If you use a 3/8 extention and socket you can sort of guidle the bolts in place.  A bit of good dexterity and you can get them started.  You can reach in there to do this, but you may need to try from several different approach angles.  It's really not that bad.

Just be sure to see the fuel pump push rod is in the up position.  If it's down you won't get the pump lined up and the bolts started.  You can turn the engine by hand and lift on the push rod at the same time to be sure it is up.  To keep it there, there is a bolt in the front of the block that can be removed, and a longer bolt installed finger tight to hold the rod in place.

If it drops and you can't lift it, just take the remaining two bolts off the plate the pump bolts to, and remove the plate.  Then you can access the rod.  It may fall out.  If you don't want to use the bolt to hold it, if you took it out you can coat it with wheel bearing grease and stick it back in place.  That will usually hold it up.  When you put the plate back, be sure to start the fuel pump bolts, without the pump, to know the plate is lined up when you tighten the bottom plate bolts, or you may stop yourself from getting the bolts started.

I just replaced my fuel pump in my 78,last weekend,the easiest way to get at the bolts for the pump is;remove the wheel,there is an opening were the brake line comes frome the top of the frame to the rubber brake hose,the opening is more than wide enough ,if you look through the opening,you will see the pump right there in front of you ,I used 2 ,6 inch extensions, piece of cake.the thing I had the hardest time with was,breaking loose the nut on the pump where the fuel line attaches,you need 2 wrenches 1 to hold the pump fitting and a flare nut wrench for the line nut,use a liberal amount of PB Blaster and let it soak for a while.I took off the flat plate afterwards and took the pump rod out and greased it and put it back in ,it will stay up for a while.I bumped the engine over with the starter until the rod was in the up position,I have A.C. and a free wheeling fan so I couldn't use the fan blade to turn the motor over by hand.as long as you have the steel line off and the fuel drained out,it's a good time to take the other end of the line at the carb off and change the fuel filter .I got my fuel pump and filter at ADVANCE AUTO $27.00 plus tax and about 2 hours install time,it won't take you that long if everything goes smoothly,but it is a 26 year old car,and nothing ever goes that way,good luck ,any problems ,give a shout

C3VR Lifetime Member #93

That sounds like the acellerator pump in the carb.  With the engine off look down past the choke plates.  At a moderate speed, fully open the throttle. You should see two continous jets of fuel shoot into the carb.  If not, repair the acellerator pump.  How?  Look at

www.vetteprojects.com   under Ken's projects.

The front vacuum pulloff is the primary.  If you have a rear one, it's the secondary.  

The primary is used to open the choke a small amount at startup to prevent it from running too rich until the choke coil starts to open the choke place.  The secondary can do the same thing,  but it's staged.

Both of these have an additional function.  When retracted and fully pulled in by vacuum, the secondaries won't open.  As manifold vacuum drops, the secondaries are allowed to open.  This is not controlling by the secondaries plates, but the air flaps.  If one of these pulloffs is failed, the car can bog.

How much impact will fuel pressure have?  Most postings about bog include suggestions to check fuel pump pressure to be in the range of 4 to 6 psi.  I also have an Advanced Auto fuel pump that pumps a volume of 12 oz of fuel in 30 sec at 4 to 6 psi.  However, the shop manual and Chiltons says my 78 should have 7.5 to 9 psi.  I'm working on a bog problem at acceleration and feel it must be a fuel starvation problem. 

Just got back from Advanced Auto doing some research.  Turns out each fuel pump is factory set for a specific pressure setting.  Mallory has one for 78's at 6-8 psi. and Holley has one for 78's set at 14 psi.  I believe mine is set for 4-6, which is too low.  For $65 I think I'll try the Mallory and hope that a little extra pressure will fill the bowl quicker.  If not, then more work on the carb.  Thanks, Wil.

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Thanks Dave and Joel, your comments are helpful.

Last night I did another test, I think Ken suggested this.  Put a tee and pressure gage in the fuel line between the pump and the Q-jet.  At idle I have 3 to 4 psi.  While driving at low rpm the pressure drops to about 1 psi.  At acceleration the pressure continues to drop to less than 1 psi then as low as 0 and then the engine bogs.  Now I'm back to "look for a restriction in the fuel delivery".  Can the metering unit, pick up and screen be removed from the fuel tank without removing the tank?  Is there a way to check and/or clean the "sock filter" / screen in place?  I think Dave is right, I need to do some more work before changing the pump.  Thanks, Wil

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Well last night I did more fuel line delivery tests with a pressure gage between the pump and Q-jet.

