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55pres
10-10-2005, 02:47 PM
I've been doing some research and found out that standard 305 pistons (3.7 bore) would fit in a Stude block, and when bored would make 311 CI (289 crank). 305 pistons and rings are a lot cheaper than 304 pistons & rings. However I realize the piston pins do need fitted to the rods to work. Has anyone else done this mod to an early Stude block? What would the comp ratio be when using stock 305 pistons? I just need to find a good machince shop now....

I do know about the risks of boring the block that much, but I won't be running any boost, and I will be checking two 55 blocks I have for cylinder walls.
thanks!

(2) 1955 Presidents

Mike Van Veghten
10-10-2005, 03:29 PM
You'll be lucky to find a block that'll go to 3.70" bore without having very "thin" spots.
I just sonic checked my second full flow block. It seems that what others have said is true....#8 and to some extent #6 are thin on their backsides (toward the back of the block). On one block one cylinder was a little off center and the other block 2 cylinders were a bit off on the odd side too. While you can move the cylinders around a bit, that would be excessive.

Don't go any thinner than .150" at the thinnest area.
Two problems, overheating and cylinder wall movement on the compression/firing stroke. It's fine to have "metal" there but if it has no support....it's useless.

I was going to go .093 over (304 cu. in.) on my better block......#8's too thin. I am also running just a carburetor.

The rods, I sure wouldn't bore the small end to .927" for a Chevy pin. Makes the wall way too thin.

DEEPNHOCK
10-10-2005, 07:10 PM
Well, if you were to add .060" to 3.565", you'd get 3.625"..
Using that bore with a 3.625" (or longer stroke ie: shorter skirt) you may have some interesting choices using the chart below, or the one at: http://www.ridgenet.net/~biesiade/Specs.htm#Chryeng

A Ford piston might work ok if the compression height is tolerable.
223 - 3.625" x 3.600" L6
or
272 = 3.625" x 3.600"

Interesting thinking....
Jeff[8D]


Studebaker
engine bore stroke rod length R/S Ratio B/S Ratio
V8-232 3.375 3.250 0.000 0.0000 1.0385
V8-259 3.565 3.250 6.625 2.0385 1.0969
V8-289 3.565 3.625 6.625 1.8276 0.9834














quote:Originally posted by 55pres

I've been doing some research and found out that standard 305 pistons (3.7 bore) would fit in a Stude block, and when bored would make 311 CI (289 crank). 305 pistons and rings are a lot cheaper than 304 pistons & rings. However I realize the piston pins do need fitted to the rods to work. Has anyone else done this mod to an early Stude block? What would the comp ratio be when using stock 305 pistons? I just need to find a good machince shop now....

I do know about the risks of boring the block that much, but I won't be running any boost, and I will be checking two 55 blocks I have for cylinder walls.
thanks!

(2) 1955 Presidents


DEEPNHOCK at Cox.net
'37 Coupe Express
'37 Coupe Express Trailer
'61 Hawk
http://community.webshots.com/photo/42559113/426827941Lsvfrz
http://community.webshots.com/user/deepnhock

55pres
10-10-2005, 10:38 PM
DEEPNHOCK,

I like your suggestions with the pistons. I still like the 305 idea if the block will take it, but from what I heard, the by-pass blocks were a little thicker. I'd have to check the blocks I have. I want to do something different. Looking at the Ford pistons, that would give you a square cylinder, 3.625 X 3.625 if you use a 289 crank. Lastly, how would one figure out compression ratio?

PS, I looked at your pics on the link you had. Nice work!!!! did the mopar manifold work out???

(2) 1955 Presidents

JDP
10-11-2005, 12:16 AM
Ford six cylinder pistons are pretty much a bolt in, I think you end up with a 308.

Studebaker On The Net http://stude.com
64 R2 4 speed Challenger (Plain Wrapper)
63 R2 4 speed GT Hawk

gordr
10-11-2005, 12:28 AM
Just a slight nitpick here. Isn't the stock 259/289 bore 3.5625, not 3.565?

I'm told that 194 Chev 6 pistons will work in 259s.

One has to wonder how well the 305 piston, which I expect is a slipper skirt design meant for a short stroke engine, will work in a 289 block, assuming you could safely overbore that much. I'm sure you'd have to have the rotating assembly balanced, at least.

Gord Richmond, within Weasel range of the Alberta Badlands

Mike Van Veghten
10-11-2005, 10:14 AM
Yea, the stock Stude bore is 3.5625".

3.625" is the same as the .0625" over, or 299.3 cu. in. (I think).
Why go to the hassle of buying a Ford/Chevy 3.625" dia. when a standard .062" over Stude piston works. Unless one likes hunting through catalogs.

As for the short skirt, no problems. The stroke has little if any to do with piston stability. The rod length has a great effect on piston stability at top.....and bottom dead center.