72 C20 LS Swap/Build

[DM72C20]

Originally Posted by TA_C10

Nice work so far. Subbed. Question, is there a special reason you decided to go with the fuel pump assembly from following thread and the brothers tank?

https://ls1tech.com/forums/conversio...maro-tank.html

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I’m using the fuel pump module from my 09 donor Silverado and using the Brother’s tank since it appears relatively flat on top to be able to cut the circle in it. Same idea as the link you posted. I decided against using the stock tank and having an aftermarket pump and pressure regulator. Mostly I was concerned about the need to have baffles for the tank. The 09 fuel pump module takes care of that concern.
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[TA_C10]

Originally Posted by DM72C20

I’m using the fuel pump module from my 09 donor Silverado and using the Brother’s tank since it appears relatively flat on top to be able to cut the circle in it. Same idea as the link you posted. I decided against using the stock tank and having an aftermarket pump and pressure regulator. Mostly I was concerned about the need to have baffles for the tank. The 09 fuel pump module takes care of that concern.
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I almost did the exact same thing. But then I found the Tanks Inc. fuel pump assembly. It's in-tank and has a baffle pan. I used the corvette filter, super cheap, and it's also a regulator for the LS engine(stock). Same tank too.

2 things. You will want to drop the tank a little(see my thread if you want) so you don't have to clearance the bed cross rail too much. 2nd thing, check out this powernation episode. It's EXACTLY what your about to do - https://www.powernationtv.com/episod...ls-engine-swap


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[DM72C20]

Originally Posted by TA_C10

I almost did the exact same thing. But then I found the Tanks Inc. fuel pump assembly. It's in-tank and has a baffle pan. I used the corvette filter, super cheap, and it's also a regulator for the LS engine(stock). Same tank too.

2 things. You will want to drop the tank a little(see my thread if you want) so you don't have to clearance the bed cross rail too much. 2nd thing, check out this powernation episode. It's EXACTLY what your about to do - https://www.powernationtv.com/episod...ls-engine-swap


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I had not come across the Tanks Inc. pump - the one with the reservoir tray. I take it that you are also using that in an under the bed tank? I had found a guy that modified his in cab tank, but I didn't want to bother with that.

Thanks for the video link. Yeah, that's the plan. Mine is a C20, so I don't know if there will be the same clearance issues, but dropping it a couple inches won't be a problem.

I am planning on doing something a bit unusual with the fuel fill. I found this post, #30 where the filler tube is routed all the way to the stock location to the under the bed tank. I like this since it keeps the original look and location as well as convenience next to the drivers side. I think the behind the taillight mounting is a bit weird and wouldn't want to have it in the bed floor.

[DM72C20]

Some recent work on the truck.

Modified the fuel tank to fit the 09 Silverado fuel pump. I had a 1/4" thick steel ring waterjet cut to weld to the tank which would allow the pump to be bolted down. The tank didn't have enough of a flat area to mount it, so a new pan was made and cut into it. Bolts were welded into the pan through the ring which act as studs to mount the pump. The ring wasn't really necessary, but reinforces the pan to provide a strong mounting location. The original 72 fuel sender was reused since it fit in the sender hole in the tank. The lines were brazed shut since it won't be carrying any fuel.

[TA_C10]

All good work man! Question, I just finished my custom gas filler(see my thread), welded a vent in the cap neck. Also using rollover vent. Curious how your doing yours. Is that the OE filler your using(already has the in-cap vent that follows the filler line to tank)?

[DM72C20]

Originally Posted by TA_C10

All good work man! Question, I just finished my custom gas filler(see my thread), welded a vent in the cap neck. Also using rollover vent. Curious how your doing yours. Is that the OE filler your using(already has the in-cap vent that follows the filler line to tank)?

Yeah, I'm using the 09 Silverado filler neck and vent tube from the donor truck. I don't really know much about venting so will have to do some reading - presumably GM included a rollover vent?

[TA_C10]

Cool man, you will be happy with a stock unit like that. Here's how I understand it all. You need 2 vents. 1 vent for filling your tank, the other vent is for driving and sitting, it's for heat expansion and such. Fill vent allows air to push out during filling so you can use the gas pump nozzle full throttle .

