Holley 650 jetting help

[Odmark]

Hello! As some of you might remember, my neighbour gave me an old Holley 650 double pumper he had laying around.

I test fired the engine with the carb and it ran good. Better idle than my old edelbrock, and waaay better throttle response. (I think my old edel was faulty as well)

Anyhow, i ordered a rebuild kit and started pulling it apart. And i noticed the carburetor is missing its jets :whistling:

No clue how it could run so good without jets...

But now since i never played around with carbs so much, i dont know where to start with jets.

I thought since it ran pretty good i would buy one size over and one size under what was already in it. But thats difficult since it didnt have any.

So Im consulting the experts here, where do you think should start?

0.30 over 351cc

Forged flat top pistons

Elgin street/strip cam. 512/538 lift

Ported 2v heads

Holley street dominator intake

Flowtech full lenght headers and dual 3" exhaust

Thunder HEI distributor

3.50 gears.

I know this probably very hard to do, but all recommendations are welcome. Or maybe someone atleast know what stock jets are in a 650 holley.

Thanks in advance

 

[TommyK]

Hello! As some of you might remember, my neighbour gave me an old Holley 650 double pumper he had laying around.

I test fired the engine with the carb and it ran good. Better idle than my old edelbrock, and waaay better throttle response. (I think my old edel was faulty as well)

Anyhow, i ordered a rebuild kit and started pulling it apart. And i noticed the carburetor is missing its jets :whistling:

No clue how it could run so good without jets...

But now since i never played around with carbs so much, i dont know where to start with jets.

I thought since it ran pretty good i would buy one size over and one size under what was already in it. But thats difficult since it didnt have any.

So Im consulting the experts here, where do you think should start?

0.30 over 351cc

Forged flat top pistons

Elgin street/strip cam. 512/538 lift

Ported 2v heads

Holley street dominator intake

Flowtech full lenght headers and dual 3" exhaust

Thunder HEI distributor

3.50 gears.

I know this probably very hard to do, but all recommendations are welcome. Or maybe someone atleast know what stock jets are in a 650 holley.

Thanks in advance

What is the list number of the carb?

 

[barnett468]

71 front and 73 rear is a good place to start.

 

[Odmark]

TommyK: the list number is 6711

Barnett: okay thanks :::thumb::

 

[Jeff73Mach1]

I was going to say 72 primaries and 74 secondaries is where I would start, but Barnett's numbers are equally good

 

[TommyK]

That is a spreadbore carb?

If so it will want a small primary jet, say 62-65 and a relatively large secondary jet say 80ish?

 

[will e]

71 front and 73 rear is a good place to start.

That's clever.

The holley street avenger 670cfm comes with 65 main and 68 secondary. This is probably a good place to start.

I run 64 mains in my Jeep with a Truck Avenger 670 at Phoenix altitudes. I was able to run 61's and get the darn thing up to 13000 feet.

It's a bit worrisome that there were no jets.

 

[barnett468]

71 front and 73 rear is a good place to start.

That's clever.

The holley street avenger 670cfm comes with 65 main and 68 secondary. This is probably a good place to start.

I run 64 mains in my Jeep with a Truck Avenger 670 at Phoenix altitudes. I was able to run 61's and get the darn thing up to 13000 feet.

It's a bit worrisome that there were no jets.

the street avengers are notoriously lean and he would likely melt his engine running a 65 on a street avenger.

 

[Don C]

That's a 4165 carburetor that was designed for emissions and has no replaceable jets.

 

[barnett468]

that would explain why it has no jets.

 

[Odmark]

But it has slots for jets in the metering blocks? Shouldnt it work like any other 650 holley?

 

[barnett468]

if those holes are threaded which it looks like they are that metering block does use jets.

 

[Odmark]

Googling a lot on the subject the 6711 is a Thermo Quad replacement for 71-72 Mopar 340-400ci.

And it should indeed come with jets, it has a very large secondary jets, #86 when stock.

Nothing on the size of the primaries though..

 

[TommyK]

Googling a lot on the subject the 6711 is a Thermo Quad replacement for 71-72 Mopar 340-400ci.

And it should indeed come with jets, it has a very large secondary jets, #86 when stock.

Nothing on the size of the primaries though..

Google-fu says:

The Holley part number for the primary jet is 122-602. The secondary jet number is 122-683. These were close tolerance jets for emission carbs.

60 primary, 83 secondary

Because these were emission type replacement carbs you may want to bump the primary up a couple of sizes, hence my original recommendation of 62-65.

You may find the idle circuit calibration is lean as well.

 

[Don C]

Some 4165 carburetors did come with replaceable jets, and some didn't, some had just replaceable secondary jets. Holley shows that the 6711 did not have replaceable primary or secondary jets. The jetting was handled in the metering block, just like the secondaries on a vacuum secondary carburetor. He said that it runs fine without having any jets installed. Remove the jets on a 4150 or 4160 and see how well it runs.

It looks like it may be possible to install jets in that metering block, but only smaller than what the metering block has built in are likely to have any effect. The threads in the metering block and the flange around them appear to never have had jets installed.

 

[barnett468]

Can you post a photo of the back side of that metering block and also the number that is stamped on the top.

 

[Odmark]

Hmm that would explain it running pretty good....

I provided the picture of the other side of the block, could not get all the gasket off but at least i got rid of it from all the channels and stuff.

The numbers stamped on top are 7499 and 7500. And a lonely 4.

 

[Odmark]

I also got another carburetor, list number 6212, 800cfm holley double pumper, also spread bore.

This carb does have jets according to holley (mine is missing them though), could i use the metering blocks from this on the 650 so i can use jets? They look identical.

 

[Don C]

I believe they should interchange, but not 100% certain. I know that the same adjustable metering block works on both 4150s and 4160s. As long as all of the openings and runners match it should work. Use a gasket and lay it on them to make sure.