Sealing around Carb Bowl Drain

[az_gila]

Originally Posted by rvbuilder2002

"Silicone sealant" is a generic statement that requires.

There are large performance differences between many "purely" silicone sealants and silicone "RTV's"

If a specific sealant like High Temp red RTV says not for use on parts in contact with gasoline, it is probably not a good choice of sealant when trying to find something to use based on the suggestion of silicone sealant.

Tank sealant is a no brainer...... it is meant for contact with fuel and is used as a sealant for many fuel related situations.

Generic or not, I can't find any "silicone sealant" that is rated for contact with fuel.

The closest is a Dow Corning 730 at around $100 for 3 oz, and that is listed as a "fluorosilicone".

Can you reference a specific "silicone sealer" that is actually fuel resistant? This is what the instructions call out.

Perhaps using a "generic statement" for products to use in the factory instructions is a poor idea?

Two respondents to this thread have already used the red automotive silicone stuff, making a Vans SB a good idea.


I agree 'tank sealer' is a good idea, and that is what the instructions should really call out. Mine, and many others apparently, did not.

[PCHunt]

I am surprised to see two of the very best posters on VAF engaging in a bit of a "flame" war!

[GLPalinkas]

Originally Posted by PCHunt

I am surprised to see two of the very best posters on VAF engaging in a bit of a "flame" war!

Pete, not sure that's what going on. Like you, knowing both of them as valuable contributors to VAF, I think it's more a semantics issue. I know that sometimes when I text (or write responses to VAF posts) it doesn't come out exactly like I planned it too.

Anyway, It's an important issue that we all learn from.

Keep up the good work guys and thank you both for your contributions on VAF. I know personally, my aircraft is flying because of guys like you who contribute so much to VAF.

[f14av8r]

I really appreciate all the responses. I've been puzzling over this one for days. You are all concerned about the same things I am - avoiding ingestion and ease of maintenance. Based on all the excellent discussion, I'm going to use RTV sealant.

Thanks for your reply too Vlad. I should have specified the type of carburetor. Mine's a MA-5.

Thanks again!
Randy

[Walt]

Just to add my 2c, I don't think using RTV to seal around the air cleaner (like on the 320 filter or the base plate) presents any hazard, if a chunk breaks loose the engine will easily injest it and spit it out, kinda like it does to loose hardware in the airbox.

There is a BIG difference in application here, using RTV as a thread or gasket sealer is definitely a major problem, using it around the air cleaner.. well I just don't see it as an issue in that application.

Quoting accidents caused by "RTV" used as a tread or gasket sealer is not the same thing as what the OP asked about (but a good reminder nonetheless), unless someone can show me a case of where RTV being ingested caused a problem.

[rvbuilder2002]

Originally Posted by rvbuilder2002

I guess you think I am lying about forced landings.
HERE IS ONE If you do some searching in the forums on Brian Denk, you can probably find some info regarding the details. I know of others but can't recall any details at the moment to point you to specific reports.

Originally Posted by Walt

Quoting accidents caused by "RTV" used as a tread or gasket sealer is not the same thing as what the OP asked about (but a good reminder nonetheless), unless someone can show me a case of where RTV being ingested caused a problem.

Actually Walt, the incident (wont call it an accident because it resulted in a safe forced landing on an airport) that I linked in my above post was an RV-8 where the builder used High Temp RTV to seal portions of the induction airbox. I fully realize that RTV on pipe threads is a totally different situation...

If I remember correctly, a loose piece of RTV that had turned to mush because of exposure from a fuel leak on the carb, lodged in a portion of the venturi in the throat of the carb. Caused a complete power loss.

[krw5927]

In the post Scott linked above, the author talks of his "stuck float" experience. How on earth does a piece of RTV on the airbox make it into the float bowl of the carb? Scott can you please shed some light here?

[rvbuilder2002]

Originally Posted by krw5927

In the post Scott linked above, the author talks of his "stuck float" experience. How on earth does a piece of RTV on the airbox make it into the float bowl of the carb? Scott can you please shed some light here?

I haven't gone back and dug for the details.... like I said , just going on memory....

I think this was a partially stuck open (or sinking?) float that cause over flow of the float bowl and fuel wetting the airbox with the eventual engine stoppage when some RTV got loose. I believe there was an ongoing problem for a while that he was trying to diagnose (interm. float problem?) that eventually ended in a forced landing.

As we know, it often takes a number of factors to align to make something become a problem........

[tracy]

So, what has been the general consensus here for the o360 carb plate sealant? I’ve never put anything in the gap because of the ingestion worry.

[abuura]

I've had RTV there since 2006, never have seen any softening or loosening due to fuel leaks. Nevertheless, upon re-reading this thread I believe I'll follow Scott's encouragement to use Proseal.