If I'm not mistaken they are to release the sand after casting. They serve no performance porpose. You can take them out when hot tanking to get the passages cleaner. But make sure they are closed up tight afterwordsyou dont want them leaking.
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1970 Stang Conv:
en:Boss351 (balanced/blueprinted)
mech cam(240*@.050/.540 lift)
Scrw in studs/comp cams rllr rkr
Mldn valves 2.19in 1.71ex
ported polished cc'd hrdnd ex
Keith Black FT pistons(10.25/1)
Weiand Excellorator manifold
Holley700 DP mech 2nds
MSD 6 box and Dis
Headers/2 1/2 inch duels
tr: modified FMX
re:9-inch/3.89 limited slip
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