More 425ci engine talk.....
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Registered User
Joined: Aug 2019
Posts: 69
From: Western PA
More 425ci engine talk.....
My 1966 Starfire obviously has the "Starfire 425ci" engine. It also now has a pretty big exhaust leak between the head and exhaust manifold (original). This is the ONLY reason I am contemplating switching to headers. The issues are......
1. Is this even possible?
2. Do they even make headers for this block? Summit claims they do but they only list the 442 as the "model". Weird I know
3. Has anyone done this?
4. If so, what company makes these?
5. Can it be done with the engine mounted in place?
Before I waste money and/or tear into my engine....Any help/knowledge would be greatly appreciated.
1. Is this even possible?
2. Do they even make headers for this block? Summit claims they do but they only list the 442 as the "model". Weird I know
3. Has anyone done this?
4. If so, what company makes these?
5. Can it be done with the engine mounted in place?
Before I waste money and/or tear into my engine....Any help/knowledge would be greatly appreciated.
Registered User
Joined: Aug 2005
Posts: 1,972
From: Braceville, Ohio
Thornton makes an aftermarket version of the driver's side factory S exhaust manifold that Starfires all ready have. Besides that I don't know of anyone making exhaust manifolds for these cars. I'd try the shiny exhaust manifold gaskets such as these. The gaskets are made to "slip" in without taking all the bolts out.
https://www.inlinetube.com/products/...BoCLAoQAvD_BwE
https://www.inlinetube.com/products/...BoCLAoQAvD_BwE
Registered User
Joined: Feb 2013
Posts: 15,411
From: Phoenix, AZ
All of the BBO header flanges are the same, but the rest of the header is made to fit a particular chassis. I doubt anyone makes headers specifically for the Starfire.
As for those gaskets, they should be available from any auto parts store: FEL-PRO MS90078
As for those gaskets, they should be available from any auto parts store: FEL-PRO MS90078
Last edited by Fun71; Aug 25, 2019 at 03:44 PM.
Old(s) Fart
Joined: Mar 2007
Posts: 50,803
From: Northern VA
No one makes headers for the 1965-1970 full size cars, period. The location of the steering box makes routing the header tubes problematic. Summit's listings are notoriously inaccurate and misleading, as they frequently show Chevy parts as applicable to Oldsmobiles. Left unsaid is that the Chevy parts fit ONLY if your Olds has had a Chevy motor swapped into it. 
To your question, if an exhaust leak is the only reason why you would even think about installing headers, why not just fix the exhaust leak instead? For starters, pull the manifolds and check the sealing surfaces for flatness and pitting. I had problems with the manifolds on my 67 Delta. I had the passenger side resurfaced and I bought the repro driver side manifold to convert to dual exhaust. While Olds does not normally use exhaust gaskets from the factory, pitting and warping can make sealing difficult. I used Remflex gaskets on my manifolds. Pay close attention to the bolt torque, as overtorquing will damage the Remflex gaskets.
To your question, if an exhaust leak is the only reason why you would even think about installing headers, why not just fix the exhaust leak instead? For starters, pull the manifolds and check the sealing surfaces for flatness and pitting. I had problems with the manifolds on my 67 Delta. I had the passenger side resurfaced and I bought the repro driver side manifold to convert to dual exhaust. While Olds does not normally use exhaust gaskets from the factory, pitting and warping can make sealing difficult. I used Remflex gaskets on my manifolds. Pay close attention to the bolt torque, as overtorquing will damage the Remflex gaskets.
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