Swapping a L26 Aluminum Intake Onto The L36 Engine

Has anyone in here actually successfully performed the L26 aluminum intake swap on an L36 to replace the junk plastic unit? I have researched all of the options that would result in me having another plastic upper intake manifold and none of them are acceptable in my book. If I'm going to spend hours working on this thing I want to end up with an aluminum intake. I just got done doing a full transmission rebuild on my 2000 LeSabre and while I had the transmission pulled out I noticed coolant leaking all over the back of my engine behind the transmission from what looks like the upper intake gasket area AGAIN. This is now the 3rd replacement plastic intake that has been installed on my engine in 4 years and the 2nd replacement lower intake which looks to be leaking oil around its gasket.
I understand there have been tons and tons of posts on this topic and I have read all of them, but people just keep talking about how to modify or install ANOTHER plastic intake. I really want to dedicate a post to getting a solid aluminum intake on this motor, its really time to walk away from the plastic BS. This shouldn't become just another upper intake discussion, I gauruntee I will figure out how to perform this swap, its just a matter of seeing what other people have learned.
I know someone posted a link before to a site with a bunch of photographs and a short discussion from someone who did this swap, but the discussion was very lacking in detail. Something was mentioned regarding the fact that the only drawback was that after performing the swap the PCV valve would be rendered inoperable or something of that nature.
Let me state quickly that I already know that the shape of the throttle body is different on the L26 and that I need an adaptor plate which is available in the aftermarket, thats no big deal at all. I'll post a link when I actually purchase one of those, I'm more concerned about the PCV valve question.

Yeah, I saw that thread a while back and the link. I believe it was on a '97 LeSabre and was posted on another auto forum. It appeared to be successful but he did mention a significant drop in fuel economy after doing the conversion. I don't recall if he ever figured that out. A throttle body adapter is required and he forgot to mention sealing off an area on the driver's side rear of the aluminum UIM that is used for a sensor on the L26.

BTW - The PCV is in the same location as the L36.

See link below on the L26 to L36 UIM swap:

Click here (http://theoildrop.server101.com/forums/showflat.php?Cat=0&Board=UBB24&Number=576310&Searchpage=3&Main=576300&Words=lght1&topic=&Search=true#Post576310)

Yeah that I've read through that thread a number of times, I can't gather enough information from his posts to determine what the issues were. If an adaptor plate needs to be designed to adapt the L26 upper intake to the L36 lower intake then i should get on top of that, I actually have access to a machine shop right now for prototyping purposes. My plan is to get hold of an L26 upper intake, an L36 plastic upper intake, and a new L36 lower intake and make my comparisons myself before I ever unbolt anything from my engine. I wonder what the differences are between the L26 Lower intake and the L36 Lower intake? I'm thinking there must be a major difference or people would just swap the L26 lower intake onto the motor first to get a perfect fit with the L26 upper intake.

I did notice that the PCV seems to be in the same location, I can even see his MAP sensor mounted nicely on the new intake, thats why I had a hard time understanding what the problem was?

A TB adapter that should work has been out for quite awhile. ZZPerformance has one with a dual design.

http://www.zzperformance.com/grand_prix/products1.php?id=255&catid=113

The L26 UIM may have better overall flow. I know the L26 and L32 throttle bodies are bigger than on the L36 and L67. On another similar issue the Eaton M90 Gen5 blower definitely out performs the old Gen3 blower so alot of L67 owners are considering that swap.

Thanks for the link bnaylor, I was looking around for someone who would sell that adaptor plate. The issues regarding the different size and shape of the throttle body are pretty clear I think, but there is still confusion surrounding the details of the PCV valve and perhaps that sensor conflict. I can't tell from any of the pictures ive seen exactly what the differences are between the L26 UIM and the L36 UIM or for that matter the differences between the two lower intake manifolds, beyond of course the obvious throttle body issue. If the L26 lower intake is a direct bolt on to the L36 motor then this whole issue should be a no brainer. I just think if it were that easy to replace both together then anyone thinking of doing the swap would simply use an L26 LIM with the L26 UIM and bolt both onto their L36 as opposed to trying to bolt the L26 UIM to the L36 LIM. Ideally I would love to use both an L26 LIM and L26 UIM and just get rid of all the half baked parts from the L36 top end. Its really sad that GM didn't consider the possibility of making an aluminum replacement for this L36 because it really is the achilles heal of this engine. Of course if they had released an aluminum replacement then they would need to admit there was something wrong with the plastic unit which is way too ethical for any modern car company. I've tried talking to GM dealer techs about this swap but going to a GM dealer now days is like stepping into the land of the living dead, they all act like zombies.

