🔧 BUILD Upside-down M90 GTP build thread

[Turbocharged400sbc]

um....leakdown is in %

your suppossed to set the pressure and the % difference between the pressures on either side of an orifice is what your looking for......% of leakage

also leakdowns at BDC/TDC are not super accurate even on nearly new bores compared to at 30* BTDC/ATDC/BBDC/ABDC old dirty ring packs may need a nudge to get the rings to set in their grooves

dont shortcut the cranking cyl press test, pull all plugs before test begins after driving the car for long enough for operating temp, block/hold TB open

you can kinda shortcut with not getting it more than warm (so ya dont burn yerself so bad) but readings are a hair lower than at operating temp

i hope youve been looking at your pre AFC MAF Hz from the begining of your project.....as thats a great overall indicator of engine airflow increase/decrease....you can use post AFC data just as long as youve never adjusted the afc and the sensor is regularly cleaned.

L67 comp test will be lower than the NA shorty. making sure one isnt way outside the mean is the main goal

 

[Turbocharged400sbc]

my gauge is to be set at 100psi on the inlet gauge and the secondary gauge downstream of the orifice is in a % scale...if yours is PSI on both your gonna have to do some math

 

[GTPpower]

Yeah, I set the inlet at 100 so there basically is no math to figure percent loss.

 

[GTPpower]

I got tired of trying to test this intercooler system with a 1.2 gallon compressor that works great on lawnmower and bike tires. I grabbed my 60 gallon compressor and stuck it in the garage. It's nice that I can test it without all the noise from the little compressor running.

The bad news, I still am not finding any leaks. So why will this thing only build 10 psi? Did I mess something up by cutting the inlet off? The coating looks good on the rotors and I don't see any red flags there. Should I go to the junkyard and get another gen 5 and try that?

 

[sktchy]

I got tired of trying to test this intercooler system with a 1.2 gallon compressor that works great on lawnmower and bike tires. I grabbed my 60 gallon compressor and stuck it in the garage. It's nice that I can test it without all the noise from the little compressor running.

The bad news, I still am not finding any leaks. So why will this thing only build 10 psi? Did I mess something up by cutting the inlet off? The coating looks good on the rotors and I don't see any red flags there. Should I go to the junkyard and get another gen 5 and try that?

I wonder if we aren't having any least some sort of similar issue here. Granted I've got some mechanical issues to sort out but I should be seeing 13 or 14 psi at wot where the gate is sprung. It sees 12 max if I'm lucky even before I ended up with noises to deal with. Same thing on the last motor.

I know it's not apples to apples and mine may come to light after further research but it's something that I haven't been able to explain yet unless it's a weak wastegate spring or something else of that sort

 

[JST_A_3800]

I got tired of trying to test this intercooler system with a 1.2 gallon compressor that works great on lawnmower and bike tires. I grabbed my 60 gallon compressor and stuck it in the garage. It's nice that I can test it without all the noise from the little compressor running.

The bad news, I still am not finding any leaks. So why will this thing only build 10 psi? Did I mess something up by cutting the inlet off? The coating looks good on the rotors and I don't see any red flags there. Should I go to the junkyard and get another gen 5 and try that?

nick you should install a boost port in the blower hat and see what the pressure drop is from the blower to the lower intake. I assume you are measuring boost in the lower intake. I just can't help but wonder if you have a flow issue with a couple of the bends you had to make in the intercooler piping? then if it is only making 10psi under(above) the blower that may narrow down whether its an inlet issue or something down stream

 

[v6buicks]

Yeah, what he said. /\

Don't you have a super narrow opening from the blower to the tubing? I never questioned it, but it always looked like a restriction to me. I used to test this kind of stuff at work all the time. You might be surprised at what can and won't cause a pressure drop.

 

[JST_A_3800]

nick you should install a boost port in the blower hat and see what the pressure drop is from the blower to the lower intake. I assume you are measuring boost in the lower intake. I just can't help but wonder if you have a flow issue with a couple of the bends you had to make in the intercooler piping? then if it is only making 10psi under(above) the blower that may narrow down whether its an inlet issue or something down stream

I even have an extra 20lb boost gauge laying around if you want to borrow it if you don't have an extra

 

[GTPpower]

That's a good idea. I'll order some more aluminum bungs and weld one in there.

The outlet from the blower is maybe 3/4" tall, but it's about 5" wide. Other than that, all piping is 3" and the intercooler is 3.5". But, I do know that where it goes into the lim, it does sneak down to less than 3"....how much less though, I'm not sure. But I am measuring boost before that point.

But this is a good idea. And I should hook up my intake air temp gauges as well while I'm at it.

 

[JST_A_3800]

That's a good idea. I'll order some more aluminum bungs and weld one in there.

The outlet from the blower is maybe 3/4" tall, but it's about 5" wide. Other than that, all piping is 3" and the intercooler is 3.5". But, I do know that where it goes into the lim, it does sneak down to less than 3"....how much less though, I'm not sure. But I am measuring boost before that point.

But this is a good idea. And I should hook up my intake air temp gauges as well while I'm at it.

do it nick!!

 

[GTPpower]

I ordered more bungs....they came in last week. I should go weld one in.

 

[JST_A_3800]

I ordered more bungs....they came in last week. I should go weld one in.

I just ordered a flex bellows for my dump tube so maybe I can finally get this shit back together...

 

[GTPpower]

I just ordered a flex bellows for my dump tube so maybe I can finally get this shit back together...

We have like 2 months and the track will be open. I also heard a rumor that onawa will run 1/4 mile sometimes this year.

 

[sktchy]

Seems like everyone here is big on the 1/8 mile stuff lately. There's kinda of a little drag and drive from here to i29 towards the end of April that'd be fun to make if I can find the ambition to pull mine apart and put it back together again by then.

 

[GTPpower]

Yeah that place puts on a good show for their heads up no prep stuff. Big crowd.

 

[v6buicks]

You got them bungs welded? I'm antsy to hear the results of this test. haha

 

[GTPpower]

I haven't. My wife goes on maternity leave starting Monday, so I will be at home with her for a week. Should be able to get some work done on the car then. I also ordered a 3 bar map sensor, so I will plan on using that in the new port.

But I also have a scissor lift and 6.0 to fix as well. So we'll see how much time I actually do have.

 

[GTPpower]

Seems like these axle clamps fall off/disappear with every track visit.



Are these with the notches supposed to be better than the smooth ones I e been using?

https://www.amazon.com/dp/B07QPRVK76/?tag=tcg21-20

 

[10sec]

Do you have the tool that tightens those smooth ones or are you just pulling them tight?

For the other ones you also need a tool to squeeze the little bridge looking thing but that is would I would suggest you use. The tool is in the "other items people bought"

 

[sktchy]

I'm not sure what kind of voodoo it takes to get those to stay on but I've never been able to get one to stay tight even with the tool. It's not real proper but a couple worm gear clamps clocked 180⁰ from each other seems to work pretty well without throwing things off balance.

 

[GTPpower]

Yeah, I have the tools for it. I'm looking at them now and I'm wondering if I did it correctly. It's been so long that I can't remember what exactly I did.

 

[GTPpower]

Looking at this more, I think my clamps just might not be great. They don't have the little ears to even hold the excess back with.

 

[Jimy Bilmo]

Some of those cheapy aftermarket boots are firm as shit and pop off clamps regardless of which you use.

 

[sktchy]

I'm not sure if the lifetime replacements will hold up to your power level but...the answer to that is a pretty good explanation of how I feel about those stupid clamps lol

 

[GTPpower]

These aren't cheap axles though. These are actual gm axles. They were just overfilled with grease. The boots are rtv'd on. It didn't even pop off this time, just the clamp.