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hyarbour 02-14-2007 01:16 PM

Pistons?
 
Hi guys,
I bought a 327 for rebuilding to put in my truck. While the block was a 327, the rest seems to be a hodge-podge of whatever the guy could get his hands on; for instance: 60cc heads on one side with 70's on the other and a 302 crank.
Right now I need to figure out the pistons, the only marks on them are 740P on the inside. They look fine, but are they for the 327, a 302 or a 350? Did those engines have different heights from the pin to the piston top or was it one size fits all?
The pistons are flat tops with reliefs and look fine; can't really tell if they're cast or forged, but I'm guessing cast. Has anyone ever come across these ones before? Any help would be appreciated before I buy a new set for new reason.
Thanks
Howard

xntrik 02-14-2007 01:41 PM

Quote:

Originally Posted by hyarbour
Hi guys,
I bought a 327 for rebuilding to put in my truck. While the block was a 327, the rest seems to be a hodge-podge of whatever the guy could get his hands on; for instance: 60cc heads on one side with 70's on the other and a 302 crank.
Right now I need to figure out the pistons, the only marks on them are 740P on the inside. They look fine, but are they for the 327, a 302 or a 350? Did those engines have different heights from the pin to the piston top or was it one size fits all?
The pistons are flat tops with reliefs and look fine; can't really tell if they're cast or forged, but I'm guessing cast. Has anyone ever come across these ones before? Any help would be appreciated before I buy a new set for new reason.
Thanks
Howard

If it is a 302 crank, then it is not a 327 cube engine.

If you intend to use that 3.00 stroke crank you will get a 302 to 310 cubes, and you need 302 parts.

DoubleVision 02-14-2007 01:44 PM

if 327 pistons were used with a 302 crank the pistons would fall short of the top of the bore by quite a distance. I would be certain the crank is a 302, these shafts are rare and many will pay top dollar for them. I would check the crank again by the casting numbers to be sure. If it is a 302 crank and the pistons make it to the top of the bore then 302 pistons were used, but I honestly don`t know of a company that makes a flat top 302 replacement pistons, it`s hard to come by a company that makes these pistons period since it`s a very hard to come by engine only produced 3 years.

xntrik 02-14-2007 01:55 PM

Check the bore diameter, 4.00 for 327 block.

hyarbour 02-14-2007 02:30 PM

Pistons
 
The block was a '66 327, I can tell someone threw a rod at one point because of a nick at the bottom of a cylinder.
I did verify the cranks casting number, Mortec says:
3815822..265,283,302.forged..small journal....3.00" stroke
and I was told that the ones with one notch in the crank flange were used in the 302's.

demonspeeder 02-14-2007 04:02 PM

re: pistons
 
Based on if you want to have a 302 or 327, if you want to make it a 302 I know wiseco makes pistons for the 302 Z28 motors. So it's not that hard to get them.

k-star 02-14-2007 05:50 PM

crank
 
I have seen the 3" cranks with the notch that were not it factory 302's

If it thas the notch and the snout is drilled and tapped for a bolt then it is a real good chance is was a factory 302... If the snout is not drilled it's not a 302.


Keith

techinspector1 02-14-2007 06:01 PM

I thought the 302 used a large journal crank. yes?/no?

If it's small journal (2.000" rod journal), then it is a 265/283 crank, yes?

junior stocker 02-14-2007 06:23 PM

O.K., so it's a small journal 327 block and obviously has a small journal 3" stroke crank; it really does'nt matter it's origin. What I really want to know is what are those "740P" pistons. Any partsmen/machinist have any idea? I'd heard at one time Ford 352 pistons could be used if the wrist pin bore on the Chevrolet rods were opened up to the Ford size and the rotating assembly rebalanced. Any truth there? It would seem if all this is true, then using small chamber heads to get some compression back would make for a fairly cheap 301/302 build. Add a cam, 180 degree intake, and a heavy flywheel and instant back-to-the-60's. Seems everyone wants a 301/302. Anyone? BUTCH.

Chevrolet4x4s 02-14-2007 08:08 PM

What about using a set of l69 305 heads 54-58cc combustion chamber but due to the high reving nature of the 302s the 1.84/1.50 valves may be too small

Shane

hyarbour 02-15-2007 08:10 AM

re: Pistons?
 
The crank snout is drilled and I've already taken care of the head problem with a set of 041's; 64cc, 1.94 in 1.50 ex. As far as journal sizes; apparently the '67 was the only year for a small journal 302, '68 went to the medium journal size.

techinspector1 02-15-2007 10:16 AM

Measure the wrist pin bore in the pistons, 0.927" is a small block Chevy, 0.912" is a small block Ford, 0.990 is a big block Chevy, etc. If the pin mikes 0.927", then measure from the crown of the piston at the very edge down to the top of the pin bore. A measurement of 1.332" to 1.337" will be a piston for a 3" stroke small block Chevy.

The diameter of the piston could be 3.875" for a stock bore 283 or 3.905" for a 0.030"-over 283 or 3.935" for a 0.060"-over 283 or whatever. For a 302 it would be 4.000", 4.030", 4.060".

Drag out your dial caliper and have at it. :)

techinspector1 02-15-2007 10:24 AM

I found it. 740P is a Nylen piston for a 327.

junior stocker 02-15-2007 11:46 AM

That does'nt make sense if it has a 3" stroke crank. The piston must be far below deck height? What are the rods? Deck height? This is'nt making sense to me now. :confused: And can anyone confirm the 352 Ford piston use? BUTCH.

xntrik 02-15-2007 12:37 PM

Quote:

Originally Posted by junior stocker
That does'nt make sense if it has a 3" stroke crank. The piston must be far below deck height? What are the rods? Deck height? This is'nt making sense to me now. :confused: And can anyone confirm the 352 Ford piston use? BUTCH.

Ford= If it fits the cylinder, then the pin/rod can be made to fit.

If a 302 used the 5.7 rod, the compression height must be tall enough to make the piston come to the deck. So it would have to be 1/4 inch more than a 350. (.240)

9.0 -1.5 -5.7 = 1.8 compression height. Center of pin to piston top.

Which is .927/2 + 1.337 = 1.8

1.337 is exactly what techie said.


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