Here's the safety part. Small vent for heat expansion, for safety reasons, gets the rollover valve. Fill vent needs to be connected to your filler cap so the gas nozzle extends past it allowing air to escape back out through it, but seals it off with cap during operation. If you get into a wreck, rollover valve closes the small valve so fuel doesn't spill out and filler cap seals the filler vent. Safe.

I would say that's the general idea behind it all for safety and function. There are more sciences to it you can read about elsewhere

[Putzer]

Originally Posted by TA_C10

Cool man, you will be happy with a stock unit like that. Here's how I understand it all. You need 2 vents. 1 vent for filling your tank, the other vent is for driving and sitting, it's for heat expansion and such. Fill vent allows air to push out during filling so you can use the gas pump nozzle full throttle .

Here's the safety part. Small vent for heat expansion, for safety reasons, gets the rollover valve. Fill vent needs to be connected to your filler cap so the gas nozzle extends past it allowing air to escape back out through it, but seals it off with cap during operation. If you get into a wreck, rollover valve closes the small valve so fuel doesn't spill out and filler cap seals the filler vent. Safe.

I would say that's the general idea behind it all for safety and function. There are more sciences to it you can read about elsewhere

I had a good conversation with a lady at boyds welding. I have the old style tank from them that doesn't have the 5/8 line fill vent next to the 2" fill. I bought a retro fit adaptor from Boyds that goes from 1/2 npt fitting to 5/8 hose barb. Then I'll drill a hole and use self tappers to secure to tank and then I'll be able to run the 5/8" line to my filler neck from an older s10.

[DM72C20]

After an unintentional summer hiatus, work is going again on the truck!

The gas tank is all welded, pressure tested, wired and mostly plumbed. Everything seems to fit nicely including the fill which involves an S bend tube, a rubber 90 and some straight hose. Might pick up an installation tool for the nylon fuel lines and fittings. I've ordered parts from FMSI since they are local for that stuff.

Wiring cleanup has been in progress too. Everything should be set to the gas tank and fuel pump. Underhood stuff is close. Gauge swap to the S10 speedo is mostly done. Still more work to do at the dash. I still don't quite get how the ignition 'talks' to the PCM yet...

There's an instrument panel connector with some vague sounding wires that remain, along with a VSS wire. I added in a VSS wire to the X1 connector but a bit uncertain about that.

I'm quite confused about the alternator after reading the other day that it needs a GCBM and BCM to have the ability to change voltage output based on load. I don't have either module, however that function sounds nice compared to its default at 13.8V. Keeping the alternator stock is appealing from a parts availability standpoint. I've read a thread about changing out the regulator on the back, but that isn't stock anymore... There was some other thread about a PWM signal generator device... Any suggestions would be helpful.

[jjzepplin]

You've been quite busy for having a hiatus..!!

[DM72C20]

Big news - the truck runs!!!!

The wiring proved to be rather tricky to get that Gen 4 engine to run, but we perservered. I started a thread about it here where the specifics are discussed: http://67-72chevytrucks.com/vboard/s...d.php?t=827216

We took it for a little spin after cleaning up all the underhood wires and it is so smooth and quiet! There is some programming yet in order to get the speedo and tach reading - so far nothing. Still need to clean up the dash wiring as well and connect the oil pressure sender - it started leaking oil on my shoes once it finally started to crank, so it was temporarily capped off.

The alternator is outputting 13.8V which is its default or limp mode and I would like the variable output capability. I'm not running a BCM, so will need to figure out where to run the wires from the negative cable sensor.

[DM72C20]

Some pics from the last while..

Underhood wiring. The alternator PWM generator is the small box with buttons. The 09' fusebox has been modified to fit into place.

The S10 speedo before installation into the cluster. Thanks to Ls1nova71 for the kit.

Dash wiring in progress. A new fuseboard was wired in place with blade fuses rather than the old one. Fixed up the instrument lights that never used to dim.

[DM72C20]

And some pics of the fuseboard stuff.

A couple weeks ago, when we tried getting it started, I had the idea to connect a wire to the starter relay from the ignition. It was pink and I think it may have accidentally went onto the powertrain relay. It started to smoke and melted part of the board instantly! It was not a great moment. Another used board was picked up and we checked through each and every contact to determine how the relays should be oriented. The crazy thing is that the manual shows one thing and the second donor relays didn't align, nor did my Dad's running 09' truck. His doesn't even seem to have a fuel pump relay or fuse??!?

