Slant Six Forum :: Stamp deciphering on block

The stamping on the pan rail and on the top deck by the tappet chamber do not look like OE factory stamping to me. Just my opinion.
Concerning what you are calling deck height, I call that piston recession. And if you are getting .157 that is with in reason of stock or perhaps the block has been rebuilt and there was a light cut on the top deck.
You also mentioned that you believe the pistons are not stock. You should measure a bore diameter and determine if it was cut oversize. Some after market pistons have the pin bore centers (compression height) reduced to keep the compression stock with the increased diameter.
Concerning the question on what deck height is best for you, that really depends upon how you intend to use the vehicle and motor. Even as a daily driver most slants will benefit from a bump in compression to 8.5 or so. If you are going to change the cam, and enter the performance envelope, then it still depends upon your expectation for the motor.
A good start would be for you to identify your goals for the motor and vehicle and then to get familiar with an on line static compression calculator.

the link below is to one on line compression calculator
https://uempistons.com/p-27-compression ... calculator

Author:	BuzzCatcher [ Tue Jun 28, 2022 4:39 pm ]
Post subject:	Re: Stamp deciphering on block
Update. I put the crank back in and measured .1575” deck height (#1). Moving forward as far as whether or not to cut the deck, what’s a good option to relay to the machine shop when I get to that point?

Author:	DadTruck [ Wed Jun 29, 2022 12:52 pm ]
Post subject:	Re: Stamp deciphering on block
The stamping on the pan rail and on the top deck by the tappet chamber do not look like OE factory stamping to me. Just my opinion. Concerning what you are calling deck height, I call that piston recession. And if you are getting .157 that is with in reason of stock or perhaps the block has been rebuilt and there was a light cut on the top deck. You also mentioned that you believe the pistons are not stock. You should measure a bore diameter and determine if it was cut oversize. Some after market pistons have the pin bore centers (compression height) reduced to keep the compression stock with the increased diameter. Concerning the question on what deck height is best for you, that really depends upon how you intend to use the vehicle and motor. Even as a daily driver most slants will benefit from a bump in compression to 8.5 or so. If you are going to change the cam, and enter the performance envelope, then it still depends upon your expectation for the motor. A good start would be for you to identify your goals for the motor and vehicle and then to get familiar with an on line static compression calculator. the link below is to one on line compression calculator https://uempistons.com/p-27-compression ... calculator

Author:	BuzzCatcher [ Thu Jun 30, 2022 9:32 am ]
Post subject:	Re: Stamp deciphering on block
Quote: The stamping on the pan rail and on the top deck by the tappet chamber do not look like OE factory stamping to me. Just my opinion. Concerning what you are calling deck height, I call that piston recession. And if you are getting .157 that is with in reason of stock or perhaps the block has been rebuilt and there was a light cut on the top deck. You also mentioned that you believe the pistons are not stock. You should measure a bore diameter and determine if it was cut oversize. Some after market pistons have the pin bore centers (compression height) reduced to keep the compression stock with the increased diameter. Concerning the question on what deck height is best for you, that really depends upon how you intend to use the vehicle and motor. Even as a daily driver most slants will benefit from a bump in compression to 8.5 or so. If you are going to change the cam, and enter the performance envelope, then it still depends upon your expectation for the motor. A good start would be for you to identify your goals for the motor and vehicle and then to get familiar with an on line static compression calculator. the link below is to one on line compression calculator https://uempistons.com/p-27-compression ... calculator Thanks for the insight Dadtruck. From a stock position at 10.68 I also see that as an uncut range. I was not aware of the piston centers possibly being different. Good tip! Learning every day. They are stamped 09 however, and that’s where I started questioning the height as well as bore size. They were quite dirty. Now as far as what I want out of this is really pushing towards the torque side as that part is the most fun for me. Trying not to be screaming rpm at 55mph either. I have no intention of high speed. Just a fun summer cruiser with a nice sound. I do plan on changing cams for that matter. Still working through and reading as much as I can. I have Doug’s book and am following that. I plan on the fuel pump oiler hole as well, which as far as I understand, staying in a certain range with the cam would allow me to keep the mechanical fuel pump. Am I understanding that correctly?

Author:	volaredon [ Thu Jun 30, 2022 10:29 am ]
Post subject:	Re: Stamp deciphering on block
Is the stamping on the piston "09" or "60"?

Author:	BuzzCatcher [ Thu Jun 30, 2022 10:58 am ]
Post subject:	Re: Stamp deciphering on block
Quote: Is the stamping on the piston "09" or "60"? No decimal or underscore that I can see on any of them Got a date with the calipers tonight.

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