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1985 Chevy C10 Silverado Squarebody

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1985 Chevy C10 Silverado Squarebody

This post is about my 1985 Chevy C10 Silverado Squarebody pickup, powered by an L98 Tuned Port Injection (TPI) engine from a 1990 IROC Camaro.  This is an old-school conversion, that my late cousin Jim Thompson did many years ago.

I have put about 800 miles on the truck during the last few months and so far, it has been a blast to drive.  The Frost White (RPO 12) paint is not as shiny as it was when new, but it is original.  For a 40 year-old truck, the body is still free of dings and most important, no rust.  The interior still has the original blue carpet and the bench seat has a stylish ‘blanket’ cover – as George Takei would say, “oh my!”.

Short History

The truck was driven by it’s first owner until sometime in January of 1988, when the second owner acquired the truck with 32k miles.  Second owner was a friend of Jim’s and sold the truck to JIm’s mom in the fall of 1993, with 101k miles.  Since then, the truck has been a member of the family.

According to the RPO build sheet in the glovebox (see below), the truck was born on April 26, 1985 powered by an LE9 5.0L V8.

Google Search result for the LE9 5.0L V8…

According to Jim’s documentation I have found, the engine started to give trouble and somewhere around the 130k mile mark, Jim decided to pull the tired engine and update it with an L98 Tuned Port from a 1990 IROC Camaro.  The gearbox is a 700R4, also from the IROC.  From the notes I found, Jim bought the IROC engine with about 32k miles.

Today, the truck shows 175k miles.  So doing the math, the Tuned Port has about 77k miles.  Barely broken in, right?  Hehe…

This is the RPO build sheet in the glovebox.  Unfortunately, I do not have the window sticker – wonder what that would look like?  No telling what this truck sold for back in 1985.  I’ve found some videos on youTube from the day, and the Silverado was “the” truck to have.

More About the Truck…

Jim had a thing for Squarebody C10’s.  He had two, actually.  The ‘shop truck’ was a tan 1985 that was once-upon-a-time in the US Forestry Service.  It was a plain-jane C10.  No carpet, no headliner.  Jim put an LSx in that one, and it was a ton of fun.  I could not keep it all, so the ‘shop truck’ has a new owner now.  This is what it looked like:

Dig that custom aluminum front bumper…

Thes second Squarebody is the Frost White C10, and has always been a bit special, perhaps because his mom (my aunt) drove it for many years.  After my aunt passed, the truck did not get driven much.  That would account for the 175k miles after 40 years.

The interior is a bit tired…  Blue carpet and blue accents on the doors – all original.  The seat cover – well, can’t beat the ‘blanket’ cover look…Next, high tech from the 80’s…  Dig those power window and power door lock switches.  Too bad the boys from GM decided to run full voltage to the window motors and locks through the switch.  Not so good after 40 years because the windows would barely move up or down.  I re-wired both doors with relays and now the windows go up and down smooth as they did in 1985.  The door locks work flawlessly too.

The dash is still decent under that blue cover…The radio still works. When it wants to.  And there are four (4) speakers that work very well.  I’ve noticed when the radio gets a bit warm, it will play intermittently.  On the list to fix is a new period correct replacement.  All instruments work, even the clock.  Speedo is off by about 5 mph.  I suppose the reluctor wheel on the 700R4 is slightly different from the one that was in the original tranny.  No worries, I’ve checked this with the iPhone app and it is consistent across the range.  Lucky it shows under rather than over actual speed…

Tilt wheel works, turn signals, headlights, check.  There is no cruise control though – who needs it?  Ditto for the windshield squirter thinggies.  And there seems to be some malfunction with the dome light.  Oh and the horn does not work either.  I need to add all that to the list of things to fix.

Check this out…  Sliding rear window!  Oh and it is nice to lower the windows, open the rear window and have a nice breeze in the cab.

About that Tuned Port Injection L98…

I think the L98 has always been a favorite of mine.  The L98 powered Camaros and Corvettes of the era.  Yeah, it ran out of breath quickly but that intake with those 8 runners each going to the intake ports of each cylinder was sexy as it gets.

But wait a minute…  The photo above shows four siamesed runners.  What’s up with that, where are the 8 runners?  Well, back in the day this intake was very special.  This is the SLP high flow version.  This was supposed to gain you a ton of foot-pounds and make your car run better.  This setup was not cheap.  Does it live up to the hype?  Who knows…  Hehe…

I do have a set of original runners, but they are a major pain in the ass to swap.  Given this has not been touched in years, I will leave this alone thank you very much.  The last thing I want to do is break a bolt and then be up the creek.

