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Maytag...<P>No, the heads are the same. <BR>Group No. 0.269<BR>Part No. 1366379 (L & R heads are interchangeable)<P>I don't have the casting number. <P>The compression difference is obtained by the pistons, with the 300/310/2V having dished pistons and the 300/335/4V having flat top pistons. The 225 V6 and the 300 V8 use the same pistons (low compression).<P>JMC

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I would have to disagree.<BR>I changed my 64 Skylark 300-2bbl (aluminum heads)to a 4bbl using a 65 300-4 (Cast heads) as the donor.<BR>I found what you said about the pistons, but the 65 4bbl heads have a slightly smaller combustion chamber and slightly larger valves! I have no production documentation to prove this, just relaying what I found.<BR>Maybe the difference in compression is part pistons and part heads? With the 2bbl having 9:1 and the 4bbl having 11:1 I figure I'm somewhere around 10:1. Also I run fine on 93 octan fuel which would not be possible at 11:1. Someday I'll verify that when I pull the motor to replace it with a 66 340 4bbl. that has been Balanced and agumented with some Kenny-Bell items.

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I am with John on this the pistons are the same for all 2V and the same but less dish for all 4V for all years. I have built 300's in every possible combo its the pistions that change cranking pressure. I have used Al 2V heads on late blocks and cast 4V heads on 64 blocks. Even though they look different all 300 heads I have checked CCs on are +/- 5cc. The biggest thing that lowers compression is the thick Fel-Pro gaskets<BR> most folks use they are .030 to .100 thicker than the stock steel used by Buick.

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URU Dale,<P>I'll stand by the information my response as correct.<P>My info comes directly from the 1965 Buick Parts Manual and the 1965 Buick Special/Skylark Chassis Manual. The PM lists the same head for both variants of the 300 and lists different part numbers for the pistons.<P>What you observed with the differences in the 1964 aluminum 2bbl heads (combustion chamber shape and valve size) would be true for both the 1964 300 variants when compared to the 1965 cast iron heads. <P>There was also a slight 'detune' of the advertised HP and torque ratings of these engines from the 1964 to the 1965 models:<P>1964<BR>300-2v HP 210@4600 RPM/Torque 330fp@2400 RPM <BR>300-4v HP 250@4800 RPM/Torque 352fp@3000 RPM<P>1965<BR>300-2v HP 210@4600 RPM/Torque 310fp@2400 RPM <BR>300-4v HP 250@4800 RPM/Torque 335fp@3000 RPM<P>Compression ratio is the same for both years:<BR>300-2v 9.0-1 and the 300-4v 11.0-1<P>Cheers,<BR>JMC

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The high compression ratio is not the same for both years. The 64 is listed at 11:1, but the 65 Chassis Service Manual and the NHRA list the 65 300 at 10.25 compression. I think it was the pistons. I remember using 300 11:1 pistons in a 340 to bump up the compression back in the early 80s.

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