JB'S LT4

Well as I have informed everybody already that I started up my new setup the other day..Now I have a problem and am wondering if anybody has experienced similar issues..Yes I know computer reprograming will be required, but the local shop can't fit me in until late next week..Well here's the detail's I went from a very small crane cam that work with the stock computer and I had no tunning done what so ever,,To now a set of stage III Ported LT4'S and a custom grind Comp cam 242' int 248'exh Duration at .50..The lift is 578' Int 599'exh..Well the damn thing won't idel ! it runs fine above 2500rpm but as soon as I let off the gas the car slowly stumbles and stalls..Will the computer tunning correct this? Is this normal for a Big cam & head swap?..I'm just a little worried and I have over a week to wait until reprogramming!

Darkside

That is a huge cam! Is it a solid roller? You will definetly have idling problems until you get the computer reburned. If you think it runs fine after 2,500 now, wait to feel the power after you get the reburn!

Eric

JB'S LT4

No its a HYD roller..About the biggest I could find :D

Darkside

If you don't mind me asking, what other mods do you have? What is your rpm range you want to achieve? Thanks

Eric@Exotic Msucle

JB'S LT4

Man I've got them all (mods)! And a big shot of giggle gas!

mackeyred96

You want that cam to idel????????

WOW, that cam is huge!!!!!!!!!!!!! Tuning may help.
Will the rest of your set up support that CAM?????????
You should have thought about idel and driveability before you put THAT cam in you motor.

:confused:

EricVonHa

Part of the problem is that the car is pulling much less vacuum (maybe none below 1500rpm). To sum it up and say that the "stock" chip is doing it is more than almost right. Serious tuning required is no joke. You'll need to get it on a dyno and do a lot of A/F ratio testing. It'll take time and $$$, but it is possible to have a cam such as yours, idle half decent, and make MAX top end power with a near perfect 12.5:1 A/F ratio across the board.

JB'S LT4

Yes my setup should handle the cam fine..And yes I expected a lopey idel,..But it won't idel period!.... It just shut's off..

EricVonHa

Anything is possible after a top end teardown/rebuild. I'd check all of the vacuum lines for starters. Pull a plug or two and see what they look like after a couple "soft" miles. Check your electrical connections, maybe even meter the TPS to make sure it's functioning... better yet throw a scanner on the car and see what the gremlins are up to. It's possible that there's too much fuel at idle with minimal vacuum, but you're definitely lean at the top end with that kind of setup and no custom tuning, so be careful. More than likely, it'll be just tuning, though. I've got a cam of similar duration, but less lift in my LT-1 with all other goodies and my idle is "weak". It's mean and sounds incredible, but there are still times when cruising about 2000rpm, if I push in the clutch, the motor will die. I've got over $500.00 worth of dyno time and a couple hundred into chip burning and it finally got to a point where I was very satisfied with what I wound up with. (I gained ~30hp over the "stock" chip also with fuel pressure adjustments)

What kinda mileage is on the car & what's the scanner say?

JB'S LT4

There's just over 40k on it..And I have'nt put it on a scanner yet.....At least what i'm hearing, is that the ECM is probably way out of wack with the cam I just installed...I hope it that simple :sad: