Im concerned that the mating surface on the intake manifold may not be perfectly flat. And, i also see a small grove or scrape in the mating surface of the intake manifold (where the throttle body meets the manifold).

My question is: Should i use rtv or get the gaskets from the local Mitsubishi dealership? Will the gaskets seal even if the mating surfaces aren't perfect?

Don't use rtv if your dealing with air, it won't hold, get a gasket it'll work fine but if you think there's a big clearance with mstibg that the gasket won't work, file it down till the surface is perfectly flat, it shouldn't get messed up if you havent messed with it

Isn't a file too aggressive? I'm just asking because i keep reading horror stories about how people use the OEM gaskets and still have small leaks.

concept4g63 said:

Don't use rtv if your dealing with air, it won't hold, get a gasket it'll work fine but if you think there's a big clearance with mstibg that the gasket won't work, file it down till the surface is perfectly flat, it shouldn't get messed up if you havent messed with it

Click to expand...

That is not completely correct. People have been using RTV silicone gasket maker for years on there charged air system. In fact, right now I am using RTV for my J-pipe gasket. All I did was applied a small thin ring around the outlet, and never have seen a boost leak in a year, boosting 11-18 psi on a 14b.

What I definitely would not do is use the gasket and RTV, and there is no need to use an excessive amount, less is more theory.

I actually just replaced my TB gaskets and I am using these right now. They are phenolic gaskets for the TB and TB elbow (same material as the thermal barrier intake gaskets from magnus).

"It insulates very well and has an operating range of -400 to 500F. Low heat expansion, easy to cut, soft enough that it will seal well between two surfaces." - How to Make A Teflon/Phenolic Intake Manifold and Throttle Body Gaskets/Spacers

I would use a fine grit sand paper and tape it to a flat surface face up. I would take the whatever surfaces are mating and make them a s smooth and flat as possible using the sand paper.

The second picture is the thickness of the gasket compared to a US quarter.

agentorange313 said:

I actually just replaced my TB gaskets and I am using these right now. They are phenolic gaskets for the TB and TB elbow (same material as the thermal barrier intake gaskets from magnus).

The first picture is the thickness of the gasket compared to a US quarter.

Click to expand...

So, where did you buy that material?

For the gaskets between the TB elbow/TB/intake manifold just use gray RTV if you notice imperfections in the mating surface, it will hold just fine. Just be sure not to go overboard on the amount of RTV you use because it will "mush" when you tighten the bolts down. Give it plenty of time to cure too, let it set for at least 3 hours or so before doing a boost leak test to make sure its good.

gofer said:

For the gaskets between the TB elbow/TB/intake manifold just use gray RTV if you notice imperfections in the mating surface, it will hold just fine. Just be sure not to go overboard on the amount of RTV you use because it will "mush" when you tighten the bolts down. Give it plenty of time to cure too, let it set for at least 3 hours or so before doing a boost leak test to make sure its good.

Click to expand...

I have used RTV with good success in the past. However, during my "research", i found that it was not recommended.

I guess my major concern is that the RTV may clog important holes of passages. Is this something i should be concerned with?

njc1064 said:

So, where did you buy that material?

Click to expand...

Mitsubishi - P2R Power Rev Racing

njc1064 said:

I have used RTV with good success in the past. However, during my "research", i found that it was not recommended.

I guess my major concern is that the RTV may clog important holes of passages. Is this something i should be concerned with?

Click to expand...

Depends what you are using it on. I would say someone using RTV in excessive amounts for gaskets like front case gasket OFH and water pump, might clog the galleys or coolant passages or get clogged somewhere remote in the system (just a bad idea, dont even consider it). Just be smart, like I said before there is no need to use an excessive amount, less is more theory.

You do need to be careful about clogging certain passages by using TOO MUCH RTV, which is why I mentioned it in my OP.

Just be sure not to go overboard on the amount of RTV you use because it will "mush" when you tighten the bolts down.

Click to expand...

I use RTV between my TB/IM and it holds 35psi with no problems during BLT's. In the past, when I used a paper gasket, it would get hard from the heat cycles in the engine bay and it would "blow out" and create a HUGE boost leak there.

gofer said:

You do need to be careful about clogging certain passages by using TOO MUCH RTV, which is why I mentioned it in my OP.

Click to expand...

In regard to clogged passages, are there any in particular on the throttle body that i really need to be concerned about?

agentorange313 said:

Mitsubishi - P2R Power Rev Racing

Click to expand...

Those are some seriously expensive TB gaskets!

agentorange313 said:

What I definitely would not do is use the gasket and RTV, and there is no need to use an excessive amount, less is more theory.

Click to expand...

I have been using a thin layer of grey RTV over one side of the stock gasket on the intake manifold, throttle body, and j-pipe for over a year now and it has been working and sealing great, way better then the gasket alone.

9!'clipseDOHC said:

I have been using a thin layer of grey RTV over one side of the stock gasket on the intake manifold, throttle body, and j-pipe for over a year now and it has been working and sealing great, way better then the gasket alone.

Click to expand...

True it probably will hold up, but like Gofer said, the stock gasket eventually gets brittle and drys out, with just RTV alone it will definitely stand up longer to the heat cycles.

Just thinking long(er) term.

9!'clipseDOHC said:

I have been using a thin layer of grey RTV over one side of the stock gasket on the intake manifold, throttle body, and j-pipe for over a year now and it has been working and sealing great, way better then the gasket alone.

Click to expand...

Is the OEM gasket between the intake manifold and the throttle body metal or paper?

njc1064 said:

Is the OEM gasket between the intake manifold and the throttle body metal or paper?

Click to expand...

It's a composite material.

agentorange313 said:

True it probably will hold up, but like Gofer said, the stock gasket eventually gets brittle and drys out, with just RTV alone it will definitely stand up longer to the heat cycles.

Just thinking long(er) term.

Click to expand...

Yeah Nate.

njc1064 said:

In regard to clogged passages, are there any in particular on the throttle body that i really need to be concerned about?

Click to expand...

Yep.

9!'clipseDOHC said:

It's a composite material.

Click to expand...

I could have sworn I've seen metal throttle body gaskets.

My one gripe regarding RTV is the clean up after removing any part. It can be a serious PIA to get those RTV'ed surfaces clean again.

njc1064 said:

I could have sworn I've seen metal throttle body gaskets.

My one gripe regarding RTV is the clean up after removing any part. It can be a serious PIA to get those RTV'ed surfaces clean again.

Click to expand...

There was a metal OEM TB gasket actually but I don't remember which years. 1gs where paper though.

After looking it up it seems that 2gs (at least some, I don't know if all did or not) came with metal TB gaskets. I was thinking about the 1g gasket which is paper. http://www.dsmtuners.com/forums/bolt-tech/348390-need-help-finding-throttle-body-gasket-my-2g-talon.html

gofer said:

Yeah Nate.


Yep.

You must be logged in to view this image or video.

Click to expand...

So, there are actually no passages anywhere on the mating surfaces themselves?

njc1064 said:

So, there are actually no passages anywhere on the mating surfaces themselves?

Click to expand...

There are on the IM side but they get blocked anyway, this is why I said not to go overboard on the amount of RTV you apply. Just go around these holes on the IM side and when you compress it to the IM it will seal up.

I used a little bit of red high temp RTV, on my throttle body gaskets.
Any reason the gray RTV is better?
Is it because it resists vibration?That is the only difference I see in the two.
Hopefully it will be alright.

I just use an OEM TB gasket, but i also pull all those vacum tubes, tap them to M5 x .80 and put set screws into them with red loctite to ensure it's a "race only" TB with no leaks, then i go to the bike shop and put a new o-ring on the BISS screw.. only thing left after that is to take some lexan scissors and trim the gasket to where it's doesn't obstruct anything and doesn't hang "out" from the sides anywhere (i like my ish CLEAN)

I seem to always get 3 or more TB type gaskets in my top end kits, then i trim them all perfectly with curved lexan scissors to be the 1g NT size, works like a charm and is cheap

So the red RTV definitely doesn't work.
I did another boost leak test and I have a crazy leak, where the throttle body meets the manifold.
I used brand new OEM gaskets and put a little red on one side of them.
I'm going to pull it back apart and try it again with gray RTV and no gasket, like Gofer said.

It's been said but I have had zero problems using a cheap auto zone paper gasket putting red RTV on both sides and then torquing down the nuts correctly. I think the answer to the OP question IMO is to use both.
And nemizis, try using more RTV with the gasket, snuging the nuts and then let the RTV sit for an hour, and then come back and torque down the nuts correctly, and then let the RTV actually cure for 24 hours. If that doesn't work you either have a warped surface or your TB is actually leaking not from the manifold surface but from the seals on the throttle plate possibly. This shouldn't be so difficult so you must be overlooking something.

NeMiZiS said:

... like Gofer said.

Click to expand...

Just remember the PB&J law when applying the RTV. You put to much J on your sandwich and it explodes out the sides, this is the case with the RTV as well.

9!'clipseDOHC said:

I have been using a thin layer of grey RTV over one side of the stock gasket on the intake manifold, throttle body, and j-pipe for over a year now and it has been working and sealing great, way better then the gasket alone.

Click to expand...

Same thing i did when i had my 14b setup, no problems!