I just got done doing a full transmission rebuild on my 2000 LeSabre and while I had the transmission pulled out I noticed coolant leaking all over the back of my engine behind the transmission from what looks like the upper intake gasket area AGAIN. This is now the 3rd replacement plastic intake that has been installed on my engine in 4 years and the 2nd replacement lower intake which looks to be leaking oil around its gasket.


:rolleyes:

Just out of curiosity pcmos I noticed more closely why you are considering going to the SIII 3800 aluminum UIM. I see you have been through 3 UIMs. What brands were these? Aftermarket such as APN or Dorman/Motormite or the revised GM UIM? And what gaskets were being used, the aftermarket or GM/AC Delco? On the LIM is it the port gaskets or the end seals leaking oil? Was this prior work done DIY or by dealer/mechanic?

I purchased this car as a used car in 2003 with 58k miles on it and an extended GM warrenty. Since the time I purchased the car the UIM has been replaced by the dealer 3 times and in two of those jobs they also replaced the lower intake under warrenty. I have no way of knowing what gaskets they've been using. This failed intake now is the one that was replace less than a year ago before the warrenty ran out. Frankly, I don't really care what was done to it before with plastic intakes, I won't install another plastic intake on this.
Any of the DIY work that I do on my car I do as a weekend hobby, I'm not a mechanic by trade, I'm an engineer. When I make repairs my goal is to solve design problems that cause this sort of repetative failure. Very briefly, I've spent a lot of time examining the mould design for the plastic upper intake and I've spotted some serious design issues that will cause continued warping in response to thermally induced strain deformations. I won't bore anyone with the details unless you really want me to point some things out, but I can't see any way to make this particular plastic intake work properly, short of re-designing the mould. I'm less concerned about the EGR passage melting, my research focused on the cause of persistent planar deformation of the gasket sealing surface. In my opinion the original mould design was seriously flawed and would require significant changes in order to develop a reliable polymer based intake casting for the L36.
I really want to focus the discussion on using an aluminum intake on this motor, most of us are already completely familiar with the various plastic intakes and updated gaskets available, the goal is to develop an alternative solution for people who don't want to mess with the plastic intake design again.

IMO it is good to get the history and background included in the thread because members are curious as to the why and hopefully whether the conversion is feasible. Unless the guy at that forum was joking we know someone has done the job. The only issue I am concerned with is the drop in gas mileage that was mentioned. I have not heard of any PCV issue. Also, I noticed not much talk about it at other auto forums. Definitely no published tech procedures posted.

Have you inspected a L26 engine? I helped a local club member do his spark plugs on a 2004 Grand Prix GT last year. From I can see it definitely looks like a direct replacement bolt on job. I noticed that extra sensor on the back left hand side by the throttle body area that L36s don't have.

Another suggestion to get your hands on the aluminum UIM and gaskets. Maybe a pull from the local salvage yard or contact Ed Morad. Maybe he has one laying around from a L26. His prices are normally reasonable. I know he sells complete L32 and L26 engines at his EBay Parts Store.

Other than that the project sounds interesting and good luck.

Yeah Morad has a complete L26 intake setup on ebay including both the upper and lower intake but I'm so bound and determined to make this work I may just put the money into buying a brand new L26 UIM to start off the project. I would like to get hold of a damaged plastic L36 UIM and LIM to compare to my new L26 so I don't have to pull the ones off my engine and disable the car to make comparisons. I should be able to convince a local dealer of mechanic to give me a junked part. What I'm really curious about is the lower intake for the L26 and how it compares to the one for the L36, but I'm not sure if I'm ready to lay out the expense to buy one. I want to spend some time studying my shop documentation for L26 equipped vehicles before I conclude that the L26 lower intake is worth buying. I asked Morad if the setup he is selling on ebay would directly bolt onto the L36 and so I'll quote their response...

