Porting LIM on L27 - <<<Updated with Photos 11/03 - Page 2>>>

[xtremerevolution]

Alright, so I figure the Regal is due for a gasket job. There are currently no leaks whatsoever and the engine sounds and runs great, but in an effort to preventatively maintain it to keep it that way, I've decided it wouldn't hurt to do some work. Besides, I enjoy it.

 

So I already have the LIM and TB gaskets, and I just bought the UIM gasket and injector o-rings. Not sure if I need anything else, but if I do it will be minor and I'll be able to buy it from the nearest auto store.

 

The question now is regarding porting the lower intake manifold. I've heard that it does a great job in improving efficiency and performance when done on L36 engines, so I figure I won't be too far off doing it on an L27. I have a dremel and plenty of tools, but I'm not sure where to start. If someone could give me some pointers on porting the LIM for better performance, I'd certainly appreciate it. Do I just gasket match the holes and use a dremel to grind away the intake passage holes?

 

So far all I have is this:

http://www.bonnevilleforum.com/t251838-3/

 

Any advice is always appreciated, since I haven't yet heard of anyone porting an L27 LIM.

[xtremerevolution]

Man, has nobody ported a LIM before?

[jman093]

Don't know about porting but if you're going to do all that you should put on the revised upper intake manifold. Return the UIM gasket and injector o-rings and get the "UIM kit." It'll come with the revised UIM and a new stovebolt pipe, which together will prevent the notoriuos manifold leaks, and it will come with a new UIM gasket and injector o-rings as part of the kit. If you just put a new UIM gasket and reuse the plenum and old stovebolt it will still leak in the future.

[xtremerevolution]

Don't know about porting but if you're going to do all that you should put on the revised upper intake manifold. Return the UIM gasket and injector o-rings and get the "UIM kit." It'll come with the revised UIM and a new stovebolt pipe, which together will prevent the notoriuos manifold leaks, and it will come with a new UIM gasket and injector o-rings as part of the kit. If you just put a new UIM gasket and reuse the plenum and old stovebolt it will still leak in the future.

 

The 95 got the L27. The 96 got the L36, which is the one that had the intake plenum issues. The L27 has a completely different UIM gasket and a completely different EGR passage that doesn't go through the LIM, so I don't have that problem.

[Timm]

This sounds cool.

I've never heard of it being done.

But hopefully someone can help, as I will be replacing my plenum within a week. Since the LIM is right there, I might take my dremmel to it also!

 

[Andrew]

just gasket matching should yield some gains. i really wouldnt start hoggin out the runners if you dont have experience doing this kind of thing.

[xtremerevolution]

just gasket matching should yield some gains. i really wouldnt start hoggin out the runners if you dont have experience doing this kind of thing.

 

I don't have much experience, so I'll go easy. I hear the right size is 0.9x1.9" for the holes. I'll match the size of my head ports to make sure I don't have any turbulence in the air going through as a result of overporting.

 

I'll definitely update you guys with pictures of my progress as I move along.

[xtremerevolution]

Bit of an update...

 

This thread is not so much asking for advice, as I found plenty of it just by using the search feature on bonnevilleclub.com's forum, but rather to show people what I've done and how much of a difference it makes. I'll do some 0-60 runs on my Passport G-Timer before and after. While some may a G-Timer is inaccurate, mine so far has been accurate down to .02 seconds in the 1/4 mile, tested and verified when I took the regal to the drag strip last year.

 

For reference, here are the times i had:

 

http://i16.photobucket.com/albums/b3...eslips0001.jpg

 

What I've gathered so far is that the last thing you want is to over-port the LIM, as that would cause you to have a lip at the LIM-head transition, and would cause turbulence as a result. IIRC, I need to make my ports marginally smaller than 0.9x1.9, and can use the LIM gaskets as reference point for finding the center of the hole so I know what I can take off. I understand that the concept is basically to port them just marginally smaller than the head openings.

