what am I missing ?

[FirebirdFrank]

I have a 1993 chevy z71 5.7 litre. Fresh rebuild, with New vortec heads. Running stock throttle body,on Edelbrock 4 bbl. manifold,with adapter plate. my issue MAY be the camshaft chosen. Speed Pro CS-274. Problem is... if I set the timing as called for 0 degrees with spout disconnected,the truck almost doesn't run. Backfires thru t-body terrible,especially trying to accelerate. If the timing is bumped to 18-21 degrees the truck is now driveable,but it aint right.Using a Moates tuner,we ALWAYS see the knock retard trying to remove about 18 degrees no matter what I do or set timing.The ecm is#16168625. We have replaced everything in ignition system,moved the disributer a dozen times...I am missing SOMETHING..

[sturgillbd]

What bin file are you using? If the mask is E6, you have change the bin file to report knock retard instead of battery volts. See this thread. http://www.gearhead-efi.com/Fuel-Injection/showthread.php?3290-24*-Knock-retard-no-knock-counts

Brian

[FirebirdFrank]

I think you are right I'm reading batt+. Where do I acutally change the bin file ? or where can I find the " L51FE" so I can change it to $020F

[jim_in_dorris]

I think you are right I'm reading batt+. Where do I acutally change the bin file ? or where can I find the " L51FE" so I can change it to $020F

What hardware are you using to modify your memcal? L51FE is an address in your calibration. If you are using new vortec heads, is your calibration for vortec heads, or is it the original calibration. Vortec heads will require a different timing table than what the stock 93 calibration has. My guess is you had 193 heads before the rebuild, very different timing tables

[Fast355]

I have a 1993 chevy z71 5.7 litre. Fresh rebuild, with New vortec heads. Running stock throttle body,on Edelbrock 4 bbl. manifold,with adapter plate. my issue MAY be the camshaft chosen. Speed Pro CS-274. Problem is... if I set the timing as called for 0 degrees with spout disconnected,the truck almost doesn't run. Backfires thru t-body terrible,especially trying to accelerate. If the timing is bumped to 18-21 degrees the truck is now driveable,but it aint right.Using a Moates tuner,we ALWAYS see the knock retard trying to remove about 18 degrees no matter what I do or set timing.The ecm is#16168625. We have replaced everything in ignition system,moved the disributer a dozen times...I am missing SOMETHING..

The cam is fine as it is the stock TBI 350 camshaft. It is the heads causing the issue. Stock throttle body at stock fuel pressure will be starved for fuel and then add in the timing advance requirements are very different and you will have a truck that starts up and idles well but is undriveable.