1970's "30mpg" V8 cams, big car, w/14:1 CR on 87oct

[oil pan 4]

Originally Posted by stillsearching

It's possible that stainless steel valves would be needed.

Stainless steel valves have been standard since the 1980s.

[stillsearching]

Originally Posted by oil pan 4

Stainless steel valves have been standard since the 1980s.

My full quote was stainless steel exhaust and valves... normal steel anywhere from combustion chamber through tailtip might rust due to the high water content otherwise. Even if just the valves being stainless since the 80's is standard it's worth mentioning as a "handy tip!" since 1970's engines were in the discussion too and i'm not sure if they all had that then.

[oil pan 4]

I have 0 rust on my cast iron intake runners or exhaust port and no new rust on the old exhaust manifolds.

In a diesels exhaust the temperature should be at least 400'F. Water causes rust, not ultra dry super heated steam.

[metromizer]

Originally Posted by slowmover

An RV cam emphasizes low rpm lift at the expense of duration (when done correctly).

Bruce Crower (to go back to the OP) was the one with high compression experiments in the late 60's/early 70's. What Yunick was doing was a bit different.

During one of the gasoline shortages, in about 1978, I installed an RV Isky Mile-A-More cam in a 327 Chevy engine. Slightly less lift, but very noticeably (even by eye) duration. Side by side, the RV cam and the mld performance grind that I removed, looked like a Geo Xfi cam next to the stock Geo cam.

With less duration, the cranking compression noticably went up with the RV cam, low end torque went up, as well, making it very easy to drive slow and easy. My goal, bet with my dad, was to get 20+ mpg.

The problem with high compression and longer durations cams is exacty as has already been pointed out, you loose low rpm torque. I think there are several drivers, but reversion back up the intake tract is a huge one. During dyno testing of race engines, I've experienced this 'fog' above the velocity stacks, at lower rpms. Late closing exhaust vale event is the culprit. However, at higher rpms, this effect is less pronounced, the 'fuel stand off' visually goes away, cylinder over-filling goes up, and torque increases. VVT (which I've never played with) seems to fix this.

[Mustang Dave]

Originally Posted by freebeard

Personally I don't think water should be allowed anywhere near an engine (it's corrosive)

Even if you DON'T inject it, water is a MAJOR by-product of the combustion of any hydrocarbon fuel. Most fuels (other than acetylene or benzene) produce more water molecules than carbon dioxide molecules through normal combustion. That's why the auto manufacturers have gone to stainless steel exhaust systems for longevity.

[freebeard]

Truth be known, that was just a setup for a joke about puppies and kittens.

It's a fascinating subject though, Faraday went on for six hours on the subject in 1908:
The Chemical History Of A Candle, by Michael Faraday

I was halfway through it before I figured out what carbonic acid is.

[stillsearching]

Originally Posted by metromizer

The problem with high compression and longer durations cams is exacty as has already been pointed out, you loose low rpm torque. I think there are several drivers, but reversion back up the intake tract is a huge one..

The question is whether better mileage is possible lugging at 1400rpm with more torque, or whether spinning 2500rpm with high compression more efficiently. I consider it something "not closed" until better researched, and since I don't even know where to find such cams, and they seem to have been rare enough that only a few people even remember or ever had one.

A v8 with the torque of a v6? That's fine if it gets the mileage of a v6 too, especially if high RPM power actually remains and with the right gear it can still get up and perform. It may actually remain one of the easier ways to improve mileage on older setups that require too many other swaps to get mileage on. (ie changing transmissions, axle ratios, etc) It was a solution for it's day, and i'd like to see how it stacks up to modern ones. Perhaps there is some situation where it would actually still even be superior.

[metromizer]

Originally Posted by stillsearching

The question is whether better mileage is possible lugging at 1400rpm with more torque, or whether spinning 2500rpm with high compression more efficiently. I consider it something "not closed" until better researched, and since I don't even know where to find such cams, and they seem to have been rare enough that only a few people even remember or ever had one...

You need to talk to Dema Elgin at Elgin cams.

http://www.elgincams.com/index.html

There's nothing magic about fast ramp, short duration, camshafts. He has ground some special cams for my race engines, and found my Geo Xfi cam interesting. He has a lot of engine knowledge, teaches classes on the subject (I've taken his 2-day seminar in 2011), he's been an invited speaker at PRI and SEMA. Not much of a website, but he's an old guy who puts his effort into working with customers one at a time, and less on internet marketing hype. I've spend many hour with the man, Dema is the real deal

There are several software packages out there that allow the curious to ask 'what if' without building that exact engine, that come pretty close to reality. Engine Analyzer Pro is one I've used (cost around $250 I think, a friend owns a copy) Oh, there are some bargin packages out there for $39.95 but those are way too general for 'out of the box' designs, and not worth your time. Be warned, if you have that deep-rooted gearhead gene in your DNA, you'll spend days fooling around with a good program. There are limitations, though, it's only as good as the data you enter. You should flow the head at various lifts, and build a library of cam profiles from which to select.

[Frank Lee]

If you're not gonna change any ratios, then you know exactly what rpm to target. The cam grinders will know what to do with that.

[slowmover]

Elgin has quite a reputation, IMO. One whose advice is well worth considering.