TSB for Additional Under Plenum Drain? - ZR-1 Net Registry Forums

Erik · 02-08-2021

I was given a link once to a TSB that was apparently for additional drainage under the plenum. However, the link was dead.

Any idea where I could find it?

Dynomite · 02-08-2021

Quote:

Originally Posted by Erik

I was given a link once to a TSB that was apparently for additional drainage under the plenum. However, the link was dead.

Any idea where I could find it?

3/8" diameter hole in the valley

GM Service Bulletin #92-307-6

Service Bulletin #92-307-6

Corvette95 · 02-08-2021

You know a trick I have done a few time although my plenum never really gets dirty, it run a long hard vacuum line up the valley drain and spray electrical clean up the hose, can also use brake clean but thats second choice due to the DIS.

Erik · 02-08-2021

Quote:

Originally Posted by Corvette95

You know a trick I have done a few time although my plenum never really gets dirty, it run a long hard vacuum line up the valley drain and spray electrical clean up the hose, can also use brake clean but thats second choice due to the DIS.

Good to know. Thanks!

Young1 · 02-09-2021

I use my rubber tip air blower on the pipe every time I do an oil change even though a dealer long ago drilled the hole.

Corvette95 · 02-13-2021

Yep, air works too. I like to do the cleaner to keep oil from building up but it?s risky but been lucky for years with it !

Sent from my iPhone using ZR-1 Net Registry

Paul Workman · 02-15-2021

Blue Loctite when torquing down the IH and the air breather dome does wonders too, far as preventing oil from leaking down into the valley in the first place. (Just sayin!)

Corvette95 · 02-15-2021

Quote:

Originally Posted by Paul Workman

Blue Loctite when torquing down the IH and the air breather dome does wonders too, far as preventing oil from leaking down into the valley in the first place. (Just sayin!)

I am glad YOU posted that Paul. I was going to but didn't want to take the heat for NO SEALANT ON PLENUM OR IH BOLTS REPLIES! After three additional torque sequences after install, yeah, next time, blue loc-tite for sure! Although dry as a bone after the third re--torque!

Gsgnz · 04-05-2022

Is it ill advised to drill this hole from the flywheel side?

Paul Workman · 04-07-2022

Quote:

Originally Posted by Gsgnz

Is it ill advised to drill this hole from the flywheel side?

I have read where some have suggested such a hole drilled there. But, I think not having a tube to channel the oil clear of the FW might be an issue. OK, I've watched this FORUM for over 15 years and have yet to see any followup from anyone who did drill an aux drain hole. But, preventing oil leakage in the fist place and/or periodically cleaning out the drain pipe (as suggested) appears to be a better solution(?) Just sayin!

02-08-2021	#1
Erik Join Date: Nov 2016 Location: New Brunswick Posts: 961	TSB for Additional Under Plenum Drain? I was given a link once to a TSB that was apparently for additional drainage under the plenum. However, the link was dead. Any idea where I could find it? __________________ 1990 ZR-1 # 996 "All Corvettes are red. The rest are mistakes." - John Heinricy

02-08-2021	#3
Corvette95 Join Date: Jan 2006 Location: Decatur, AL Posts: 1,119	Re: TSB for Additional Under Plenum Drain? You know a trick I have done a few time although my plenum never really gets dirty, it run a long hard vacuum line up the valley drain and spray electrical clean up the hose, can also use brake clean but thats second choice due to the DIS. __________________ Corvette95 Registry and Forum (*************) 1989 C4 Conv Wht/Gry Auto Hardtop Top Flight SOLD 1995 C4 Coupe Purple/Blk 6 Speed 1989 C4 Conv Wht/Red Auto SOLD 1996 C4 Conv Black/Tan Auto SOLD 1994 C4 Coupe Wht/Blk SOLD 1995 C4 ZR-1 White/Gry #278 Dual Dunn Head SOLD 1986 C4 Coupe Black/Red 4+3 SOLD 1990 C4 ZR-1 Red/Red #0454

02-09-2021	#5
Young1 Join Date: Sep 2016 Location: Ocala, FL Posts: 900	Re: TSB for Additional Under Plenum Drain? I use my rubber tip air blower on the pipe every time I do an oil change even though a dealer long ago drilled the hole. __________________ Steve Young 1991 ZR-1 Quasar Blue Metallic/Black #729 Second Owner 1991 ZR-1 Dark Red Metallic/Black #2040 SOLD 1990 ZR-1 Dark Red Metallic/Saddle #1670 SOLD Double your happiness.....complain half as much.

02-13-2021	#6
Corvette95 Join Date: Jan 2006 Location: Decatur, AL Posts: 1,119	Re: TSB for Additional Under Plenum Drain? Yep, air works too. I like to do the cleaner to keep oil from building up but it?s risky but been lucky for years with it ! Sent from my iPhone using ZR-1 Net Registry __________________ Corvette95 Registry and Forum (*************) 1989 C4 Conv Wht/Gry Auto Hardtop Top Flight SOLD 1995 C4 Coupe Purple/Blk 6 Speed 1989 C4 Conv Wht/Red Auto SOLD 1996 C4 Conv Black/Tan Auto SOLD 1994 C4 Coupe Wht/Blk SOLD 1995 C4 ZR-1 White/Gry #278 Dual Dunn Head SOLD 1986 C4 Coupe Black/Red 4+3 SOLD 1990 C4 ZR-1 Red/Red #0454

02-15-2021	#7
Paul Workman Join Date: Nov 2007 Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri Posts: 6,493	Re: TSB for Additional Under Plenum Drain? *Blue Loctite* when torquing down the IH and the air breather dome does wonders too, far as preventing oil from leaking down into the valley in the first place. (Just sayin!) __________________ Good carz, good food, good friendz = the best of timez! 90 #1202 "FBI" top end ported & relieved Cam timing by "Pete the Greek" Sans secondaries Chip & dyno tuning by Haibeck Automotive SW headers, X-pipe, MF muffs Former Secretary, ZR-1 Net Registry

04-05-2022	#9
Gsgnz Join Date: Apr 2021 Location: Colorado Posts: 21	Re: TSB for Additional Under Plenum Drain? Is it ill advised to drill this hole from the flywheel side?

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