I want to duplicate the 440 build that Car Craft did. They got 535 hp and @590 ft lbs, however i'm at 6000 feet above sea level and want to know how much power that would take from those numbers Would a compression increase be needed to get those same numbers? Their build used eddy heads,the Speed Pro six pack replacement pistons which netted them about 10 to 1 (i think) and a fairly mild Comp cam. Anyway, I would like to hear about some "mile high" builds.
Thanks.
britt

Another denverite here, I to would like to hear any advice anyone has for this altitude. Please.

Hard not to loose 100 to 125 hp but they can correct it to those sea level numbers for you. I think You can get some back with higher compression and bigger carbs. You really do need an engine builder or someone that has them done at 6000 feet.

Do a search on Compression Ratio in the racing section.
Seems the higher elevation (less oxygen content in the air) will allow you to go higher in compression but I cannot remember specifics.

A blue bottle in the trunk is sounding better and better.........
britt

After suffering thru the altitude blues. I built a 471 400 based stroker. This was based off the engine masters competition build of a few years ago. You could build a 440 at .030 over with close to the same specs.
Zero deck the block with pistons and machine work. Balance entire assy. Heads Eddy RPM cnc'd with Jeff. Eddy RPM or the new Holley street dom. and an 850 dbl p. carb. Cam is where it gets stickey. You need to build cylinder pressure here so the cam layout or plan needs to be done. I've got fast ramp SQ series lobes on a Comp cam in the 260-256 at .050. range. With that plan you should do well. Compression ratio is another way to build that cylinder pressure and is less critical here than at sealevel. BUT, quench is your friend and should be planned ahead of time. .040 quench and you will not detonate even close to 12 to 1 compression. You will love a combo close to this. The plan tho is critical here. Moreso than at sea level.
Good luck.

That was a good article in PHR on the 440 engine build. The Engine in the aricle used 0.040" over TRW#2355 pistons, and they claimed the compression ratio was 10.23:1, but to get that compression with 84cc heads I think the block was decked about 0.020"? to get the pistons at a zero deck height.
The one thing I would do different is use a lighter weight piston. Those #2355's are very heavy, the piston/pin weight is 1071 grams, Compression height is 2.061" with 7cc's valve relief volume (I think these may have 4 valve reliefs?)
The Ross #820101 piston/pin combination is only 802 grams, and the compression height is slightly taller (2.065") so the block would only need about 0.010" cut to zero deck the pistons. Compression will be nearly the same, maybe 0.05 point higher because the valve relief volume is only 4cc's?
On the budget side, the KB#237 pistons/pins weigh in at 961 grams, and they have the tallest compression height 2.067", and 5cc valve reliefs.
All the pistons are flat tops.

The Edelbrock RPM cylinder head ports are pretty efficent as they flow well for the runner volume. The good port velocity will really help at this higher altitude. I have seen many M/W and Hemi head "street" cars not run very well at this altitude because the large ports hurt port velocity. In a race car with high compression and alot of stall and converter they do work good, but for the street and street/strip applications stay with the stock port size unless building a stroker.
The 10.2:1-10.3:1 compression would be fine and allow using pump gas. You could use slightly more compression because of the altitude, but I don't think you will gain that much more power compared to the possable hassles it can cause.

A stroker engine is a good option and will increase compression and add cubic inches, and also allow a larger cam to be used. The main issue is the additional cost of the stroker kit.
I think a stroker crank and rods will add about $1,000 to the cost of the rebuild, but the crank and rods will be stronger than stock too.

Nitrous is an option, but you should consider the cost of having to refill the bottle every few runs. Supercharging or Turbos are somewhat popular to this altitude, most on Mustangs and GM products where there is more aftermarket support and they are mostly installed on fuel injected cars. The cost of the supercharging option is why you don't see very many.

Thanks for the info. My block is 30 over and my crank was recently ground 20 under. I have a RPM intake so I'm practically there! 67 belvedere I saw your car and met you briefly last summer at a cruise before a nasty T-storm hit. I was with Dave Walters. Hopefully, I'll be driving mine soon.
britt

A properly built quench engine will stand quite a bit of compression at this altitude. For an experiment in the 90's we built a 11.5 to 1 360 with KB pistons at .040 quench and then shoved 7 or 9 lbs of boost into it. In a 68 Barracuda it would run low 13's at Bandimere with 400 lbs of tools in the trunk and still spin the tires about 120'. It held up just fine on pump gas for quite along time. It eventually died but not related to the compression. Don't let water freeze in the carb!

The PHR engine is a quench engine. It uses zero decked flat top pistons and the 84cc (partly)closed chamber Edelbrock RPM heads, and a 0.040" head gasket, but that only get you to about 10.2:1-10.3:1 compression.
To get more compression you have a few choices like milling the heads, but that can cause issues with head bolt lengths, pushrod lengths, intake manifold fitment (if the intake is not milled to compensate.)
You could also try a domed piston, but I prefer the flat tops as they are usually lighter and easier to check the head to piston clearance on.
There is also some debate on how the domed piston flame travel compares to a flat top, plus you would want to smooth any edges on the dome to prevent hot spots.
You can also stroke the engine, this increases the piston swept volume while retaining the same quench and cylinder volume, plus you get a bigger engine too.
Lastly you could choose a different cylinder head like the B-1 B/S that has a small 65 cc heart shaped chamber that gives more quench than the Edelbrock heads, but with 65 cc chambers and flat top pistons in a stock stroke 440 your compression would be about 12.4:1-12.5:1 which would probbably be too high a compression ratio for pump gas and a mild cam, but might run on pump gas with a big duration race cam.

Anyhow, I think that the basic 10.2:1 or so compression is fine, and probbly the easiest and least expensive option.

I don't care what you do, just get off your lazy ___ and do it!

Small domes won't kill you if the rest of the build is right. Dust off that wallet of yours, and get your block done first. I've got the precision tools covered.

I was just asking some questions on the new Edelbrock RPM XT heads and someone mentioned they are like ported RPM heads with smaller 80cc chambers? These heads would increase the compression ratio and the extra flow would make more power too.