Join Date: Jan 2015
Location: Injun Territory, 'Merica!
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98 casting heads were used on YG coded 455 big car engines for 71 model. Have only found this engine in relatively bare bones '71 Bonnevilles. The YG coded 455's were few far and far between even in the mid 80's. Having a Pontiac engine core program going for over 2 decades, I usually came across the '71 YC coded 455 engine in a good 20-1 ratio over the lower horse YG coded '71 455's. interestingly, the first '71 YG 455 I ever pulled in the mid 80's was an extreme early 483677 block cast G080. A factory screw-up, assembled with factory 4 bolt caps, still have the shortblock.
As factory cast and the chamber fully machined by Pontiac, '98's are a 115 cc chamber head with 2.11 intake valves and press in studs. Not much demand for this chamber size head, know at the warehouse I have several pair of '71 66 casting 455 heads off '71 YC engine cores. Personally I wouldn't build a naturally aspirated 455 with them, but have sold a few pair of 66's to restorers needing cheap dated core heads for their 71 455 Dport GTO's. The last 10 years there has also been more interest in budget turbo and budget supercharged 455 engines and a few builders have used cheap 66's, 7M5's, 4X-1's in their builds to keep C/R low on 4.25 stroked 400 and 464+ cube 455 block combo's.