Project Deimos: An LS '65 Coupe Build: Engine no longer overheating!

[JimStone]

Wow, your engine sounds like it's running great. That's a beautiful purr! I think we have the same engine. I also got the BP 427 LS engine for mine. Good to know I will need the C6 oil pan. I'll just go ahead and buy that now which will make the 3rd oil pan I bought for this... ha. What windage tray and pickup tube did you use for yours? Were you able to reuse from the pan supplied by FFR?

I'll be using an 8HP75 transmission with mine instead of the T56. I just picked that up last week. Hopefully I won't have any clearance issues with the bellhousing since it's rather large on the Ram version I have (it's from a 2024 Ram 1500 2wd).

I'm really enjoying seeing your progress and hopefully learning from some of the hard-earned experience you're sharing. Thanks!

Thanks Aaron

I have work to do fine-tuning the idle through the Terminator X . The big cam wants a bit higher idle RPM and maybe advance the timing a little. But I'm just getting started, running leak down tests and longer heat cycles. It is a sweet engine. I am a complete novice when it comes to tuning, so it's will be a learning process. I ultimately will probably get a professional tune once it's on the road.

The oil pickup tube for the C6 pan is this: https://www.summitracing.com/parts/ADO-12624497
Noticed the price went up by nearly 50% since I bought mine a year ago

The windage tray that comes with the Blueprint 427 works for the C6 pan, so nothing needed there.

I gave the pan that came with the Blueprint engine to a local kid who is rebuilding an LS for his Camaro., along with some other spare parts I had.

I don't see how one could use that F-body pan on a Coupe. Don't know about the Roadster, but MKV is essentially same frame. Just too deep. Would be the lowest point on the car, so inevitably would get sheered off on a speed bump or road debris

Good luck with your build!

[460.465USMC]

I fit in there when I test mounting the seats with the body on over a year ago... Maybe I grew? Might need to incorporate a Gurney Bubble

If I recall, you're using the Braum seat base/sliders, correct? By about how much does that raise the seat? If memory serves, I think I'm very close to the same height as you (6' 1"), and I'm planning to buy the Braum seats as well. I hit my forehead against the wall enough on this build, so no need for me to bounce my head off the roof.

[JimStone]

If I recall, you're using the Braum seat base/sliders, correct? By about how much does that raise the seat? If memory serves, I think I'm very close to the same height as you (6' 1"), and I'm planning to buy the Braum seats as well. I hit my forehead against the wall enough on this build, so no need for me to bounce my head off the roof.

Chris,

The seat base/mounts I used add 1 1/2" of height. I felt that was comfortable. Lower and I couldn't see over the dash board.

I think the video is deceiving. Yes,the top of my head is about even with the top of the lateral roll bars, but those are 1 1/2" lower than the front/back roll bars (which are in themselves about an inch lower than the ceiling of the coupe body. I had plenty of head room when I mocked this up with the body on early in the build. I think even with a helmet I'd be fine.

[Power Surge]

Congrats on the start up! This is such a wild build, I love seeing the progress.

[AaronR]

The seat base/mounts I used add 1 1/2" of height. I felt that was comfortable. Lower and I couldn't see over the dash board.

What you said here has been sticking with me for the last 24-ish hours. I haven't sat in a coupe yet. I'm working through different iterations of what I would like my dash to look like. Long story short, I want cameras for side mirrors and I've been working on where to place the monitors. How much am I going to hate and/or not be able to see over the dash if I tried to put these monitors and gauges on the top of the dash like this? I'm 5'10" if that matters at all.


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[JimStone]

What you said here has been sticking with me for the last 24-ish hours. I haven't sat in a coupe yet. I'm working through different iterations of what I would like my dash to look like. Long story short, I want cameras for side mirrors and I've been working on where to place the monitors. How much am I going to hate and/or not be able to see over the dash if I tried to put these monitors and gauges on the top of the dash like this? I'm 5'10" if that matters at all.


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Hey Aaron, cool ideas and renderings.

I don't want to say for sure it won't work, but I do think you'll have trouble seeing over the video screen and gauges. The coupe has a long nose and relatively tight viewing angle out the windscreen.

Of course, a lot depends on how tall those screens and gauges will be, and how high you mount your seats.

At 6'2", my seat is also mounted as far back as possible, so that may also affect things.

You may want to think about how to lower the screens/gauges on the dash, which will create some engineering challenges, but would be doable.

[Namrups]

I would do a cardboard mockup before buying anything. I'm 5' 8". I have Corbeau seats on sliders which gets me a good 4" off the floor plate. Looking over your rendered screens I believe would be a challenge.

