308 crank in a 262

51Comm,

Some of the major aftermarket piston manufacturers will do it, but I'd say you're looking in the neighborhood of $800-1000. Ross will make custom pistons, so will JE, and I have heard that Mahle will but not for sure on that. The good news is, they'll be forged, not cast. I've put a lot of custom pistoned stroker motors together, not Hudson though, and considering that OE syle cast replacement pistons aren't cheap for that thing...... It may be worth a try! The other side of the coin is, what, a 30 or so cubic inch gain at the most... I'd think a good heavy-breathing 262 could make up that difference.

Doh! You need six of them.... I was thinking of 8.

I don't know if I would advise that. First of all, if you cut the block deck surface, you're going to have to cut the piston top more, not less, as you will be decreasing the distance between the centerline of the crankshaft and the deck. Secondly, regardless of where you cut, with a stock piston the top compression ring is going to ride .125" higher in the bore. What is the piston head size for the stock piston, that is the distance between the top ring groove and piston top? Add this to the deck clearance of your particular assembled engine, which is measured with a deck bridge and dial indicator, and that's how much you've got to play with. If the total number is less than about .200, you're in trouble. .200 leaves only .075 at the top of the hole.

Next, running pistons out of the deck on an L head engine is bad news for combustion chamber turbulence, nevermind having to cut and reshape the chamber anyway. The intake charge will encounter a dramatic airfoil in the way, that is .063" of a piston edge sticking out the block. That will send the charge up to the roof of the modified chamber, slow down the turbulence, and cause all sorts of problems. Even on an OHV engine, running more than about .010 out of the bore is bad news. I'm not trying to be a buzzkill, but even if you can make it work, it's marginal results with cut-up cast pistons and butchered heads, when $600 sounds like a DAMN FINE deal for some FORGED Ross'.



While you're in there filling it with good slugs, put some for-real valve springs in it, a better cam, balance the reciprocating assembly to within 1/2-gram, and put it on the JUG!

jamcoats wrote:

I don't know if I would advise that. First of all, if you cut the block deck surface, you're going to have to cut the piston top more, not less, as you will be decreasing the distance between the centerline of the crankshaft and the deck. Secondly, regardless of where you cut, with a stock piston the top compression ring is going to ride .125" higher in the bore. What is the piston head size for the stock piston, that is the distance between the top ring groove and piston top? Add this to the deck clearance of your particular assembled engine, which is measured with a deck bridge and dial indicator, and that's how much you've got to play with. If the total number is less than about .200, you're in trouble. .200 leaves only .075 at the top of the hole.

Next, running pistons out of the deck on an L head engine is bad news for combustion chamber turbulence, nevermind having to cut and reshape the chamber anyway. The intake charge will encounter a dramatic airfoil in the way, that is .063" of a piston edge sticking out the block. That will send the charge up to the roof of the modified chamber, slow down the turbulence, and cause all sorts of problems. Even on an OHV engine, running more than about .010 out of the bore is bad news. I'm not trying to be a buzzkill, but even if you can make it work, it's marginal results with cut-up cast pistons and butchered heads, when $600 sounds like a DAMN FINE deal for some FORGED Ross'.



While you're in there filling it with good slugs, put some for-real valve springs in it, a better cam, balance the reciprocating assembly to within 1/2-gram, and put it on the JUG!

I don't think you understood the advice. The ring groove would only be .063" higher in the bore. The distance change to the top of the engine is 1/2 the increase in stroke or .125 divided by 2 - not the total increase in stroke. So, your .125 higher in the bore, is incorrect. To be completely correct, the rings/piston would be moving .0625" higher in the bore and .0625" lower in the bore for a total of .125" increase.



Generally, the factory deck clearance is around .025". I've had some a bit more, and an equal number a bit less - but .025" is the general average. This means that a stock 262 piston hooked to a 308 crank with no deck shaving at all, would only protrude out of the block .038" on an unshaved deck - give or take .002". My advice on a minimum of .053 - .043" cut on the piston head still stands depending on the amount your block has been shaved. At a stock deck height, .043 off the top of the piston would leave you .005" deck clearance. Deck your block .010" and the .053" piston cut would apply likewise.



The real wildcard is the length of your rods from center of the journal end to center of your wrist pin bushing. I've seen these vary as much as .015", so it would pay bigtime to know your rod length for each individual rod before making any cuts on piston heads. Three measurements you absolutely need are the deck height of the block, the compression height of your piston, and the length of each rod in order to pull off the modification. Assume any one of these three dimentions - and you could be in for a nasty surprize.



I just have no idea what point you're trying to get across here - " Add this to the deck clearance of your particular assembled engine, which is measured with a deck bridge and dial indicator, and that's how much you've got to play with. If the total number is less than about .200, you're in trouble. .200 leaves only .075 at the top of the hole." I need some further clarification on this.



Personally, I'd recommend a zero deck clearance, as the head gaskets I've seen leave just the right amount of squish once bolted down.