1) 5.75 psi at idle, warmed up, both with gas cap in place and with it removed.

2) Took the supply line off at the pump and installed a temporary fuel line from a clean 5 gal gas container to the fuel pump.  Now the pump is up to 8 psi at idle, warmed up.  Nice.   I think this means Dave is right and the pump is not the problem.

3) I siphoned a gal of gas out of my fuel tank off the bottom to see if I would pick up any dirt or debris.  Put it thru a coffee filter and there is no dirt, just clean gas.  So I don't think the tank is loaded with rust or debris.  Also, I never find anything in the filter on the carb.  Is it possible that the pick up line is moving and pulling air?

4) I put some compressed air on the supply line pushing back toward the tank in hopes of pushing any clogs off the "sock" filter.  Reattach the supply line and now have 6 psi.

5) Test Drive.  Fuel pressure now responds correctly to RPM.  As RPM goes up the fuel pressure goes up from min of 6 to a max of 8 psi.  Sweet, no Bog.  It's gone.

6) Another test drive just for the fun of it.  No bog.

7) Next move is to get into the tank, replace the pick up filter and make sure the tank is clean.

Joel Adams
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Sorry I havent been on for a while.  Sounds like you found it.

But just one more thing.  Not only can the tank filter (sock) cause this, so can a small air leak in the line fairly high up on or near the tank.  It drops volume due to sucking air instead of fuel, but won't show a leak due to the higher location.

Also you need to watch for neoprene (rubber) hose.  A short section is fine, but longer sections can sometimes collaspe under high flow, and cut off the supply.

Neither of these seem to be any part of your problem, but I wanted to throw it in there for others who may have the same symptom.

[QUOTE=Adams' Apple]Sounds like you are on the right track, Wil!
There doesn't have to be any trash in the tank to stop up the filter there. Over time, fuel deposits will accumulate there, and turn to muck. I'll bet a new pick-up fliter will solve your problem. [/QUOTE]

another problem ive seen is collapsing lines..  an old worn out section of rubber line will collapse internally under suction..  looks fine from the outside.

The tank is now on my garage floor.  The strainer has what appears to be red rust clogging it.  My tank, with original build sheet on it, has an internal bladder.  The bladder has large cracks at both ends.  That is probably how the rust started showing up.  I assume there is no way to repair the bladder.  I'm having trouble finding a replacement fuel tank for the 78.  The hard decision is; I would like to keep as many original parts as possible but I don't want to pull the tank in the future if something fails.  So do I replace parts or not?  Metering unit looks good, it just has old rubber and a film of rust.  The tank does not leak but with cracks in the bladder it may not last long.  Fuel lines look ok except the soft connection lines that must be replaced.  My goal is to keep it as a reliable cruiser.  We just enjoy taking it out for rides.

You are right, no 78 fuel tanks to be found, so I'm planning to clean and reuse for now.  At the time I pulled the tank it seemed hard but now that the tank is out it seems easy.  Here are some of the leasons learned. 

The books say remove fuel lines to the metering unit before dropping the tank.  However, there is limited access to the lines.  So, what I did was drop the tank about 4 inches and then cut the rubber connection lines.  They are short, inexpensive and easy to replace after the tank is out.

The tank support rail is held in place with two bolts at each end.  The bolt heads are inside the frame rail and difficult to prevent from turning while loosening the nuts.  I made a tool with a socket, a piece of 3/8 key stock 3/4 inch long, a flat sheet metal wrench (dog) and some duct tape to hold it together (don't drop your socket inside the frame or else say good bye to it).  You'll understand when you see the small access hole on the side of the frame.

There is a fuel line clip inside the rear fender well on top of the frame member.  You can not see it, but removing it allows some flex in the fuel line during removal. 

Common sense, hydraulic jacks, patients and plenty of liquid wrench will take care of the rest.

  Thanks for all the help.  My bog problem is gone.  Two days of test drives and no more problem.

It was the strainer on the metering unit.  I cleaned the tank and replaced the entire metering unit (with a new strainer) while it was out. Problem solved.

Thanks again for all the help. 

Wil

Joel Adams
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"