Progress Thread Komo's 1990 GT - Parts Gathering Purgatory & Home Remodel

gkomo · Mar 25, 2026

AeroCoupe said:
So that compression number isn’t anything to be worried about. Now you need to perform a leak down test and that will tell you if you have a leak around the rings or the valves.

Good news in baby steps. Hopefully not 'worn' rings. Valves and/or valve stems seals would be a good excuse to put my TFS heads on though...

nicholase · Mar 25, 2026

gkomo said:
Ok picked up that Maddox hand vacuum/pressure pump. Will try diagnosing the boost gauge tomorrow.

Nice. That should give you some information.

Your symptom of the guage going up to 3 psi but not building any more even with the engine RPM's increasing is not typical of a centrifugal set up. A pressure leak to the guage could be a cause of that issue. Also with it tied to the FMU a leak there would be effecting fuel pressue under boost. Which isn't good.

Could be nothing, could be something. But a good first diagnostic step IMO. I'd think you'd be around 4psi give or take. But the fact it's not increasing as RPMs goes up is what strikes me as something being off. Not so much the number, the behavior.

As far as precisely calibrating the guage I think AutoMeter does it for free if you send it to them.

gkomo · Mar 25, 2026

nicholase said:
Nice. That should give you some information.

Your symptom of the guage going up to 3 psi but not building any more even with the engine RPM's increasing is not typical of a centrifugal set up. A pressure leak to the guage could be a cause of that issue. Also with it tied to the FMU a leak there would be effecting fuel pressue under boost. Which isn't good.

Could be nothing, could be something. But a good first diagnostic step IMO. I'd think you'd be around 4psi give or take. But the fact it's not increasing as RPMs goes up is what strikes me as something being off. Not so much the number, the behavior.

As far as precisely calibrating the guage I think AutoMeter does it for free if you send it to them.

Alright, pressure tested the gauge and it is accurate. I pumped up the vacuum gauge to 5psi and the Autometer boost gauge also read 5psi. However, it would not hold pressure and slooooowly came down when i let the vacuum pump sit, like 1psi every 5-10 seconds (wasn't actually counting)? Is that indicative of a leak in that line/connections or is that supposed to do that? Either way, here's how i tested it:

I unplugged my vacuum hose from the B/R port on the vacuum tree. So all i'm left with is a "T" with three vacuum lines off it, with one side going to my FMU and the other side going to my boost gauge,. I added the vacuum pump to the now open third side of the "T" that went to the B/R port.

Any thoughts? I couldn't remove the vacuum lines from the boost gauge or FMU on the "T", they were stuck on too tightly. So i used some of the pumps attachments and with a cone type nozzle stuck it in the line that normally goes to the B/R port on the vacuum tree but is now handing off the "T". So, basically, i can't guarantee that connection was sealed 100% and may be where the slow pressure leak is coming from.

Or did i fubar this test using the wrong ports/nozzle connections?

Edit: i'll try again this time pinching the FMU line to see if it holds pressure, unless thats pointless?

gkomo · Mar 25, 2026

Ok, redid the test pinching the line going to the FMU. Still slowly leaks pressure. I'm wondering though, if i fubar'd the boost gauge line and the ferrule that holds the plastic line secure inside the fitting:

Kind of looks like it pinched inside there, but kind of not. Hard to tell its so small.

gkomo · Mar 25, 2026

Well now i know not to work on cars while at work. So i went out again just to look at some stuff, jiggle the boost gauge line around and see if anything was off. The whole brass connection to the plastic "T" was hand tight, i could remove it without tools (but i installed it with a wrench...?) so it must have worked itself loose. Anyways, me being a dummy started unscrewing it so i could get to the ferrule holding the boost line in and the boost gauge line (white plastic line) snapped off. Ruh roh!

Damage has been done, so i take the brass fitting inside to inspect it. I take it apart and the ferrule is all deformed and looks like the boost line is somewhat bent inside the ferrule. I actually couldn't get the sheared off boost line out of the ferrule it was all jacked up so much.

So, being at work I am going to temporarily cap off the open boost line fitting from the "T" with one of the caps that come with the vacuum pump kit, not confident this is air tight! Its snug but I will drive the car gingerly home not to get into any boost.

And heres how the ferrule looks:

So, now where to get a replacement ferrule! Thankfully i left an abundance of extra boost gauge line in the engine bay for when i can reconnect it. I should also actually replace the plastic "T" with a brass one as that one seems jankified.

gkomo · Mar 25, 2026

Ok kind of rapid fire today but I was having a mini panic attack after this debacle. I didn't feel comfortable with that "T" capped off that way, so i frantically got the "T" removed from the FMU line, removed it completely and hooked the FMU directly to the B/R port as I have to leave work at a certain time to pick up my daughter from school. So that should actually be solid and maybe better since i may have had a small leak with the boost gauge stuff. Now I can get the "T" fixed separately while still being able to drive the car confidently. Just won't have a functional boost gauge until then.

Had to order new boost line in order to get the ferrules, but only $12 from summit. They get you on free shipping, so ordered 7/16th rocker studs to stockpile for the future engine rebuild.