Scott

[JTG]

What you said here has been sticking with me for the last 24-ish hours. I haven't sat in a coupe yet. I'm working through different iterations of what I would like my dash to look like. Long story short, I want cameras for side mirrors and I've been working on where to place the monitors. How much am I going to hate and/or not be able to see over the dash if I tried to put these monitors and gauges on the top of the dash like this? I'm 5'10" if that matters at all.

We sat in the carbon fiber coupe they had at the open house, which has a dash with a curved top that matches the height of the steering wheel.
Just my 2 cents but I wouldn't make it any higher than that. I'll second what Scott said, and suggest making a cardboard mockup.

[Jeff Kleiner]

We sat in the carbon fiber coupe they had at the open house, which has a dash with a curved top that matches the height of the steering wheel.
Just my 2 cents but I wouldn't make it any higher than that. I'll second what Scott said, and suggest making a cardboard mockup.

The CF Coupe has the seats flat on the floor so take that into consideration. If you use sliders, raise or tilt the seat things will change.

Jeff

[burchfieldb]

What you said here has been sticking with me for the last 24-ish hours. I haven't sat in a coupe yet. I'm working through different iterations of what I would like my dash to look like. Long story short, I want cameras for side mirrors and I've been working on where to place the monitors. How much am I going to hate and/or not be able to see over the dash if I tried to put these monitors and gauges on the top of the dash like this? I'm 5'10" if that matters at all.


Screenshot 2026-02-11 172126.jpg
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Definitely do a mockup. I did a custom dash on mine with a curved top and it sits at 29 inches from the floor. I wouldn't want it any higher than that. Here is a picture or it and one of my view point sitting in my seat that is all the way back and mounted to the floor with no rails. I am 6 ft tall and 190 lbs.

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[JimStone]

It's been a bit since my last update.

Have been busy with work, kid's basketball, flag football, swimming, robotics, coaching baseball. I don't remember winter being nearly so busy when I was a kid.

But I have been making some progress. Mostly on random projects.




I received the FormaCars electric windows kit a few months ago. At first blush, all the parts in the crate and boxes looked overwhelming, but after reading through the instructions a few times and watching TTimmy's YouTube videos, I feel better.

I'm still months away from fitting the doors, but I did want to get the wiring completed. It mostly was straightforward, but then I decided to complicate things.

I didn't like the plastic window switches that came with the kit.





I wanted switches to match my other Billet Automotive Buttons. I got two pairs of buttons and make a mount plate. It will go on the trans tunnel so both driver and passenger can reach.




Getting those buttons to actually control the window motors turned out to be more challenging.

The doors have computer modules in them that control the window motors




The signal from the window switch to the computer is not a simple on/off signal. It took some experimentation to determine that it's specific voltages the computer reads.

5.0 V = neutral/resting voltage
0.4 V = Auto-open
1.2 V = Open
2.4 V = Close
3.4 V = Auto-close

The FormaCars switch modulates the voltage returning to the door computer depending on whether you push or pull up/down and how hard you push/pull.

In order to replicate these voltages with my buttons, I needed to use specific resistors. I found that a 2.2k ohm resistor was needed for a up/close signal and 330 ohm for a down/open signal.

There was no way for me to replicate the auto-open and auto-close function, but I'm ok with that.







In other news,

Yesterday, a fuel leak sprung from an AN to NPT fitting at the fuel filter.






It's leaking through the PTFE sealant at the NPT fitting. A new fitting is coming. Should be an easy fix. I'm glad it happened now

Then I'll get back idle tuning on the Terminator X






I'll be posting more about some other random projects I've been working on soon.

[Skuzzy]

What type of teflon sealant did you use?

[JimStone]

What type of teflon sealant did you use?

Uh oh, now you have me nervous.

I have Permatex 80633 Thread Sealant with PTFE

[Skuzzy]

Well,...that particular sealant works real well with diesel fuel and hydraulic systems, but not so much for blended fuel. Permatex has a better solution for blended fuel fittings. Their "High Performance Thread Sealant" is what I use for AN fittings carrying fuel. Never had a leak with it, regardless of the pressure.

My brother and I worked in oil fields for a time and learned a lot about various sealants.

By the way, teflon is not the problem with 99% of the applications. It is the binder the teflon is in which is usually the problem.

[JimStone]

Well,...that particular sealant works real well with diesel fuel and hydraulic systems, but not so much for blended fuel. Permatex has a better solution for blended fuel fittings. Their "High Performance Thread Sealant" is what I use for AN fittings carrying fuel. Never had a leak with it, regardless of the pressure.

