I've got these engine air filter cover screws in my 1991 Bonneville SE that are so rusted in that I'm not even sure they will come out with an impact wrench. When I do get then out, I would like to have four new screws on hand to do an immediate replacement. I know this sounds trivial, but can someone please tell me the thread and length of the air filter compartment cover screws for the 1991 Bonneville? I've ordered a owner's repair manual but am hoping to get to the screws before the manual arrives. Thanks!!

My recollection is that they are machine screws, M6.0 thread. Approximately 30mm long.

They thread into a brass insert on the bottom half of the air filter housing. Soak them with penetrating oil for a week, re-apply daily, if you can. It will be difficult to get them with the phillips head, if you can get them without breaking the insert out of the lower housing, I would recommend replacing with a socket head cap screw or Torx screw and use anti-sieze.

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The Fleet:
'93 SSEi - Twincharged + manual Build thread
'97 Camaro - Top swap
'05 STS - V8, AWD, her DD
'92 Trofeo - Fair weather DD
'99 Montana - top swap 3800
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'92 Bonneville SSE
'87 LeSabre T-type
'67 LeSabre

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'93 SE - L67

Thanks for the reply! I called a dealership and luckily found the exact size M6.3-1.81 X 20mm (#14 x 25/32"). Those buzzards are seized up and I will hate to have to use an Ease Out bit to extract them, but it may come to that if impact does not work. Thanks for the warning about the cover. Fortunately I have a way to repair it should it break and the new screws are socket heads. I really appreciate the response.