"It will bolt directly onto the block and heads. You may need to change / block off some EVAP and vaccum lines. And you will need a throttle body adapter plate. The lower intake different due to the EGR port and the 2 coolant ports."

He is talking about the combined assembly including both the L26 LIM and L26 UIM mounting to an L36 block and heads. I just don't understand what he means by "change/block off" if he's talking about something that can be done simply by minor external routing mods or if he is talking about having to fabricate a plug of some sort. I also need to research what he means by "2 coolant ports" and a different EGR port. I should be able to gather some info just reading through my GM shop manuals for L26 equipped vehicles.

The photographs posted in that other thread are just a few of a series of about 40 photos that were posted by someone else in a CLUBGP forum a couple years ago. Who knows if its the same person with different SN's or what, but in reading the CLUBGP forum the writer states that the valve cover vent is installed due to "loss of PCV functionality" or something like that. He implies that the PCV is rendered useless or disabled by performing the swap which means that an ugly valve cover vent was used to provide some crank case ventilation. That wouldn't be an acceptable option in my book, so that is why I'm anticipating the need for some complex machining or fabrication to make appropriate modifications.

... I finally found the link to the series of photos posted on a GP club site by someone whose SN is No_Boost, the photos show a comparison of the L36 and L26 UIM but the details are tough to spot even in the high res images.

http://www.conncgp.net/gallery/Project-L26

I want to make sure people reading this understand that these are not my photos, they have been circulating on a number of forums for a while now.

I talked to a guy who put this one on and he said it is the best one. I ordered this and have it sitting in my house (My mom went to the hospital a few days after I got it). Looking at it I'm happy with it.

I know this is biased, when talking to the person on the phone, we ended up talking for about 10 minutes. They knew what was going on and said this solves the problem, not just fixes it. They sounded very convincing.

I saw on another message board about these and all where happy. Recommended. I'm excited to have one like this.

I know your frustrated, just trying to add anything I can.

Here is a Link.

http://www.automotivepartsnetwork.com/store/pc/viewPrd.asp?idproduct=229679

Chris.

I'm already familiar with the aftermarket intake you pointed me to, but it will do nothing to solve the warping problem, it may be well suited to handle the EGR passage temperatures, but that issue is only half the problem that occurs on this UIM. I've never had any of my plastic UIM's leak through the EGR passage as many people have, but I've had three of them warp. The bolt pattern and the design of the base of the intake are all done as though it was intended to be cast in aluminum, all you have to do is compare this plastic intake to plastic intakes on other engines and you'll get an idea of how subtle changes to the mould design make all the difference. The base of the intake should include a cast permiter ridge that would surround the entire unit, the bolts should be located towards the interior of the flange as opposed to jutting out. The ridges that are cast accross the top and terminate at the base should include reinforcing fillets where they intersect the base flange. The entire design of this intake lends itself to warping, it was obviously designed originally to be cast in aluminum and was quickly modified to be cast in a high temp. thermo plastic, which some engineer figured would be acceptable so long as he specified a polymer that was rated to a specific temperature, thermal creep and fatigue deformation were overlooked. I drive my car VERY hard and I want something that will resist warping and deformation due to thermally induced stress. The aluminum L26 intake fits the bill and I gauruntee that a large percentage of people who have used these aftermarket replacements have not clocked enough miles yet to have the problem occur again. The ones who have, probably drive less aggressively and were more prone to have issues with the EGR passage as opposed to warping of the gasket surface. Most people probably havn't even put the same number miles on the replacement as they had on the original when it failed. The bottom line is that I'm going to use an aluminum intake. I'm sure people will read this and disagree but the debate has been hashed out in countless forums previously.

