Starting on a 01' 3100 GP

[carsan57]

I have a 01 gp with a 3100 i wanted to begain mods but i dont know were to start. From what i'v read the upper end is the same as a 3400, is that true.

It will be a driver so i just wanna get a little more out of it for now i do hope i will beable to stick in a 3500 some time in the near future. Please if anyone can give me a point in the right direction that would be great. Thanks

[IsaacHayes]

Yes, the heads and intakes are the same as 3400. The TB may be 52mm and not 56mm like the 3400 though. If you had some calipers you could measure the inside bore where the plate is and find out for sure. If it's 52mm you could get a 3400 TB. If the linkage isn't the same you can swap them easily. Or you can get the 65mm TB on the store here.

You can also put a 3500 upper intake on for now, with a little modifications to get it to fit. You can look into exhaust work (2.5", high flow cat, muffler), and an under drive pulley (UDP). A good air filter setup, I suggest a K&N cone located away from the engine bay heat, or a K&N drop in and modify your stock air box to open it up for more flow if it needs it.

More radical stuff would be headers (I think the front mount needs notched to fit the www.ssheaders.com headers), or a whole 3500 top end. Which would be heads and lower and upper intake.

Take a look around and search to see what some members are running. Basically anything the 3400 guys are doing you can do.

[3100 MPFI]

I agree with most of the things he said, but not the underdrive pulley. The underdrive pulley does NOT have a harmonic balancer, so it can cause engine damage long term. If the UDP does not have that little rubber ring in it, then you do NOT want to use it.

read up on this:

HARMONIC BALANCER

[carsan57]

I found a upper from a 3500 for 60 bucks it does come with throttle body, can the tb be used off a 3500 and what mm is it.

Is 60 fair price i have know idea

[3100 MPFI]

60 is a really good price, and no, the 3500 throttle body will not work. It is DRIVE BY WIRE (electronic controlled), and your 3100 is a normal throttle CABLE control.

You will have to buy an adapter to use a 3100/3400 throttle body on the 3500 upper intake.

[carsan57]

O.k. i was looking in the store here for adapter for the 3500 upper. and i cant seem to find one also theres a guy who states that a stock 3400 will out perform a 3500 i will be running a 56mm tb so will it make a diffrence and where can i find a list of mods that need to be down to the 3500 upper?

[alerored04]

if you decide against the 3500 uim i have a ported 3400 uim fs in the buy/sell/trade area.

[geldartb]

I agree with most of the things he said, but not the underdrive pulley. The underdrive pulley does NOT have a harmonic balancer, so it can cause engine damage long term. If the UDP does not have that little rubber ring in it, then you do NOT want to use it.

read up on this:

HARMONIC BALANCER

arent the 3x00 engines internally balanced.

[carsan57]

We'll i think ill stay with the 3500 uim, i tried a search for a list of mods to stick a 3500 on a 3400, i can do it blind but i'd rather talk to someone that has done it and do they offer the tb adapters here or can someone tell me where to look.

[IsaacHayes]

$60 is a good price for the 3500 upper. The 3500 TB is 65mm but electronic so you need the adapter and run your 52mm TB, or a 3400 56m or the store's billet unit as stated before. Here is the link to the adapter.

Stock 3400 upper will outflow a stock 3500 upper (3500 ports are a tiny bit smaller), but the 3500 will make more power due to it's different design. With a simple gasket port match (easy to do because there are no runners so not much to grind) the 3500 will outflow the 3400 then.

The 56mm TB will be just fine. Later you can go to the bigger billet unit if you wish, but without heavy modifications (headers, cam etc) I don't think it's that necessary. Remember the 3500 motor has 65mm stock, but it also has better flowing heads, and dual exhaust manifolds with runners, where a 3100 has logs which flow terrible.

Yes our motors are internally balanced, we just have a dampener. Some people argue that not having a dampener and just a pulley will hurt the engine, others have ran them hard for a long time with no ill effects. It's a debated topic. The UDP does free up power though. I'm considering one to put on my ~200,000 mile motor.

Mods to put the 3500 on, Run some vacuum line to the FPR (tap the IAC port with a 1/4 NPT and put barbed fitting on). Use the 3500 MAP and splice the pig tail on, or run your old MAP and run vacuum line to it. Grind the neck for FPR clearance or turn it to the side a bit or get the spacer in the store. You need m8 x1.25 65mm bolts (6). I *think* that's it for putting it on a large port 3100/3400.

You can check out this thread, for stuff needed for the 3500 plenum. Not all will apply to you of course since it's talking about also putting on the large port lower on an old 94 small port.

[3100 MPFI]

arent the 3x00 engines internally balanced.

Yes they are, BUT they still need the little rubber ring in the pulley to cancel out the harmonics caused by combustion.

You see the little rubber ring between the outer area and the inner? The underdrive pulleys don't have that. That little rubber ring is what cancels out harmful harmonic resonance.



If you read that article, it states:

"At certain engine speeds the torques imparted by the cylinders are in synch with the vibrations in the crankshaft, which results in a phenomenon called resonance. This resonance causes stress beyond what the crankshaft can withstand, resulting in crankshaft failure."

IMHO if you have the money to blow when your engine does the same as your money (blows), then go for it. When I built the high compression 3100 MPFI I knew to NEVER use an underdrive pulley that didn't have the harmonic balancer built in.

If you email any company that makes the underdrive pulley and ask them if it is also a harmonic balancer, they will tell you no, it is not. It is JUST an underdrive pulley, and is not intended for continuous street use. Also, ask them if they will pay for your custom built engine if it fails due to cracks in the crankshaft due to resonance. They will just laugh at you.

[3100 MPFI]

Just for laughs, here is a harmonic balancer for the supercharged buick pos. Notice how big it is? In the event of a harmonic balancer failure, the spare tire can be used as a substitute. The 90* engine is not as balanced as the 60* engine, so it needs a MUCH LARGER harmonic balancer with a larger rubber insert to cancel out resonance.