3.75L Build thread

[futurevr4man]

Oh, I see where your confusion is coming from... Hope that's not hostility I'm sensing, lol.


heh, no hostility i was surprised you were questioning it though lol.


A couple things -

I've never put much thought into the valves because it's never been an issue. It seems that when a 6G72 is turned off, either the intake valves AND/OR the exhaust valves of EVERY cylinder are closed.

Here's an animated V6 because I don't want to think through this.



Seems feasible...


...Pressure testing from the middle of the system just means that after you finish and reassemble, there's a potential pressurized leak point that's gone untested. If it's at all possible (in your case it absolutely IS), remove PRE MAF components on the vacuum side to pressure test........ like your air filters. Cap one intake tube and pressurize through the other.

If your engine is well sealed with loose rings like mine, you'll need to cap the hose coming off the rear valve cover so that you can disconnect the compressed air hose (regulated at 30+ psi) and listen/feel-around/spray-with-soapy-water, in silence, for leaks. Sometimes I wonder if I'm going to find broken ring lands when I take the heads off, haha.

i understand what you are saying. you have more experience than i do with these engines, im sure. i find it unlikely that all of the valves would be closed, but i guess its possible. just want the system to hold some kind of pressure even for just a bit so i can once-over everything. like i said earlier, i will do it tomorrow and report back with results!

one time when I really wanted to isolate a leak I unhooked the y-pipe from the plenum and put a freezer bag over the throttle body. then I just put the y-pipe on. This eliminates any ring blowby.

I had a pipe off down by the driver side when the sidemounts used to be and the leak was so big it sounded like it was coming from everywhere until I did that to the y-pipe and it helped me pinpoint it.

Picked that up from cbatters.

im assuming this is when you were in stock drawr though? i will be pressurizing where my maf is, and capping the turbo inlets... pretty much pressurizing the system from the opposite side. i have thought it through i think, but i guess we will find out tomorrow haha

[Chris@Rvengeperformance]

yeah I was (and still am) in draw through

[futurevr4man]

yeah I was (and still am) in draw through

aww thats cute hahahaha j/k

[futurevr4man]

what a day what a day. im over here in an utter loss for words right now.

so i went out and pressure tested the car. i immediately get blasted in the face with air as soon as i pop on the hose, so i knew there was at least one big leak somewhere. was it the maf? no. was it my pipes?! no. was it a coupler?!?! NO!!

my god forsaken turbos compressor covers have 2 bolt holes in each one. a sane person would probably assume that they are mounting points for something like a wastegate actuator (considering these are internally gated from the factory). well, they MAY be waste gate actuator mounting points however, the holes go ALL THE WAY through the compressor housing!! WTF! these are like M8 size holes and there are 2 of them on each compressor cover! that is a LOT of air coming out!




so as im just laughing out loud i go get 4 bolts and plug the holes with them. figure, ok, now lets test the couplers. HAH! if only it were that easy.

so i put the hose on the tester again and STILL im getting blasted in the face with air! WTF?! so i feel around, and there is still a hole on each compressor cover that is open! except this one is really small and not threaded! GAHH!




the plan is to use some JB weld and fill those small holes. it should hold the kinds of pressures i wanna push. after that dries, and i get some nice looking bolts before work this afternoon, i will try again and see if everything else is good.

the good news is that the car has A LOT more left in it, which is great! its great because its already pretty quick! i will get vids of it soon. i am waiting until its in tip-top shape though

[j2k4]

Good news, Nateworth.

[Chris@Rvengeperformance]

that should certainly improve everything.

Stuff like this makes it a REAL bitch to tune, no matter what tools you have.

[futurevr4man]

never in a million years did i think those holes went all the way through. all i can do is shake my head haha

and yeah, this should help EVERYTHING

[AdamVR4]

Trying to cleanly apply JB weld into those holes looks like it's going to suck (and what happens if the JB weld runs inside the housing?!)... I'm getting the impression you'll just ignore my advice, but I see a few CHEAP options that I would try before JB weld...

- remove the turbos to tap those holes and use a button head cap screw with RTV on the threads to seal

- buy small stainless steel tubing (slight interference fit in hole), cut it to length, chamfer the ends, coat it in RTV, tap it in with a hammer and use a rubber cap or short length of hose and a plug...

- order "high temperature resilient rubber plugs" (they're tapered) from mcmaster, and hope they don't get blown out

- buy an aluminum dowel pin, assuming you can get a slight interference fit, and tap it in with RTV...

- design an aluminum plug with a head (so that it can't ever go into the turbo) and have it turned on a lathe at a local machine shop...

[futurevr4man]

I wasn't going to apply a ton of JB weld, just a little. The hole is about 3/4" deep so it's got quite a bit of room before it would drop. Taking the turbos off means pulling the engine so I'm not doing that. I thought about a dowel pin as well. I'm going to see what the hardware store has before I do anything.

JB weld is pretty thick stuff. It doesn't really drip. It is my last resort method of fixing this though.

[Chris@Rvengeperformance]

from what I can tell it looks like a good welder could get in there with a tig. If it were mine I'd tap it for a pipe plug though if you can find one that small