So yeah, I'd build a stroker 262/308 with slightly shaved replacement 262pistons. I have yet to hear a valid reason why not?



I do use a deck bridge, and run flatheads at a zero deck. This one is actually .002" proud.





Pop up pistons in flatheads are the berries, I've built too many 45 harleys to be told otherwise. I'd do that to a Hudson in a New York minute if it had enough meat in the head for me to dig into. Unlike the solid cast Harley heads, I have water jackets to worry about in the Hudson. Measure the degrees of obstuction and feet per minute the piston is travelling, and tell me just how long that "airfoil" is in the way - a terribly small fraction of time during the intake stroke, and arguably the least critical moment in the intake cycle. The trick is to get the pop up and the transfer slot working together - then you've the ticket.



I use custom pistons when the feet per minute of piston travel at rpm exceed what most replacement pistons can handle. However, if I were going to use the engine in a rpm range that didn't exceed 4500 rpms for any sustained amount of time, the modified 262 replacement pistons wouldn't bother me for one second.



Mark

.0625" higher in the bore is correct. I misread your original post and assumed you meant to take .0625 out of the head for clearance, and .0625 off the piston head, and wondered what you were smoking. Because of that I assumed you were increasing the stroke by 1/4"; I had to go back and look at another post to see that there was a 1/8" difference. It would be absolutely necessary to do your blueprinting with a no-ring mockup and all six pisons in and see how much deck clearance there is, in order to come up with a number to cut the piston heads. You have brought up a point that I failed to mention, rod length, and you are right it is a considerable wildcard, plus the slight addition to length for stretch. This wouldn't be bad at 4500 rpms, however. If there is as much variation as you say, I would recommend measuring each rod's center-to-center and compare them to each other, then number the rods to the pistons in case cutting one piston head more or less than another was necessary to make up for a difference in rod length.



You know, come to think of it, if there's that much variation in rod length, that's all the more reason for balancing things.



The -.025" deck clearance on a Hudson is not unusual for any manufacturer. Almost every engine I have ever assembled, F head, L head, OHV, 4, 5, 8, 12 cylinder, has been .020-.030" in the hole from the factory. Most engines are also milled out-of-square from the crank centerline, so it will vary from corner to corner. Take a clean up cut off the block if necessary and mock it up and see what happens. If the gods are with you and the rods are short, and the deck is high, your piston head cut will be minimal.



When I am setting up an engine and have the OPTION, I set them at -.005" deck. This enables you to come back and take a clean-up cut off if necessary. I don't care if it's a dead stock rebuild, I still do it, and there's a million reasons why not to leave a piston .030" down in the hole. The last Chevy 388 I put together I put at 0 clearance, because with a .060" overbore, if it ever breaks I'm going to trash the block anyway. Your +.002" wouldn't bother me, no valve clearance problem on a flathead. .063" out of the hole as I misread earlier would scare me, and not only because of the intake charge coming in, but the modified shape of the effective chamber at the moment of combustion.



Down to brass tacks, the Ross pistons are $600, what do the new ones from Dale cost?

I really like the way this thread is headed...... Now, how about some numbers that you have achieved? (HP/TQ) I'am looking at taking a 308 pretty much to the max (naturally aspirated) for my '32 Essex to KILL some Hot rodded flat head Ford V8's. I really like what Uncommon is capable of but the shipping's got to be a killer. Is there any machine shops in SoCal with the tech. and ability?



Joe

Joe C wrote:

I really like the way this thread is headed...... Now, how about some numbers that you have achieved? (HP/TQ) I'am looking at taking a 308 pretty much to the max (naturally aspirated) for my '32 Essex to KILL some Hot rodded flat head Ford V8's. I really like what Uncommon is capable of but the shipping's got to be a killer. Is there any machine shops in SoCal with the tech. and ability?



Joe

How max'd are we talkin' here?



I think Bill Albright has a stroked 7x engine in a Hornet already. I don't know much more about it other than he stated that it has a healthy appetite for fuel.



Randy Maas is the one to talk to regarding the max'd Hornet engine, in my opinion. Most of what I'm doing with my engines, was information from Randy or confirmed by Randy when I proposed it. Randy has your hot parts. I've got one of his Hot Street cams, had it spec'd out on a machine, and was pleased with its numbers. Particularly lobe separation, which is something he and I talked about many years ago when I first began to excercise Hudson fever.



My project in search of concrete numbers for not only the hp/tq, but also flow numbers and relief comparisons - got put on hold this past spring. Randy has the firsthand experiance, I'm just trying to put numbers to the application. I hope I can get back on track with the project this winter.



I'm fairly young and definitely not rich, so my projects take a bit more time.



I'm also envious of people with 32 Essex coupes! I'm tickled you're considering a Hudson powerplant - I'll try to help any way I can.



Mark

OH..... Dad is in Ontario



Dany

Thanks for all of the feed back guys. 51Comm6 sorry for hijacking your thread. I found some good info using the search function also.



Joe