Andy’s 1995 CCLB 7.4L TBI to Vortec Swap

[PlayingWithTBI]

I haven't heard of HLC before. Is that something that requires a 0411 swap?

GM came out with Hiway Lean Cruise around 87 on the 1227747 ECM but, they couldn't pass emissions so, they disabled it (hence EGR for NOx). Other folks have "hacked" the code to enable it through a "patch". Then you can play with SA (Spark Advance) and AFR (Air Fuel Ratio) based on MAP (Manifold Absolute Pressure or how much air you're sucking down the intake). If you look at the HiWay AFR it's commanding 16.10 to 15.40 when you normally run at 14.70 (Stoich).

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[ZRoe]

GM came out with Hiway Lean Cruise around 87 on the 1227747 ECM but, they couldn't pass emissions so, they disabled it (hence EGR for NOx). Other folks have "hacked" the code to enable it through a "patch". Then you can play with SA (Spark Advance) and AFR (Air Fuel Ratio) based on MAP (Manifold Absolute Pressure or how much air you're sucking down the intake). If you look at the HiWay AFR it's commanding 16.10 to 15.40 when you normally run at 14.70 (Stoich).

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That's pretty cool that they started that back I 1987. That's before I was even born! Thanks for the education. It makes sense that it would improve mileage. Heck Mazda is getting up into 30:1 AFR range with their diesels on the race track, but I'm sure it is too dangerous or doesn't pass emissions to put on a production car.

Is anybody doing HLC on the newer Vortec motors?

I've already grabbed a 0411 pcm at the junkyard, now I'm just collecting the money and guts required to take the plunge and tell my wife [emoji51]

Sent from my moto e5 supra using Tapatalk

 

[Christian Steffen]

How is it that my speedometer in the truck reads +4mph at 55 but in HPTuners the speedo is right on? (Verified with GPS). Aren’t they using the same signal that’s coming from the VSS in the transfer case?

I don't have my laptop on me, but i think there are two separate spots to adjust it.

That's pretty cool that they started that back I 1987. That's before I was even born! Thanks for the education. It makes sense that it would improve mileage. Heck Mazda is getting up into 30:1 AFR range with their diesels on the race track, but I'm sure it is too dangerous or doesn't pass emissions to put on a production car.

Is anybody doing HLC on the newer Vortec motors?

I've already grabbed a 0411 pcm at the junkyard, now I'm just collecting the money and guts required to take the plunge and tell my wife [emoji51]

Sent from my moto e5 supra using Tapatalk

It can be done with the 0411, just need to switch the platform type and throw your settings into the tables for it.

 

[andy396]

Still working on the EGR issue and the stalling. I caught some interesting activity today logging in HPTuners. Slowing down and coming to a stop light, transmission shifts down from 4-3-2-1 and then the engine starts to stumble. When I catch it stumbling I throw it into N, but looking at the log, I see the line pressure jump from 62% to 90% and the current gear jumps to second gear. What the...? For you guys with HPTuners, would you be willing to take a look at this log and share your thoughts? It occurs right at 5:32 timestamp. I had to rename the file with a .txt extension to get it to upload. You'll have to rename it with the .hpl extension after downloading.

Edit/update: I suspect that shift into 2nd and going to 90% line pressure is the transmission going into limp mode. I caught it doing it again today, but it recovered on its own. It’s always after coming to a complete stop, but doesn’t do it every time.

 

[andy396]

Worked on fixing the exhaust issues today. It was leaking at the intermediate pipe flange. I knew it wasn’t flat when I installed it and tried using some high temp silicone but it just blew out. So this time around I tried some ceramic/metallic paste stuff from JB Weld. I kind of gooped it on and let it smoosh out. I didn’t use any sort of gasket this time. I really hope this works because I think the only thing left is to fix it right and cut off the flanges and weld in some pipes to accommodate to use us band clamps. Not the kind of effort I want to put into it at this point.

I also went after an extremely annoying rattling catalytic converter. It was the aftermarket converter I welded in. I probably rattled it loose in the process of cutting it with the sawzall.

The fix was some open cat surgery.

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The one on the right was good. It still had some ceramic gasket-like material still surrounding it, but the left one had nothing and was rattling all around in there. So I stuffed as much cotton candy (aka fiberglass home insulation) in there as I could.

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Stitched it back up and tacked the heat shield back down. Not the prettiest of weld jobs, but should function just fine. @kennythewelder will never see it from his house [emoji846]

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[andy396]

When I went to put gas in it at the gas station the other day, after a short bit the guy next to me hollers, “Hey buddy! You’re leaking gas!”. Wonderful [emoji849]

I look underneath and all I can tell is it’s running out of the plastic cover for the tank which isn’t very helpful. I don’t fill it any more, which left me with about a half a tank.

I tightened the hose clamps afterwards but the next time I tried to fill it up it was still pouring out. So yesterday I lifted the bed off to see what the cause was. Turns out my $10 gas tank wasn’t such a good deal after all. It was rusted out around the filler neck.

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I cleaned it up the best I could put marine-tex epoxy all around the filler neck and vent neck.

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I was really hoping that would solve the problem. I stopped at the gas station today to try again. Everything was great until I got about 7/8 full, then a smaller leak emerged. An improvement at least, but not solved. [emoji17]

I’ll lift the bed up one more time and take a look, but I might just have to bite the bullet and buy a new tank.

 

[kennythewelder]

A 2 part epoxy should have done the trick. Thats what we used to use when I worked at Lincoln Mercury as a mechanic, about 100 years ago. Ha Ha. Mater of fact, I ran over a wrench on the road a few years ago. It put a hole in my gas tank. I used some 2 part epoxy putty. I didnt even pull the tank. I siphoned out enough gas so that is was well below the hole in the tank. The putty was just that, putty. I cleaned around the hole, sanded it as well, then mixed the putty, and put plenty enough to cover the hole. I let it sit over night. About 14 to 16 hours, before I put gas back into the tank. Its been several years, and it has never leaked again. The epoxy has to cure before gas make contact with it.

 

[98chevy2500SS]

Hmm, I should try a 2 part epoxy on my 97's tank, it started leaking a few weeks ago when I filled it clear full, wouldn't surprise me if the filler neck rotted out, I can only fill it 12.5 gallons when on the 1/4 mark on the gauge. Anymore than that, it will leak. It would save me over $100 in parts...

 

[andy396]

I agree. Marine-Tex is a two part epoxy that is pretty amazing stuff. It should have worked, but I must have missed something. I’ll let you know what I find.

 

[JSlezak83]

Back in the day, my dad used Marine Tex to patch connecting rod escape holes in outboard motor crankcases.

The original tank in my ‘87 Blazer had pin holes all along the pinch weld of the tank. By design, the seam was hard against the rear crossmember of the frame. This caused 25 years of road grit to collect. I’m not familiar enough with these trucks yet, but maybe that is an issue. Take a look where the straps contact. There may be junk hiding between the tank and rubber too.