Anyway, after testing for current, we oriented the relays so that 30 was battery hot in each case. Pink wire is signal from key on to 86 on the run/crank relay which powers up the ECM. Purple is signal from key crank/solenoid which goes to 86 on starter relay. These two wires were all that was needed to get it running.

There is relatively little wiring coming into the fuseboard, but it still makes use of the factory connectors and board. If there is any issue, these parts can be swapped out.

[jjzepplin]

Wow! You have great patience sir. Congratulations are in order!!!

[DM72C20]

Update on the truck. Some observations on having a working LS swap done.

It took many attempts to get the speedometer setting to work properly. There isn't much in the way of guidance for this sort of thing. Part of the problem I was having was relying on the HP Tuners Scanner speed rather than reading it from a separate GPS speed on my phone. It's now set within 1mph on the speedo and is around 2% high on the odometer over a long distance when compared with the GPS distance. I might modify the setting yet again to try and get it within a %.

The truck starts instantly, no matter what. I had it parked outside in -18C (around 0F) weather and no problem at all. In that cold, I found that it was a bit stiff to shift into drive from park, but the engine had no trouble whatsoever.

There is so so much power on tap! Even though it is just a 4.8, it is fast! I'm loving that aspect of it.

Mileage has been a respectable 12.8 - 13.8mpg. I've been having fun with it, so I'm sure I could get it even higher if that was the priority.

It's got new Cooper AT3 tires now which were part of an attempt to eliminate vibration at highway speed. The old tires weren't worth balancing apparently.

The vibration is certainly distracting when cruising along at 75mph. The mirrors all shake so much it makes you dizzy. Might get it in for an alignment next, and possibly replace suspension bushings and whatnot. The motor and trans mounts are all new with the swap. Cab mounts were replaced in the last few years.

Also trying to reduce the wind noise at highway speed. I added some cut to width pipe insulation along the top edge of the door frame hoping to cut down on potential entry points for noise. The insulation is EPDM and actually looks quite good. I adhered it with double sided tape. It made a slight difference, but could be so much better. The engine is whisper quiet now which at least rules that out at speed.

[Palf70Step]

Enjoying this. You are doing great work. Looking forward to the progress and updates.

[Low Elco]

On Vibration- That factory shaft is huge around for a reason. the added diameter keeps the long shaft from "whipping" at speed. A bigger shaft helped me.

[rickcdewitt]

Nice looking truck. Have you checked the slip yoke and bushing for excessive play? That would make a driveshaft vibration. Bent rims also comes to mind.

[rickcdewitt]

Another thing comes to mind if the truck had a carrier bearing driveshaft previously(plus the fact it has a new drivetrain with output possiblyin a new location). You want the working angle of your u joints to be equal while going down the highway.. Your rear pinion was not angled correctly for a non carrier driveshaft.for leaf springs that means having the pinion a degree or two lower than the trans output so it rises under load. A cheap magnetic base degree measuring unit will let you check both ends with the driveshaft out on the yoke and trans to compare and adjust with a shim in the back or reweld the perches

[Mike Bradbury]

^^ yes

[DM72C20]

Been a bit since posting any updates. The truck is still running great - totally pleased with the engine and transmission.

The highway speed vibration is still around and shaking the patience out of me. Every moving part of the front end has now been replaced, bushings, control arms, steering, shocks, steering gear, etc. Alignment was done and I won’t have to think about that for a long time.

The tires are new and were re-balanced. Driveshaft has been in and out several times and re-balanced. The transmission extension bushing and seal replaced.

I tried to get the tires road force balanced today but apparently the steel wheels were too out of whack to run them. I watched as all 4 were spun up and two looked noticeably bad. So the simplest thing seemed to be the thing. I’m now trying to find a good set of steel wheels, 16”x7”, 8x6.5” hole pattern. I want to keep the hubcaps and steel look for the truck. Wheel Vintiques has some with those specs but 8-10 week wait to get stock, so that’s not a great option.

Aside from the wheels, the vibration seems to change when coasting or slowing. I theorized the rear end gears could be a factor there, but not too sure.