 

I plan on doing this with a dremel, as I really don't have any other tools. I've been given the impression that using a coarse drum sander would probably work best in this scenario, though i have a few more tools I can use if required, and a small budget for buying a few more dremel attachments.

 

I'll also be smoothing/polishing the runners. Any advice on other ways to do this would be appreciated. For the time being, I plan on using a flapwheel on a drill to sand them out, though I have a feeling my flapwheel may be too large.

 

Thanks for the help. I'll be posting pics of my progress.

[slick]

IIRC, you want to have a sort of rough texture on the intake runners, and smooth finish on the exhaust runners. Maybe this was only on carb'd engine's, where it helped with the mixture. I can't quite remember though.

[xtremerevolution]

IIRC, you want to have a sort of rough texture on the intake runners, and smooth finish on the exhaust runners. Maybe this was only on carb'd engine's, where it helped with the mixture. I can't quite remember though.

 

Reading through L36 porting threads on other forums, it seems that smooth runners improved performance. Then again, I'm not sure how many people ported, tested, then smoothed, then tested, or just smoothed without porting to compare the difference. I think it would be a good idea at least to prevent carbon buildup. I don't see how it could hurt.

[jman093]

Don't know about porting but if you're going to do all that you should put on the revised upper intake manifold. Return the UIM gasket and injector o-rings and get the "UIM kit." It'll come with the revised UIM and a new stovebolt pipe, which together will prevent the notoriuos manifold leaks, and it will come with a new UIM gasket and injector o-rings as part of the kit. If you just put a new UIM gasket and reuse the plenum and old stovebolt it will still leak in the future.

 

The 95 got the L27. The 96 got the L36, which is the one that had the intake plenum issues. The L27 has a completely different UIM gasket and a completely different EGR passage that doesn't go through the LIM, so I don't have that problem.

 

Oh sorry, I can never remember all the right RPO for the different series 3800's.

[Spilly]

Update us on this because im willing to damn near anything to this L27 for a little more balls.

[xtremerevolution]

Update us on this because im willing to damn near anything to this L27 for a little more balls.

 

Will definitely be posting pictures.

 

One more thing:

 

http://www.zzperformance.com/grand_prix/products1.php?id=208&catid=110

 

"In an effort to put out the best possible PEMs we've researched and hit a wall. The problem lies in the front header piece. Opening the inlet as people are isn't doing anything because the inlets are already 1.53" (as big as the port in the head). The problem is the lower section of the manifold. It's 2" OD and 1.63" ID. At that section you're sharing with the other ports.Trying to exhaust all 3 front cylinders out of a single 1 5/8" pipe is crazy. It's no wonder so many people pop front pistons and have questionable gains from other PEMs on the market. The rear manifold and crossover aren't as bad. Notice the crossover is also 2" OD, like the front mani, but because it's thin wall you get 1.91 ID. So, the front mani is the narrowest section of the exhaust, giving you 2.09 sq/in of exhaust area. The crossover and rear manifold are up to 2.89 sq/in. So the front manifold section is over 30% smaller than the entire rest of the manifold network and it's the only section that guys selling PEMs aren't doing!

 

Fortunately ZZPerformance now offers a cost effective solution. The powerlog uses 1 5/8 primaries which feed a 2 1/4" pipe into the crossover. Uses factory mounting, so all the factory bolts and gaskets can be re-used. "

 

I'm going to see if I can port that exhaust manifold a slight bit. I'm not sure how far I can go with it, but I'm willing to try. Might need to find someone with a welder though in case I screw something up.

[xtremerevolution]

Bump!

 

Job is starting TODAY. Pictures to come soon.

 

Oh, and I've decided that if i can get them off and find a replacement gasket, I'm also doing the front exhaust manifold.

[xtremerevolution]

Alright, engine is in pieces and I've done a LOT of porting on the L27. There's definitely a lot of room for improvement here.

