99 L29 454 build
- Thread starter Scottm
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Supercharged111
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What is the IFR programmed in the PCM? Those flow 42.5#/he at 4 bar. Which is what you have.
The log file isn't going to say what they actually programmed into the tune. It would be interesting to see if they programmed in the right flow rate. Since you have a vacuum referenced FPR, it should have a flow rate of 447cc/min at all points in the table. If you didn't have it vacuum referenced, your flow rate would actually be 447 at full throttle and higher at lower throttle because the pressure differential would be more than 58psi at a high vacuum condition.
That's what I mean. Vacuum referenced fuel means that all flow rates for a given manifold pressure will be the same. If you have fixed pressure then the actual flow rate will change with manifold pressure. So if they put the wrong values in, then it will be no good.
Had a good day working on the ol truckster. There have been a lot of ticking noises at idle that have slowly gotten worse. I hoped it was exhaust leaks rather than valvetrain problems, so I loosened the left side header and pulled out the felpro gasket. It was perfect, no leaking was happening. That was a small relief because these headers have heavy flanges and it didn't make sense that they would leak.
I took off the throttle body and both valve covers. Took off several rocker arms to look for galling or weird wear marks. Checked the contact marks on the valve stems and confirmed that the rocker roller tip movement was properly centered on the valves. Everything was good; no wear on anything but slight polishing on the pushrods from contact with the guide plates. There was nothing else to suspect but too little preload. I put a half turn on them originally, and a few had become looser. They are stock lifters of the non-adjustable rocker era, and apparently they need more preload. So I adjusted them in sequence with 3/4 turn preload. Success! Noise was reduced 75.66% approximately. What does remain is probably related to the pushrods contacting the guide plates. As of now I'm confident to drive it anywhere.
While the plugs were out I checked the compression. Just under 1,000 mi so far. Here's the result - 177-184 psi cold. Awesome!
I took off the throttle body and both valve covers. Took off several rocker arms to look for galling or weird wear marks. Checked the contact marks on the valve stems and confirmed that the rocker roller tip movement was properly centered on the valves. Everything was good; no wear on anything but slight polishing on the pushrods from contact with the guide plates. There was nothing else to suspect but too little preload. I put a half turn on them originally, and a few had become looser. They are stock lifters of the non-adjustable rocker era, and apparently they need more preload. So I adjusted them in sequence with 3/4 turn preload. Success! Noise was reduced 75.66% approximately. What does remain is probably related to the pushrods contacting the guide plates. As of now I'm confident to drive it anywhere.
While the plugs were out I checked the compression. Just under 1,000 mi so far. Here's the result - 177-184 psi cold. Awesome!
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I had my laser shop cut and form this little instrument panel slash coin tray. Got it in and hooked up today. I can hardly wait to drive around this summer and see how hot the oil and trans really get. I bet it's crazy hot.
In tuning news, I got it back from Black Bear after the 3rd adjustment. To recap, it had only 22 deg advance at wot after the first initial tune, still only 22 degrees after first adjustment and still only 22 after the second adjustment. They said that's what it should be and any more was risking 'destruction'. I said nonsense, any chevy v8 and for that matter any wedge-head v8 engine wants 34-36 deg at wot. Low timing in a stock tune is to reduce NOx and protect the trannies in abused fleet vans, not to protect the engine from destruction. So I sent it up for a 4th time. I said I want the wot advance curve to be 20 deg at 2000, 30 deg at 3000, and a very conservative total of 32 by 3500 and up. And again I included this mechanical advance graph showing the curve of an out-of-the-box MSD distributor. So it comes back again and guy said they advanced the spark tables 'as I requested'. I don't really know what that means, but now it pings at part throttle (have not recorded a data log yet). I requested more timing only at wot. Is it not possible to add timing only at wot? It has to go up across the board? I don't believe it. The 0411 is supposed to be a very capable ecm. How can it be less tunable than the advance curve in a distributor?
In tuning news, I got it back from Black Bear after the 3rd adjustment. To recap, it had only 22 deg advance at wot after the first initial tune, still only 22 degrees after first adjustment and still only 22 after the second adjustment. They said that's what it should be and any more was risking 'destruction'. I said nonsense, any chevy v8 and for that matter any wedge-head v8 engine wants 34-36 deg at wot. Low timing in a stock tune is to reduce NOx and protect the trannies in abused fleet vans, not to protect the engine from destruction. So I sent it up for a 4th time. I said I want the wot advance curve to be 20 deg at 2000, 30 deg at 3000, and a very conservative total of 32 by 3500 and up. And again I included this mechanical advance graph showing the curve of an out-of-the-box MSD distributor. So it comes back again and guy said they advanced the spark tables 'as I requested'. I don't really know what that means, but now it pings at part throttle (have not recorded a data log yet). I requested more timing only at wot. Is it not possible to add timing only at wot? It has to go up across the board? I don't believe it. The 0411 is supposed to be a very capable ecm. How can it be less tunable than the advance curve in a distributor?
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L31MaxExpress
I'm Awesome
Timing is all based on gm/cyl airflow. Unless you have an accurate datalog with gm/cyl being recorded, impossible to know where the timing value will be pulled from in the spark map.
As for your timing request, non sense. Those 454 vortec heads do not like nearly that much timing. They like a curve similar to a TBI small block head. 24-26* is more than enough to cause it to knock on a hot day. The L31s generally do not like more than 31* (mine only wanted 29*) and the L30s like 28-30*. No Chevy V8 built with a swirl ports or vortec heads since ~1986 wants more than ~30* and many less than that.
As for your timing request, non sense. Those 454 vortec heads do not like nearly that much timing. They like a curve similar to a TBI small block head. 24-26* is more than enough to cause it to knock on a hot day. The L31s generally do not like more than 31* (mine only wanted 29*) and the L30s like 28-30*. No Chevy V8 built with a swirl ports or vortec heads since ~1986 wants more than ~30* and many less than that.
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