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aussiebill
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Last Active: 6 Years Ago
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Don, thanks for that bit, pretty much what we were thinking. regards bill.
 AussieBill YYYY Forever Y Block YYYY Down Under, Australia
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Don Woodruff
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This from Teds original Post With the 2” four hole carb spacer, the aluminum heads outperform the iron heads at all rpm ranges. With the 2” tapered carb spacer and below 2800 rpms, the iron heads are only marginally better in torque than the aluminum versions, but after 2800 rpms, the aluminum heads simply run away from the iron versions with the best peak horsepower numbers.
I believe this indicates it is about a wash below 2800 rpm but above 2800 rpm the Al heads are superior with this combination. A guess that with a shorter cam, a smaller carb, the advantage of the Al heads may move a bit lower in the RPM range . Ted is the expert though.
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aussiebill
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Hollow Head (5/15/2010)
What are the Hp and torque numbers at the same rpm's as tested with G heads? I know the new ones are better at higher rpms but are they waste of money at the lower rpms  ? Can we see some graphs to compare? Seppo, i initially wondered the same thought, re the Hp @ same RPM and figured the hp or torque nosed over at those rpm,s round the 1st heads results? ted will know for sure. And with the growth rate on the new heads,that amount Ted mentioned is great point, so initial settings can be allowed for. For all my time rebuilding most earlier engines, i,ve allowed .002" cold set and when engine is ran, its nearly spot on for clearance. so this new figure for our new heads is a big help. regards bill.
AussieBill YYYY Forever Y Block YYYY Down Under, Australia
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Hollow Head
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What are the Hp and torque numbers at the same rpm's as tested with G heads? I know the new ones are better at higher rpms but are they waste of money at the lower rpms ? Can we see some graphs to compare?
 Seppo from Järvenpää, Finland
www.hollowheads.net (just click the hole in the head to proceed)
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Ted
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Y block Billy (5/14/2010)
Ted, Wouldn't the push rods grow maybe .001" after warm up? we always used the calculation of .003" of growth per foot of material (steel and Iron) for every 100 degrees above ambient temperature for the equipment I set up around the globe. Also I know that the aluminum grows at a much faster rate, the number 1 cause of snowmobile/dirtbike/four wheeler piston failures is the fact that people don't let them warm up before reving them up and the piston grows faster than the cylinder and they get a cold seizure. I don't have handy the exact growth of the aluminum versus the steel for the same temperatures, but as the steel catches up, might it change that figure? I guess I should have clarified growth as ‘net growth’. The net growth is 0.004” regardless of which parts are growing. The aluminum heads could be growing 0.006” while the pushrods are growing 0.001” and the valves themselves are also growing 0.001" which still makes net growth 0.004” when performing a cold versus hot valve lash adjustment. At this point, all that needs to be known is net growth so that when the cold lash is adjusted, hot lash is in the ball park. The difference in lash with aluminum heads from cold to hot is a 0.004” increase.
  Lorena, Texas (South of Waco)
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Ted
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jepito (5/14/2010)
What are the chamber sizes of the two heads tested?Chamber sizes are 65.7cc for the iron heads and 60.0cc for the aluminum.DANIEL TINDER (5/14/2010)
I am also interested in what % of power increase could be attributed to higher CR?For a ½ point compression ratio increase on iron heads, figure a 2% increase in peak horsepower numbers. In this case where the heads were switched from iron to aluminum and the aluminum ended up being 0.6:1 higher for the compression ratio (cr), it’s a wash or net zero increase. Simply put, aluminum just isn’t as efficient as cast iron in converting the combustion heat into power. To offset the inefficiencies of aluminum in the combustion process, a given increase in cr is required to keep the power levels the same with everything else being equal. Had the aluminum heads been designed with the same size combustion chambers as stock, then a portion of the power that was a result of improvement in head flow and combustion chamber design would simply have been lost due to having to make up for the lost power due to the thermodynamic properties of the aluminum. That’s the simple explanation.
Lorena, Texas (South of Waco)
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Y block Billy
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Wow! Great job "John" and "Ted" Ted, Wouldn't the push rods grow maybe .001" after warm up? we always used the calculation of .003" of growth per foot of material (steel and Iron) for every 100 degrees above ambient temperature for the equipment I set up around the globe. Also I know that the aluminum grows at a much faster rate, the number 1 cause of snowmobile/dirtbike/four wheeler piston failures is the fact that people don't let them warm up before reving them up and the piston grows faster than the cylinder and they get a cold seizure. I don't have handy the exact growth of the aluminum versus the steel for the same temperatures, but as the steel catches up, might it change that figure?
 55 Vicky & customline 58 Rack Dump, 55 F350 yard truck, 57 F100 59 & 61 P 400's, 58 F100 custom cab, 69 F100, 79 F150, 82 F600 ramp truck, 90 mustang conv 7 up, 94 Mustang, Should I continue?
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DANIEL TINDER
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jepito (5/14/2010)
What are the chamber sizes of the two heads tested?I am also interested in what % of power increase could be attributed to higher CR?
6 VOLTS/POS. GRD. NW INDIANA
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jepito
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What are the chamber sizes of the two heads tested?
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Don Woodruff
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Great results. I would have estimated 320-330 horse. Not knowing the specifics of Teds engine I could not put it into EAP. If an engine were built specifically for these heads with 0 deck, about 10.5 cr and possibly a bit shorter, higher lift cam and mildly ported heads 350+ horse power may be possible with a very streetable "Sunday go to Meeting", not racing, engine. This would back up my paper engine very closely. John you did good. Thanks for the info Ted. The ported heads should shine on your Engine Masters engine.
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