 

Luckily, because of the way the whole thing intake is designed, I was able to exact head port-match the LIM. Basically, once you put the intake on the engine, you can feel the edges between the intake and the heads with your fingers so you know where you need to port further. So far, everything is looking great. After finishing only one half of the LIM porting, I had enough aluminum filings on the ground to fill both my hands cupped full.

 

On a bad note however, I managed to break the plastic tips of two of my injectors. IMO those tips don't make the slightest bit of a difference aside from holding in the o-ring. If I don't figure out a way to get those o-rings to stay on there tomorrow, I'll probably head over to a junkyard and buy two more injectors. I'm guessing they shouldn't be too expensive.

 

On another bad note, after I had finished porting half of the LIM, I started sanding the vanes and my dremel started smoking. I've used this thing a LOT in its lifetime, and today it seems that it didn't like sanding with a flapwheel and pretty much started sparking blue-green internally and smoking up like a Cherokee Indian chief. So tomorrow I need to find myself a new Dremel to finish my work.

 

The front exhaust manifold took a while to get off, but I managed to remove that as well. Those bolts are a total bitch to get off.

 

I'll take pictures again today before I start my work again.

[xtremerevolution]

Alright, the job is done! When I finished I must have had a good 3-4 cups of aluminum shavings left over.

 

This job was especially easy, as I was able to put the manifold back on the car continuously to check if the holes line up. Not only can you see right through the head ports when the manifold is on, but you can feel the edges with your finger so you know where you still have some room for porting. This allowed me to get extremely close to the size of the head ports. All in all I measured just a hair smaller in length and width than the heads.

 

I also pulled the front exhaust manifold, and took off about 1/8" from each of the holes using a grinding stone on a dremel. Once I put the car back together completely, it fired right up and sounded perfect. No leaks, knocks, or any unusual behavior. It was quite satisfying having everything perfect when you put it back together. I also used anti-seize lubricant on all of the bolts I put back on except for the LIM bolts when putting it back together.

 

The first thing I noticed is that it revved a lot more freely than before, which was a pretty good sign. My first few WOT runs showed much better mid and top end performance, which counts a lot because the L27 doesn't have much of a top end. I suppose I still need to wait for the computer to get used to the new airflow, but so far its been a pretty good improvement in performance.

 

One thing to note is that the car has 188,200 miles on it now. Given that, the LIM gaskets were in amazing condition. Definitely a LOT better than the ones on my girlfriend's sister's L36-powered Regal at 110,000 miles. By that wear rate, it looked as though I could easily have gotten another 50,000 miles out of them (if not even more) before running into any issues at all.

 

One strange thing I noticed is that I ended up with one extra bolt that looks completely different from all of the others, and that the front exhaust manifold didn't have a gasket when I took it off. It was just bare metal on metal straight to the heads. Pretty weird if you ask me, but I did put a gasket there when I put it back together.

 

However, this job wasn't without failures. First off, I dropped two of my injectors on the ground and the plastic tips broke. Oops? So far as i can tell, their only purpose was to keep the o-rings from falling into the manifold. So I bought some solid retaining rings that fit very well along the same groove that the plastic tips were held onto and snapped those on, and they just BARELY cleared the injector ports on the manifold. No problems yet **crosses fingers**. Also, the metal pipe that runs the coolant to the heater core had a small o-ring on the manifold side, and i had taken that piece off when I soaked the manifold in gasoline and left it in the gasoline on accident. Well, that o-ring expanded to all hell and I couldn't use it anymore. Yeah...good luck finding another. After some doing, I found a similar sized o-ring that was a lot thicker, and used my dremel with a sanding piece to file it down to where it would fit. Another thing that went wrong was the alternator. I somehow managed to unscrew the bolt right out of the alternator, and the nut on the other side got loose. So i figured what the hell, I'll just take apart the alternator an it will be just fine. Stupid me, right? Long story short, all 3 bolts that hold the alternator together broke off, and when I tried to pry it apart, the alternator seized up. $100 "uh oh." Luckily, it was my birthday on the 28th and my mom told me to charge the new alternator on her card. I figure it was bound to go sooner or later though, since I replaced it at 80k the first time, and have used it for 100,000 miles. I also ripped the terminal for the alternator in the process, so I bought a couple of 2 AWG copper terminals and crimped one to all hell to replace it. The last idiotic thing was that I burned out my dremel while sanding the LIM vanes with a flapwheel. It basically started sparking up blue-green bright as hell inside, followed by a ton of smoke. There's another $50. Luckily, its under the 5 year warranty so I can get it replaced. It was giving me issues before that though.