Engine management you ask?  This is controlled by an OBD I ECM.  There was an outfit called Street & Performance in Mena, Arkansas that made a killer wiring harness.  Jim had a contact there that was on speed-dial on his phone.  Tony was his name.  We used to call Tony and he would help us out with L98 and LT1 setups.  That guy was a genius.  No telling what happened to Tony but that is who Jim got the harness from.  I don’t think Street & Performance exists anymore.  But back in the day, they where the shit when it came to this kind of stuff.

This photo shows a closeup of the siamesed runners.  They have a partition inside but the first inch or so, is the entire width of the runner.  Towards the back of the intake is a cover that hides the HEI distributor.  The Camaro came with a cheap, plastic version.  What you see in the photo above is the Corvette version – it was all metal and fits and looks nicer than the cheap plastic one.

“Does it have AC?”, you ask…  Well yes it does!

“Is it cold?”…  Hell yeah, it is!!!

Jim mounted an aftermarket compressor.  This enabled the use of modern refrigerant, not Freon.  Yeah, he added a big-ass condenser in front of the radiator and yes, it works.  We have cold air!  Not too shabby for a 40 year-old truck.

Another problem that I recently fixed was the vacuum check-valve leading to the vent system in the cab.  The only thing working was the heater vent.  The dash vents did not work.  Googling and watching some youTube videos pointed to a possible issue with the check valve.  Sure enough, a couple of bucks fixed that.  Now all vents work.  Even the defroster works!  Amazing what you can learn on youTube.

A keen eye will notice the absence of radiator fan.  Right?  Well, Jim was very fond of SPAL fans – that is what the red cars with the little prancing horse on the hood come equipped with too!  This is what the air movement mechanism looks like…

Two 13″ SPAL electric fans keep things cool.  One is wired to a thermostat pickup plumbed into the bottom coolant hose and the other is wired into a trinary switch on the AC side of things.  So when refrigerant pressure reaches a certain point, it kicks the fan on and this keeps the refrigerant happy.  Brilliant!

Here is a picture of the red-top Optima battery.  I added the quick disconnect to prevent it from draining down.  Behind is the custom made overflow tank – Jim made that from aluminum.

Oh and check this out…

Lurking behind the grill is a MOCAL cooler.  Its plumbed as a transmission oil cooler.

And, I added the #3 tag.  Long live The Intimidator.  My friend Mike said this was a very “period correct” accessory.  So there.

What about cooling engine oil?  For this, we need to check out the oil filter.  Have no idea what this originally came on, but Jim decided to hang the largest oil filter he could find.  Check out this monstrosity of a filter:

8 inches long – the stale orange Cheeto could only dream his Johnson was this big…

This will hold an extra quart I suppose, and is also giving more surface area to keep engine oil cooler.  And we can get away with that because this is a C10 – try this on an IROC…  Yeah right!

The other side of the L98.  Unfortunately the cast iron headers were not JetHot coated.  They are rusty and I can’t imagine how hard it would be to get those bolts off.  So they stay put.

In Closing

When I first started driving the C10, it would shut down at red lights for no good reason.  Turns out the intake where the butterflies live was filthy, covered in carbon residue.  I took the idle air controller out and replaced it.  It helped some.  So I took throttle body apart and cleaned it in an ultrasonic cleaner.  What a difference that made.  Bought some new gaskets and put it back together.  That solved the problem.

I bought a new set of tires and had them mounted.  The old tires were just unsafe.  Yes, I’ve thought about getting a set of drop-spindles and maybe relocating the rear spring to lower the truck.  I asked Jim about this time or two, and he would always say “leave it stock”.  So for now, it stays stock.

The truck is fun to druve.  I’ve had many thumbs’ up from other folks at red lights.  Yeah, this is a keeper.  It runs decent, just have to remember this is not a modern LSx and the 700R4 is dated, but for what it is, it does the job very well.  I also have to remember the rear-end is a 2.73 and is not a posi.  But, it is plenty fast for what it is.

Does anyone know where this dealership was located?

Thompson Wood Lathe – For Sale

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Please click on any image for a larger version of the picture.

For more information please check an entry in the American Association of Woodturners with more information about this lathe for sale – CLICK HERE.

New Fuel Pressure Regulator and Braided Lines

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On this 2023 July 4th weekend, bowtie6 got treated to a new fuel pressure regulator and braided lines.  The old setup consisted of a GM style non-adjustable pressure regulator and a set of E85 resistant rubber fuel lines – I wrote an article about that (click here).  I was never really pleased with the rubber hoses because the braided lines are much nicer and bullet proof.  So I pulled the trigger and ordered parts for the new setup.

