throttle body

[nattyice08]

does any one know the diameter of the stock throttle body on the 3.1L V6 Grand Am engine. thanks

-nathaniel

[Azrael]

For 94-98 3100's the diameter is 52mm. In 99 the 3100 was upgraded with 56mm throttlebodies when GM decided that it should share as many parts with the 3400 as possible to cut costs.

[nattyice08]

thank you for the information. i was also wondering if you knew if the 59MM throttle body would fit on my car? i've talked to engineers and mechanics alike who say that a larger throttle body and less restriction on your intake can bring you decent power increases. do you think this is true?

[Azrael]

The 56mm is almost a direct bolt-on. All that needs to be done is that you have to swap the throttle cable linkages around. Look at the www.3400swap.com guide (http://www.3400swap.com/guide_ver_2_5_5.pdf) and go to page 22 for instructions on how to do this.

But keep in mind that, unlike most other engines, the throttlebody is not the bottleneck in GM's 60degreeV6's. Chances are you won't see much of a gain from a larger TB untill you open up the rest of the intake system.

[96GreenGaGT]

and by opening up the rest of the intake he means the intake manifold and the exhaust fromt the headers all the way back to the muffler. after all that you will see about 15 or 20 hp. prob more with a full exhaust. more like 30 to 40 hp with intake, tb, intake manifold, and exhaust headers back with higher flowing cat and step up to 2.5 inch tubes on the exhaust. all that your prob lookin at 1500 for it. maybe less.

[nattyice08]

thanks for all the input.....im really appreciative. however, i have looked for exhaust pieces, especially replacement exhaust,,,,,and can't find them. By replacement i mean like bolt-on's from magnaflow, dynomax, flowmaster, or borla...the only company that makes exhaust for my car is SLP, but they dont make it for my year. i have a 95 and am having a tough time finding parts. thanks for the help again.

-nathaniel

[MantaGreen97]

^ You're correct, exhaust parts aren't made--you have to have it custom done at an exhaust shop. Mandrel bent 2.25" or 2.5" piping is what most people go with and you can select muffler(s) and tip(s) that go with it. That is pretty much the only way to do it for the older years...

As for the intake manifolds, keep in mind the upper and lower intakes from the LG8 3100 (the 99/00+ 3100) and the LA1 (3400) are much better flowing than the UIM/LIM on the L82 (the 3100 you have). Even ported upper and lower L82 manifolds aren't as good as stock LG8 and LA1 manifolds.

I thought before that you could simply swap the UIM/LIM from an LG8 (or an LA1) onto the L82 but recently I've heard this isn't 100% compatible--so you might want to make sure before attempting it (if you were planning on it).

You might want to think about an entire LA1 swap depending on how many miles you have on your engine, etc.

[Azrael]

Swapping the intakes from the newer 3x00 isn't 100% compatible for two reasons:

1) The EGR port changed to accomodate a linear EGR system and was later changed again from a verticle to a horizontal port. Make sure to find a 3400 UIM from 96-98 (they were used in minivans then) and get an EGR adapter plate from www.60degreev6.com/store.

2) The coolant line to the LIM changed from a threaded fitting to a push-in fitting. Easily fixed by tapping the new LIM with a 1/2" NPT hole tapper.

[MantaGreen97]

^ Oh right, for the 95 the EGR will be an issue, but 96-99 L82s have the same EGR as the LG8, so in that case you don't have to worry. The horizontal mounting is just a change in mounting so the 96+ EGRs should work there too. I think you can also just use a newer EGR on the 95 instead of having to use the adapter plate but I'm not 100% sure about that.

The heater line there or whatever, yeah that too but that's not too bad as you mentioned.

But, and I'm just going on what someone recently said in another post--it was mentioned that the upper and lower from the LG8 or LA1 don't line up 100% on the L82 either. Again that might not be true in every case and/or it might be an easy fix to make it work but I'm just mentioning it just in case.

[nattyice08]

im planning on just getting the 62MM throttle body and adapting it to the stock UIM and getting the 3400 intake tube.....then putting a K&N cone on the end of it. i know someone who can weld aluminum so i am also going to make my own custom heat shield to put in place of the old box and hopefully keep most of the engine heat out of the cone. if not, oh well. i just want the larger throttle body and cone filter.... bad idea or no? by the way....thanks for all the input....i really appreciate it.

-nathaniel

[MantaGreen97]

Well it isn't necessarily a "bad" idea, but the throttle body won't do that much for you, as I think someone mentioned.

Not saying it won't do anything but it won't do that much. The intake idea is probably best either a WAI or CAI... I mean by all means get the TB but if you aren't planning to do any mods thereafter, then you can probably save a bit of money by just doing the intake system and foregoing the TB. The stock L82 intake manifolds will probably bottle-neck the larger TB, I'd imagine.

[voyager]

another issue with the newer manifold swap is that if you don't have the roller rocker heads ( and 95 doesn't ), you'll have to grind away a good 1/4" of material from the LIM else the rockers won't clear it and you won't even be able to bolt it down. good news is that the 3400/newer 3100 heads bolt right up to your existing block; more good news is now i've told you in advance so if anyone tries to do the swap they won't be so shocked when they find the LIM balancing on top of the rockers instead of laying flush on the heads lol.

a larger throttle body by itself isn't going to help much. you should at least port out your plenum to match the larger TB or you'll have turbulence and possibly worse flow than you started with.. the best thing to do for your intake i think is, as stated, swap to a 3400/newer 3100 ( they are identical other than what's stamped on top of the plenum, "3100" or "3400" ) the major restriction to airflow is your downpipe and the log-style exhaust manifolds.. a CAI, intake and exhaust pipes will help, especially if you can replace the downpipe, but the exhaust manifolds do not flow well and i think you won't see more than 15-20hp from intake/exhaust mods as long as there are no headers on the market for 3100's. that being said, i wouldn't spend more than $30 for a TB. it may make 1-2hp difference at WOT at best. if you can get a cheap 3400 TB, like $20, it'd be worth it i guess, but spending $80 or something ( just a guess ) on a 62mm TB for a 3100 with stock manifolds is a waste IMO.