 

This is what I replaced:

LIM gaskets

UIM gasket

Thermostat housing gasket

Thermostat seal

Injector o-rings (all 12 of them)

Front exhaust manifold gasket

 

The last thing that needs to be done is to have the MAF sensor cleaned. Same old story; cotton swabs, alcohol, and a steady hand.

 

I'll upload pictures when I get home from work tonight.

 

Things to note for anyone planning to do this job in the future:

Make sure you have tools, and I mean good ones, with adapters and extensions to all hell. You'll need a good torque wrench and plenty of standard wrenches of all sizes. Most common you'll need is a 10, 13, 14, and 15 size wrench. Make sure you also have deep sockets, as you'll need some of those too. I didn't have deep a 14mm socket for the exhaust manifold bolts, and had to unscrew them with a standard wrench, which took forever, and it hurt. I cut them down to size before putting them back in so I could use a socket instead. Also, make sure to put back the LIM-TB bracket before putting the UIM back on, because its a bitch to do it afterward. Grab some egg cartons to arrange your bolts. Also, you'll need some GM quick-release tools for getting the fuel rails off. I didn't have them and it made the job a bit annoying, so I just set the rails aside without removing them, but those tools would have made the job a bit easier. Note that the LIM bolts are tightened to 11 ft-lbs, and the UIM bolts are tightened to 7 ft-lbs (correct me if I'm wrong on that one). Buy a tube of anti-seize lubricant. It will make putting the engine back together a lot easier. Lastly, if you haven't yet replaced the pot metal fitting screwed into the LIM that the hose from the water pump goes into, do that during this job, because trust me, it will crack eventually and when it does you'll need to be towed home. The replacement is a steel fitting.

 

I'll post all the pictures from the project later tonight.

[99RegalGS]

How oil/egr caked was your LIM and UIM? I ripped off the UIM on my old Regal around 160k and there was a bit of buildup in the UIM.

[xtremerevolution]

How oil/egr caked was your LIM and UIM? I ripped off the UIM on my old Regal around 160k and there was a bit of buildup in the UIM.

 

There was a slight bit, but not too much. enough to notice though. I just wiped it off with a rag.

[xtremerevolution]

Alright people, I finally have some photos!!!

 

Unfortunately, I was too lazy to take before shots of the LIM, but as you can see there was a very extensive amount of porting to do. I definitely took off at least 1/8" length and width off of each port and they were *still* slightly smaller than the head ports. I also took about 1/8" off the exhaust manifold ports.

 

 

 

 

Old gaskets: not bad for 188,000 miles eh?

 

 

 

 

 

[RareGMFan]

Should have just replaced that UIM with a supercharger!

[xtremerevolution]

Should have just replaced that UIM with a supercharger!

 

The amount of work needed to put an Eaton M62 on an L27 would be more than just swapping a Series 1 L67. Trust me I've considered the possibility many, many times.

[Euro]

Nice job!!!!! Looks pretty good

[AWeb80]

I've considered porting my exhaust mani's when I get my Impala.

 

and I'll deff be making a bigger DP.

[slick]

Too bad there aren't really any before pictures to compare with. However, not too bad for your first try

 

Probably isn't too much else you can do before ripping off the heads and re-working them.

[AWeb80]

I'm Considering Putting My Impala In My Dad's Shop For A Week Or Two While I Still Have The Honda, And Doing A Bunch Of Small Stuff To It. DP, Port Mani's, Undercoating, Splash Guards...Etc.