On my wife's '99 Regal LS (SII 3800) we're still waiting for it to fail. Nothing yet. 120K miles to date. Since my GTP and Regal GS are L67s I don't have to worry about UIM problems just LIM gaskets and/or possible head gasket.

In the meantime it would be appreciated if you could document as much as possible to include pics. We have a Tips & Maintenance subforum where the procedure can be posted and you get full credit for it. Thanks.

Buick Tips & Maintenance Forum (http://www.automotiveforums.com/vbulletin/forumdisplay.php?f=2144)

BTW - I'm working on getting the GM part numbers for the SIII 3800 aluminum UIM and LIM.

Hey guys. Came over from pcmos's invite to lend a hand with your L36 to L26 swap information.

Read over what you've been discussing and you're pretty much on the right track.

Couple of things:

- The L26 is a direct bolt on replacement for the L36UIM

- I did notice some gains after installing the L26UIM and I believe this pic is they key to that. The inlet on the L36 is 'oval' whereas the inlet on the L26 is actually round. Imagine that... it matches up to the L36 TB rather than creating a "turbulance ridge"...

- The 'throat' of the L26 is longer than the L36, making space a little cramped in the airbox/CAI area.

- Your PCV, EVAP, EGR systems will still work with the L26UIM!

- The EGR 'stack' however will need to be cut down (I had to go ~ 1/4").

- You will need a TB adapter plate (Gen V to L67/L36 TB adapter plate from ZZP will work fine)

- You can and will want to re-use the runner inserts from the L36. They fit perfectly into the L26.

- You will need to plug two (2) ports which are not used/needed for the L36 engine

- You can use a stock L36UIM gasket (your original if it is decent shape).

- Recommend using some "Right Stuff" made by Permatex (avail. @ Advanced, Kreger, Wal-Mart, etc.) just for extra insurance. I found I had a small leak on the TB side (gasket problem, not the L26 to L36 mate).

This is available through GMPP (www.gmpartsdirect.com (http://www.gmpartsdirect.com))

GM PART # 89017555
CATEGORY: Engine Fuel Intake Manifold
PACK QTY: 1
CORE CHARGE: $0.00
GM LIST: $196.08
OUR PRICE: $116.24

Also available through Ed Morad from time to time.

I currently have ~40k since the swap with ZERO issues. The swap from start to finish took me about 3.5hrs (LoL, same time it took to install my GMPP suspension). Less mechanically inclined ppl with require a little more time.

Hopefully, there's enough info here to help convince you that the L26UIM is the way to go. Mind you, I did this ~2yrs ago, and relying on my pics to refresh my memory. But trust me, it's all there.

The only other thing I can think of is to make sure you know the torque specs and pattern for re-installing the UIM. If anyone needs that, lemme know (I have factory manuals to refer to).

The Dorman UIM and even the "new" plastic GM UIM WILL EVENTUALLY WARP! Yes, I said that. They are both made out a different injected thermo plastic with some 'new' polymers and fillers, but they are still plastic. I'm the supervisor for the production shop which makes IMM robot and automation systems for Delphi (who used to make the UIM for GM), and have seen quite a few UIM's the sent us for testing. Just trust me, it'll warp.

I drive my '98 hard. 120k on the odo as of tonight and have been lucky to not have many issues. This is an investment you will not regret guys/girls.

Hope this has helped. Feel free to contact me if you have any other questions.

:popcorn:

Oh, btw, here's the link again to my gallery with all the pics: http://www.conncgp.net/gallery/Project-L26

Hey guys. Came over from pcmos's invite to lend a hand with your L36 to L26 swap information.

All right speaking of the devil. Welcome to AF and thanks for weighing-in. :wink:

I sent you a PM message and a special request. Thanks.

