[Jack_K]

1980 with a newly rebuilt .030 over 305, flat top pistons, Edelbrock Performer cam, Performer intake, Holley 80570 (570 cfm) carb, CompCam roller rockers, stock fuel pump (new), HEI distributor, ported vacuum. Yeah, I know I should have built a 350 instead, but it's over and done.

It has a decent idle at 800 RPM but has a slight miss. The vacuum is steady at 15 psi. That's a bit low. Advancing the timing doesn't increase the vacuum so I assume it's because of the cam timing.

The fuel pressure is jumping wildly around 10 psi to maybe as low as zero, but it's hard to tell exactly. It seems to vary in sync with the RPM (high to low in sync with the cam lobe driving it) best I can tell

When I shut the engine off the pressure gradually drops to zero over a period of about 30 seconds. I thought it should maintain pressure? The fuel pump is a standard 2 line (inlet and outlet) design with no return line. After the car sets awhile it takes several cranks to get the fuel pressure back up to where the engine will start. Does that mean the fuel bowl has leaked dry?

Both carb fuel bowls have the float level set to where fuel almost runs out the sight hole. This is how the manual with the carb says they should be set.

The exhaust smells good at idle with no black smoke. Throttle response is fairly sluggish. It doesn't rev as fast as I think it should. A friend said he thinks the carb is starving for fuel and recommends an electric fuel pump. I think it's a carb problem, but no idea.

What do you guys think?

Jack

[edit] No charcoal cannister, just open return line.

 

[1980SteelBeast]

I wouldn't say just jump into an electric fuel pump so fast. I'm more concerned on why you oil PSI is so low. What type of oil pump do you have? I think a 305 should have at least 20psi with a max of 40-45psi.
When's the last time you changed the spark plugs,oil,and fuel filter?
Are you running a QJET? Has the in carb filter been changed?

 

[woody31]

I wouldn't say just jump into an electric fuel pump so fast. I'm more concerned on why you oil PSI is so low. What type of oil pump do you have? I think a 305 should have at least 20psi with a max of 40-45psi.
When's the last time you changed the spark plugs,oil,and fuel filter?
Are you running a QJET? Has the in carb filter been changed?

he is referring to fuel pressure beast ,,,(read again beast he said holley) no it will not hold pressure unless you have a check valve,,, soundsl like fuel leaking into intake,, double check float bowls, and all vacuum lines as for slight miss, what kind if cam is in it??:beer:

 

[JJLT1]

sounds like a bad fuel pump,, maybe trash in the outlet valve..
what is the initial timing at,, and i'd switch to manifold vacuum and check the curves..:texas:

 

[Jack_K]

he is referring to fuel pressure beast ,,,(read again beast he said holley) no it will not hold pressure unless you have a check valve,,, soundsl like fuel leaking into intake,, double check float bowls, and all vacuum lines as for slight miss, what kind if cam is in it??:beer:

Oh no, Woody. he said it's an Edelbrock Performer cam (read again Woody).

Jack

 

[Jack_K]

sounds like a bad fuel pump,, maybe trash in the outlet valve..
what is the initial timing at,, and i'd switch to manifold vacuum and check the curves..:texas:

New fuel pump and new fuel line. I may run manifold vacuum later, but I think it has nothing to do with this problem (IMHO).

 

[Jack_K]

I wouldn't say just jump into an electric fuel pump so fast. I'm more concerned on why you oil PSI is so low. What type of oil pump do you have? I think a 305 should have at least 20psi with a max of 40-45psi.
When's the last time you changed the spark plugs,oil,and fuel filter?
Are you running a QJET? Has the in carb filter been changed?/QUOTE]

Fuel pressure, not oil pressure. New plugs and wires. Oil and filter changed right after break in. That was about 50 miles ago.

 

[woody31]

could be a bad lobe on the cam??:beer:

 

[Jack_K]

could be a bad lobe on the cam??:beer:

I guess it could be. I broke it in at 2000 -2500 RPM with ZDDP added to the oil.

 

[woody31]

start on pulling valve covers and checking visually if you see any problems under adjusted over adjusted?? rockers it would be helpful if you could post a video:beer:

 

[Jack_K]

start on pulling valve covers and checking visually if you see any problems under adjusted over adjusted?? rockers it would be helpful if you could post a video:beer:

A video of what?

 

[woody31]

ummm of it running so i could hear the miss

 

[steelybill]

It's unlikely that fuel could be siphoned from the carb bowls after shut-down. Sounds like your new pump has a problem with one of the check valves in it, and maybe that's the reason for the erratic fuel pressure readings (?) Just a thought.....

Have you looked at the spark plugs ? Maybe one looks different it that cylinder has a miss-fire etc.

 

[woody31]

it should still start with the fuel in the bowls - it may be boiling out after shut down- perhaps a spacer is in order:beer:

 

[464elky]

Woody is right in that the engine runs off the fuel in the bowl not from the fuel coming in from the pump directly like a fuel injection setup. The fuel bowl/float works just like the water tank and valve in your commode. An electric pump won't fix the running/starting problem you are describing unless the pump is not maintaining the fuel level in the bowl and it is actually running out of fuel.
X2 on re-setting the valves with it running.

 

[Jack_K]

A video of what?

First video should be here:
http://youtu.be/u4MZ0QDOJoo



Second video should be here:
http://youtu.be/zvM4zMYV7Zw

 

[80v6]

Miss at idle.

Is it a miss or does it sound like a popping sound? Popping sound is to rich at idle. Edelbrock tech says a real slight lump to the idle with this cam. Since you put it in a 305, the cam will seem just a might bit "bigger/lumpier" than in a 350. If vacuum is steady like you say and there is no valve train noise, run it for a while and see what happens.

 

[80v6]

Holly carb

According to my holley manual, there is no 80570 listed. If its an 80507 (just a thought) this is a 4150 390 cfm carb. Possibly reverse idle.

 

[woody31]

sounds fine to me but im from texasoke:really it sounds good like said above that cam will act bigger in a smaller motor, does it smooth out when you rev it up to about 2500 if so id say it is cam lope your hearing not a miss:beer:good luck

 

[Beepster]

Jack, just as a querry, did you know that roller rockers don't require a break-in or ZDDP? That's one of the design benefits.

I have a Holley 600, and it holds fuel. BUT, I also use a spacer on a Performer intake (350). This is the '56. It will start and run about two seconds. Then it needs fuel from the pump to keep it running. That's because I only start it about two times a week (maybe). My Elky is a horse of a different color - full of problems that are slowly being resolved.