Feeling a little better now.

gkomo · Mar 25, 2026

Maybe in my head but maybe not the car did seem to run better with the FMU hooked straight to the tree.

I knew I should’ve smoke tested the engine like a year ago.

AeroCoupe · Mar 26, 2026

I’m pretty sure it’s the same plastic line and ferrules that you use on air shocks. They typically have those lots at the parts stores.

gkomo · Mar 26, 2026

If its not one thing its another. My battery light started flickering on the way to work today after merging onto the freeway and getting up into the higher RPMs. It would flicker for a bit sporadically, then disappear for a while, then come back flickering. Then stopped flickering all together ones i got onto side streets.

I know its just a dummy gauge basically, but my voltage gauge always is in the 3/4 from the top of the gauge range. Its never low, and it also bounces around a bit (but staying within the top range of the gauge).

Couple other things i noticed is i need to clean my positive terminal, has some corrosion. I also notice some weeping coming out from under the fluid caps. I guess i should check the water levels in there.

Battery is dated 08/2022 just FYI.

Edit: took the positive terminal off and cleaned it the best i could. Its pretty corroded. probably needs to be replaced at this point, but for now i will clean it and see if that helps. Need to buy one of those terminal cleaner wire brush things because i couldn't really get the wire brush i do i have inside it too well.

Water in the battery all looked good.

gkomo · Mar 26, 2026

I think i'll just replace the entire positive battery cable. It looks a little jerry rigged with like a second large wire cut off going to no where in the terminal crimp. Is 4awg cable good or should i try to find a lower gauge cable since i have the 130amp alternator upgrade?

Edit: ordered P/N E8ZZ-14300-A

gkomo · Mar 26, 2026

Just an interesting note, the boost gauge now sits directly in the middle of the zero box when disconnected.

AeroCoupe · Mar 26, 2026

gkomo said:
I think i'll just replace the entire positive battery cable. It looks a little jerry rigged with like a second large wire cut off going to no where in the terminal crimp. Is 4awg cable good or should i try to find a lower gauge cable since i have the 130amp alternator upgrade?

Edit: ordered P/N E8ZZ-14300-A

4 ga from the alternator to the battery and from the battery to the starter solenoid is more than enough. If you have not be sure to put a 125 A fuse between the alternator and battery.

gkomo · Mar 26, 2026

AeroCoupe said:
4 ga from the alternator to the battery and from the battery to the starter solenoid is more than enough. If you have not be sure to put a 125 A fuse between the alternator and battery.

Ok great. I’ll have to double check if there is a fuse between the alternator and battery as the PO did the upgrade.

AeroCoupe · Mar 27, 2026

Make sure you have a 4 ga ground from the battery to the motor. I did mine from the battery to the k-member and then k-member to the engine block.

gkomo · Mar 27, 2026

I'll double check but i recall from being under the car a lot that all the 'big 3' cables are redone with lower gauge cables. There is a big fuse up by my radiator that looks like a stereo system fuse (but the car has no big stereo) so i'm assuming thats for the alternator. I will follow the wire to see where it goes. The only one that looks suspect is this positive battery cable with some weird second cable thats just cut off for some reason.

The whole wiring area by the starter solenoid is a rats nest and looks somewhat suspect.

AeroCoupe · Mar 27, 2026

If the big 3 was done do a voltage drop test on them. This will ensure they are working properly. I have literally found lugs that were improperly crimped causing issues.

gkomo · Mar 27, 2026

Side bar question back to my boost gauge. I bought the UPR aluminum vacuum tree. Should i use Permatex Thread Sealant 80633 or Permatex Form-a-Gasket (#2) 80015 to seal the barbs to the distribution block? There is also a Form-a-Gasket RTV Silicone 27036.

nicholase · Mar 27, 2026

gkomo said:
Should i use Permatex Thread Sealant 80633

Yup

gkomo · Mar 27, 2026

nicholase said:
Yup

Haha good cause that’s the one I bought. I also bought some additional barbs to expand the distribution block so I can run dedicated lines the FMu and boost gauge (and future bypass valve) instead of using tees.

gkomo · Mar 27, 2026

I mentioned these guys and this series before but here’s their latest video after rebuilding the previous motor that broke:

View: https://youtu.be/CMa2aQS80Go?si=jpmCvre3FmAKZFoy

I think they are pretty entertaining

Progress Thread Komo's 1990 GT - Parts Gathering Purgatory & Home Remodel

now i can hopefully expect to receive the shaft

I lubed and pushed, until it was all the way in

now i can hopefully expect to receive the shaft

now i can hopefully expect to receive the shaft

now i can hopefully expect to receive the shaft

now i can hopefully expect to receive the shaft

now i can hopefully expect to receive the shaft

lube between the nut and the face. I know my lubes

now i can hopefully expect to receive the shaft

now i can hopefully expect to receive the shaft

now i can hopefully expect to receive the shaft

lube between the nut and the face. I know my lubes

now i can hopefully expect to receive the shaft

lube between the nut and the face. I know my lubes

now i can hopefully expect to receive the shaft

lube between the nut and the face. I know my lubes

now i can hopefully expect to receive the shaft

I lubed and pushed, until it was all the way in

now i can hopefully expect to receive the shaft

now i can hopefully expect to receive the shaft

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