My brother and I worked in oil fields for a time and learned a lot about various sealants.

By the way, teflon is not the problem with 99% of the applications. It is the binder the teflon is in which is usually the problem.

Well sh*t


Thanks Skuzzy, I'll get the High Performance version.

Now I'm thinking of all my other fuel line connections I used that on... fortunately, I think most are actually ORB type fittings, so didn't use the sealant.


Factory Five Forum Brain Trust to rescue again!

[Skuzzy]

Don't panic. You may never have an issue with the sealant you used. Quite frankly, AN fittings should not need any sealant if they are decent quality and properly torqued. I, usually, put a touch of non-detergent oil on the contact surfaces (male and female side) to insure it will not gall.

[JimStone]

Don't panic. You may never have an issue with the sealant you used. Quite frankly, AN fittings should not need any sealant if they are decent quality and properly torqued. I, usually, put a touch of non-detergent oil on the contact surfaces (male and female side) to insure it will not gall.

Thanks Skuzzy

The leak is actually coming from a 3/8" NPT connection at the fuel filter. It's a 3/8" NPT to male 6AN fitting, but I only put the sealant on the NPT side

I did some more research and the original Permatex sealant I used is only gasoline "resistant".

The description on the Permatex website says "Seals and resists pressure in air, oil, diesel fuel and hydraulic systems". No gasoline, like you said


Live and learn

[Skuzzy]

You can also use yellow teflon tape on those NPT threads. The yellow teflon tape is rated to handled blended fuel. Silver/gray teflon tape is okay as well. White teflon tape should never be used on any automotive thread which carries anything other than water.

I figured you were using the sealant on the attachment thread and not the AN side. I just wanted to clarify what I had said earlier about where to use the sealant. I may have nerfed that as well. Sometimes my brain outruns my ability to type.

[JimStone]

Fuel leak fixed.

I used the proper sealant this time (Thanks Skuzzy). Says right on there it's for NPT fittings and confirmed it is for gasoline




I actually found that the fuel filter was leaking from both NPT fittings, so that original Permatex thread sealant definitely was to blame. Thankfully, those are the only two NPT fittings on my fuel system.

All good now








Btw, it's incredible the quantity of different sealants, lubricants, etc that one acquires while building a car. I'm sure there are several more that I've used that aren't in this photo








Some random updates:

Powder coated my Microflex Labs turn signal to match my theme.







Thanks to Microflex Lab's Kevin Cessac for pointing out to me there is a magnet that needs to be oriented correctly for the signal to work. I had reassembled it incorrectly




My cupholder got even more tricked out. Added my Project Demios logo, made by Send-Cut-Send out of aluminum and powder coated gold, then covered with clear epoxy for protection









Less frivolous update:

My engine has been overheating after idling for about 5-6 minutes. The thermostat isn't opening. So... drained the coolant (2nd time so far) and have a replacement thermostat arriving this afternoon. Fingers crossed that fixes it

[PNWTim]

Jim - LS engines are kind of notorious for air pockets in them, particularly in the rear of the heads. I would suggest you test your thermostat in some hot water on your stove and see if it was opening in the 185 to 190ish area. If so, depending on what you have available, either use a coolant filling system/tool or you can raise the front of your coupe so the radiator or fill tank is higher than the engine. Fill your system and if possible, once coolant is flowing through the return hose, massage the hose (full disclosure, forearm workout) to force any air out of the system. Let it run like this for a bit and the air pockets should work their way out of the fill tank.

[JimStone]

Jim - LS engines are kind of notorious for air pockets in them, particularly in the rear of the heads. I would suggest you test your thermostat in some hot water on your stove and see if it was opening in the 185 to 190ish area. If so, depending on what you have available, either use a coolant filling system/tool or you can raise the front of your coupe so the radiator or fill tank is higher than the engine. Fill your system and if possible, once coolant is flowing through the return hose, massage the hose (full disclosure, forearm workout) to force any air out of the system. Let it run like this for a bit and the air pockets should work their way out of the fill tank.

Thanks Tim

I'll test the thermos like you said.




I do have a concern that I may have the wrong thermostat and it may be preventing proper flow.

I'm using this 180 degree thermostat







I thought having a slightly lower temp thermostat would be appropriate given the bigger cube version of the engine (me trying to out-think GM engineers. )

Now I wonder if it's even the right size and is blocking something.

I'm going to use the OEM thermostat this time







Some of the symptoms:

The upper radiator hose gets warm, but the lower stays cool.

