact your local hotrod club and see what info they have to offer.

MM

[RMS]

Bolt a 251 straight in

I'm already there mm and have close to 30,000 very hard miles and i have had my speed'O pined a couple of times at 65 reading the stock 5.83 tcase gear running with 4.89s reaching a whit knuckle velocity of 78mph verified with a gps

i have zero dollars invested and everything i need to complete the build including a fully machined block. i can afford to do a little extra. im looking to get 20% to 25% gains compared to my 40over 251 @ 8.2-1

[Monkey Man]

Apologies RM, I had read the thread and gotten it into my head you had a 230, not sure why, maybe I need to read a bit more carefully huh??
I have a 318 V8 in mine, La block but the truck version, a lot of parts are not interchangable with the car engine but I am unsure why, could be simply be piston to valve clearances or something. My truck had a 251 in it, I always thought it was a 230 but when we yanked it the numbers just didn't add up, it's only recently we found out it was a 251 after doing a number search and I think someone waaaay back in the "bigelectric" days told me it might have been a 251 based on simply how well it pulled up hills. Moot point after the rings cracked and stood up in cylinder 6, totally stuffed the bore as it gouged it out 100 thou plus and I was left with the conundrum of repair or replace, well, replace was the way to go given it was $2K+ to repair the Flatty or $1K to fit a V8, history shows which way I went.
If you want more go, maybe a pertronix fuel injection kit, not too expensive and makes for better fuel metering and delivery plus it's programmable, cheaper option is an electric fan and remove the mechanical one, better lubes etc., as you know there are hundreds of ways to save a little power and they all add up but some are not very practical but it's old school thinking you need, hence the hotrod club suggestion plus I saw it on TV once, somewhere in the US is a drags club dedicated to old tech, flatheads in particular, maybe look them up and have a chat to someone in the know.
P.S. - post pics of what you come up with and achieve

MM

[RMS]

I had read the thread and gotten it into my head you had a 230

no worries mate

its stories like yours about failing rings and pistons that have me asking questions. i read many other forums and try to share the knowledge i discover that can be applied to our beloved M37's.

from what i can gleam out of the internet is that long block Chrysler engines are tougher than short blocks, but the 230 is way more common. stories ive heard about chucking rods and flat heads littering the autobahn after ww2 were probably about the short blocks. the short block with its offset rods dominated the American car market compared to the long block which was mainly a industrial and marine motor it was in some large cars and more common in Canadian cars . i was not familiar with the short blocks till i picked up a 230 powered m37 with a couple spare motors. i was surprised to see how small the bearing caps were on the 230 compared to the long block rod and main caps of the 251/265. granted the 265 crank weights 90lb

maybe a pertronix fuel injection kit

i had considered direct injection but due to the orientation of the intake runners and valve placemen on this L head it would be hard to get an injector to point up at the valve. throttle body injector/s for the hassle seem like nothing more than a computer controlled carb. that adds more parts that could fail in the field. plus a injected vehicle that could sit parked for weeks or months at a time does not sound fun to maintain. at least with a carb you can vacuum the crud out of the bowl and poke out the jets..... im starting to dislike gas, it stinks, has a 6month shelf life and is expensive. I'm going propane its cheaper, never goes bad, and if the end of the world comes it would be easier to convert to wood gas. I guess i've walked faraway from the box this build will get propane if I cant get it <9to1 with out shrouding the valves. if I can't get the cr up I will be running at 7.5to1 with a turbo making no more than 8lb of boost(the boost regulator would spend most its life around 3-4lb)

it was $2K+ to repair the Flatty or $1K to fit a V8,

i spent $2500 to rebuild mine its .020 on the rod 0.30on the mains and each piston skirt had a hole on the thrust side. iv been racing dump trucks and supper bees up hills for 8 years and i'd like to be able to beat'em when their empty for the 16,000 i have put into m37s over that time it is still less than the depreciation of a new truck over the same time.

[RMS]

with pistons and the 265 build on my brain ive been thinking a lot about the combustion chamber. I've seen a few different head configurations over the years and I was wondering if it a $1k head is cost effective and whats the best head?

as there's no numbers listed from dyno days put on by.....lets say: "the rubber crank crew" im left with only hear say. I have noticed that many aluminum heads have the spark plug moved from above the valve to between the valves. also the ramp length, depth and angle changes.what do these small changes do? so I find myself researching the finer points of the internal combustion engine, such as flame propagation and travel. here is an open source book with some light reading http://www.intechopen.com/books/advance ... chnologies