High Altitude Cam
Thread Starter
Instructor
Joined: Dec 2017
Posts: 169
Likes: 29
High Altitude Cam
Hi guys,
I recently found out the wrong heads were installed on my L46, so I tracked a set down. While I've got the heads off I'd like to upgrade the cam to something that may have been a little closer to LT1 specs. Problem being, I live at 7,000 feet, and this will never see anything near sea level driving. I'm hesitant to throw an aggressive cam in due to the high altitude. Does anybody have experience with spec'ing one out for this situation?
I recently found out the wrong heads were installed on my L46, so I tracked a set down. While I've got the heads off I'd like to upgrade the cam to something that may have been a little closer to LT1 specs. Problem being, I live at 7,000 feet, and this will never see anything near sea level driving. I'm hesitant to throw an aggressive cam in due to the high altitude. Does anybody have experience with spec'ing one out for this situation?
Thread Starter
Instructor
Joined: Dec 2017
Posts: 169
Likes: 29
Pro
Joined: Mar 2014
Posts: 529
Likes: 113
From: Texas
Yes I have...Why would you change out heads for the L46 heads? Better heads out there. As far as running at altitude, adding a turbo will bring back any lost power and more that you would lose from the thin air density. We run our race car at mile high every year with no power loss.
Thread Starter
Instructor
Joined: Dec 2017
Posts: 169
Likes: 29
Yes I have...Why would you change out heads for the L46 heads? Better heads out there. As far as running at altitude, adding a turbo will bring back any lost power and more that you would lose from the thin air density. We run our race car at mile high every year with no power loss.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
https://www.compcams.com/xe268h
I urge you though to either buy a pair of modern heads like a Dart 180 Pro 1 Platinum or at least have the L-46 heads pocket ported with a good 5 angle valve job and blending......you will not be disappointed.
Jebby
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Joined: Oct 2004
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From: altered state
St. Jude Donor '05
Thread Starter
Instructor
Joined: Dec 2017
Posts: 169
Likes: 29
Go with the old Comp 268H.....it will be great for what you are doing....power everywhere......easy break-in with its slow ramps.
https://www.compcams.com/xe268h
I urge you though to either buy a pair of modern heads like a Dart 180 Pro 1 Platinum or at least have the L-46 heads pocket ported with a good 5 angle valve job and blending......you will not be disappointed.
Jebby
https://www.compcams.com/xe268h
I urge you though to either buy a pair of modern heads like a Dart 180 Pro 1 Platinum or at least have the L-46 heads pocket ported with a good 5 angle valve job and blending......you will not be disappointed.
Jebby
I will check that cam out in some detail - thanks!
Thread Starter
Instructor
Joined: Dec 2017
Posts: 169
Likes: 29
Thread Starter
Instructor
Joined: Dec 2017
Posts: 169
Likes: 29
Somebody swapped out heads at some point for 400 heads. The original L46 heads should return me to 11:1. Chamber is 64cc, valve 2.02, 1.6. I don't know the port sizes off hand. I plan to run premium.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
dunno if straub does flat tappet cams
for flat tappet, these two
https://www.camcraftcams.com/
http://jonescams.com/
for flat tappet, these two
https://www.camcraftcams.com/
http://jonescams.com/
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Generally they say that you have a 3 % loss of HP per 1000 feet. Temp and humidity are a factor. but lets just say that you will have a 21% loss. I live about 5000 and have driven my vette to 12,183 feet on my way home through Rocky Mountain National Park. Right here I drive to almost 9000. You want to build for the most power, knowing that you have a big loss.
Like mentioned compression really helps. My static C/R is 11.2 in one and 11.7 in the other. I use big roller cams. I can really feel the difference driving at sea level and I just go up two jet sizes
You didn't say what type of cam you would like to install.
Like mentioned compression really helps. My static C/R is 11.2 in one and 11.7 in the other. I use big roller cams. I can really feel the difference driving at sea level and I just go up two jet sizes
You didn't say what type of cam you would like to install.
Thread Starter
Instructor
Joined: Dec 2017
Posts: 169
Likes: 29
Generally they say that you have a 3 % loss of HP per 1000 feet. Temp and humidity are a factor. but lets just say that you will have a 21% loss. I live about 5000 and have driven my vette to 12,183 feet on my way home through Rocky Mountain National Park. Right here I drive to almost 9000. You want to build for the most power, knowing that you have a big loss.
Like mentioned compression really helps. My static C/R is 11.2 in one and 11.7 in the other. I use big roller cams. I can really feel the difference driving at sea level and I just go up two jet sizes
You didn't say what type of cam you would like to install.
Like mentioned compression really helps. My static C/R is 11.2 in one and 11.7 in the other. I use big roller cams. I can really feel the difference driving at sea level and I just go up two jet sizes
You didn't say what type of cam you would like to install.
Thanks!
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
The cam is very wimpy. I know because my L-82 wasn't a sports car!
So knowing what you have you can make a wise choice of cams. Hydraulic Flat Tappet Camshaft
- 1968-81 Small Block Chevy L-46 and L-82 Corvette
- 222 / 222 Duration @ .050''
- .450'' / .460'' lift
- 114 Lobe Separation Angle
So my first cam was a crane and I used 1.6 rockers to get more lift. Talk to them about what springs and retainers to use.
Good mid-range to upper RPM torque and HP. Daily driver with street/strip performance. 2800+ stall. Fair idle. Compression 9.5 to 10.75.
113531 11353222 Z-274-2 Hyd Hyd .473 .486 274 280 224 230 110
https://cranecams.com/powermax-hydra...0-small-block/
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
All this talk of 11.1 compression and the factory engine was really lower then that. All that goes out the window at 7000ft. If you think of it at sea level the original engines were really more in the 10.5 range and at 7000ft it would be like maybe 8.5 engine at sea level maybe worse. Throw in a 240s at .050 old tech Lt1 cam now you have nothing in bottom in tq. Go for a lower duration faster ramp more lift modern cam.
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Last edited by Little Mouse; Oct 22, 2019 at 08:58 PM.
