Base Timing for 1994 TBI

[Connor Fischer]

So I just finish building a 1994 350 tbi I used a rv style camshaft with 204/214 duration @ 50 with vortec heads and and carb intake 9:1 compression. I'm having trouble getting it to run decent and I think it's a timing issue right now I'm at 5* advance at TDC with the computer disconnected. Should I go higher or is the computer just going to back it down when I hook the wire back up?

 

[90halfton]

The computer may not like the things you have done.

 

[jkeaton]

Yes the computer will put it back where it's supposed to be for stock. May need a custom tune.

 

[sntrym]

With that cam you'll need a custom tune. I've used tbichips.com with success, other vendors are out there as well.

 

[Connor Fischer]

I'm working on getting a custom tune done by a buddy but for right now I'm just trying to get it drivable I know people have put bigger cams in With a stock computer and made then run enough to be able to drive. Has anyone done anything like this cam wise that has a good idea of where to time it?

 

[L29Sub]

Are any codes set? How did the engine run before mods? Whatever codes appear may reflect odd fueling related to cam
heads-intake-intake port match-etc.
Are all engine sensors returned and correctly wired?
Look at O2 sensors and cam position sensor for data and codes. Any incorrect sensor will set a code.
Firing order correct...plug wires?
Cam may be mistyped. Cam may want more fuel than your maps allow, creating lean condition. Fuel ratios are visible on each bank with a scanner. Once you see O2 data you can chase some of your problems.
Not sure about small blocks, but Vortec heads don't easily interchange on BB.
Are you running an automatic?
As stated, the ecm will attempt to return the timing to factory settings...if it can do so.
Leave any rags in the intake or heads? ,o)

 

[Connor Fischer]

Well I got it running decent at 14 degrees advance but now it has great Low end power and decent top end but mid range suffers so when you step on the gas it just falls flat on its face and bogs till it gets to higher rpms or till it dies. Think it's running lean or is my timing to much and causeing this? Right now it idled beautiful and revs up nicely though the rpm range but as soon as you put a load to the motor it acts like it just runs outta fuel

 

[L29Sub]

Did you install a carb along with the "carb" intake? If so, the ECM is not going to manage your timing accurately. Find an HEI and install. If still running the TBI, get a scanner and it'll show you L and R bank 02 sensor counts. You'll know whether lean or rich. Must be warmed up and into closed loop for this function. Also check knock sensors for overcounts...if so, too lean or too much advance. If the knock sensors are detecting too many noises (including noisy valve train) it sets the engine timing back and may go into limp mode.
If the engine backfires thru the intake, it's too lean or too much adv timing. If it just bogs, real-time scan tool will allow you to sort it out.
An RV cam is not (typically) radical enough to cause much change in performance..unless the cam is timed up wrong.
The cam provider may recommend a "program", but they recommend such if left stock.
What is cranking compression?
Are correct plugs for your heads installed?
What engine was the cam spec'd for?
The intake ports and heads match?
Head gaskets correct?
How did the EGR work with your intake? L
Are all sensors that were originally on the factory intake returned to your new intake? If not, it won't run correctly.
If it runs that poorly, you gotta have some codes set. Resolve them.
SOLUTION: Snatch that puppy out and drop an OBD1 LT1-LT4 in there! Live happily ever after! At least until the Opti fails