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The Shop Truck

1971 Chevy C20 with a custom flat bed.
Overview Gallery Discussion
I hate wiring. So many ways to go about doing it. I've got a third of the circuits you do and I'm giving consideration to tearing them all out and redoing it. I've got bus bars for 12v, switched 12v, and ground plus a 6 relay box.

What's the point of the MSD solid state relay? Seen that mentioned a few times while I research stuff for my terminator x.
 
centexk5 said:
I hate wiring. So many ways to go about doing it. I've got a third of the circuits you do and I'm giving consideration to tearing them all out and redoing it. I've got bus bars for 12v, switched 12v, and ground plus a 6 relay box.

What's the point of the MSD solid state relay? Seen that mentioned a few times while I research stuff for my terminator x.
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There are a few advantages to the MSD box. It's basically 4 heavy duty (they call them 35 amp) solid state relays in a single package. They are internally protected from overcurrent and temperature so you don't need fuses on the individual loads, just one supplying the box itself. Each of the relays can be triggered by a +12V or ground signal and since they are a solid state relay you can use a PWM signal to turn them on and off rapidly to bring your fans up to speed gradually to eliminate the big inrush current. I'm also using PWM on the nitrous solenoid to bring it on gradually over 1/2 second.
 
Careful with the MSD solid state, it doesn't like to get wet. Even with my truck sitting outside during the rain it would randomly trigger my fans on and drain the battery.
 
I wanted to mention that I will be going to Firebird this Saturday night for Midnight Madness drag racing. The first run will be a 100 shot which should put me in the 12s now that it's tuned properly. After each successful run I'll check the logs and add another 50 shot. Assuming I get 4 runs in, I think a 250 shot will get me into the 11s, but we'll see.
 
Babaganoosh said:
Careful with the MSD solid state, it doesn't like to get wet. Even with my truck sitting outside during the rain it would randomly trigger my fans on and drain the battery.
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That's odd, my only thought is that the water would short the ground triggers to ground. The truck is parked in the shop 99% of the time, not to mention it shouldn't ever get wet where I have it mounted. It's fully potted so the issue has to be external shorting.
 
I have mine where you do, although I have a much bigger hood gap I'm sure. Holley replaced it when it was out of warranty and when I was waiting on it I bought another.
 
r3dd0g said:
Before I do any long road trips, I'll have a spare in my toolbox.
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I currently have one on the passenger side controlling the fans, and on the drivers side controls the fuel pump and headlights. Plenty of open spots for extra stuff.
 
I took the truck out for a test drive to make sure all the fans and everything else was working properly. It was running poorly and backfired a few times while I was putting around the neighborhoods so I pulled out the FLIR when I got home and #2 primary was cool.
I didn't have time to mess with it yesterday, but got out there today. After making sure everything was hooked up I swapped #2 and #4 coils and #2 and #1 plugs and wires. Now everything works :mad2:. I hate it when I fix something and have no idea why what I did fixed it...
Regardless, I have 2 new coils that will be here tomorrow for spares if needed.
 
It's going to be hot and humid Saturday night, the forcast is currently showing it will be 97°F at midnight... Somehow even though I believe this is going to be the hottest (temperature) night for the Midnight Madness, it's also sold the most tech cards that I've seen. Over half of the 150 cards have been sold already.

There is another Drift and Drag event on Sep 13th and the first Friday Night Drag event of the season on the 19th, so I can get a few more test runs in before Duct Tape Drags.
 
Babaganoosh said:
Dang I should have looked or sent you a text I drove right by on the 202 and looked at the track.
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You didn't miss much.

I got 3 runs in, it was stupid hot and humid. Something in the nitrous system isn't working properly. I really need to test this stuff before I go to the track, but it's so damn loud at WOT and even louder with nitrous it's hard to do without attracting a lot of attention.
Last time I went to Firebird, the truck was running like a bracket car. I ran 3 [email protected] runs with the 100 shot. When preparing for last night I realized I only had added 1/2 the amount of fuel that it should have needed (the flow chart for my nitrous plate lists the flow through each jet, but there are 2). I corrected that issue even though looking at the logs it didn't seem to be running lean at all, this should have clued me in to a problem. I'd also like to mention that we didn't add the purge solenoid until after the last time we went.
  • First Run - Nitrous didn't fire. I swear I tested the Nitrous solenoid on the MSD SSR box, but I obviously didn't. I had it wired to the +12V trigger on the box and it should have been wired to the ground trigger. All the fuel and timing retard got added for the 100 shot, but no nitrous. I think it ran a 16 something...
  • Second Run - Nitrous fired, it instantly went pig rich a bucked, but cleaned up. Datalogs showed that it was pulling 20% fuel out for the whole run.
  • Third Run - We talked and decided to throw the 200hp jets in and test again. Now it added even more fuel and pulled even more spark. It went pig rich and bucked, then it cleared up but there was obviously no nitrous. Datalogs show it went super rich, pulling 50% fuel out (the max it can) then went super lean and triggered the safety to cut the nitrous.
This is what I think happened, we'll be doing some work to test it today. I'd like to preface this with saying we really don't know what we're doing here and just figuring it out as we go. I think the last trip, every pass was made with high pressure nitrous vapor which is why it only needed 1/2 the fuel and ran consistently. When we swapped the engine I increased our nitrous lines to -6AN from -4AN but didn't run a purge initially. I think the 8 feet of line plus the filter had enough capacity for the entire run with the 100hp jets in. Now I put the old purge valve in (still a -4AN) and I have the line hidden for stupid reasons rather than right in front of my face. I don't think I purged enough the second run, I purged more the 3rd run and it was spraying twice as much nitrous so it finally got liquid into the jets after a couple seconds.

