I also think incorporating a sacrificial anode can be beneficial to aluminum heads, even in fresh water.

I was thinking about camshafts, the overlap effects on chamber temperatures today.

I know some guys are all about aluminum heads, cold water temperatures, and intercoolers, to help reduce detonation, and its true. But I think everyone overlooks the impact a camshaft design has on combustion temperatures. Theres still plenty of engines out there with aluminum heads and superchargers, burning pistons, blowing head gaskets, and tuliping valves. While the Iron vs aluminum debate is certainly worth talking about, I also think there are other things to consider when building a detonation free supercharged engine. Everyone wants a cam that simply will "make power". I want a cam that makes power, doesn't beat up my valvetrain, and possibly can help cool down my cylinders. I can care less about mpg in my application.

Back when the "EGR" valve was introduced, its goal was to reduce combustion chamber temperatures. What it did, was pretty much take the burnt exhaust gas, and recirculate it back into the engine at certain engine loads. It basically was diluting the intake charge, with gas that can't be burnt again, as its not really combustable any longer. Modern engines, can achieve this, through VVT, or variable valve timing. By being able to manipulate when the valve opens and closes, it can lower combustion chamber temperatures.

So, when not using a EGR valve, or not having VVT, the basic camshaft design, can have an impact on the combustion chamber temperatures. Heres a good read on the EGR effects.

http://www.aa1car.com/library/egr.htm

Heres a list of BDS blowers cams they use. All 110 LSA cams. Check out the footnote at the bottom saying **For use with alcohol avail in 112-114 LSA

http://www.blowerdriveservice.com/blower-cam-specs.html

I think Harold Brookshire may have been onto something with this statement

Blown engines are quite different from unblown ones; clean air and fuel starts entering the combustion chamber as soon as the intake valve cracks off the seat, generally around .001" of valve lift. Unblown engines don't start putting clean air and fuel into an engine until a little while AFTER TFC. Before TDC, the piston is moving upwards and pushing the exhaust gases out the exhaust port, there is no air/fuel intake until after TFC and the piston starting down on the intake stroke.
This is just for blown gas engine, as blown alcohol engines require different cams, as do turbo-charged engines.
Because gas burns HOT, pumping a lot of fuel into the combustion chamber causes a very hot cylinder head, and detonation problems. The more racier blown gas cams are on 108-110 LSA, and use the intake overlap to COOL the combustion chamber down. Needless to say, they don't make that good of a gas mileage. They also have all of the normal actions of tighter LSAs, plus a lot of torque. Tight LSAs don't make good street engines, too snappy.
Wider LSAs make flatter torque curves and deliver better mileage, particularly at lower boosts---6-8 lbs. The blower will add lots of power.
When you get up in real racing blown gas engines, 36 lbs of boost lets you accomplish with 116 LSAs what you used to do at 110 with 8 lbs of boost.
I generally go with wide LSAs on the street with low(6-8 lbs) boost, moving to tighter LSAs (108-110) with higher boosts and racing use, then back to very wide LSAs with very high (24-39 lbs) boosts.
I also tend to pay lots of attention to those who make this their field of expertise.

UDHarold

ARP headbolts rot fast too, right, when they go in water jackets ??? Talking salt water here still.

Heck, when I rebuilt my engines a few years ago, that NEVER seen salt, all my ARP head studs were junk. Thats in freshwater!

The GM one's are plated/coated but I don't think they offer the 4 bolts that need to be longer on most aftmkt heads exhaust holes.

I've found liberally coating the end of the bolt with sealer helps with corrosion

Speaking of and I'm not sure if anyone else has noticed this but what I've noticed over the years is that studded Gen IV engines would corrode the studs faster than their head bolted counterparts in salt water. Because of it, once Cometic head gaskets got popular I would run those engines with head bolts instead of studs (blown and un-blown).

Anything with an aftermarket block or Gen V/VI that is blown, I run studs since the bolt boss' are blind.

Too small a camshaft for an engine will also affect this. Sometimes folks say, "it's a blower engine, no need to put a big cam in it." Which might be true but putting a small cam in it can be detrimental. Some 15+ years ago I learned that lesson the hard way when I allowed someone to choose a small cam for me. The "right" cam made over 100hp more but made the engines more reliable.

An engine needs the right size cam depending on what's right for the whole combination. I've learned enough over the years to get myself a "ball park" cam but I've come to rely on various industry experts to help me in my selections.

From MT's post

"Back when the "EGR" valve was introduced, its goal was to reduce combustion chamber temperatures. What it did, was pretty much take the burnt exhaust gas, and recirculate it back into the engine at certain engine loads. It basically was diluting the intake charge, with gas that can't be burnt again, as its not really combustable any longer. Modern engines, can achieve this, through VVT, or variable valve timing. By being able to manipulate when the valve opens and closes, it can lower combustion chamber temperatures.

So, when not using a EGR valve, or not having VVT, the basic camshaft design, can have an impact on the combustion chamber temperatures. Heres a good read on the EGR effects. "



My 06 Cummins uses the camshaft to accomplish EGR during the combustion cycle. It's more prevalent than we might think.

Can anyone recommend where to get some accurate flow numbers on the EQ-CH454A heads?