roller or flat tappet cam?

[92_lumina]

So my next build is going to be my winter beater the 92 lumina. I'm sticking with the MPFI intake& heads because I like the low end grunt better. I know I like it better than the 3100/3400 because I've owned them both. My question is should I use the stock roller cam in the new engineI have (95 grand prix) or put a nice flat tappet in it? It will be a 3100 short block with the MPFI heads and intakes with 1.6 rockers, 2.8 head gaskets, CAI made by me, 3100/3400 intake valves, chip,2 1/4 exhaust,50 or 75 shot of nitrous. what do you guys think?

[3400-95-Modified]

Dumb... BUT on topic Why put a SFI bottom end together with a MPFI top end? Don't even bother using a 3x00 block if your using MPFI parts, just stick with the 3.1 and 2.8 stuff... Also IIRC there is no flat tappet option for a 3x00 block, so you would have to be doing roller no matter what.

[92_lumina]

Dumb... BUT on topic Why put a SFI bottom end together with a MPFI top end? Don't even bother using a 3x00 block if your using MPFI parts, just stick with the 3.1 and 2.8 stuff... Also IIRC there is no flat tappet option for a 3x00 block, so you would have to be doing roller no matter what.

Dumb for doing what I'm doing... why so? I'm not putting one together the bottom end in the lumina has a thrust bearing going south so it's just a matter of time untill it fails. I already have a 3x00 pulled and just sitting on the shop floor from a past project. So why not put the 3x00 bottom end in it higher comp ratio and it has 1.6 rockers on it (non-roller rockers) and a roller cam. I also thought that you could convert a roller to a flat.

[3400-95-Modified]

With a 3x00 bottom end and 3.1 top end you will only get a 9.38:1 CR, where do you think it will be higher? Higher than a 3.1 Gen II but not higher than a 3100 or 3400...

It makes no sense to put a low flowing top end on top of a 3x00 bottom end, it's taking the power potential of the lower end and dropping it. Thats why I call it dumb.

And no, as far as I know unless a 3.1 cam fits a 3100 block, and I don't know about it, you can't drop down to flat tappet cams, and once again why bother, Ben can grind you anything you could ever desire.

[geoffinbc]

The difference in low end grunt is due to the camshaft difference not the heads and intake. Get the roller cam ground to make low end power and you will get it. You will get more of it too because you can get a ton more lift with less duration on a roller cam.

[Superdave]

flat tappet cams will work in the roller block just fine.. you need to use the gen1/2 timing set though.

Don't put gen2 crap on a gen3 engine.. the 3100 makes more torque than the 3.1, and considerably more HP. The 3100 top end will also get you better gas mileage.

3.1 140 HP/180 TQ
3100 (small port)160 HP/190 TQ
3100 (large port) 175 HP/195 TQ

[torq455]

Also consider- a stock 3.1 head, especially exhaust, won't benefit with more than what a 1.6 rocker will give for lift. The combination of the restrictive intakes and the short duration cam is why there is good low and stout mid torque. They keep the velocity up to make torque. As far as powerband goes, you see my list of mods, I have to say the 3100/3400 has more TQ below 1500 rpm, less TQ between 2000-4000 rpm, and way more HP over 4500 rpm. Although, I'm comparing my Z to my 04 GASE with headers, PCM tune, CIA, and 65mm TB. Previously comparing the two cars as they sit, that is how the cars feel. I do know that if I could swap the GA's 3400 in the Z, I would feel differently.

I can never find a consistent hp rating anywhere.

What I've seen usually:
3.1 140 HP/ 185 TQ
3100 sp 155-160 HP/ 195 TQ
3100 lp 170 HP/ 195 TQ

[92_lumina]

Ben can grind you anything you could ever desire.

OK, how much does Ben charge to grind a roller cam? This car is just the winter beater not the summer truck or the drag car (460 BB mustang) so I'm doing this project as bang for the buck and in my opinion there is no more bang for the $ better than nitrous.

[92_lumina]

The difference in low end grunt is due to the camshaft difference not the heads and intake. Get the roller cam ground to make low end power and you will get it. You will get more of it too because you can get a ton more lift with less duration on a roller cam.

So the small long runners in the 3.1 intake have nothing to do with TQ? (not being a smart ass)

[torq455]

umm.....

The combination of the restrictive intakes and the short duration cam is why there is good low and stout mid torque. They keep the velocity up to make torque.

[geoffinbc]

There is a point where high velocity meets restriction. Just because the runners may be small does not mean the velocity is always going to be high either. And just because the air is screaming down the runner does not mean enough is moving to fill the cylinders. It takes a lot more than just guessing to build a good combination. But the number do show that a 3400 will beat a 3.1L on every aspect of performance.

[torq455]

granted, i just didn't think i needed to go that far into detail. as far as the 3.1/3400 comparison, well, it was more of my Z24 vs. my GA is all. not to mention the 3400 is more efficient as well.

[92_lumina]

Ummm...

The difference in low end grunt is due to the camshaft difference not the heads and intake. Get the roller cam ground to make low end power and you will get it. You will get more of it too because you can get a ton more lift with less duration on a roller cam.

[3400-95-Modified]

OK, how much does Ben charge to grind a roller cam? This car is just the winter beater not the summer truck or the drag car (460 BB mustang) so I'm doing this project as bang for the buck and in my opinion there is no more bang for the $ better than nitrous.

Go to the WOT-Tech Store and look at 3x00 roller cams... there are tons and the price is 330 IIRC and then add in custom pushrods. All and all I think the cam, pushrods and a set of the comp springs (not always needed) will be around $600-700, I think I paid 650 for my whole setup.