Tuning help needed - '91 TBI 383 w/ Vortec heads

[Daveo91]

Some rings take a different grit hone. Its possible if between the two machinists, the wrong grit was used the rings may take longer to seat or may not seat at all. The plugs look really good, so not a lot of oil is getting in there. I made the mistake of ordering Jegs crappy vortec heads, the guide seals leak even with under a 1000 miles on them. i will have to tear them down this winter.

Thanks for the info. I know there was something with the hone. The first guy did his own, but I know the final machinist did a cross-hatch hone too. He didn’t want to rely on the other guy’s work. I’m going to change the oil one more time and see if that helps. Initial start up and first few hundred miles were on conventional oil (Chevron Delo, I think) but then I went to Mobil 1 synthetic. Sounds like there’s at least a possibility that’s making things worse. I’m going back to probably Shell Rotella, put a couple hundred miles on it and see if there’s improvement. Also ordered a new AC Delco PCV valve tonight - just in case the parts store one in there now is adding to the problem.

[tayto]

how are you breaking in the engine? with a flat or hydraulic tappet cam, after initial break in i will dump the oil, but why are you changing oil after a few hundred miles? i normally goto a "normal" oil change interval and just add oil to make sure it stays at full until next oil change. i would do at least 2 normal OCIs befote switching to synthetic, but that's me. im also a fan of "beating on it" vs the old school way of driving like grandma.

[Fast355]

how are you breaking in the engine? with a flat or hydraulic tappet cam, after initial break in i will dump the oil, but why are you changing oil after a few hundred miles? i normally goto a "normal" oil change interval and just add oil to make sure it stays at full until next oil change. i would do at least 2 normal OCIs befote switching to synthetic, but that's me. im also a fan of "beating on it" vs the old school way of driving like grandma.

I am a little different. For my roller cam small blocks. Mobil One in the pan, prime the system with a drill and priming tool, then start it up. Run it at 2,500 rpm long enough to get it warm and shut it off. Check it over for leaks, loose bolts, etc. Then take it out and beat the absolute crap out of it from the first stop sign. At 60K on the short block I used 1 qt over 2,200 miles and much of that was 75-90 mph. I am not even sure it was all the rings fault even. The valve seals were also a bit hardened and the front crank seal had a seep at the time as well.

[Daveo91]

how are you breaking in the engine? with a flat or hydraulic tappet cam, after initial break in i will dump the oil, but why are you changing oil after a few hundred miles? i normally goto a "normal" oil change interval and just add oil to make sure it stays at full until next oil change. i would do at least 2 normal OCIs befote switching to synthetic, but that's me. im also a fan of "beating on it" vs the old school way of driving like grandma.

It's a roller cam, stock L31 to be exact. I really didn't break it in. Everything I read said I didn't need to. But first start up was on an engine stand with a carb, radiator and water pump not hooked up. I had water in the block, but it wasn't circulating and I only ran it for a minute or two at a time and didn't take it much past idle. Really hoping that's not the cause of all this. Even when I got the motor in I didn't run it real hard at first. Wish I would have now, but I was also worried about the tune and having it run too lean. Since then I've definitely taken some hard pulls on it with high load, but perhaps it was too late. I changed oil because I eliminated the factory oil cooler (wanted to rule that out as cause of oil loss) and also wanted to check for any metal on the magnetic drain plug. (only a light fuzz)

[donf]

Thanks for the info. I know there was something with the hone. The first guy did his own, but I know the final machinist did a cross-hatch hone too. He didn’t want to rely on the other guy’s work. I’m going to change the oil one more time and see if that helps. Initial start up and first few hundred miles were on conventional oil (Chevron Delo, I think) but then I went to Mobil 1 synthetic. Sounds like there’s at least a possibility that’s making things worse. I’m going back to probably Shell Rotella, put a couple hundred miles on it and see if there’s improvement. Also ordered a new AC Delco PCV valve tonight - just in case the parts store one in there now is adding to the problem.

Sounds like a good plan. I use to work in front of a machine shop. I had to do their R&R's sometimes when things went wrong. The big thing that got them over and over was hone grit. They would get in a hurry and just hone it with what ever they thought was standard. Different brands and ring types will tell you what grit to hone the cylinders. As far as beating on it, vs not I really don't think that makes the difference compared to having a machinist who reads and follows the ring manufactures instructions. Some cylinder pressure behind the rings though will push them out against the walls harder. I do think if your rings have not fully seated, switching to conventional oil may help. It doesn't even have to be the good stuff if you do not have a flat tappet cam. If it does, one with zinc will help.

[PlayingWithTBI]

I bought an 84 Dodge (new in 84) W150 with a 360 4BBL, it burned about a qt/1000 miles for about a year. 1 day it wouldn't start (turns out the distributor reluctor was bad), after cranking forever it finally started. I drove it home 15 miles with almost no oil pressure. I wound up sucking about a gallon of gas into the crankcase. After changing the oil and distributor it ran great and didn't burn a drop of oil. LOL. I drove it hard including pulling goose neck trailers for 206,000 miles before rebuilding it.