This is what the old setup looked like:

The new regulator is a high pressure version from Aeromotive with a matching fluid filled gauge.  This is the setup after the first fitment.  However, with all this bling that bracket just did not look good…And this is what I mean…

We had to cut the old mount and in the process the aluminum mount got scratched up pretty bad.  I tried to sand this down but didn’t make much progress.  Instead, why not just use some carpet material?

Ah! Much better!  A keen eye will also notice the difference in pressure.  I checked what the E67 PCM expected, and that was 58 lbs/in, so I bumped that up a bit.

The photo above, shows the whole setup.

  • On the left the box with the silver lid holds the high pressure fuel pump
  • The line going up from the pump goes into the regulator and from there is a return line back to the pump container and to the left the line going to the engine.  That is a hard stainless line that goes under the body to the engine compartment.
  • And finally the lines that feed the pump container.

High pressure fuel pump inside this enclosure

I’ve written about this setup in a prior post Ecotec Fuel System and ECOTEC Fuel System – Part 2 in case you want to read more about that.

And this is what the front looks like.  This is another braided line going into the fuel rail.  The other side connects to the stainless tubing under the frame of the car…

How to Control Electric Cooling Fans with an E67 PCM

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E67 PCM and the C1, C2, C3 plugs

In this article I’ll go over how to control electric cooling fans with an E67 PCM.  I thought it might be nice to put this down in this long post in an attempt to help somebody else figure this out.  But first a little background…

HPTuners is our preferred method of modifying the engine computers (PCM’s) on the engine swaps I’ve helped my cousin Jim with through the years.  The tool consists of an interface that connects to the OBDII port on one side, and a USB adapter on a laptop.  There is the Editor and Scanner software components that let you do pretty much anything you want.  The proverbial catch is, there is so much to learn and not enough time…

I got an email from the good folks at HPTuners with an offer to upgrade our interface to the latest-and-greatest.  Included with the deal were several credits, so why not?  Well, this fired up my curiosity – once again – of getting bowtie6‘s PCM to control the SPAL electric cooling fan fitted to the radiator.  I say “once again”, because I have been down this path before with sub-optimal results.

The First Attempt

Engine management of the Solstice sourced ECOTEC in bowtie6 is handled by the  E67 PCM.  This PCM interacts with the engine by way of a modified Solstice wiring harness.  By this I mean, many circuits have been removed, such as anything to do with Air Conditioning – for example, the wires and plugs for the compressor, pressure sensors etc.  The wiring harness meets the PCM via 3 plugs:  the C1 plug has 56 pins and the C2 and C3 have both 73 pins.

When Jim and I prepared the wiring harness, we removed the wires that handled the fan relays.  We used a separate fan controller made by Centech as shown in the following picture:

Centech cooling fan controller

The controller makes ground and is connected to the fan relay.  The controller also receives a signal from an engine coolant temp sensor – NOT the one used by the PCM, instead Jim made a special adapter in the cooling system that houses the temp sensor for the Caltech device.  in the picture above you can also see a small knob on the left, and that is where you control when the fan “starts”.  So for all these years the fan has successfully been controlled by this device.  But in the back of my mind, the PCM has the ability to do this so why not let that control the coolant fan?

The Solstice comes with two coolant fans controlled by two separate pins on the harness.  The PCM makes ground, and in the stock setup they are connected to the control side of the fan relays.  I have only one fan installed in bowtie6 so in theory, I figured I could use the FAN 1 wire, connect it to my fan relay and that would control the fan.

Fully shrouded SPAL high-speed cooling fan

And much to my surprise, the PCM as it reached the fan “ON” temp, would ramp up the engine by adding a few more RPM’s and after a short delay, the fan started.  I thought “success!”:  the fan ran, extracted heat from the radiator and I was able to see the engine coolant temp come down.  But wait…  The fan refused to stop.

All this was done many years ago, soon after we got bowtie6 on the road.  I spent many hours trying to get this figured out, with no success.  I posted on the forums but went nowhere.  So, i gave up.  I left the wire in the harness, going nowhere.

The Second Attempt

A few weeks ago, after the new HPTuners interface came in, I decided to re-visit this issue once again, so I gave it a go.  I thought that surely, after all these years have passed there would be a solution somewhere on the web.  Well, not really.  I had to put together a few bits and pieces from several forums to find the solution:  turns out the E67 PCM needs to know how fast the vehicle is going and factors that in controlling when the fans turn OFF.

