Aftermarket Cams in the 3.1L

[Superdave]

It wouldn't take much to get that TBI to work well with a big cam. just basic tuning. TBI actually works very well, lots of the new aftermarket systems are going back to it for carb retrofits.


there are constants that will increase the idle speed when the A/C is turned on, same with an electric fan. I'm guessing the idle just needs to be kicked up a few hundred RPM anyways, that's normal for a big cam.


My cam is on a 110 LSA but with tons of duration, over 70 degrees of overlap and i have to idle at about 1100-1200 RPM with the regular plenum. With the ITB's i can idle around 800 but that's a whole other world there.

[Mad Max]

I wouldn't run a 108 with lots of duration on a FI car because I'm sure the lack of idle quality would be make tuning a bitch.

Yes, that is exactly why I posted the info. The 3.4 idles (OK) with the Holley 390, although it's way choppy, when I turn on the A/C, it will die at idle. I am pretty sure TBI can't handle this cam unless you're pretty talented with a fuel log/ program tuning on the earlier OBD 1s...
I have given up on TBI... it s too primitive compared to OBD II multi port or any system afer TBI.

[ericjon262]

I wouldn't run a 108 with lots of duration on a FI car because I'm sure the lack of idle quality would be make tuning a bitch.

[Superdave]

Trotterlg is right, 108 is fine. Especially with that low of a lift and duration. you aren't going to have hardly any valve overlap.

[trotterlg]

A LSA of 108 isn't really that tight, depends on the duration also, the cam I have has a LSA or 99.5, but I am running a carb and 12 to one CR. Larry

[IDCavalier]

I've heard that the 3.4s are real powerhouses.

Good for you!

I really enjoy hearing about success stories..I hope I can tell one in the future!

With my setup, even the Comp cams website, along with the guys here say that my cam will work fine with fuel injection.

But it's only a .390/.390 at the valves with a 108.0 lobe separation (is that what "split" means?)

Then, after having power problems, I called the Comp cams tech line. - He told me that 108 is way too tight to run FI. Why do they say 1 thing and then another?

Swapping the cam is tough to do on this li'l FWD!

[Mad Max]

you should start your own thread... but yes, you could tune that engine to run on EFI. I've got a bigger cam than that and was running ITB's on my Camaro.

Did you check for coil bind at all? that's way past what should be possible on stock valve springs.

I did check for coil bind - no prob. I don't think I could have gone much more for lift though. The rocker geometry is at the maximum travel. I can feel the valves float at about 5500 rpms. I don't run it to 5500 much, but it has no complaints visiting that slot.
I will start a thread, I have been WAY happy with this engine, and the CRAZIEST part is: it has close to 300K miles on it!! How??
I've been waiting for it to go bang but it still runs way hard and strong.
I just drove it from Baton Rouge to Denver, then towed a '67 GMC pickup chassis back to New York State...
Defying gravity every inch of the way.

[stephen0500]

Haha I thought that was you with that 3500 cavi

the value you have for Initial SA seems wrong. I haven't used an EBL but in the other OBD1 masks for the 60v6 initial SA is 9.14 degrees. ($A1 code which is stock for your car)

In the standard masks we also have a value called "Spark reference angle" which is 59.86 degrees (60).


Your value of 69.96 looks like he added those 2 together.. which is what his mask may need but I'd ask him about it, he may have more info as i know nothing about how he's designed that mask.



Also, that extended SA table needs some work



I looked into the EBL for mine, it has some cool features but i just stuck with the '7730 and bought an emulator to tune the code that was built for the engine/platform. i ran that in my '91 Z24 with various wild engines for 9 years and have had the same ecm in my Camaro for 3 years now. (Search user "Whitelightning2" on Youtube for videos of my Cavalier and Camaro)

Since your car is still stock the most you'll pick up from tuning is like 5 or 6 HP, IMO it's just easier to run the stock tune till you get into wilder engine builds. Then you'll at least get to enjoy the car.

[Superdave]

you should start your own thread... but yes, you could tune that engine to run on EFI. I've got a bigger cam than that and was running ITB's on my Camaro.

Did you check for coil bind at all? that's way past what should be possible on stock valve springs.

[Mad Max]

I guess I've been lurking here for a while, no posts though. This cam thread had me lit for some info.
I have a 1st gen S10, which I swapped in a '95 Maro 3.4. I run non TBI, so it has an Eddy/Holley and every other conceivable mod without changing any reciprocating parts.
So, the cam is a .515/.525 lift, .292 adv duration, 110 split. Yes, it idles like a prostock car and it sounds WAY radical. I have driven 32K miles like this and it gets 20-22 mpg @70 with A/C on the hiway (!!??). Around town though, it SUX. Anyway, my best 1320 is 14.9 @ 94 MPH.
Here's the specs:
Mallory HEI dizzy
Cloyes double roller chain advanced 4*
Heddmen hedders with 3" exhaust
Eddy/ Holley 390 CFM
Compudyne radical cam
Crane roller rockers - stock ratio (had to - busted a rocker stud. It now has ARP studs)
4.10 rear w/ Eaton clutch posi
T5 w/ Exedy comp clutch
Stock valve springs!! (my rev auto limiter!)
This is a daily driver and is a gas to drive in town. It spins tires hard, and outruns most stock 5.0s. The ricers bum.
So, this cam was spec'd for a 3.1, according to the cam sheet. I bought it on Ebay and the auction said it was a mild cam - haha
I guess the right combo of parts works every time...
Sorry guys, EFI is way to PIA to tune correctly for this combo. I am pretty sure this cam would never run with the TBI - even modified.

[ericjon262]

Yeah, he's good!

I am new to tuning so I don't know what a constant is.

I know that the EBL P4 Flash is badass tho. I just wish I could make the most out of its potential.

There are a lot of things called scalars in the advanced xdf that I don't know how they might affect performance.

Bob has been a great help to me.

What is TGO?

thirdgen.org The big 3rd gen Fbody forum.

[IDCavalier]

ha ha! I am of course kidding. But I did try really hard to put it together correctly.

I ran into trouble with a couple of rod caps that got switched. I never had more than 1 apart at a time, and my machinist swears that he never made a mistake.

But I noticed that the markings he made on the rods - his 6 looks like a 2. And those were the two that you got mixed up.

I was extra careful when installing the timing chain. It's funny that you should mention that because it a local speed shop asked me if I had indexed the cam. I don't think I can without a special cam gear, which I don't think exists.

[trotterlg]

Not even getting the chain off just one little tooth advanced? Larry

[IDCavalier]

yeah. I think it's worth a try.

there's SOMETHING up with this setup.

The reason I blamed the cam was because that was the only thing I changed and there's

NO WAY I MADE ANY MISTAKES AT ALL! Ha Ha!

[robertisaar]

that BIN only contains calibration...... no algorithm. so in reality, you were running in limp-home mode, Ben.


i would just set the "initial advance" to 60* and see what happens. if you have a timing light, you could verify that what is being commanded is actually being seen by the engine.