Factory 350 Intake Gasket or RTV? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

DetroitIron · 12-24-2020, 10:33 AM

Hi all
I have an 85 K20 with original engine. I noticed while rebuilding the quadrajet that the front of the intake has a squished bead of black rtv visible. Would this have been done from the factory or might this be a sign that the original intake was off and resealed? Did the factory use rtv or the rubber like gaskets for the front and backed the intake manifold?
Thank you for any insight

SunSoaked · 12-24-2020, 10:36 AM

Quote:

Originally Posted by DetroitIron

Hi all
I have an 85 K20 with original engine. I noticed while rebuilding the quadrajet that the front of the intake has a squished bead of black rtv visible. Would this have been done from the factory or might this be a sign that the original intake was off and resealed? Did the factory use rtv or the rubber like gaskets for the front and backed the intake manifold?
Thank you for any insight

After 35 years, I guarantee the intake has been off at least once. Nice choice of truck btw, I have the same.

DetroitIron · 12-24-2020, 10:50 AM

Thanks! The truck runs very strong for all stock and doesn’t burn much oil (just leaks here and there)or have any internal engine noise so I was wondering if it was rebuilt at some point....160,000 miles on the odo

**Palf70Step** · 12-24-2020, 01:21 PM

Factory sets have a rubber front and rear seal/gasket. Personally I know of no one that ever used them when replacing the factory intakes. They just never stay in place well and leaked, so the black RTV across the front and rear was what I saw everyone use.

Tx Firefighter · 12-24-2020, 01:48 PM

I was a dealership mechanic a long time ago. My memory is fuzzy by now, but I remember us changing over to using silicone in the early 90s. GM put out a service bulletin about it so we started doing it any time we had an intake off. It works way better than the rubber end gaskets. In the end, it's all about the money, and GM figured out that doing away with the end gaskets in lieu of silicone drastically cut down on warranty oil leak repairs.

Between that, the one piece rear main seal, and the head redesign with center bolt valve covers, the SBC series of engines really improved as far as being truly oil leak free.

DetroitIron · 12-24-2020, 02:05 PM

Thanks guys! Very helpful. I’ve owned this truck for 11 years and I’m starting to think about some projects over the winter that might include pulling the engine

Funny how these old squares become part of you....I don’t drive it much anymore but like to fix on it and keep the ole rusty pos running well for the occasional camping/canoeing trip in Northern MI

Pontiac1976 · 12-31-2020, 08:27 PM

I think maybe 87 was the first years that GM factory started to use silicone on some of the parts.

12-24-2020, 10:33 AM	#1
DetroitIron Registered User Join Date: Jul 2010 Location: Hudsonville, MI Posts: 174	Factory 350 Intake Gasket or RTV? Hi all I have an 85 K20 with original engine. I noticed while rebuilding the quadrajet that the front of the intake has a squished bead of black rtv visible. Would this have been done from the factory or might this be a sign that the original intake was off and resealed? Did the factory use rtv or the rubber like gaskets for the front and backed the intake manifold? Thank you for any insight __________________ _______________________________________________ 1985 Chevy Scottsdale K20 350 with 700R4 running 3.42 gearing aka "The Honey Badger" 1993 Silverado C3500 Ext. Cab Dually 6.5 turbo diesel

12-24-2020, 10:50 AM	#3
DetroitIron Registered User Join Date: Jul 2010 Location: Hudsonville, MI Posts: 174	Re: Factory 350 Intake Gasket or RTV? Thanks! The truck runs very strong for all stock and doesn’t burn much oil (just leaks here and there)or have any internal engine noise so I was wondering if it was rebuilt at some point....160,000 miles on the odo __________________ _______________________________________________ 1985 Chevy Scottsdale K20 350 with 700R4 running 3.42 gearing aka "The Honey Badger" 1993 Silverado C3500 Ext. Cab Dually 6.5 turbo diesel

12-24-2020, 01:21 PM	#4
Palf70Step State of Confusion! Join Date: Jul 2002 Location: Gulfport, MS USA Posts: 47,216	Re: Factory 350 Intake Gasket or RTV? Factory sets have a rubber front and rear seal/gasket. Personally I know of no one that ever used them when replacing the factory intakes. They just never stay in place well and leaked, so the black RTV across the front and rear was what I saw everyone use. __________________ Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God!

12-24-2020, 01:48 PM	#5
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	Re: Factory 350 Intake Gasket or RTV? I was a dealership mechanic a long time ago. My memory is fuzzy by now, but I remember us changing over to using silicone in the early 90s. GM put out a service bulletin about it so we started doing it any time we had an intake off. It works way better than the rubber end gaskets. In the end, it's all about the money, and GM figured out that doing away with the end gaskets in lieu of silicone drastically cut down on warranty oil leak repairs. Between that, the one piece rear main seal, and the head redesign with center bolt valve covers, the SBC series of engines really improved as far as being truly oil leak free. __________________ I'm on the Instagram- @Gearhead_Kevin

12-24-2020, 02:05 PM	#6
DetroitIron Registered User Join Date: Jul 2010 Location: Hudsonville, MI Posts: 174	Re: Factory 350 Intake Gasket or RTV? Thanks guys! Very helpful. I’ve owned this truck for 11 years and I’m starting to think about some projects over the winter that might include pulling the engine Funny how these old squares become part of you....I don’t drive it much anymore but like to fix on it and keep the ole rusty pos running well for the occasional camping/canoeing trip in Northern MI __________________ _______________________________________________ 1985 Chevy Scottsdale K20 350 with 700R4 running 3.42 gearing aka "The Honey Badger" 1993 Silverado C3500 Ext. Cab Dually 6.5 turbo diesel

12-31-2020, 08:27 PM	#7
Pontiac1976 Registered User Join Date: Oct 2015 Location: Ottawa, Ontario, Canada Posts: 766	Re: Factory 350 Intake Gasket or RTV? I think maybe 87 was the first years that GM factory started to use silicone on some of the parts. __________________ 1977 REG cab Long Bed with a 1984 Front Clip, 82 305 .60 over 9.0.1 flat top pistons, 4bbl, TH350, w/84 SS-intake & cam , w/ 1977 big block rad, 1975 gear box, 1984 master w/ metric fittings top & SAE fitting @ portion block, 1975 3.42 gear open diff. Duel 77-87 Factory air cleaner, duel inlet from rad support . Down sized 9' to new 8' Steel flat bed Was a 77 454 w/308 gear. Taken out 550 lbs. up front with motor clip change.



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