When we installed the Solstice sourced LE5 ECOTEC, we also included the Solstice’s 5 speed AISIN manual gearbox.  This gearbox was used in the Solstice/Sky as well as the Colorado pickup.  On the side of the gearbox is a reluctor that sends out the vehicle speed signal (VSS) to the PCM.  And this is done via a twisted pair of wires, a purple wire with the LOW signal and a yellow wire with the HIGH signal.

In my setup, I used the VSS signal to make the VDO speedo work.  The VDO speedo requires a constant pulse and the VSS signal worked perfect.  The VDO speedo has a “learn” mode where if you travel a mile it calibrates the pulses sent by the VSS and that translates to an accurate speed.  Sure enough, all this worked and is accurate when checked with a GPS signal on my iPhone.

Since the fitted gearbox is a manual, my research indicated there is no need to send the VSS signal to the PCM.  So we took out the VSS wires and pins when we modified the harness.  This left the PCM clueless as to how fast the vehicle is traveling.  And along with that, since the PCM had no frame of reference for speed, the fans would never shut off.

Solving this problem then, starts by splitting the signal from the VSS to a) feed the VDO speedo, and b) send the signal to the PCM.  It took a little effort but I did just that and found the correct location in the correct connector to supply the VSS to the PCM.  If you look at the photo of the PCM you will see I labeled with a Dymo tape, the three plugs – C1, C2, C3.  Suffice to say, it is much easier to modify the harness on a workbench than on a car already installed!  This can get confusing.

VSS Settings

I fired up the HPTuners Scanner and went for a drive.  The speedo signal was now showing but it was off.  And this comes as no surprise.  The PCM still had the original Solstice settings.  So the first change with the HPTuners Editor, was to enter the proper tire size and rear-end ratio.  Once I entered that in the Editor and downloaded that to the PCM, speed now shows dead-nuts on the Scanner.  I suppose for the purpose of the fans this might not be really necessary, but if we are going to go through all this trouble, might as well do it properly.

Fan Settings

The Solstice has two cooling fans.  They are controlled by relays and the ground on the control side of the relays is connected to two pins on the PCM.  One is labeled as “High Speed fan” and the second as “Low Speed fan”.

Since I did not want to go through all this trouble and still come up empty handed, wired up a spare relay base and relay, and connected a test light so I could make sure I had the right fan wire coming out of the PCM.  Using the HPTuners Scanner, there is a page where one can manually command a fan to come ON or OFF.  And sure enough, the test light came on when the high-speed fan was selected.  Next, I removed the test light setup and the fan relay instead.  I did the dry-run again and this time the relay clicked and the fan started up.

Now to the fun part.  First, the main Fans page:

Fan Settings

For starters, the Fan Type:  I have left the fan as “Discrete”.  The other option is Pulse Width Modulated (PWM).  The discrete fan settings is used when the PCM is controlling a relay for an Off/On type setting.  The PWM setting is for when a fan that can run at different speeds is installed.  For the purpose of this post, I am working with a relay to control the fan.

Also, note where you can select the Number of Fans Fitted.  In this case, I left it at two.  More on this later.

Next, comes the confusing part.  The E67 PCM has to two tables that control fan behavior:  Fan Desired Pct vs Engine Coolant Temp (ECT) and Fan State Transition Desired % vs Current State:

Fan Desired Pct vs Engine Coolant Temp (ECT)

Fan State Transition Desired Pct vs Current State

The top chart is used to set the coolant temp required to turn the fan ON or OFF.  The bottom chart is used to set when the fan should turn ON or OFF.  Confusing?  Join the club.

OK – this is what I have so far:  I have left the Number of Fans Fitted at two.  Therefore this means we have a “Low speed” fan and a “High speed” fan as far as the computer knows.  I wired the “Low speed” ground to the relay control side.  Since I don’t have a second fan, the “High Speed” fan is irrelevant.

The “ON” conditions:

  • By reading the charts above, the “Low speed” fan transitions to the ON position with a Fan Desired setting of 36 (the 0->1) and that translates to ~214 degrees on the top chart.
  • If I had a second fan wired in, then the second fan would be ON at Fan Desired setting of 56 (1->2) and that translates to ~225 degrees on the top chart.

And now the “OFF” conditions:

  • If I had a second fan wiring in, the second “High Speed” would be OFF at Fan Desired setting of 48 (2->1) and that translates to around ~221 degrees on the top chart.
  • Finally the “Low Speed” fan (which is fitted) turns OFF at Fan Desired setting 28 (1->0) and that is ~210.

BUT remember, the only time the fan actually turns OFF is when the vehicle is moving.  So at a red light, the fan would continue to run even though coolant might be below ~210 degrees.  It is only when the VSS sends a signal the vehicle is traveling at ~15-20 mph that the fan will actually turn OFF once the ~210 threshold has been met.

