[TA Tony]

Does anyone know for sure what the compresion ratio was for a stock 1969 400 WT with #48 heads would be? Thanks for the info.

[TA Tony]

Does anyone know for sure what the compresion ratio was for a stock 1969 400 WT with #48 heads would be? Thanks for the info.

[TA Tony]

Oh Yeah, what size valves would these heads had came with? Thanks

[Paul Spotts]

There were 2 combustion chamber volumes in 69 #48 heads. I think it is 69 and 72 CC's. The 350 4 bbl or HO used a smaller chamber and it is rumoured that certain RAIII 400's recieved these heads. They built a lot more RAIII's (TA's and Judges came std.) then 350 4 bbl's so I would guess the factory used up 350 heads. The valves were the standard performance head sizes of 2.11 and 1.77. The compression was rated at 10.75 to 1 but was more like 10.5 to 1.

All this does not matter if you change pistons. The current Fed Mog forged piston L2262F will lower the compression below 10.00 to 1 - more closer to 9.6 to 9.8 to 1. Perfect for pump gas. The Fed Mog cast piston with the dual stepped valve reliefs will lower the compression even more.

[TA Tony]

Paul, thanks for the info. How unstreetable would this combo be in my 79 TA. From what I have read, 10.5:1 is reportedly too much CR for the street. If this is true, how did the GTOs back in 69 successfully us this CR. Also, what roller cam/lifters/rockers would you recommend for this application and what type of HP are we talking about. Thanks a lot.

[Rick Lightfoot]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by TA Tony:
Paul, From what I have read, 10.5:1 is reportedly too much CR for the street. If this is true, how did the GTOs back in 69 successfully us this CR. <HR></BLOCKQUOTE>

Back in '69, the fuel you bought had a much higher octane rating than even todays best premium pump gas. The fuel back then had tetraethyl lead added to boost the octane to 100 plus and about 108 if you bought Sunoco 260. The highest CR I would run on the street today would be 9.5:1 with iron heads and 10.5:1 with E-Heads.

[TA Tony]

Rick, will installing hardend valve seats help any? Can this combo be ok on the street with 92 and a bottle of octane boost?

[Txbobcat]

Moving topic to "Pontiac Drivetrain-street"

[TinInjun]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by TA Tony:
Does anyone know for sure what the compresion ratio was for a stock 1969 400 WT with #48 heads would be? Thanks for the info.<HR></BLOCKQUOTE>

I have built two WT motors with #48 heads. I can tell you this much, both sets of heads cc'ed in a 66cc's. These heads were never milled. Both of these motors would run on pump gas, as long as you didn't put your foot in it, then it was like WW III under the hood. About the only gas this engine liked was AvGas, but thats another topic I don't want to get started again. [img]/infopop/emoticons/icon_wink.gif[/img]

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"Run wild with an Indian, not with the crowd in a Chevy"