Carl, uk

Ok so I know my engine has been replaced with what I'm told a 1979 403 oldsmobile engine from a trans am around 5 years before my ownership..
Block casting number 557265
Heads 554717
Large 4A stamp
All these numbers confirm 1979 403...
Shopping around for some nice chrome valve covers and why is it everywhere are showing the 10 bolt stud pattern for my engine...
My existing valve covers are a 5 off set stud pattern (like Chevy)
Any help anyone .......??? Thanks in advance... :-)

Fun71

No, not like Chevy, which has 4 bolts; more like 5 of the 10 available bolts that were used on the earlier Olds engines.

The typical 10 bolt Olds valve covers will fit on your heads but use only 5 of the bolts to hold them down. I think your heads have the other spots but they are not drilled and tapped.

joe_padavano

Starting in the late 1970s, Olds deleted five of the ten valve cover bolts as a cost savings measure (hey, when you're selling a million cars a year, saving a buck on each car adds up). The five bolt valve covers are exactly the same shape as the ten bolt ones, they just didn't drill the extra holes. You will only find ten bolt covers in the aftermarket. You need to plug the extra holes with RTV.