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Thanks for the info! Yeah I always see mileage numbers on other forums and it makes me scratch my head.

The heads took the CR down to like 8.25, but the plan is to eventually stroke it and make...

Hey all - I have a built up L29 that is running well (not great) and I am finally into the build where I need to do some rounds of tunes.

It's in a 1999 K2500 Crew Cab. Heads, Cam, Adjustable...

Ok so favorable update on this issue:

I've been driving with the map disconnected for the past few months and taking it easy. I just had no time to dedicate to hunting this down over the winter. ...

On vacation for a week but I will look at map reading key on engine off and see if I can rig up a way to see voltage from map next weekend. Is there a way to see that within HP scanner of do I need...

Let me know if you find cmp anywhere in HPT. I would be very handy to be able to do that setting while also looking at the tune in real time.

If you?re getting no cmp (cam retard) data make sure the cam sensor on the dizzy is plugged in. I got that same code (I think) because the sensor plug had not been seated in the connecter all the...

What you're seeing is exactly the drivability issue I am experiencing. That's a very keen observation. As I increase normal throttle input from a dead stop, the ecu drastically retards timing as the...

Here is a log for the problematic area. 1200rpm column in timing advance.112242

Hey everyone - have a head scratcher here.

Just rebuilt a GM 454 (7.4L L29) with some aftermarket heads and the stock EFI system. I got some very gracious help with the tune here that has really...

I have more info on this as I have been diagnosing for the past week.

What I am experiencing is a dramatic decrease in intake vacuum without much throttle input. The ecu is seeing the high kpa...

This may or may not be a clue, but the weird misfire and dipping into the 70kpa region only happens when the engine is warmed up and in closed loop. I did a log this morning of a cold start and drove...

Yeah the O2mv corroborates that. I'll get the 5 degrees out of the dizzy and see what happens. Many thanks for your help and the tune mods.

Roger that. Gracias.

Here is the latest log. Still got that weird bog at 70kpa and 1200. Does is need a touch more fuel? My first impression is that it feels like it a bad burn in those sectors.

My first steps...

Closest cam retard I can get is -5, so I am 5 degrees retarded from 0 basically. Crank relearn seems to not have done anything.

The cam does have"4 degrees" of advance ground into it from crower...

The summit distributor will not zero out with cam retard measurement given it's shape and clearance to the intake. Advancing or retarding teeth will only make it worse, it's like the keyed table that...

oops here is the log

I loaded this tune and attached the log. Doing a crank relearn I did get a couple backfires around 3500 and above with significant throttle input. Gradual throttle kept the backfires at bay. Did not...

I loaded your tune and it is dramatically better thank you. Truck is starting to pull more normally. I am starting to get the hang of what to look for and what I'm noticing is that the biggest...

I found the timing tables and it is doing just what is listed in those tables. Are the heads just moving that much more air at 1200 rpm that I need to adjust the timing tables? If I just cruising...

That's where I am confused. It only really does it in closed loop and my timing starts at 26 at idle. Once I get into the throttle it starts dropping timing like crazy and I (assume) it is because of...

Hi everyone. I'm a seasoned tech but have no experience with EFI tuning. I recently rebuilt the top end of my personal pickup's 454 (L29) and had a mail order tune done but something is off.
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