1969 L-46 350/350 Hp Fuel Pump Bolts & Mount Plate

[Kevin S.]

Trying to determine if the fuel pump mount plate and the two larger upper bolts used to secure the fuel pump on my car are NCRS correct?

Both upper fuel pump mounting bolts on my car are the same size. My 5th edition NCRS book, P. 149, par. 2 states "one style bolt has a 7/16" hex and another style is a 9/16" hex". If I am interpreting this corectly, the book is saying the two larger upper bolts that hold the fuel pump to the block are 9/16" and the two lower smaller bolts that hold the lower mount plate to the block are 7/16" hex head bolts. I think I have that part right.

The two larger upper bolts are both exactly the same dimensions and type:
9/16" wrench, indented hex head with 3/8" x 3/16" wide integral split ring lock washer, zinc-plated with anchor head mark
3/8" - 16 x 1 1/2" long

Question #1: I thought the foreward bolt was longer so that it could be removed and reinstalled in the front of the block to hold the internal plunger rod for the mechanical fuel pump. Both of my bolts are 1 1/2" long. Seemed odd to me.



On to the mount plate PN 3719599 in my '69 AIM book P. J207 item #10 in detailed parts list. My NCRS 5th edition book says the mount plate is a flat natural-steel unplated plate. Mine is painted. no big deal, I can strip that off. I am not sure that the right mount plate is on the car. Is there a way to tell? Should there be a PN stamp, an embossed number or letter(s) stamped on the mount plate if it is original.

Question #2: Someone along the history of the car globbed on a gray silicone sealant all over the fuel pump mount plate I assume to stop a leak or prevent a leak. Makes me wonder if I have the wrong mount plate on the car. There is a PIERCE "made in USA" aftermarket fuel pump on the car now. It is being replaced with a correct PN 40658 fuel pump for a 350 Hp motor. I want to make sure that I have the right mount plate before I bolt on the NCRS correct fuel pump. I do have two new gaskets that go between the mount plate and the block and between the fuel pump and the mount plate.

Question #3: is it a good idea to put a little bit (of gasket sealant) on each side of the gaskets to help get a better seal or will the gaskets seal just fine all by themselves.

Questiion #4: My AIM book P. J207 shows the torque spec for the larger upper 3/8 - 16 x 1 1/2" fuel pump mounting bolts that secure the fuel pump itself to the block as 25-30 LBS FT. Okay that makes sense to me - they are good size bolts. However, the torque specs for the smaller 1/4" - 20 x 1/2" two bolts that hold the mount plate to the block are shown as 32-40 LBS FT. Is it possible a 1/4" dia. bolt the holds the mount plate has a higher torque spec than the 3/8" dia upper bolts that secure the fuel pump itself to the block. I sure DO NOT want to break off a bolt inside the engine block by following a torque spec that is wrong???

Note: I would normally put orange thread locker on all of these bolts just to help prevent them from loosening over time.

Thanks in advance for your input and observations.

Kevin

[James G.]

Re: 1969 L-46 350/350 Hp Fuel Pump Bolts & Mount Plate

Here is a discussion from 2009, https://www.forums.ncrs.org/showthre...h-1969-350-350
Long story short the plate was installed at St Louis, so it would not have gotten painted orange with the engine, I have seen them natural steel and also painted black.

[Kevin S.]

Re: 1969 L-46 350/350 Hp Fuel Pump Bolts & Mount Plate

Hey James,

Question #1 answered. Thank you for the link and the clarification on the mounting plate - painted or not painted. I've media blasted the orange paint off of mine and will reinstall it in it's natural-steel (no paint) finish. I did not see any PN stamp or manufacturer stamp under the paint. I assume that it is OEM until I figure out otherwise.

Thank you for the help on the fuel pump mounting plate.

Kevin

[Terry M.]

Re: 1969 L-46 350/350 Hp Fuel Pump Bolts & Mount Plate

Kevin, as you have observed the listed torque value for the 1/4-20 bolts is way out of line for that size bolt. I suspect the value given should be in pounds-inch See the standers chart offered in the link below.

https://www.fastenal.com/content/merch_rules/images/fcom/content-library/Torque-Tension%20Reference%20Guide.pdf

[Joe L.]

Re: 1969 L-46 350/350 Hp Fuel Pump Bolts & Mount Plate

Kevin, as you have observed the listed torque value for the 1/4-20 bolts is way out of line for that size bolt. I suspect the value given should be in pounds-inch See the standers chart offered in the link below.

https://www.fastenal.com/content/mer...ce%20Guide.pdf

Terry------


Yes, the specification of LB/FT was an error in the 1969 AIM. It was corrected in later model year editions of the AIM. It should read 32-40 LB/INCHES.

If one tried to torque these bolts to 32-40 lb/ft, one would likely snap off the heads of the bolts.

[Joe L.]

Re: 1969 L-46 350/350 Hp Fuel Pump Bolts & Mount Plate

Trying to determine if the fuel pump mount plate and the two larger upper bolts used to secure the fuel pump on my car are NCRS correct?

