With advice from this forum (Thanks), I replaced the gaskets and heat shield for my Rochester carb (69 427-390). While doing that it became apparent there are some other fuel line problems I need to address. I want to correct the fuel lines from the fuel pump to the carb.

1) The in-line filter on the outlet of the fuel pump is not the same item as is in the mail order/on-line catalogs. There is a Hastings GF-19 installed - it appears similar to the GF-432 they carry, but I havent successfully cross referenced that. At any rate, it is not supported by anything but the fuel inlet, outlet and return lines. The on-line suppliers sell a bracket for the filter. What does this mount to? Can anybody post some photos? (I have the AIM, but it didnt give much detail)

2) There was no filter in the carburetor. I've seen at least two types available for this. Which is recommended? Or should I leave it out?

3) I want to make sure the fuel return line is open. With the gas cap off, is it safe to apply very low pressure air (1/2 psi) to verify it is open?

I have also noted a buildup in pressure in the fuel tank, which pushes fuel through the lines. Reviewing previous threads I learned that gas caps changed between 69 and 70. I suspect mine is from a later year, so I've ordered a replacement.

 

The GF-432 from Paragon is a bit pricey. However, they also have a cheaper filter that is not quite correct. Forget that stupid bracket...it is only for small blocks. Over on the NCRS board this has been discussed several times and there is no way to attach the bracket to the AIR mounting. The AIM only shows it on the small block, but not really where it attaches. For L36, it doesn't show it at all. The NCRS TIM & JG says it should be there, but then again they do not mention that is only for small blocks. These on-line vendors have sold a pile of those brackets, which are now just sitting in our unused parts boxes. Nobody has ever seen that bracket on an original '68-'69 L36.

I'm still looking for the small metal clip that holds the metal supply and return lines together underneath the filter.

 

Thanks for the info.

I've decided it best to install the carburetor filter. I can find the filter itself, but havent been so lucky with the spring that holds it in place. Does anybody have a part number for it?

 

You can get it from Carbs Unlimited. The other thing you can do is to break open a junk Q-Jet Choke Pulloff from '69 (one of the plastic ones) and use the spring out of it - it is almost identical to the fuel filter inlet spring.

Lars

 

Thanks. Filter is installed - no leaks - car ran good on a short road test. Now I'll just have to wait for warmer weather and see how it behaves.

 

OK - I still have the problem when trying to start when the engine is hot. So, next step will be a carb rebuild. I've been searching the forum and gather Lars is no longer doing this. There are a number of other recommendations, but I've also received some pretty strong recommendations for a local shop, so I will give them a try.

Question - the on-line catalogs have carb mounting kits that consist of 2 longer bolts (front of q-jet?) and 2 studs. My carb is mounted with 4 bolts - 2 long in the front and 2 short in the back. Other than originality, does this matter?

 

Some thoughts:

If you're not going to use the original in-line fuel filter, AC Delco GF-432, and instead use a filter in the carb, what did you do for a fuel line? What are you going to do with the return line? Or did I miss something?

If your Vette was equipped with the GF-432, the peanut filter at the carb would not have been installed. Q-Jets of that era used only one or the other.

Q-Jets had long mounting 'bolts' in front and either (shorter) studs or bolts in back.

If you suspect a clogged return line, disconnect the rubber hoses at the tank and at fuel filter, and blow out the steel line. They DO clog up being 1/4" dia.

Pressure in the fuel tank is common on 1970 and earlier Chevys. Heat from the exhaust, agitation (sloshing) from driving, and changes in atmospheric pressure, will all conspire to create some "whoosh" when you remove the fuel cap. Nothing to worry about.

Fuel caps prior 1971 are "vented" which will allow air into the tank to replace spent fuel. A vented cap does not allow fumes from the tank to escape for obvious reasons (except if under a lot of pressure).

Difficult 'hot-starts' could be a lot of things incuding the carb. Do you have the correct carb mounting gasket "sandwich" which included the four-hole stainless heat shield? (Required if you're running the factory 1969 Q-Jet intake manifold and exhaust crossover set-up).

 

- Right now, both filters are in - fuel pressure (lack of) is one problem that does not exist.
- The bypass line has been check to be open (lp air).
- The carb was pulled a few weeks ago to check the gasket / heat shield assy. It was in place - the 3rd gasket was added as suggested by Lars to create the "sandwich".
- The gas cap was replaced as it was clearly the wrong type (stamped in the cap). There were several inches of pressure buildup in the tank (i dont know what's considered excessive) as evidenced by fuel being pushed several inches above gas tank level in the fuel line.

The problem of carburetor flooding (which literally includes fuel flooding onto the intake) when trying to start the engine hot still exists.

The use of studs on the back of the carburetor would make locating the gaskets easier during reassembly. Other than that and a possible "originality" question (which from your post doesnt sound like it exists) - i wasnt sure if there was any effect on torque requirements for securing the carb to the intake.