Originally Posted by JHZR2
So I know upfront that this design took some liberties, to say the least. And you hit the point exactly - Al is going to expand quite a bit more, shearing or otherwise affecting the HG somehow...
The 3.5L "rod bending" set of theories is an interesting set of discussions to read.
Essentially lots of folks started to observe high oil consumption, then found out of round bores, especially in cylinder 1, due to bent rods. Of course this is a bored out 3.0L, so there's less material, less gasket, etc.
One main theory is that the HG gets breached, starts to allow liquid into cylinder 1, which then causes a "mini hydro lock" which in time causes the rod to bend, causing an oblong stroke, causing an ovoid bore and consumption, which around 1qt/400 miles starts to affect drivability.
Another theory that I heard 30 years ago (not for this specific issue, but for engines that were originally all iron and retrofitted with Al heads) was that the differential expansion makes the engine into a "bimetallic strip", some of the engine builders claiming that they'd measures the 6 cylinders flexing like one when hot and loaded.
I can't vouch for the veracity of this claim, as I've never tried even simple beam calcs to get a feel.
But the early engines were all flat deck, and flat bearing mating and sump surface (give or take), rather than deep skirted and cross bolted like a lot of stuff is now.
I've not discounted it as a theory...
I've had great success fitting the thermostat on the lower hose (inlet) side of the pump...much more stable operation, and warmup is incredibly even...freezing days, my V-8s wouldn't even warm the radiator, they lost enough heat simply circulating it around themselves.
As opposed to what eljefino has hinted at, providing the radiator with a constant temperature fluid source, batchwise, while throwing a slug of relatively cold water at number one cylinder in particular...my Holdens would always have a major ridge on #1, that progressively lessened with cylinder count.
So I know upfront that this design took some liberties, to say the least. And you hit the point exactly - Al is going to expand quite a bit more, shearing or otherwise affecting the HG somehow...
The 3.5L "rod bending" set of theories is an interesting set of discussions to read.
Essentially lots of folks started to observe high oil consumption, then found out of round bores, especially in cylinder 1, due to bent rods. Of course this is a bored out 3.0L, so there's less material, less gasket, etc.
One main theory is that the HG gets breached, starts to allow liquid into cylinder 1, which then causes a "mini hydro lock" which in time causes the rod to bend, causing an oblong stroke, causing an ovoid bore and consumption, which around 1qt/400 miles starts to affect drivability.
Another theory that I heard 30 years ago (not for this specific issue, but for engines that were originally all iron and retrofitted with Al heads) was that the differential expansion makes the engine into a "bimetallic strip", some of the engine builders claiming that they'd measures the 6 cylinders flexing like one when hot and loaded.
I can't vouch for the veracity of this claim, as I've never tried even simple beam calcs to get a feel.
But the early engines were all flat deck, and flat bearing mating and sump surface (give or take), rather than deep skirted and cross bolted like a lot of stuff is now.
I've not discounted it as a theory...
I've had great success fitting the thermostat on the lower hose (inlet) side of the pump...much more stable operation, and warmup is incredibly even...freezing days, my V-8s wouldn't even warm the radiator, they lost enough heat simply circulating it around themselves.
As opposed to what eljefino has hinted at, providing the radiator with a constant temperature fluid source, batchwise, while throwing a slug of relatively cold water at number one cylinder in particular...my Holdens would always have a major ridge on #1, that progressively lessened with cylinder count.