superdave269

I wanted to post an update. I received the carb back a couple of days ago. I put it back on and just took it for a test drive. It runs much better. No more popping or bucking. It has nice throttle response. My car is not 100% though. When I rev it up or down shift instead of bucking it now has a flat spot. This is a lot better but not perfect. The flat spot is around 3750-4000 rpm. So for now it looks like I will have to shift when I hit that spot. The car is really moving by then but I wonder how much faster it would go if I could get more RPMs out of it. I wonder if I put the gold Mr. Gasket distributor springs on it will help. I plan on doing this soon. Any other ideas?
Oh yeah a big THANK YOU to LARS for all of the carb help. He saved me from doing more harm than good as I was going to re-jet the carb no doubt making things worst.
If I drive the car civilized it drives fine, but you don't buy a big block corvette to always drive civilized do you?

lars

Dave -
Sounds like the classic fuel starvation problem. You can do a couple if things:

First, pull the inlet checkvalve out of the fuel filter in the carb. If your fuel pump is a little weak, removing the filter checkvalve will provide a little better fuel flow.

If that doesn't do the trick, install an inexpensive electric fuel boost pump back by the tank (after you verify that you do not have any kinked or damaged fuel lines or rubber hose connections). This tends to solve the high-rpm lean-out which is very common on these cars.

Lars

...Roger...

Great right up Lars,thanks for posting,how can anyone think your jerk ?

Superdave -looking at the pic you posted above , that old EGR valve would get my attention as soon as I opened the hood. Not saying its bad but they do carbon up and hang open causing bad running conditions.

7t2vette

Nice work Lars, but I have to say I am a little disappointed with your methods.......since when did you start using a digital A/F meter?!?! The Lars I remember relied on his eyes, ears, and nose to tune cars...must be getting soft in your old age!!!!

Next time you are up here, a few cold one's on me!!

superdave269

Thanks for the tips. Do I just drill out the check valve in the gas filter? Do I pull it out with needle nose? I think I have an old one around I can check out.
I never thought about the EGR valve. I'll look for a new one too.

...Roger...

EGR problems is more of an idle thing,if it is sealing you could just remove the hose and plug , then drive it.

7T1vette

No need to drill on the check valve. I think it just pushes into the end, so you just pry it out.

Also, check to see if the "S" shaped fuel hose on the pump is the proper molded hose...or if it is just straight hose that is bent around to make it fit. If it is the latter, it will be kinked in the turns and that will block fuel flow. You really need the correct molded part in that application.

scottyp99

Sometimes, when you fix one thing, you find that it had been masking something else, and now it's symptoms can be seen. It's all part of the tuning process.
Doesn't make it any less of a pain in the neck, though, does it?


Keep the shiny side up!
Scott

...Roger...

One thing is for sure since Lars checked it out,you know its not the carb.

superdave269

I just checked out the EGR valve. I put my vacuum pump on it and it moves fine. I did destroy the gasket though. Its back on with out one now.
I did not see any check valve in the paper gas filter, looks hollow to me.
Burns out are no problem, just high RPMs are a problem for now. I know we will figure it out.
It has a metal fuel line right up to the carb. I know what you mean about a kinked line though.
I think LARS is right about the fuel pressure. When I took it out earlier the first thing I thought to myself was this thing isn't getting gas, so I filled the tank just in case it was to low and sloshing around instead of getting to the carb.
I never put in a booster fuel pump before but I have the feeling that I will be doing that soon.

cardo0

If u ever decide to reman Qjets full time u will have a full time business.
Makes me jealous as i have plenty of good core Qjets and not enough time to rebuild one. But at least i have plenty of spare carb parts. Lately a lot of the 800cfm carbs with APT.

Super D, if your timing is "all in" by 3000rpm (like i expect) then changing spring won't help. U could check this with timing light but don't rev to 4,000rpm in neutral (and u shouldn't have to) - just not good for the vlv train. If lars just set up the carb then i would look else - ignition yes but also compression and leak-down tests. Vlv springs?

Thx again lars,
cardo0

superdave269

One of the problems that I was having was the mechanical fuel pump (from Pep Boys) was defective. It is made by Carter but wasn't putting out any real pressure. I took me a while to figure it out because I assumed it was new(9 months old but only 150 miles on it) so it must be good. I now have NAPA fuel pump and a Mr. Gasket#12S booster pump by the tank. I now have good fuel pressure.
This car reminds me of the movie the Money Pit. Honestly as soon as I think I have one thing fixed I have to start on another. Good thing it's a toy and not my only transportation..

6inarow

Lars, your PM box is full. Can you help me with thw quadrajet on my 72?

lars

Just e-mail me. I don't know what "PM," "IM," "Twitter," "Facebook," "MSNMessenger," "LinkedIn," and all that BS crap is. Hit the "eMail" button and send me a note or give me a phone call on my well-publicized number. I drink Martinis, smoke cigars, restore Vettes, build carbs, and repair tach-drive distributors. The kids can play with the IM, PM, and all the other stuff. I'm working, helping enthusiasts, and having a good time.

Lars

Big2Bird

Tuning for Martinis just sounds wrong Lars. How you doing these days? J

...Roger...

IMO all this new stuff is stressful and often dangerous.