I think my best time from the night was a 14.9 or something sad like that.

We've got to do more testing and get set up for the drift n drag event in 2 weeks.
 
I forgot to mention a couple of other fails from the day. We had decided to trailer the Shop Truck to try to keep the engine bay temps down a bit. The Silverado slave cylinder started failing while we were getting the trailer positioned... Too bad GM stopped making that and I have to go aftermarket now, I think this one only lasted a couple years.
Also, on my 2nd run my drivers side window regulator fell apart when I tried to roll it up to pull into the water box. This is the second time this has happened and it happed in exactly the same situation last time... I managed to get it to roll up for the most part, enough for the safety official anyways.
 
Before I do any more tuning on the truck, I had fix the drivers side window. I pulled it apart and 2 of the 3 brackets that are glued to the window had broken. I pulled the other side apart and one of those had broken as well.
This is what the bracket is supposed to look like. It's a bad design made of a single piece of metal folded into a U channel then creased over 180° to make the tab that the stud is in.
IMG_20250827_142658010.jpg

Getting the brackets off was challenging. I ended up using Knippex plier wrenches to shove razorblades between the glass and bracket, then I hammered a pick through the bottom and used a flat blade to gently pry the bracket off.
IMG_20250826_141721091.jpg

All 3 broke the exact same way.
IMG_20250826_141927829.jpg

I welded the broken seam back together and ground it down so there were no high spots against the window, then I added a couple welds on the bottom to prevent this from happening again.
IMG_20250827_142545415.jpg

Finally I glued them all back on with 3M windshield glue.
IMG_20250828_110114948_HDR.jpg


I called the vendor I purchased them from, of course they claim they've never seen this happen before... I have a hard time believing that unless my brackets missed a step like being spot welded together after they were bent over. He offered to send me a new set of brackets, but I had already welded mine up by that point.
I need to let the glue set up for 48 hours before I reinstall, so hopefully I'll have it back on the road tomorrow so I can do some more testing with the nitrous.
 
The windows are all back together now, I didn't realize how much they were rattling before. They are much smoother now and quieter.

I put the 100hp jets back in and took the truck for a drive with a relocated purge line. After a thorough purge and two test hits, I had the exact same effect. It went pig rich, then half the fuel was pulled out. I'm going to pull the top off the intake manifold when it cools to make sure the nitrous is flowing properly out all 8 jets.
 
This new engine is still kicking my @$$. I pulled the plugs yesterday to put the street plugs back in as I needed to use the truck. #2 cylinder is still not firing properly, but it is firing sometimes??? I looked at my datalogs from the last drive and when I'm just cruising (no nitrous) the right bank is about 1.5 AFR numbers leaner than the left bank. I know some of this is from it missing, but the other 3 holes looked lean on the plugs as well.
Odd number plugs all looked similar (sorry for the blurry pictures):
IMG_20250903_123605726.jpg

Carbon is burned off to the base of the strap and it looks good although maybe a bit rich.
3 of the even plugs look lean.
IMG_20250903_123614574.jpg

Carbon is burnt off half way around the base of the spark plug so they were running way hot.
#2 was "running" but not very well. Either way too much or way too little fuel.
IMG_20250903_123555695.jpg


I suspect this is an injector issue, I ordered a second set of injectors (1300cc FIC High Impedence) that will be here Sunday so I can test that theory.
I also pulled the top of the intake off to make sure I didn't have any plugged ports in the nitrous plate. They all look like they're flowing about the same to me, what do you guys think? This is a 500ms spray slowed down to 30% speed shown from both sides.
 
I did one more test.
I removed the nitrous bottle and weighed it - 22lbs 1.3oz
I hooked the bottle back up, filled the lines, closed the bottle, purged the lines, removed the bottle and weighed it again - 21lbs 13.6oz
I hooked the bottle up a 3rd time, opened it up, sent 6 1000ms pulses 1ms apart to the nitrous solenoid, removed the bottle and weighed a 3rd time - 21lbs .5oz
Much math = 352.5pph of nitrous flowing with the 100hp jets (2x.036") which should flow 364pph EACH...

The old system performed flawlessly, it had a 10 foot 4AN hose that ran from the bottle up to the nitrous solenoid with a single 150hp nitrous jet and matching fuel jet. The new system has a shorter run (8') with 6AN hoses and isn't flowing properly. I do have a 90° fitting, a 45° fitting, a bulkhead fitting, and a high flow NOS filter now where before it was all straight hose. I'm going to test again with the filter removed, if that doesn't make a difference I will test with bigger jets just to see if it's proportional.
 
I tested again without the filter this time, it showed it flowed less, but I'm guessing that's because the bottle was a little lower pressure and I didn't recalculate how much nitrous it took to fill the lines without the filter. Regardless, the filter isn't the issue.
 
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