1998 Oldsmobile 88 - L36 to L26 intake swap

UrbanXplorer

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I bought a sweet one owner 1998 Oldsmobile 88 with 95,934 miles on the 10/10/14. About two weeks after buying it acted like it blew a head gasket. Being a mechanic and hearing about all the GM flaws I got down to it to see if it was true or false. Well it was false. Upon further inspection I came to the conclusion the the EGR stove pipe had melted the L36 plastic UIM (upper intake manifold) and let coolant into the engine. The engine is fine and will live again.

I'm posting this as a way to bring attention to everyone with the Series II 3800 engine. All is not lost my friends. I'm doing a L36 UIM to L26 intake manifold swap on my 98 Olds 88.

A li'l history for y'all. The Series II 3800 was built up to 2003. In 2004 GM realized they had a problem. How do they fix the problem? The Series III 3800 aka L26. It had an aluminum UIM and some cars equipped with this engine had aluminum coolant elbows replacing those faulty and very pesky plastic ones our cars came with.

Cars equipped with the L26 engine; 2004+ Buick LaCrosse
2004+ Buick Lucerne
2004+ Grand Prix ....... Just to name a few common salvage yard finds. Wiki provides more of a thorough list.

I got my intake manifold from a 2005 Pontiac Grand Prix GT. This car also had the aluminum coolant elbows which will save me money and time in the future. Upon my romp through the salvage yard I found a 1998 88 LS with the UIM uninstalled already. So using the 88 as a test I found out the L26 UIM will swap out with some trimming of the L36 EGR stove pipe (about 1/8" to 1/4"). Since I'm replacing the LIM gaskets anyways I'm just swapping the entire thing. The LIMs are identical from the L36 to the L26. So you have options. Trim the L36 EGR stove pipe or if it will come out without a lot of hassle just swap it out with the L26 EGR stove pipe. You will require an adapter bracket from ZZPerformance to get the L36 throttle body to play nicely with the L26 UIM (L67 Gen 3 to L32 Gen 5 supercharger adapter bracket) Now here comes the tricky part and a li'l research comes into play. There is other information through other forums and YouTube where people have done this swap with success. Some chose to use the L67 throttle body because its round and not oval like our L36 TBs air passages. Another thing is that you'll have to block off the EGR port on the back of the UIM. The nipple on top will have to routed to another nipple you'll have to drill and tap into the throttle body to keep from throwing a code.

Note: IMPORTANT GASKET SET INFORMATION! Use Felpro Gasket set #MS95812 - Intake Plenum Gasket Set & Felpro Gasket Set #MS98014T - Lower Intake Manifold Gasket Set

Follow along and I'll show you my project. Acquiring all the parts currently to do this swap. Takes between 1.5 to 4 hours depending on how mechanically inclined you are.
 

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jlay

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looking into this swap for myself. not for performance but longevity, replacing to the same plastic intake seems dumb to me. I have 96 olds 88 L36 series 2 V6 How well did this swap work for you its been a few years. just wondering thanks for the help \.
 
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