Stock LT1 DCR? Intake closing point?
#1
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Join Date: Mar 2002
Location: Johnstown,PA, USA (Flood City)
Posts: 294
Stock LT1 DCR? Intake closing point?
Dynamic compression ratio on a stock LT1? Just curious.
Tried a search, but it isn`t working. Anybody do a Dynamic compression ratio calculation? Or does anyone have the stock LT1 cam intake closing point?
Thanks
Tried a search, but it isn`t working. Anybody do a Dynamic compression ratio calculation? Or does anyone have the stock LT1 cam intake closing point?
Thanks
#3
Re: Stock LT1 DCR? Intake closing point?
I have also asked for this before. Part number on the nose of the my 95 cam is GMPT 242 BC, and I should have degree'd it in when I re built the motor.
Please...someone doing a motor right now degree the cam in and get the valve timing data....
Please...someone doing a motor right now degree the cam in and get the valve timing data....
#4
Re: Stock LT1 DCR? Intake closing point?
From my math, the intake valve closing point is between 60 - 64* ABDC. This puts the DCR between 8.3 - 8.6. Hopefully someone else chimes in with a concrete number.
Last edited by 97bowtie; 02-20-2006 at 10:01 AM.
#5
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Join Date: Mar 2002
Location: Johnstown,PA, USA (Flood City)
Posts: 294
Re: Stock LT1 DCR? Intake closing point?
97bowtie, what specs did you use? here`s what I used, and the results are similar to yours:
54cc chambers
8cc piston head volume (did a search on this)
gasket .049
gasket bore 4.125 (just a guess here)
bore 4.00
deck .015 (guess also)
stroke 3.48
rod 5.7
With the above data the CR comes out to 10.455. I sorta reverse engineered the deck, and gasket bore to get the known CR for an LT1 (10.4/10.5).
Then with the 60-64* ABDC I got: 8.396 - 8.643.
How did you get the 60-64*?
ADV DUR minus .050" DUR divide by 2 and add that to the INT CLOSING @ .050"?
54cc chambers
8cc piston head volume (did a search on this)
gasket .049
gasket bore 4.125 (just a guess here)
bore 4.00
deck .015 (guess also)
stroke 3.48
rod 5.7
With the above data the CR comes out to 10.455. I sorta reverse engineered the deck, and gasket bore to get the known CR for an LT1 (10.4/10.5).
Then with the 60-64* ABDC I got: 8.396 - 8.643.
How did you get the 60-64*?
ADV DUR minus .050" DUR divide by 2 and add that to the INT CLOSING @ .050"?
Last edited by cdb95z28; 02-20-2006 at 10:44 AM.
#6
Re: Stock LT1 DCR? Intake closing point?
I used:
54cc combustion chamber
8cc piston (valve reliefs)
.046 gasket thickness
4.1 in. gasket bore
.02 deck clearance (piston .02 in the hole)
This gives a static compression of 10.344 and the DCR values I posted earlier.
54cc combustion chamber
8cc piston (valve reliefs)
.046 gasket thickness
4.1 in. gasket bore
.02 deck clearance (piston .02 in the hole)
This gives a static compression of 10.344 and the DCR values I posted earlier.
#7
Re: Stock LT1 DCR? Intake closing point?
Originally Posted by cdb95z28
How did you get the 60-64*?
ADV DUR minus .050" DUR divide by 2 and add that to the INT CLOSING @ .050"?
ADV DUR minus .050" DUR divide by 2 and add that to the INT CLOSING @ .050"?
(((254/2)+117)-4)-180 = 60*
Some other sites I found said to figure the intake closing point using the duration @ .050", then add 25-30* to that to figure the actual intake closing point. That's where I came up with the 60-64* range.
It would be nice if someone knew the advertised duration of a stock LT1 cam from any year.
#8
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Join Date: Mar 2002
Location: Johnstown,PA, USA (Flood City)
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Re: Stock LT1 DCR? Intake closing point?
Thanks 97bowtie,
I use SStrokerace`s easy method for the intake closing point. Maybe some of the cam gurus here might chime in!
I use SStrokerace`s easy method for the intake closing point. Maybe some of the cam gurus here might chime in!
#9
Re: Stock LT1 DCR? Intake closing point?
Originally Posted by cdb95z28
Thanks 97bowtie,
I use SStrokerace`s easy method for the intake closing point. Maybe some of the cam gurus here might chime in!
I use SStrokerace`s easy method for the intake closing point. Maybe some of the cam gurus here might chime in!
#11
Re: Stock LT1 DCR? Intake closing point?
Originally Posted by cdb95z28
Advertised Duration minus the .050" duration, divide by 2 and add that to the Intake closing @ .050'
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