In Summary

I have been able to successfully test the above settings.  The one SPAL fan does kick in at roughly ~214 degrees.  Once engine coolant reaches 214, I can audibly confirm the engine speeds up slightly and then after a slight delay, the fan kicks in.  If you look at the Fan Settings screenshot, you can see there is a Startup Delay setting.  I compared that to the settings on my 2014 Camaro SS with an L99 V8 (I know, apples and oranges) and for the Camaro, the delay is zero.  But duh, double the cylinders so I suppose in that case it does not matter.  For an engine with half the cylinders, this gives it a few seconds to “ramp up” before the hit of the fan kicking in.

The next experiment will be to play with the Number of Fans Fitted setting.  I ran into self-inflicted error when I wired up the single fan:  I wired it as the “High Speed” fan.  Clearly that was a mistake because the first fan to kick in is the “Low Speed”.  Wha happened when I did this was the fan would turn ON after coolant had reached ~225 degrees.  So the take-away here when using only ONE fan, is to use the “Low Speed” pinout to make ground in the relay control circuit.

This is a very long-winded version of my experiment.  And I know, might be a little confusing.  Especially the last two charts above.  I am still trying to wrap my head around all this.

But what about PWM?

Ultimately this is where we want to be.  I had a very long talk with my friend Michael Y. and we talked about PWM fans.  Michael has extensive knowledge of this and I tried to draw from his experience in the matter.  Perhaps we might get lucky and he might give some words of advice in the replies section.

The big advantage of the PWM fan would be to try to keep coolant temps consistent, rather than the way I have them in my purely ON/OFF settings.  In my case, the primary goal is to keep the engine from overheating at stop-and-go traffic.  But, it ultimately it would be nice to have the one SPAL fan running as a variable speed setup.

Griffin aluminum radiator – image taken from the bottom of the radiator facing forward

Width of Griffin radiator

 

Fusebox Repairs

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This weekend, I had some fusebox repairs to make on bowtie6…  But first, some background…

Some time ago,  I found evidence of squatters under the hood.  Sure enough, I found a critter taking residence inside the main engine fusebox.  Undoubtedly our new resident found his way in via the opening for the PCM harness.  There I found several wires feeding the relay bases had been damaged.  On several the outside casing had been chewed almost through and on others, the casing was just damaged.  Great!  All that was left to do was evict the critter.

So, I made a quick repair by wrapping some 3M black insulation tape around the most damaged wires and decided to leave the proper repair for later.  “Later” finally arrived this weekend, and I made plans to properly repair things.  This is what some of the damage looked like:

I got started by sorting things out, and assessing what needed to be fixed.  The more I looked at this, the more I found “wrong”.  And as usual,  a small job turned into a more elaborate repair.  I found certain wires just did not look good, others were not long enough and the fuse block needed relocating.

So, after getting the wire cutters, crimpers, soldering gun, solder, shrink wrap, hot air gun, and assorted tools, this job turned into a major redesign.  Funny how the hours just stack up when you are having fun!  Fortunately the weather was perfect, had some good tunes playing on my vintage 70’s stereo and all was good.  This is what the fusebox looks like now…

Fusebox lid…

All damage repaired…

 

So what do we have here?

  • On the left with the three big plugs is the engine PCM.  You can see the main engine harness top left.
  • On the right are the seven purple relays.  Ignition, starter, lights, horn and radiator fan controller.
  • And the two fuse blocks.  They feed various PCM circuits.  Some of these are hot all the time; others are switched.
  • Below the relays we have 6 breakers, each have a little black button used to reset them in case they get tripped.

Relays, hot breakers, and fan controller…

 

On the left is insulated hot post.  That post is wired direct to the battery’s hot lead.  And from there, power feeds the bank of red breakers.  In the middle is the radiator fan controller.  It is fed by the temp sensor and it has an adjustable knob that controls when you want the fan to kick in.

Fuse box from another angle…

 

And so it goes…  I probably have 6 hours on this “repair”.  Lots of time spent cutting, splicing, replacing connectors, soldering and adding shrink wrap.  Oh and towards the end, a few tie-wraps to make things tidy.And before you start making comments about how “busy” it might look, then I’ll ask:  have you ever wired a car before?  This is all home-made and this stuff takes time.  Finally, this box is not that big so working all the wires through is a pain!

Is it over-engineered?  All those relays and circuit breakers and stuff.  One could argue this could have been done much simpler, but then what fun is there in all this?  😉  At the end of the day, I plugged the relays back in, re-connected the battery and…  No smoke and all works as expected.  Overall this was a good weekend!