LT1 Heads : Iron Vs Aluminum
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LT1 Heads : Iron Vs Aluminum
The iron head is supposed to flow better than the aluminum one, but the aluminum one would be much better for more timing and heat.
Once ported, will both heads flow close the same, or can the iron head make bigger power numbers?
Once ported, will both heads flow close the same, or can the iron head make bigger power numbers?
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The iron heads do flow more than the aluminum heads. Roughly 220 CFM @ 0.5 inches lift, 28 inches water column for the aluminum heads and 230 CFM @ 0.5 lift and 28 inches water column for the iron heads. The only problem is that aluminum has a higher specific heat than iron and thusly allows you to run a higher CR without risk of detonation.
#4
well every set we have flowed came up with a 1-3 cfm diffrence in no order at all.
they will make the same power with both being ported by the same guy but the irom you gain weight and loose max compression without detonation. but who runs stock heads anyway?
they will make the same power with both being ported by the same guy but the irom you gain weight and loose max compression without detonation. but who runs stock heads anyway?
#5
Originally Posted by METALBEAST
The iron heads do flow more than the aluminum heads. Roughly 220 CFM @ 0.5 inches lift, 28 inches water column for the aluminum heads and 230 CFM @ 0.5 lift and 28 inches water column for the iron heads. The only problem is that aluminum has a higher specific heat than iron and thusly allows you to run a higher CR without risk of detonation.
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Originally Posted by Squat13
Well kind of.... the aluminum disapate the heat more and do not get as hot, also the weight less, but I seriously doubt that Alloy heads withh hold more compression than Iron heads.
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Originally Posted by Squat13
Well kind of.... the aluminum disapate the heat more and do not get as hot, also the weight less, but I seriously doubt that Alloy heads withh hold more compression than Iron heads.
Not kind of, its cold hard fact. Specific heat is defined as the ratio of the change in internal energy of a substance to the amount of incremental change in temperature per unit volume. The specific heat of iron is numerically higher than that of aluminum. Therefore it takes a greater amount of temperature change to raise the internal energy of aluminum than it does iron (aluminum does not absorb as much heat as iron) and thus not be as susceptible to detonation (spark knock, preignition) as iron.
The temperature of a fluid will increase with a corresponding increase in pressure ( this is accomplished when by increasing your CR for example). Therefore aluminum heads can run higher compression ratios than equivalent iron heads.
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Thanks for the replies guys. I have the oportunity to pick up a rebuilt Iron head LT1 with 0 kms for $800 cnd and was wondering if it was worth it. I am looking to get a rebuildable block and aluminum heads for my winter project and thought this may be a good choice. Looks like I will have to keep searching.
Thanks.
Thanks.
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Originally Posted by Boother
Thanks for the replies guys. I have the oportunity to pick up a rebuilt Iron head LT1 with 0 kms for $800 cnd and was wondering if it was worth it. I am looking to get a rebuildable block and aluminum heads for my winter project and thought this may be a good choice. Looks like I will have to keep searching.
Thanks.
Thanks.
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Iron heads outflow the 95 and earlier aluminums the 96-7 aluminums are roughly equal in flow to the irons. If you want to get into thermodynamics aluminum transfers heat faster sucking more heat out of the chamber, now think for a moment what does an engine do turns heat into rotation right so every bit of heat not used to turn the crank is wasted. aluminum does allow more compression due to the lesser themal effiency, the extra compression is then used to make up for the power lost though cooling. The weight difference is only about 35# as per a source I trust a whole lot more than the average forum poster.
The irons can be ported to flow well if going all out on the porting though I think the best are the early aluminum heads because there is more material to play with.
The irons can be ported to flow well if going all out on the porting though I think the best are the early aluminum heads because there is more material to play with.
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Originally Posted by FIREHAWK#608
EBAY OR EVEN HEAD PORTERS HAVE PLENTY OF LT1 STUFF AROUND. $800 SHOULD BUY A GOOD BIT.
Right now, Ebay cannot touch that deal.
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Originally Posted by 96capricemgr
Iron heads outflow the 95 and earlier aluminums the 96-7 aluminums are roughly equal in flow to the irons. If you want to get into thermodynamics aluminum transfers heat faster sucking more heat out of the chamber, now think for a moment what does an engine do turns heat into rotation right so every bit of heat not used to turn the crank is wasted. aluminum does allow more compression due to the lesser themal effiency, the extra compression is then used to make up for the power lost though cooling. The weight difference is only about 35# as per a source I trust a whole lot more than the average forum poster.
The irons can be ported to flow well if going all out on the porting though I think the best are the early aluminum heads because there is more material to play with.
The irons can be ported to flow well if going all out on the porting though I think the best are the early aluminum heads because there is more material to play with.
TE = 1- (CR)^(1-K) where
TE = Thermal efficiency
CR = Compression Ratio
K = specific heat ratio of the working fluid ( in our cas the air/fuel mixture which would be identical regardless of head material)
I underdstand that real IC engine are not ideal since we must also take into account friction, head design etc. But it hold true to an extent. Therefore the engine with a higher CR will be the most efficient engine. Just my $0.02