L27 Intake Manifold onto LN3 Heads- - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Performance, Brainstorming & Tuning Talk about modifications, or anything else associated with performance enhancements. Have a new idea for performance/reliability? Post it here. No idea is stupid! (please use Detailing and Appearance for cosmetic ideas)

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Old 01-14-2011, 01:42 PM   #11
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F17 2.84 Gear Ratio. Damn.
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Old 04-08-2011, 01:05 AM   #12
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It'* good you only have 2.84'* that explains the lack of power. My 90 Royale has 2.84 and my 92 L27 Regal has 3.06. #.06 is way better and gets about 25mpg on the hywy just like my Olds.

I'm getting rid of the Regal and would like to remove whatever can be used. I'd like to use the heads and tranny if they swap over easy.
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Old 04-08-2011, 06:18 AM   #13
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This is something that i want to try as well. i have a LN3 in a Holden commodore. I know a guy who has got a L27 intake manifold on a our version of the L27 (which still uses the LN3 style intake manifold because of the rear wheel drive configuration) but he has it turned around 180 degrees. the major issues that he'* noted for us is the fact that the alternator is in the way and that you guys only use a 55mm throttle body?

i'm keen to get my hands on a L27 intake setup preferably a alloy upper
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Old 04-08-2011, 02:44 PM   #14
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Quote:
Originally Posted by Granny'* Delta View Post
I could upgrade rockers and get a little more lift I suppose.

Any idea where I can find the list of RPO codes to figure out what my gear ratio is?

This car does not run too bad to begin with. The original owner was my grandma, and it was fairly well taken care of. Its definetly a LN3, but its got what are essentially steel headers on it that was supposed to come with some earlier version of the motor.

With a L27 Intake Swap, CAI, Cat Delete, and 2 1/4" free flowing exhaust what could I expect to run in the 1/4 mile depending on my gearing?
Not sure if the throttle body will bolt up. Is the 89 LN3 also MAF based? Are the throttle body sensors the same?

1/4 mile might be in the mid 16'* if its running right. I ran a 16.1 in my 95 L27 Regal with 1.8 ratio roller rockers, open exhaust, CAI, and no resonator.

You could upgrade the rockers, but its a dumb idea IMO because the gains are not worth the price. The only way rockers will benefit you is if you are running a Series 1 L67 (Supercharged version) with the Eaton M62, and you ALSO port the heads and intake manifolds. Otherwise, don't expect much of anything on a N/A Series 1 3800 with rockers because the just isn't enough flow.

If you really want to go faster with this motor, the first thing you will need to do is pull the heads and port them. I did this with a dremel and grinding stones and I can provide pictures. You're mostly porting some of the exhaust ports to remove the exit ridges you'll see, widen the bowl a bit, and smooth out the rest of the exhaust port, while keeping it a D shaped port. For the intake, you'll be removing casting imperfections that restrict flow and cause turbulence. There are a *lot* of serious casting imperfections, and the bowl itself is a big restriction point that you can widen at least 1-2mm safely so long as you don't touch the valve seat. This is the biggest problem with L27 heads with regard to flow.

Pictures to come for those who are interested. Porting these heads, with the roller rockers, and with a port matched intake manifold pushed me over to 92% injector duty. My wife even said she felt a huge difference, especially off the line.
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Old 04-08-2011, 09:04 PM   #15
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We have had fair bit of success with just bolt on mods on our LN3'*. i went from a 15.9 to a 15.1 with a enclosed POD setup with CAI, headers and full 2.5" exhaust (no cat) and 3.45:1 diff with LSD and a little bit of tuning.

I have now fitted 1.9:1 high ratio rockers which has made a good improvement in the way the engine pulls right from idle and it doesn't fall over just after 4500rpm any more. a company called MACE has used LS1 style rockers on a custom base with great results. with these rockers fitted i have no doubt that it would be into the 14'* on the strip.

just gotta assemble my new wide band O2 sensor controller so i can work up a decent tune.

all our LN3/L27 equiped cars are MAP based using the 808 and 165 ecu'*. it wasn't until we went to the series 2 3800 (L36) ecotec motors that we went to MAF based ecu'*
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