No Boost,
Thanks so much for contributing your experience on the matter, when I look at your project photos I can see that you installed a valve cover vent. Is there something about doing the intake swap that requires the use a valve cover vent or was that simply an unrelated modification? I'm also wondering if you can see any reason why I should continue researching the use of the L26 lower intake instead of just using another L36 LIM. If the PCV system will work fine after mating the L26 UIM to the L36 LIM then theres probably no reason for me to worry about using an L26 LIM.

bnaylor,
I'll do a full report on the project when I finish and post it to the tech tips section (also in PDF form). Please forgive me though if it takes me a few weeks to get going on this, I'm still suffering from a little post traumatic stress disorder after the transmission rebuild :) After I get back from a vacation in a couple weeks I'm going to order a new L26 intake and get started.

OK, Sounds good.

I have 150,000 on my original GM Plastic UIM. I run my 97 like a race car on the street. If I get anywhere near the life I got from the stock, I'll be happy.

There's absolutely no reason to explore the L26LIM option IMHO any further. You will not gain anything from it as far as performance, and I do not believe there's any significant difference between the L36/L26LIM's. The only one possibility is the EGR stack... and the solution to that is a hacksaw!

As for the breather cover... totally unrelated to the L26UIM swap. No need for it.

Like I said, there's only the need for a TB adapter and shortening the EGR stack. Stock L36 gaskets work fine.

Where is the leak you're getting on the LIM? One of the most common causes is lack of sealant (Right Stuff by Permatex) in the corners of the sides gaskets (4" long either side between the LIM & UIM). Lots of ppl either forget it, or don't know about putting it there.

happydog, you're lucky getting 150k... most don't make it to 80k!

I went back through my shop documentation and I don't see anything about using a sealant along the sides of the LIM, but it looks to me like the dealer did use some sort of RTV since there are globs of it all over the sides of the LIM and block. The leak that I have seems to be coming from the rear edge (long edge) but more towards the drivers side rear corner and its definately oil. When i pulled the transmission from the engine and took a look in there its cascading down the rear and drivers side of the engine and dripping off the oil pan. At first i figured it was a rear main seal leak based on the fact that i was seeing oil collect on the flywheel cover and oil pan but after getting the transmission pulled im convinced its leaking from the LIM or perhaps is a valve cover leak. It can't be a cylinder head gasket leak because theres oil soaked grime above the level of the head gasket, assuming oil can't leak upward then i think its safe to rule out the head gasket. Either way ive definately got coolant pooling up around the front of the engine from the intake so I plan to replace both intakes and the valve cover gaskets and probably all 6 fuel injectors (for no particular reason).

What shop documentation are you referring to? I recall if it is GM FSM material sometime in 2000 and up GM may have omitted the mention of RTV at the corners where the end seals and port seals meet. Now on older 1999 and under FSM material the RTV part is there in black and white. I'll be happy to send you what I have on the UIM/LIM in a PDF file. I can't post it here due to copyright.

Unless you are having problems with your fuel injectors replacing them could be a waste of money but it is up to you. Definitely replace the upper and lower o-ring seals.

http://i5.photobucket.com/albums/y186/lizzywiz/lim_seal.jpg

I have the SI 2004 software from GM and I have the print version of the GM OEM shop manuals specifically for my 2000 LeSabre and I can't find any mention of the use of sealant. I checked the SI software for a 1998 LeSabre and theres still no mention. They do mention using threadlock compound on the LIM bolts. I can see how it would be a good idea though, I probably would have used some anyway.

Yeah there are definitely discrepancies in the GM documention. Here is what I have. As you can see there is an extra annotation on page 2: "Apply GM approved sealer to the ends of the intake manifold seals." :dunno:

Click here (http://www.aogusma.org/soc/elpaso/lim3800.pdf)

Also, I noticed the UIM bolt torque figure changed. In older documentation it says 89 in-lbs. In newer it says 11 ft-lbs (132 in-lbs).

Wow thanks for showing me that information. It gets really frustrating when you think you have the latest documentation available and then you find out theres more. Half the time I spend working on cars these days is spent trying to work against the efforts of the manufacturers to keep that information out of my hands. If you have any advice for me on how to purchase more recent service information please let me know. Thanks again for the heads up.

Just to post an update, I placed the order for my L26 Aluminum Upper Intake manifold from gmpartsdirect.com. Aparently it's a special order part so it may take a while for me to actually get it.