Looking forward to getting this sorted and taking it for some long road trips this summer!
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[Mike Bradbury]

Originally Posted by Low Elco

On Vibration- That factory shaft is huge around for a reason. the added diameter keeps the long shaft from "whipping" at speed. A bigger shaft helped me.

Yes I agree, it sounds like the vibration is drive train related not alignment. Best to get it on a dyno and run it up to speed and see if the shaft is the cause. Either that or wait for it to come flying out the back of the truck one day

Although on my C20/LS swap I did not change to a one piece shaft but I did have a couple tries at balancing the shaft just right.

Since I am just joining the fun-- that is a great looking C20, you have done a real good job with it. It would have taken all the wind out of my sails for a week if I smoked my board. Glad you kept at it.

[Palf70Step]

How's your pinion angles? I have heard that issue on a fair amount of LS swaps and it turned out to be that.

[DM72C20]

Update on the truck since it has been ages and ages. Some of the long lasting sagas in sorting things below...

I've mostly eliminated all of the highway vibrations after ordering a new set of steel wheels. One of the four (new from a tire shop) turned out to be out of alignment and they had to order in 4 others to find one straight replacement. This was after I decided to get them powdercoated white. Live and learn that it is worthwhile to spin up the wheels themselves to check first. They are really basic 16" x 6.5" steel wheels since I wanted to run hubcaps. The closest alloys that I thought would have been tolerable were the 8 hole Pro Comps.

Once I had the wheels all set, the tire shop discovered that one of the tires was out of spec. They are Coopers, purchased in 2020, with very low mileage. That tire was replaced under warranty and I got it road force balanced along with the others.

Oh and I also removed the new polyurethane engine and trans mounts and put rubber ones in their place. And found a spot or two where there was interference between a heat shield and the frame and corrected that.

There is still some minor vibration at 70+ mph but I can live with it now.

After that, I managed to find a set of 72 hubcaps on ebay and my dad painted them up with blue bowties to match the truck. Will have to do new photos this summer.

I also found a set of oem 72 sport mirrors on ebay and recently installed those.

My power steering caused all sorts of issues in the last 10 months. I am trying to recall the sequence since it was such a saga. I think when the front end suspension was all replaced, the steering box was in need of rebuilding or replacement. I ordered a rebuilt Cardone from amazon. Seemed fine until coming home from a camping trip last summer when it blew the upper seal on the drive home. Rather tricky driving and especially parking it like that! It was sent back and I found a local rebuilder for the original box. They had a rebuilt one on the shelf, so I exchanged mine and installed it. That one was extremely sloppy with inches of play at center, so I had the shop rebuild mine. It was still sloppy, just not as much. I learned more than I care to know about steering boxes.

Somewhere along the way, the pump went as well and I learned that perhaps the LS power steering pump puts out too much pressure for the original box. I ordered the Borgeson 899001 pressure reducing kit to try that out. I think the pump was cooked when the box went, so a rebuilt one went in from the same shop.

My rebuilt box was still sloppy and adjusting the nut on top only made it harder to steer without actually reducing the slop. The shop insisted that the internal bearings do not wear out, however in speaking with Red Head Steering, they said that they size new ball bearings for each rebuild to eliminate play. Being in Canada, it wasn't really cost effective to send my old box to them and so I hemmed and hawed for months about dropping $800 CAD on a new Borgeson 800132 steering box and 990012 coupling/rag joint. Finally bit the bullet recently and installed it last week after getting a $50 off deal at Jegs. Now that is how it is supposed to steer! It has no slop, responds nicely and overall it drives on the highway without requiring any thought or constant corrections.

Oh yeah, had a frustrating day back in the dead of winter. I was running errands all day, picking up lumber, fasteners, etc. and on one of my last stops, it would not start. I could hear relays but no crank. I had power, pulled and checked fuses, checked the fuseboard and swap wiring and thought it could be a dead starter. Was a couple doors from a parts place, so got one of those and spoke with my dad about all this. He decided to drive up to see if we could install the new starter in the truck to get it going. I walked to a coffee shop to stay warm and my partner came to keep me company. She drove us back to the truck and I was texting with a friend about it. He suggested the neutral safety switch and sure enough, I threw it in neutral and it started right up! My dad arrived a few minutes after that and I bought him a burger for his troubles.

Other than all that, it is still running great and is better than I expected from a LS swap. Wouldn't hesitate to do it again even after all the fuss.