Quote:
Originally Posted by trishieldchief
Here is some interesting detail on GP 428 engines.
All 69 428 GP engines received 62 heads.
Standard GP SJ 428's had very mild cams 066 for XF auto and 067 for 4 speed 428.
Keep in mind, standard 69 Firebird YT and GTO YS engines with auto trans had bigger 067 camshaft. So in a bigger cube 428 these cams are even milder!
Auto trans XG code 428 HO engine received 067 camshaft which is the standard camshaft in a lowly YS code 400 in a regular auto trans 69 GTO and Firebird.
Only the 69 GP 428 HO WL code received the O68 Ram Air camshaft.
Also, all 69 GP standard 370 hp and 390 hp 428 HO's received the same standard non ram air carbs 7029268 auto and 7029263 for 4 speeds.
When you consider that the 428 HO engine upgrade was $184.80 all you really got especially in auto trans application were long branch exhaust manifolds and thus oil filter rotator block.
Pontiac made great money and essentially gave you very little for the 69 GP 428 HO engine upgrade.
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Excellent info "Trishield" except for the cylinder head. I have seen 3 HO 4-speed cars in my life and all three of them had head cast #48. There is conflicting info on this cylinder head - perhaps someone else can clarify. From what I have found the 48 head was used on the 350HO engine and had a combustion chamber volume of 65 cc's. I think these heads were used on the HO 4-speed cars to give a boost to the compression ratio. This was something that was covered in "Pontiac Enthusiast" magazine before the magazine was discontinued. I will have to dig it up - I have it somewhere. Just wanted anyone who reads this and has head cast 48 on their HO 4-speed car - that it is not necessarily incorrect - to my knowledge anyway!!! Would love to hear more from the Pontiac tribe??