I am getting circulation through the Surge tank and heater hoses




There are two coolant sensors, and they are measuring widely different temps:

1) Passenger rear cylinder head sensor shows rising temps consistently until I shut it down around 225 ( Used for the Terminator X)

2) Driver's front sensor never gets above 150 (used only for Speedhut gauge)




The steam vent hose to the surge tank is gushing fluid continuously. That should just be steam (right?) so somewhere there is a blockage shunting fluid through the steam vent pathway








So lots of weirdness




Maybe it is just air pockets.

I'll rule out the thermostat then if still acting up, will do what you said and jack up the front. I did vacuum fill the coolant system this last time, and will do that again this time

[PNWTim]

Your car is doing exactly what my Camaro did and it was air trapped in the system and preventing flow. If your lower hose isn't warm there is no flow through your entire radiator and system overall. Your setup is a little different than my car but the cold lower hose is kind of a dead giveaway. I can't speak to the thermostat you bought but

[JimStone]

Your car is doing exactly what my Camaro did and it was air trapped in the system and preventing flow. If your lower hose isn't warm there is no flow through your entire radiator and system overall. Your setup is a little different than my car but the cold lower hose is kind of a dead giveaway. I can't speak to the thermostat you bought but

Thanks Tim

That's actually really reassuring. I was having doomsday thoughts of having to take the engine apart to fish out a shop rag or something.

[JimStone]

New OEM (AC Delco) thermostat on the left (187 F)

"Old" Michigan Motorsports thermostat on the right (180F)

The OEM is definitely more beefy a part, but the diameter of the seal is the same, as well as the length. So I think they're functionally the same


And the old one did open in boiling water. So, probably wasted my time, but at least now I can now eliminate the thermostat as the problem.





Everything hooked back up

I love the AN hoses. Makes it super easy

I will refill with coolant tomorrow (vacuum fill with my Vevor tool) and see what's what

[lewma]

Jim, what temperatures are you seeing while idling ?

[JimStone]

Jim, what temperatures are you seeing while idling ?

I've gotten it up to around 230F before shutting it down. At least that was the reading from the right cylinder head sensor. The left was maybe 160. And thermostat never opened. So clearly coolant wasn't flowing all the way through the engine.

I've only fired up the engine maybe 7-8 times, for 3-5 min at a time. Trying to figure out this coolant issue.

[jemorgan3]

I really like the AN hose setup in the coolant system! Did you detail that (routing, parts used, ect) in your build? I might steal the ideas from you, if you get it sorted out that is

[lewma]

I've gotten it up to around 230F before shutting it down. At least that was the reading from the right cylinder head sensor. The left was maybe 160. And thermostat never opened. So clearly coolant wasn't flowing all the way through the engine.

I've only fired up the engine maybe 7-8 times, for 3-5 min at a time. Trying to figure out this coolant issue.

Do you have the heater hoses hooked up so coolant can flow in/out of that unit ?

[JimStone]

Do you have the heater hoses hooked up so coolant can flow in/out of that unit ?

Yes, the heater hoses are connected and they do seem to get warm.

I know that does make sense then why the thermostat didn't open since the heater hoses then send fluid right past the thermostat

[JimStone]

I really like the AN hose setup in the coolant system! Did you detail that (routing, parts used, ect) in your build? I might steal the ideas from you, if you get it sorted out that is

I very briefly discussed it, but didn't do a thorough post. I'll do that for you in the next few days.

It did require quite a bit of thought and planning (mostly for the lower radiator hose because of the dumb way the radiator neck is angled right into the frame rail)

[JimStone]

I re-bled the brakes yesterday because I wasn't satisfied with a previous attempt. The rears were the problem. Finally got the air out and was feeling a nice firm brake pedal when "splat", a bunch of brake fluid spurted down onto the pedal box floor.

Immediately, I knew it was a master cylinder issue. And yet again, the leak was coming from the NPT connection at the end of the MC. Same thing happened several months ago, only this time it was the rear brakes MC instead of the front brakes MC






Last time, I wasn't sure if I had over torqued and damaged the MC NPT threads, or if the adaptor was to blame. This time I know it's the adaptor.

You can see the difference in how deeply the adaptor threads into the MC:

First the Rear/leaking fitting (is essentially bottoming out):




Versus the refurbished front MC (several threads exposed):






Last time I replaced the whole MC and adaptor. This time I'll just replace the adaptor.

The adaptor that failed/wasn't machined probably is actually a Wilwood product, so that's disappointing.

Since I don't have to remove the whole MC this time, it won't be too big a job



-------


I also flushed the coolant system with distilled water 3x because I was getting a bunch of dirty coolant and sediment out.