[Daveo91]

Sounds like a good plan. I use to work in front of a machine shop. I had to do their R&R's sometimes when things went wrong. The big thing that got them over and over was hone grit. They would get in a hurry and just hone it with what ever they thought was standard. Different brands and ring types will tell you what grit to hone the cylinders. As far as beating on it, vs not I really don't think that makes the difference compared to having a machinist who reads and follows the ring manufactures instructions. Some cylinder pressure behind the rings though will push them out against the walls harder. I do think if your rings have not fully seated, switching to conventional oil may help. It doesn't even have to be the good stuff if you do not have a flat tappet cam. If it does, one with zinc will help.

Thanks for the confirmation. Yeah, it's a roller cam so no need for high zinc oil, but Shell Rotella seems to be a good heavy duty oil from stuff I've read. There is some debate if it will cause premature cat failure (I'm running a cat) but I gotta resolve the oil consumption problem and then I'll worry about my cat!

[stew86MCSS396]

Sounds like a good plan. I use to work in front of a machine shop. I had to do their R&R's sometimes when things went wrong. The big thing that got them over and over was hone grit. They would get in a hurry and just hone it with what ever they thought was standard. Different brands and ring types will tell you what grit to hone the cylinders. As far as beating on it, vs not I really don't think that makes the difference compared to having a machinist who reads and follows the ring manufactures instructions. Some cylinder pressure behind the rings though will push them out against the walls harder. I do think if your rings have not fully seated, switching to conventional oil may help. It doesn't even have to be the good stuff if you do not have a flat tappet cam. If it does, one with zinc will help.

What he said to seat rings...wind it up and let the compression slow the vehicle down repeat like a dozen or so times.

[Daveo91]

What he said to seat rings...wind it up and let the compression slow the vehicle down repeat like a dozen or so times.

Switched to Rotella T4 (conventional) over the weekend. We'll see what happens. Back to tuning.

I like the idea of winding it up and using compression to slow it down to seat the rings but there's a problem......that's where I have my worst tuning problems. After oil change I took it on a home depot run and it ran great until I came off the freeway on a downhill ramp. I dropped it down twice, when I hit second it went up to about 3000 and I started getting some popping/light backfiring out the tailpipe. And it seems like after that event happens, my idle gets messed up. 100-200 higher than commanded and some hunting with a range of about +/- 75 rpm. Then after an engine stop and restart, it seems to be back to normal, idling at commanded speed and no hunting. I have only seen that behavior a few times though so I don't know if it's consistent.

I've been shopping for a WB kit. Suggestions? I'll probably just go with a typical AEM kit with gauge and sensor. How does logging work with a kit like this? Sorry for the dumb questions, but does data go through my ECM (extra channels?) or does it go directly to my laptop/tuner pro and then logged simultaneously? I've read some threads on the former method and it seems like that may be out of my league. Or maybe I should forego simultaneous logging altogether to keep it simple? Again, if it sounds like I don't have a clue what I'm doing, it's because I don't! Is there a WB tuning for dummies thread that someone could point me to?

[donf]

Popping out the tail pipe is rich, not unusual, I had to take some fuel out there too but I only have 19.5 psi. I think it will be especially bad if you have the fuel pressure jacked way up to almost 30 lbs. That is why I don't like to run any higher fuel pressure than really necessary as there is a trade off sometimes in transitions not being as clean. Hopefully you can work it out by adjusting the VE table more. I like the AEM X-series that has some improvements over the older version you linked to. I use the wide band sensor in that series, you have to redo the math, but its fairly easy.

[Daveo91]

Popping out the tail pipe is rich, not unusual, I had to take some fuel out there too but I only have 19.5 psi. I think it will be especially bad if you have the fuel pressure jacked way up to almost 30 lbs. That is why I don't like to run any higher fuel pressure than really necessary as there is a trade off sometimes in transitions not being as clean. Hopefully you can work it out by adjusting the VE table more. I like the AEM X-series that has some improvements over the older version you linked to. I use the wide band sensor in that series, you have to redo the math, but its fairly easy.

Thanks. My fuel pressure is only 13 psi, so that shouldn’t be the problem. I think my surging, popping, and general bad behavior during decel are timing or O2 sensor related. I’ve been noticing O2 output readings drop to near zero (low double digits) every time it surges.

I’ll take a look at the AEM X-series, thanks.

[Daveo91]

So I tried an experiment today. Burned a new chip that had closed loop tuned out - wouldn’t come on till 150 deg. C. Runs great, all decel surging problems are eliminated by running in open loop only. Of course I know I can’t keep it like that, but at least I know for sure that this is a closed-loop problem. Now just to figure out what it is.