496-on Pump Gas?

[gn7]

That means hp #'s where corrected from 3600ft to show what you'd probably have at 0ft.
Therefore you could contribute real good info for this thread if you could show corrected vs uncorrected #'s. This would show what the elevation does to motors - in your case 0ft vs 3600ft.
ditto

[cfm]

This is the man you need to talk to. He just helped me put together my 502 with AFR heads and 9.2 to 1 compression and it made 712hp on the dyno last week at 6200 rpms....oh yeah one more thing corrected elevation that day was 3600'. Not bad for a pump gas motor....
My last post above (I just edited it) would lead to confusion as to what I was trying to say for my brain doesn't transfer to my fingers (ie:typing) very well.
So.......let me try it this way and then I'll go further when the below is answered.
Widowmaker, I see you are in San Diego. San Diego is listed at 72ft above sea level. You mentioned your engine was dyno'd at elevation of 3600ft. When and where (what town/state/shop) did you dyno your engine ?

[steelcomp]

The higher in elevation = the stronger the choke hold.
If your, say 6000ft elev, who gives a rats ass about our sea level hp quotes. You'll be nothing near it.
This is where uncorrected vs corrected dyno sheets come into play !!!
Your '700hp' will be way more difficult to acheive than our 700hp.
Yes, you could (depending on actual elevation) run more measured compression than us but you can't back back the lossed oxygen without a supercharger.Don't forget, if you build an altitude specific combination, (depending on how close you're cutting it), if you ever get below a thousand feet, you'll be in trouble without better gas.
Ther are a lot of build specific things that can be done to increase power and reduce detonation. Attention to detail is going to go a long way here. Clearances, piston dome shapes, hand blending, port and chamber work, parts matching and careful assembly. Reducing friction in every way as much as possible, proper valve train geometry, valve job, etc. There's as much as 50hp in just building the engine properly.

[MACHINEHEAD]

I actually lost a engine build up for a 22 schiada because the other engine builder told him he had a "special altitude cam" . Maybe you should give him a try. HaHa. Cant remember the exact name of the shop, but I think it rymes with roostpower. By the way I think its super charger time for you. The build will be about the same price hp for hp and the blower motor will still be better sans fuel consumption!

[widowmaker]

My last post above (I just edited it) would lead to confusion as to what I was trying to say for my brain doesn't transfer to my fingers (ie:typing) very well.
So.......let me try it this way and then I'll go further when the below is answered.
Widowmaker, I see you are in San Diego. San Diego is listed at 72ft above sea level. You mentioned your engine was dyno'd at elevation of 3600ft. When and where (what town/state/shop) did you dyno your engine ?
It was dynoed at Westech up in Mira Loma, taking into elevation, temp and humidity is how the 3600' number was derived.

[lifter]

So to run your number it will take a "head scratching" build. Will have to over cam the engine somewhat to help stuff the cylinders as much as possible. We need to look at other areas to help make HP.
Actually, this post is “head scratching”. Given a fixed C/R, any incremental increase in altitude, and the resulting decrease in atmospheric pressure, will always result in a loss of cylinder pressure. While adding duration (as altitude increases) may seem “logical” (additional time for cylinder fill?), it doesn’t work that way in the real world.
Lengthening duration extends the IVC event, lowering the dynamic compression (and cylinder pressure), resulting in killing off additional mid range power. The negatives in doing so are compounded by the likelihood of moving your TQ/Power bands up and out of your useable range.
Simply put, with a fixed compression ratio and power band, if you go up in altitude, you must go down in duration to maintain reasonable performance levels. While any solution for this scenario is a compromise, it will be less frustrating than trying to “stuff” the charge with additional duration.

[cfm]

It was dynoed at Westech up in Mira Loma, taking into elevation, temp and humidity is how the 3600' number was derived.
Westech ie: Mira Loma is approx 710ft above sea level. Huge difference between 710ft and 3600ft elevation.
How can you change elevation ? You can't, unless you physically change locations.
What where the weather conditions for the day ?
I'll go further with more info and answers.

[cstraub]

Actually, this post is “head scratching”. Given a fixed C/R, any incremental increase in altitude, and the resulting decrease in atmospheric pressure, will always result in a loss of cylinder pressure. While adding duration (as altitude increases) may seem “logical” (additional time for cylinder fill?), it doesn’t work that way in the real world.
Lengthening duration extends the IVC event, lowering the dynamic compression (and cylinder pressure), resulting in killing off additional mid range power. The negatives in doing so are compounded by the likelihood of moving your TQ/Power bands up and out of your useable range.
Simply put, with a fixed compression ratio and power band, if you go up in altitude, you must go down in duration to maintain reasonable performance levels. While any solution for this scenario is a compromise, it will be less frustrating than trying to “stuff” the charge with additional duration.
Can you show me in my post where I say anything about duration?

[widowmaker]

Westech ie: Mira Loma is approx 710ft above sea level. Huge difference between 710ft and 3600ft elevation.
How can you change elevation ? You can't, unless you physically change locations.
What where the weather conditions for the day ?
I'll go further with more info and answers.
They were hot!! It was about 95 outside and very humid!
Anyways, the boat with this motor runs right at 100mph in the quarter mile. ( 10.4 at 99mph )It is a 19' daytona with dual 750's. B impeller, 6000k rpm. Like I said before. Talk to Cstraub about a cam for your application. Work with him and I promise you will be happy with the outcome!

[widowmaker]

I said corrected elevation, not hp numbers.