This is what drained after the 3rd flush




Less sediment, but still dirty



Is this normal?

[jemorgan3]

I would say that is not "normal".. Especially when all new components are used. Is it a fluid contamination or is it grit? I'm sure blueprint cleans their blocks before assembling, so i wouldn't think its junk from the coolant passages. May be worth shooting them an email with a picture of whats coming out.

[JimStone]

I would say that is not "normal".. Especially when all new components are used. Is it a fluid contamination or is it grit? I'm sure blueprint cleans their blocks before assembling, so i wouldn't think its junk from the coolant passages. May be worth shooting them an email with a picture of whats coming out.

It seems to just be fine grit. And lots of it.

After the first flush, there was about a 1/2 cup of dark brown/gray grit at the bottom of the bucket.

2nd flush had maybe a a few tablespoons

3rd flush a teaspoon


I did make all my AN coolant lines, so there may be some dust from that. But I flushed and cleaned them before installation.

Sand from block casting?




I keep reminding myself that Blueprint did Dyno this engine, so there must not be a defect or blockage in the coolant passages or it wouldn't have made it through the Dyno session

[PNWTim]

Jim - I don't want to freak you out but a 1/2 cup of any kind of grit is not normal by any stretch. I can't imagine there is anywhere near that amount of residue inside your lines so it either came from the coolant, the engine or the radiator. Some obvious questions:

Did you use brand new coolant?
Did you put an additive in it?
Is the grit magnetic?

It is possible it is casting sand? from the block or head manufacturing process (or maybe the radiator but it's made differently) that just somehow didn't get flushed out of one of the water jackets during the dyno process. I think I would call Blueprint and ask them if this is even possible. I would also use whatever method you are using to flush until there is none.

[JimStone]

Jim - I don't want to freak you out but a 1/2 cup of any kind of grit is not normal by any stretch. I can't imagine there is anywhere near that amount of residue inside your lines so it either came from the coolant, the engine or the radiator. Some obvious questions:

Did you use brand new coolant?
Did you put an additive in it?
Is the grit magnetic?

It is possible it is casting sand? from the block or head manufacturing process (or maybe the radiator but it's made differently) that just somehow didn't get flushed out of one of the water jackets during the dyno process. I think I would call Blueprint and ask them if this is even possible. I would also use whatever method you are using to flush until there is none.

Thanks Tim,

I used new new coolant without additives. It was a nice clear orange color when it went in.

This stuff:



I didn't think to check if it was magnetic. I'll test it when I get home


Thanks for freaking me out Tim. J/k.

[lewma]

Jim, if you made those coolant lines yourself, did you blow them out before connecting up ? Could that just be residue from the lines ?

[JimStone]

Jim, if you made those coolant lines yourself, did you blow them out before connecting up ? Could that just be residue from the lines ?

Hey Mark,

With the lines, I blew them out, flushed with soapy water then rinsed, then blew out again. Only thing I didn't do (and maybe I should have) was use a long bottle brush or something to scrub the insides of the hoses. And/or flush with a solvent




Tonight I'm going to do major flushing. Take the radiator hoses off and thermostat out, and flush through the block and radiator continuously until clear. Then flush the heater hoses and heater core too.

I've already used 8 gallons of distilled water and looks like I still have a lot more flushing to do, so I'm going to switch to the hose. Then do a final flush with distilled to get any minerals out.



I'm also thinking of using a cooling system cleaner like this:

[Papa]

My BPE 347 was the same way. When they dyno the engines, I think they just run plain water, not antifreeze in the engines. Mine sat a few months before installing it and filling with coolant. I had to drain it and flush multiple times to get all the crud out of the engine that I think was just rust from the block being wet with no coolant for so long.

[JimStone]

My BPE 347 was the same way. When they dyno the engines, I think they just run plain water, not antifreeze in the engines. Mine sat a few months before installing it and filling with coolant. I had to drain it and flush multiple times to get all the crude out of the engine that I think was just rust from the block being wet with no coolant for so long.

Thanks Papa!! I think that explains it!

I bought my engine in June 2025 but didn't fill with coolant and have first start until 2 months ago. So it sat for 8 months

(And mine is a cast iron block, not the aluminum casting)



That is a relief, actually



Here is what we flushed on the 6th flushing cycle tonight:




Still nasty, but at least there is no more sediment at the bottom of the bucket.


If the coolant passageways are rusted, maybe it will never fully clear


I'm going to try the cleanser tomorrow, but I'm getting pretty tired of the his flushing procedure

[Papa]

You might try a power flush like this video demonstrates:



The guns are relatively inexpensive on Amazon.