Both upper fuel pump mounting bolts on my car are the same size. My 5th edition NCRS book, P. 149, par. 2 states "one style bolt has a 7/16" hex and another style is a 9/16" hex". If I am interpreting this corectly, the book is saying the two larger upper bolts that hold the fuel pump to the block are 9/16" and the two lower smaller bolts that hold the lower mount plate to the block are 7/16" hex head bolts. I think I have that part right.

The two larger upper bolts are both exactly the same dimensions and type:
9/16" wrench, indented hex head with 3/8" x 3/16" wide integral split ring lock washer, zinc-plated with anchor head mark
3/8" - 16 x 1 1/2" long

Question #1: I thought the foreward bolt was longer so that it could be removed and reinstalled in the front of the block to hold the internal plunger rod for the mechanical fuel pump. Both of my bolts are 1 1/2" long. Seemed odd to me.



On to the mount plate PN 3719599 in my '69 AIM book P. J207 item #10 in detailed parts list. My NCRS 5th edition book says the mount plate is a flat natural-steel unplated plate. Mine is painted. no big deal, I can strip that off. I am not sure that the right mount plate is on the car. Is there a way to tell? Should there be a PN stamp, an embossed number or letter(s) stamped on the mount plate if it is original.

Question #2: Someone along the history of the car globbed on a gray silicone sealant all over the fuel pump mount plate I assume to stop a leak or prevent a leak. Makes me wonder if I have the wrong mount plate on the car. There is a PIERCE "made in USA" aftermarket fuel pump on the car now. It is being replaced with a correct PN 40658 fuel pump for a 350 Hp motor. I want to make sure that I have the right mount plate before I bolt on the NCRS correct fuel pump. I do have two new gaskets that go between the mount plate and the block and between the fuel pump and the mount plate.

Question #3: is it a good idea to put a little bit (of gasket sealant) on each side of the gaskets to help get a better seal or will the gaskets seal just fine all by themselves.

Questiion #4: My AIM book P. J207 shows the torque spec for the larger upper 3/8 - 16 x 1 1/2" fuel pump mounting bolts that secure the fuel pump itself to the block as 25-30 LBS FT. Okay that makes sense to me - they are good size bolts. However, the torque specs for the smaller 1/4" - 20 x 1/2" two bolts that hold the mount plate to the block are shown as 32-40 LBS FT. Is it possible a 1/4" dia. bolt the holds the mount plate has a higher torque spec than the 3/8" dia upper bolts that secure the fuel pump itself to the block. I sure DO NOT want to break off a bolt inside the engine block by following a torque spec that is wrong???

Note: I would normally put orange thread locker on all of these bolts just to help prevent them from loosening over time.

Thanks in advance for your input and observations.

Kevin

Kevin-----


Both upper bolts were GM #3778526 and, therefore, of the same length. GM never provided "assistance" with a bolt used to retain the fuel pump pushrod when changing the fuel pump. The installer has to come up with their own bolt ( I use a nylon or brass bolt to prevent nicking the pushrod). Your bolt head looks correct as these were unusual GM 275M material grade bolts with indented heads.

The fuel pump mounting plate, GM #3719599, did not have an embossed GM part number. Most did not have any manufacturer's ID mark but I have seen a few with such a mark (an "A" or an "M" as I vaguely recall). My 1969 did not have any manufacturer's ID mark.

By the way, the 3719599 plate, originally released for the 1955 model year, remains available in SERVICE to this day------68 years after its release! However, I believe current examples are supplied painted black (probably to prevent rust while in SERVICE stock).

It's a good idea to apply a SMALL amount of oil resistive sealer to both sides of the gasket between the plate and the block as oil seepage is often seen here. No sealer is necessary on the pump-to-plate gasket.

If you use thread locker on the bolts, use BLUE, not red. You may need to remove them someday.

[Kevin S.]

Re: 1969 L-46 350/350 Hp Fuel Pump Bolts & Mount Plate

Hi Terry,
Wow, what a nice reference guide to have for torque specs.

Question #4 answered: I'm in agreement with you and Joe that it must be a typo in the AIM and should have been listed as LBS IN, rather than LBS FT for the lower two 1/4" - 20 x 1/2" bolts to secure the mount plate. Snapping off a bolt in the block = a really bad day.

Thank you.

[Kevin S.]

Re: 1969 L-46 350/350 Hp Fuel Pump Bolts & Mount Plate

Hi Joe,

Question #2 answered: Looks like I have the correct fuel pump mounting plate on the car. After media blasting and polishing, I applied a light coat of matt clear acrylic laquer to both sides of the mounting plate to prevent future rust. Looks like "natural-steel" as intended.

Question #3 answered: 10-4 on the oil resistant sealer on both sides of mounting plate between plate and block. No sealer necessary on pump-to-plate gasket. That makes sense to me.

And finally, I have blue thread locker. I will use that instead of orange or red on the fuel pump bolts.


Thank you Joe. Appreciate you sharing your knowledge and experience with me. Thank you!

I am on my way again - thanks everyone for helping me out.

Kevin