Holley help- 3 days to Power Tour!!!

[strangler]

Fresh 396, 10.5:1, too large of solid FT cam, MSD, etc.

Engine ran great on a test stand with a 1407. I bought a Holley 770 Street Avenger and just fired it up and i'm way too rich.

I have taken some shortcuts in order to get this car up and running for PT this weekend, some of which include:

I zip tied the electric choke open

I removed the brass fuel filters in order to use a Summit dual-feed kit

I dont know what jets are even close as I bought the carb used- currently 73 primary 84 Sec

primary fuel trim screws are happy around 2 turns out (highest rpm) while the secondarys need to be merely cracked to acheve that same highest rpm..... and I understand that all 4 corners should be the same.

My major question.... is there more to the choke than just the throttle blade? Is it utilizing an enrichment circuit of some sort? Way too rich and unresponsive to mixture screw tuning. Float levels look good and I'm using a Holley mechanical pump. Thoughts? Thanks for any insite. -Scott

[MrQuick]

Is this a double pumper?
Did you backfire it at all? blown power valve?

The choke horn blade is the enrichment and the choke cam has stepper on it to keep the idle up. Push the red lever down.

[JD'sTT55]

The choke has no other enrichment other than restricting airflow through the primary's and increasing primary throttle blade position for faster idle.
According to what I found the 770 should've came with 72 primary and 75 secondary jets. And should be lowered 1 step for every 2000 ft. In elevation change. Your particular engine may have different fuel needs. The power valve would be a good thing to check. If ruptured would make it way rich. But usually when ruptured turning the idle mixture screws doesnt change much. I have had problems with used Holleys that have had gaskets shrink between the main body and metering blocks when filled with fuel and used and then sitting with out fuel for a while.
Also you didn't mention it but did you put a comparable fuel filter in line where you took out the brass Holley ones? I'm guessing you did but just thought I'd mention it to be sure.

[Chevelle598bb]

The street avenger has power valve blow out protection an of the power valve was ruptured the engine would not run. First thing to do is break it down and make sure no gaskets need replacement. I would also open up the secondary throttle blades a small amount. Then set the idle mixture screws. All should be out the same amount. Sometimes with a big cam you have to open the secondaries a bit at idle for more airflow. Ideally you want te secondaries and primaries open the same amount on a four corner carb.

Of course make sure your timing is correct before setting the carb. If you change the timing you need to retune the carb.

[strangler]

Thanks for all of the ideas guys- you have been a lot more help than the Holley tech line.

I put my Edelbrock back on and attended a couple days of PT, but now im back in the shop and really want to figure out what is wrong.

I'm only pulling 5 of vacuum, which Holley said will never idle below 1800 (my Edelbrock idles nice at 850??)

I switched to the stock sized jets- 72/75

I opened the rear plates until I can just see the slot, same with the front

I set all 4 screws to 1.5 out

Currently it will only run with a constant feathering of the pedal - essentially only run on the squirter.

It is completely unresponsive to changes of the mixture screws.

Seems to run nice from 2000+, crisp and clean, but no fuel is being delivered at idle. The power valve is not blown, the gaskets apper to be sealing everything, carb spray has revealed no vacuum leaks, and I sprayed the air bleeds with spray and compressed air. Any other thoughts? Thanks again -Scott

[strangler]

Mod, this can be moved to the carb section now, as its less of an emergency and more of a tuning issue. Thanks.

[dcozzi]

Have you checked for debris and casting/machining flaws?

After a reread, you need more vacuum for a Holley.

[AM.MSCL]

If you are only pulling 5lbs of vacuum then you need to drop your power valve down to a 2.5 (if they make them that low). Most Holley carbs come with a 6.5 PV to be used with 13 or more lbs of vacuum.
Is your cam so extreme that 5 lbs of vacuum is all you are going to be able to get?

[strangler]

Would a bad float bowl-to-metering block gasket on the primary side cause the idle circuit to not want to pull fuel? One gasket is questionable, directly above the plastic transfer vent. 12 o'clock.

[sam 74]

change your power valve to a 2.5 like mentioned above, Holleys usually come with a 6.5 from the factory and your vac is just letting it stay open. my engine idles with 6.5-7 inches of vac at 1000 rpm and i have a 4.5 PV in my carb.