New Aussie head info
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New Aussie head info
With all the hype around the Aussie 302C "quench" heads we rarely get into the specifics about the other head common to Australia.
For the longest time, I thought they were essentially the same as the US 351C/351M/400 open chamber heads, but I've come across a few images recently that have me believe these are "semi-quench" heads.
Based on the image, there doesn't seem to be any valve shrouding issues so they should flow just as well, if not better than the 302s. Installing larger valves shouldn't require any major re-working of the chambers. No thermactor boss in the exhaust ports. As far as I know, they aren't usually sought after so they should be a dime a dozen + shipping of course.
The only question remaining is whether or not there is enough quench area to gain quench benefits. Does anyone own a set?
For the longest time, I thought they were essentially the same as the US 351C/351M/400 open chamber heads, but I've come across a few images recently that have me believe these are "semi-quench" heads.
Based on the image, there doesn't seem to be any valve shrouding issues so they should flow just as well, if not better than the 302s. Installing larger valves shouldn't require any major re-working of the chambers. No thermactor boss in the exhaust ports. As far as I know, they aren't usually sought after so they should be a dime a dozen + shipping of course.
The only question remaining is whether or not there is enough quench area to gain quench benefits. Does anyone own a set?
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With any quench chamber, a matching piston is the key
The chamber pic was taken at angle so I had to distort it somewhat to get it near the size of the others. The piston below was one of my Ebay bargains, image is reversed for comparison.
I think there is a little quench with the right piston, decking the head would add more. Some people may be looking for a .5 point increase in compression over the open chambers or possibly a .5 to 1 point reduction in place of the quench heads. It never hurts to have more options.
I think there is a little quench with the right piston, decking the head would add more. Some people may be looking for a .5 point increase in compression over the open chambers or possibly a .5 to 1 point reduction in place of the quench heads. It never hurts to have more options.
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Sorry, but you're giving me too much credit. I don't have the time to read every member's post, nor do I remember who posted what link a week and a half ago.
This thread is an update to the AU 351C info I posted on the 25th of last month, looking for some feedback as to whether this head would offer any quench benefits.
If you notice anyone else repeating info with their posts, please bring it to our attention.
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The piston shown is a custom made JE 351C forging. The dish is an irregular shape and appears to conform to the semi-quench style chamber. If there are no quench benefits, why else would a person go to so much trouble and expense, when a simple round dish would be 10Xs easier?
This thread is an update to the AU 351C info I posted on the 25th of last month, looking for some feedback as to whether this head would offer any quench benefits.
If you notice anyone else repeating info with their posts, please bring it to our attention.
----------------------
The piston shown is a custom made JE 351C forging. The dish is an irregular shape and appears to conform to the semi-quench style chamber. If there are no quench benefits, why else would a person go to so much trouble and expense, when a simple round dish would be 10Xs easier?
Posting Legend
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I would think that a round pattern would be easier but then with modern CNC machine tools it does not make a whole lot of difference. As I understand it the quench effect comes from the two combustion chamber surfaces coming close together and producing a high speed jet of gasses that creates turbulence and breaks up the pressure wave from the initial ignition point. Kind of like the swirl effect that is used on some engines. Of course the larger the area and the more lopsided it is the better. There does not seem to be a large enuf area or enuf of an area on one side of the chamber to produce much of a "jet" effect.
-Just my 2 cents.
-Just my 2 cents.
Lead Driver
Joined: Nov 2000
Posts: 6,648
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From: Albuquerque
I think to get the full quench effect the piston would have to have more flat area under the flat section of the combustion chamber. In my view it would be somewhat isometrical in order to get a usuable comp. ratio for the street. I wonder if it would create problems with pushing the piston sideways.
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