Aluminum Head Question

[toolboxchev]

Doing some research, would like some Professional thoughts about deck thickness.

2 Competitors come to mind, AFR and Trick Flow.

Would a thicker deck from .450 to .500 be better for detonation resistance? Planning a build utilizing everyday fuel for maximum torque and hp.

Flat top pistons and possible zero decking a block.

[AussieinNC]

Either head deck thickness will be fine for everyday driver use....

Detonation is more likely with lean fuel mixtures and incorrect timing...coolant flow issues would also contribute to any detonation occurring.

Detonation is generally caused by excessive heat, excessive cylinder pressure, improper ignition timing, inadequate fuel octane or a combination of these.

Of the previous, excessive heat is usually the culprit.

So keep it "cool"...

Have fun...

[Ziegelsteinfaust]

Detonation is also a symptom of to high a mechanical compression along with or because of to much dynamic compression. It is fuzzy logic, and increasing the quality of the build can help with the issue.

Such as polished piston or coated help.
Pistons that are designed for the actual head your run help.
Running as close to a zero deck as possible.
A cam such as a Duntov 3030 is very tolerant with 11-1 compression on 92 octane.
Where as a LT1 cam gets hairy starting above 10-1 with the same 92 octane.
LT1 350's or LS series engines are more tolerant because of reverse cooling.


So consult your cam company for recommendations as they are pretty decent with them.

Deck thickness is better for clamping forces, and unless exceptionally thin. Does not effect detonation in any meaningful way at or on street builds.

[Tom]

Deck thickness has literally zero to do with detonation.

[Ziegelsteinfaust]

Originally Posted by Tom

Deck thickness has literally zero to do with detonation.

Yes it does, but it takes effort to get there.

If you have thin wall castings, and mill them to much it will effect it. The thin wall absorbs heat much faster, and this can cause detonation. But, and I mean but here. A few other things have to of been done to allow for detonation.

With the deck thicknesses he said he will have no head caused detonation issues. Unless he goes for some off the wall build where he heavily decks his cylinder heads.

I built a 80 over 350 sbc, and I had wild block temp spikes. It had the them new Vortec heads with beehive springs which were heavily decked. Running at constant speed it was allright, but hit the hills to get out of LA. The damn thing was honestly on the verge of overheating. It litterly had the biggest radiator that I could fit into that C10, and get at pick a part. I used to run 165 degrees cruising the highway at 75. Then if I hit the Cajon pass it would spike to 220, and settle at around 205.

[toolboxchev]

Kinda what I thought Zig, everything always will affect other things. Its just how things are, an I am a things kinda guy.

Aluminum heads are new to me also, so I am growing out of those old smog chambers. I want the most power I can get out of a small block on cheasy peasy 87 octane.

The SCA's run or wear out of Prestone after a year, and you know what happens next.

[Tom]

Thin castings will heat up faster and will shed heat/cool faster as well. This should only affect warm up, once its at temp the metal is at temp. An 80 over 350 with heavily decked vortecs sounds like a high compression build, in which case all variables count to the heating and detonation issues.

[Ziegelsteinfaust]

Originally Posted by Tom

Thin castings will heat up faster and will shed heat/cool faster as well. This should only affect warm up, once its at temp the metal is at temp. An 80 over 350 with heavily decked vortecs sounds like a high compression build, in which case all variables count to the heating and detonation issues.

They heat up faster due to lack of mass effectively not being able to reflect heat back into the chamber, but once steady state cruise is re-introduced they cool down very quickly. This relatively compared to a block that still has thick cylinder walls, and decks. Rather the block or the heads. This can over tax the cooling system since more heat gets through the engine parts into the water when you are on the throttle.

The build came about due to my finding a gmpp forged crank, bearings, arp studs, and pink rods at the Pomona swap meet. Oddly enough they had "low" compression forged 80 over pistons included. I called to verify specs after purchase. I had a useless wore out already 40 over block, and it was a 2pm Sunday buy. I got a great deal at something like $200.

It was not a high compression engine, but what I had to do get the combo to work decently. Going off memory here.They were supposedly blower pistons with a nominal 7.5-1 to 8-1 compression range with the camel hump 65cc chambers. So it took alot of shaving to get the 9-1 wanted. I believe with the math I did I was sitting at 9.2-1 with the thin mls gaskets.

The down side is the engine effectively ate itself to death due to the wild temp swings in roughly 50,000 miles due to excessive oil consumption. The constant shedding heat at cruise along with my 160 stat to get it to have a safety margin did not allow it to heat to full ideal operating temp. Toss in the high duty cycle heat of just going over the hills hurt the rings due to slight overheating, and then the quite sudden cool down. Then I rebuilt the good parts at 60 over with a truck block that was sonic checked, and new for then 54cc heads. I had a machinist cut the pistons down 20 thousandths for less then new cast pistons. I had slightly higher compression at 9.4-1, and ran a hotter cam. I ditched the too mild comp 268 for a modern at the time version of the LT1 mechanical cam. With the same cooling set up I could tow, and haul stuff. With litterly 1/2 the temp swings in temp or time swing. This engine I had for 80,000 miles, and accidently killed it when I over revved it on a missed the 2-3 power shift. It tacked 8500 where my tach stopped btw, and developed a knocking soon after. I made it home 450-500 miles on 60W oil, and the engine just needed new bearings to be back in good running condition. It still had excellent cross hatch, and minimal ring ridge.

The original block was not sonic checked, and it took me 4 blocks to find one capable of 60 over with a high enough safely margin. If I could of afforded a high quality war hawk block maybe 80 is reasonable, but 60 over is stretching factory items alot. Which is why it took me 4 blocks to find the right block.

[Ziegelsteinfaust]

Originally Posted by toolboxchev

Kinda what I thought Zig, everything always will affect other things. Its just how things are, an I am a things kinda guy.

Aluminum heads are new to me also, so I am growing out of those old smog chambers. I want the most power I can get out of a small block on cheasy peasy 87 octane.

The SCA's run or wear out of Prestone after a year, and you know what happens next.

Just flow best practices with aluminum heads. Even basic cheap heads typically are light years ahead of early versions due to technology, and experience of the metal casters.

This was somewhat true in the 90's but probably not anymore. It was recommended to only use cast iron, and aluminum in the engine/cooling assembly. Or cast iron, and brass. Not all 3. Something about dielectric issues between the brass, aluminum that the coolant could not always protect from. So when I went with aluminum heads I got a aluminum radiator. As I always had some aluminum rotting away on my intake manifolds. Especially where the rear water passages were blocked by the manifold. It even would be there with 4 corner circulation that I am a fan off.

It takes quite a long time so I am not trying to portray a scare story here