How do I get the top off this Holley carb?
 

Eng running very rich and doesn't want to idle.
Discovered eng would still run with both idle mixture screws closed so I need to open it up and inspect/cln. Can't figure out how to get the top off. It's loose on both ends, but seems to be held together in the middle near the choke plate area. Surely I don't have to drill some plugs out..

If someone could identify what model it is, that would be helpful too..

Thx for any help!

Ya may need to remove the center stud that holds the flame arrestor on. hf...

Well after doing a few quick searches on this carb, the only thing that I found so far is that its a MODEL 4010 and cfm is 760. But that came off of a guys web site so the info is as good as it is, I personally can verify the info but it sounds good, hope this helps a little.

center stud. Remove it.

Looks like something Ford would have used on their marine engines back in the day

Thx for help with identifying the carb.
I was able to confirm it is a 4010 model. Re-build kits are not to be found locally. Will take a few days to get one.
Is there a way to confirm if a power valve is bad or not with it removed from carb?

After the kiddo goes to bed, I'll go back out to the shop and remove the center stud:eureka:

not to be a downer but I have had several of these model carbs and tossed them all. they were not very good which is why Holley stopped making them. if it is clean inside and rebuildable I would use it but if you find any issues with it like corrosion, etc. get rid of it and buy a 4150 model.

I agree with what Compedgemarine said...Not one of Holley's better carbs..

I agree

I'd wrap it up and give it to your Mother-in-law for Christmas.

id give it the sink test:party-smiley-004:

fixx
 

or what i di is the bat test,,then the .500 mag test..

This oddball Holley isn't at the top of my wish list either, but that's what I have for now.
I did find on the net that they were originally designed for Ford by Holley. Then Holley started making their own version later.

Anyway, got it apart and the insides look pretty good. No corrosion at all.

I think the primary power valve has a ruptured diaphragm. I squirted some carb cleaner into one of the 2 holes and it appeared to be leaking thru to the other side of the diaphragm. Didn't see any check valves to prevent power valve damage during a backfire. Must be pre 92.

The current power valves are 6.5's so I shouldn't have a problem finding them locally.

Does the power valve determination formula (manifold vac/2) apply to marine engines?
I haven't measured my vacuum yet, but I'm assuming it"s >13"...

yes,,i try to find a maximum vacume at a higher rpm and divide by 2 and that would be your power valve number..