DCR @ altitude?

[bobnkathy]

So I'm crunching my numbers for my build and trying to get the DCR where I want it but since I live at 4300' and rarely go much below that with the jeep should I be focusing my build around the DCR-ALTITUDE? It seems to me that that is the magic number for those of us above sea level. I'm working on getting quench where I want it, dishing etc but I'm just not sure if I should be shooting for an 8:1 to 8.7:1 for DCR or DCR at altitude. Thanks in advance

[TR1Hemi]

I am @ 3000 feet and I did take into consideration altitude, in my build. BUT, I have low altitude fuels avail. Last time I was in Montanna/Wyoming, and it has been a while, I noticed that instead of 87, 89 and 92, I saw 85, 87 and 89. Think I once pulled into a station that had 85 and 87 as max. At the time I wondered why that was.
Depends on what you have avail and want to run. All other things being equal I would either not dish, or not dish as much, or deck more and use 4.2 rods and cheaper 4.0 pistons.
I used 4.2 rods, .060 over 4.0 speed pro pistons, and decked for .005 (can't remember exactly how much was shaved), and used 72-76 4.2 push rods (9.594 versus 9.639) which made up for the decking. What I did so I can run cheap gas at MY altitude was open up the chambers in the head to 68cc. Not sure if I could run 92 at sea level, but being in West. Nebraska, that is prob. not an issue, lol.

You are looking for 8.1ish DCR after inputting cam and altitude, regardless.

[bobnkathy]

Kewl that's good info. Yeah We have 87, 89, and 91 here but I really don't want to have to run high octane as thirsty as this thing is. Definitely decking the block (they took .010 off the head already to make it true and flat). I'm working pretty close with a machine shop here in Reno. Going with the 4.2 rods, 4.0 pistons and I'll have to look at my numbers again but was lookin at a 15.1cc dish, and the 232 grind cam bla bla bla. Thanks for the help.

[TR1Hemi]

I have a theory on the narrow lobe cams that I can't prove with out a narrow and wide to compare and it has to do with lobe spacing versus lifter bore spacing, not only are they narrow lobe but they are centered under the lifter so the rear edge of lobe, the higher edge, is not positioned at the edge of the lifter so it has better leverage to spin it. A lifter should travel on the cam lobe like you would move a 55 gallon drum. A bit of tilt in relation to the ground and spinning. My theory on the narrow lobes is that they dont produce enough spin. I went with a Mopar 229.

[TR1Hemi]

Check out the picture of a narrow lobe cam in amceagles thread, viewtopic.php?f=5&t=5139 . I just dont see how that lobe is gunna get much spin on that lifter. Wish I had taken a pic of my 229 cam in my block, showing the relationship of the edge of the lobe and lifter bore.