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By OlWeldinrig - 7 Years Ago
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Any one in Canada have a parts stash?Closer to Sask the better.
I am looking for a set of 471 casting heads to pair up with my Jahns dome pistons.
Thanks Dave
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By NoShortcuts - 7 Years Ago
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Dave. I suspect that your concern in using the domed Jahns pistons is that you may have a static compression ratio that may cause pre-ignition / detonation.
Static compression ratio is to be considered, but the camshaft you use comes into play as well. Mild duration aftermarket performance camshafts hold the intake valve open longer on the intake stroke than your original or a standard aftermarket replacement camshaft. The result of this is to lower the dynamic compression ratio of your engine.
Consider checking with Ted Eaton, Tim McMaster, John Mummert, or someone else knowledgeable on this issue as to what you can get away with for cylinder heads. The 471 heads will drop your static compression ratio down, but you don't want to do that unless you have to. Compression ratio has a tremendous effect on your vehicle's low end performance.
Food for thought and something to dig into. 
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By OlWeldinrig - 7 Years Ago
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Charlie,
Ted actually suggested using the 471 heads a while back.I was actually not wanting to drop to that big of a chamber until I was told that the 471 flows better.Maybe gain where I lost compression.If I can find the sheet I will list the specs for cam,286 with .529 lift I believe.I know previous owner ran it on av gas in 70s,It would be nice to have a engine I could run on a fairly regular bases with pump gas.This cam is probably way to big but I'd like to try it first.
Dave
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By miker - 7 Years Ago
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Jahns pop up, and av gas. My 312 with those back in the late 60's needed the "white" pump scrubron, at 11:1. Or 11.5, don't really remember, and I never checked which head castings I had. That was as high an octane as the good Sunoco, and it leaded the plugs like av gas. Probably 113 heads, but I know they had the big valves. The guy that built that engine drove a AA fueler, and was pretty into the racing scene. That motor had an Isky RPM300, straight up. So, the question about the pistons, and the heads, and the av gas is all adding up.
I'm running 471's, ported and matched by Mummert on my F code 340 in the roadster. I don't remember how far down the piston was, but cc'd and checked, it's an 8:1, with flat tops. 8 lbs boost. So, my gut feel is the pop ups with the big chambers would breathe better, have better flame travel, and run on today's fuel. Ted would know much better than me.
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By marvh - 7 Years Ago
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I sent you a PM as I have set if you want.
marv
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By PF Arcand - 7 Years Ago
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Oldweld; just a thought on the Cam, which you say is likely to big.. On a Y-block, given the labour involved, the cam install is one area where you don't want to have to change it once it's in service!..
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By OlWeldinrig - 7 Years Ago
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Paul I hear what your saying but I'd really like to hear this thing run.Its going together pretty slowly.I may end up with another cam we'll see.I am reassembling a stock 272 as a practice run first.And I haven't %100 actually decided what I am going to put 312 into yet.I've planned on looking at about 3 different 55 tudor posts and a 56 Metoer hardtop which is a little pricier.
Thanks Marv but I need to hold off just a bit till I check on a set locally,after reading Charlie Brown's post in "Truck Engine"thread about the ECR casting truck heads having the large valves,posted and very similar chamber.I have one of those in my pile,also have a 59 school bus that I believe has a set when I drag it home.
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By OlWeldinrig - 7 Years Ago
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I don't see the message,I'll try the other dirrection.
marvh (2/9/2017)
I sent you a PM as I have set if you want. marv
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By OlWeldinrig - 7 Years Ago
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Well back looking again....I thought I had lined up a set then another fell through. Finally a buddy had an original 59 Y but it ended up being 113s.
Marv do you still have set of 471 heads?
I found home for my 312 so I am getting ancey to put my engine together.
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