Upper intake discussion

[SappySE107]

I was replying to an email question, and remembered this wonderful site:P So here goes.

I just bought a 65mm tb from you guys for a 3400 Grand Am and I'm wanting to know what the best upper would be. I see the stage 3 3400 and stage 2 3500 but im unsure which is better (although i think the 3500uim is). I'm also looking at purchasing the Phenolic spacers so i dont know if that turns up any problems with what i can choose. Thanks for your time.

The upper intake selection is really based on a couple things. Are you going to port the lower intake? If not, then the stage 2 3500 is not a good idea. While it is always better to port the heads, lower, upper, you want to minimize size differences in the system. The stage 1 3500 upper would be the best for the stock heads and lower, but will require a throttle body adapter. It is already 65mm so there is less work there. To clear the FPR, you will need the FPR bracket and phenolic spacers. You will also need to either use the 3500 MAP sensor, or block off its location on the 3500 upper and run the original MAP. Vacuum line routing needs to be made up as well.

The stage 3 3400 upper drops right on and is obviously easier to deal with. Not a bad setup by any means with the 65mm TB.

Budget is the next question. For the money, I would port the 3400 lower and upper over just doing the 3500 upper with related parts. If you port the lower, you can go with the 3500 upper, or if you port the lower to the 3500 upper gasket, you can get a lot more potential for HP from both flow and intake port taper. The 3500 gasket sized phenolic spacer are not available yet but should be soon

[99gav6]

This was actually my email. My lim is stock but my heads are ported so i was gonna do the lim port whenever i can afford it. Is there anything in particular that i would have to deal with by going with a 3400 stage 3 uim on my current setup?

[SappySE107]

It would bolt right up for you so long as you get the proper year. 1999 has a different EGR setup than 2000. I haven't done a 99 yet so I haven't broken them down by the same stages, but you can get a 99 ported for the 65mm TB all the same.

When you are ready for the lower, I will need to know more about the ported heads.

[99gav6]

Ok, well i have a 99 but i just referred to it as a stage 3 cause i would want it ported for the new tb. Also i don't really have a lot of info on what is done to the heads. I had a head gasket blow out early this past summer and my dad sent them off to a racing shop (in st Louis) and had them done then. I have a receipt for it but all it show is a price for "shop work". I could try though to find out more. I know they were ported, decked, new springs, i'm not to sure on anything else or specifics.

[SappySE107]

As far as the lower goes, I would like to know how much they opened up the intake port, and which gaskets they used for reference.

[99gav6]

thanks. ill let you know as soon as i can about the rest of the info

[99gav6]

i got the tb in today.. and realized, what gasket should i use for this with a 3400 uim? the 3500 tb gasket i guess?

[SappySE107]

You will need to use the stock 56mm TB gasket and cut it out for the 65mm.

[IsaacHayes]

Yup. The 3500 doesn't use a gasket. It uses an o-ring.

[silvergtjrad]

I would suggest buying a few gaskets , they will be very thin near the edges when you cut it to 65mm. They are under $3 a piece, so its not too big of a deal to break one. I ruined the one that was already on the car and cut all the way through another one as well when I did mine.

[IsaacHayes]

Or buy some gasket material and cut whatever shape you want.

[SappySE107]

Guess I should just make them.

[IsaacHayes]

They probably would sell. Seems lots of people don't like to do too much custom stuff on their own. Or convenience/time comes into play. I had to make a custom gasket because the 3400/3100 gasket came no where near close to sealing up the 3400 TB on the 3500 TB adapter. The o-ring groove wasn't covered by it on either side. Some thin paperboard from the felpro gasket packaging worked great in a pinch.

[LeftVentricle]

The Gen2 2.8 ported intake in the store, is it both upper and lower? Would it make any improvements on stock heads, and if so, how much, power-wise?

[SappySE107]

Its both upper and lower. I have no idea what the improvement would be.