When they start squeaking!!!!! at least that's how the Street Outlaw boys do it.
Sorry couldn't resist.
Aluminum heads
- Thread starter Dan s
- Start date
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When they start squeaking!!!!! at least that's how the Street Outlaw boys do it.
Sorry couldn't resist.
When they start squeaking!!!!! at least that's how the Street Outlaw boys do it.
Sorry couldn't resist.
Oh god. Lol
nm9stheham
Well-Known Member
The word chamfer needs some explanation because that is part of the issue, and seems to be unique to the 340, not the other SBM blocks. Look at the block pix in post #94... you can see the chamfers at the tops of the bores. 340 only... no one seems to know why! The other SBM blocks is have the bores extending straight to the tops, no chamfer.
Be prepared to spend a lot of $$ for sleeving the lifter bores if you think of going that way.. like $500 + or -. That kind of $$ does not match up with thinking of using a cast crank to save $$, so you maybe should start looking at $$ for all of this. Roller cams and lifter are more costly by quite a bit, and when you get into the lift range and lift speed where they really are needed, the spring and rocker package is going to have to be right (not cheap). A solid flat lifter will achieve some pretty darned good lift rates and high lifts with less cost. Flat lifters just have the disadvantage of needing to watch the oils more and having to follow proper break-in etc.
I got a running tab on parts so far. Not near as bad as I thought it was gonna be. I hope to find a machine shop in Tampa next week when I get there. I’ll have about a week to do some looking around then it’s back to 13 hour shifts till Xmas.
When they sleeve the lifter bores do they just put a longer sleeve in to stop the lifter from loosing oil pressure
When they sleeve the lifter bores do they just put a longer sleeve in to stop the lifter from loosing oil pressure
nm9stheham
Well-Known Member
Yes, have seen that. The machinists would be the best to comment
A big mistake folks make when installing aluminum heads is not increasing the compression ratio. Aluminum by itself does not make the head better from a power output standpoint, it can reduce power! The aluminum head dissipates heat out of the combustion chamber much faster than cast iron, which results in reduced cylinder pressure, just like reducing the compression ratio. When switching from cast iron to aluminum heads, you should raise the compression ratio about 1 to 1.5 points. Modern aluminum heads flow much more air than OEM iron heads and most of them do have smaller chambers to bring up the compression ratio.
You asked about stroker kits - we have them! 360-426 kits and 340-435 stroker kits.
You asked about stroker kits - we have them! 360-426 kits and 340-435 stroker kits.
Compression ratio and cylinder pressure are both results from mechanical features. Aluminum or cast iron has nothing to do with either, as long as the chambers are the same volume. The only positive attribute aluminum has on combustion is, the quicker heat dissipation, which does allow for more compression, but only through the more effective heat dissipation. The physical compression or cylinder pressure is unchanged from cast iron to aluminum all other things being equal. A compression test would surely be the proof there.
yellow rose
Overnight Sensation
This just isn't true. The ability of aluminum to reject heat at a quicker rate is way over played. You can't possibly think that aluminum will reject heat fast enough to eleimate detonation because of compression ratio is a bald faced fantasy. You can run the same CR on iron as you can aluminum.
The cooling system is what controls heat rejection.
Got to kill this wrong headed thinking. Been hearing this my whole life and it was wrong then and it's wrong now.
j par
Well-hung Member
I was under the impression that aluminum conducts heat more evenly that's why our barbecues are made of them..
I believe he speaks for the metal itself. Not the cooling system or the cooling passages within the head. If the iron head can cool as well as the aluminum head, then the compression ratios can be the same same fuel. But this is not the case.
j par
Well-hung Member
Can you say that again a little bit slower...
What I find utterly flabbergasting is that a representative from a so called professional engine company would believe such nonsense. It doesn't matter one iota what material the heads are made of. They could be made of wood and it would not have an effect on compression or cylinder pressure all things being equal.
Has do not believe he said that but said increasing the compression would be a good idea with aluminum heads. Not that the heads increase compression by themselves unless of course the chambers are smaller than what they replaced.
I don’t know. It is possible but I’ll need a lot of beer.
Conducting and dissipating heat even would require the thickness of the metal to be the same.
Your BBQ’s are aluminum?
G’s! You must go through a couple of them quickly.
Cast iron, Stainless Steel or steel here.Anything lesser is ridiculous & cheap garbage.
He said point blank that aluminum heads decrease compression and cylinder pressure. That's just flat out wrong.
I'm in agreement "there". lol
Would you quote that for me please?
"The aluminum head dissipates heat out of the combustion chamber much faster than cast iron, which results in reduced cylinder pressure, just like reducing the compression ratio."
That statement cannot be anymore false. Aluminum does dissipate better than iron but it has zero effect on either cylinder pressure or compression ratio. Just doesn't happen. I don't care who says it. lol
yellow rose
Overnight Sensation
This just isn't true Rob. Think about it. The time it takes for detonation to occur happens so fast that the metallic structure of the head has zero influence on it.
Somewhere on here I typed out several AJ length posts explaining the cooling system and how it affects CR much more than aluminum or cast iron heads. I had to type so much my hands swelled up and I couldn't type anymore.
If anyone knows where that is, move it up and I'll finish it.
The rate of change of temperature from cruise temp to detonation temp is so fast that there is no metal I know of that can affect detonation.
That's why I harp on the cooling system so much. Slow turning, low flow water pumps, junky assed electric fans, cramped shrouds and more make it nearly impossible to control detonation rather than head material.
I could actually run a 160 thermostat and my cooling system would keep the engine at 160 even on a 100 degree day. If I take the Thermostat out, I doubt I could get 130 degrees into the engine on a 100 degree day.
That's one reason I'm running 11:1 on iron heads on pump gas with full timing. Coolant temp control and flow are WAY more critical than an aluminum head is.
yellow rose
Overnight Sensation
My question is...even if the head rejects heat quicker, does the medium used for coolant accept heat any quicker, or does the coolant not know (or care) what they head material is?
The answer is the head can only reject heat as fast as the coolant allows.
Again, this is no different than setting a Holley power valve with idle vacuum. It was wrong from the start, is wrong now and will be wrong forever. And guys wonder why they can't tune a Holley.
Same thing here. The cooling system controls heat. Period.
ValiantRacing
Well-Known Member
I have aluminum heads on my 9.4 to 1 318, and it runs pretty good
j par
Well-hung Member
Why is it my car runs great on pump gas but won't turn off...
yellow rose
Overnight Sensation
Agreed.
If ya can find it, I’d enjoy the read.
But fact is aluminum will cool faster than a factory iron head. Heat both up in your oven and stand by with a heat gun.
That I think we can agree on.
Now the heads, the cooling liquid (not the entire system)
And the path it takes around in the head is the other story in controlling head and thereby to an extent, cylinder temps. By this, we will assume the air fuel mixture is perfect. And when it’s off, the story changes and the topic swings. We can get to that later.
Agreed?
Agreed
Absolutely!
Let’s take a step back and say that we are testing two identical heads with the exception of the metal used. These heads are placed on two identical engines. The compression ratio is 12-1. Fuel is 93 octane, no additives.
The test is to see which head has detonation issue first and there only change is a camshaft from “OFF THE SHELF” (Pick any manufacturer but just one.)
Who has problems first and why?
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