real compression numbers

[petepedlar]

I had the chance to do some stuff at the machine shop ........ here are the results.

with stock GM valves:
333's have a 22 cc chamber
817's have a 12 cc chamber

didn't do the 690's yet

The Ross pistons I have are supposed to be 10 to 1...... I have the job number from Ross so I will get all the info on them.

Installed in a std bore block that's never been decked:
.015 squish
in the truck block there is a 77cc chamber
the notch in the block is 9cc
makes the car block 68cc

with a .020 gasket & 4.450 gasket bore:

truck block with 333's = 9.05 to 1
truck block with 817's = 9.91 to 1
car block with 817's = 10.85 to 1

with a .043 gasket & 4.450 gasket bore:

truck block with 333's = 8.62 to 1
truck block with 817's = 9.39 to 1
car block with 817's = 10.22 to 1

as per the compression calculator at the machine shop. The numbers may be a very little bit high as I put a thin layer of grease on the cyl wall to seal the rings. There would have been a little grease above the rings.

Dave

[fatride]

That's great info for me. I have a .030" over 409 truck block with the ross 10:1 pistons and the steel shim .021" gasket. I have the 690 heads. I was hoping that My compression was closer to 10:1 than 9.5:1.

[CDNpontiac409guy]

Dave,
The NHRA spec for a high performance 11:1 409 engine, is 65.8 cc's in the combustion chamber in the block.
It would seem that those Ross pistons are actually designed for use in a truck block:dunno

Are you sure tht little notch in the truck block, is 9 cc's ?

[petepedlar]

Hey fatride..... I'm glad that I could help you after all the tripower stuff you've helped me with.

Aubrey, I filled the notch perfectly with putty and re-did the test.... that's what it said....
Jim Richmond, from Richmond Engines was instructing me and looking over my shoulder..... also don't forget the pistons I have are new never used but I did buy them second hand..... as I said I will get the job sheet from Ross...... it's job # 35300 if you have anyway of getting it quicker.

Dave

[jim_ss409]

That's great information Dave!:deal

[Skip FIx]

Great info. Are the pistons completely flat, no valve relief at all?


Throw a 4" stroker crank in the mix and see where it ends up:)

[Skip FIx]

Aubrey don't know how accurrate the 409 NHRA data is , but Pontiac sure fudged the data they sent them! Most heads when virgin are larger IE NHRA specs end up higher compression ratio.

[CDNpontiac409guy]

Dave, I just checked with my guy at Ross...
That job card number is from 1992. Supposed to be 10.5:1.


Gee Skip, if the data is fudged, I wished they would have went farther with it:p .... could sure use some power with this thing:yawn:

[petepedlar]

1992....... that's a little bizzaaaaaar......... those pistons have been around that long and haven't ended up in a block yet !!!!...... I bought them off of Ebay quite a while ago & the price was definately right

Thanks for the info Aubrey...... you're the expert.... I think that makes my measurements & calculations look better does it not ??? It would make 65.8 with 11 to 1 pistons and my 68 with 10.5 to one pretty close I think.

I don't have a picture of the pistons but I'll get one in the next few days. They do have a valve relief in them. I'd love to do a stroker one day....... but this one is just going to be a nice cruiser...... it's looking like it'll be a little hotter than I first planned..... Oh well ?? I can live with that.... (smile)

Dave

[fatride]

So where does that put my Truck block with the 10.1 piston?

[rstreet]

So where does that put my Truck block with the 10.1 piston?

at the county landfill loader truck:brow
robert

[petepedlar]

Be careful................................. Ronnie likes those truck engines...... and you Don't (wan'na) Mess With Texas:takethat

[Ronnie Russell]

Just learned today that I have another 4 in stroke truck motor to do. Guess the golf clubs and fishing stuff will have to wait til next year. :doh

[skipxt4]

at the county landfill loader truck:brow
robert
Robert? What's getting into you, lately?:rofl That's not nice!:dunno :rofl

[fatride]

Robert? What's getting into you, lately?:rofl That's not nice!:dunno :rofl

May have something to do with my post on dual quad 348s! :dunno

[Ronnie Russell]

:rofl :rofl :rofl :rofl :rofl

[rstreet]

now even??
robert