[dauber65]

I have a friend who's grandfather gave him a Holley carb. My friend is letting me borrow it because it is a spreadbore carborator and my intake is a spreadbore type. The carb is very clean looking and appears to possibly never been used before.
His grandfather told him it was a marine type of carborator that he was going to use on his boat but never did. I'm curious how it would do on my SBC XE262 vortec headed 71 chevelle. I have done some research and I believe it is a basic 650 VS Holley. However there is one thing that confuses me.
There is a sticker around the mixture screws that shows "lean" with arrows going counterclockwise. Also this mixture "screw" has a large yellowish plastic cap over it with a phillips screw head on it to turn. It appears you are supossed to turn the plastic cap, but other Holleys I have seen do not look like this. I know most Holley's are clockwise to lean out the mixture. I'm not sure if I'm ready for another odd ball Holley. It is really clean though. I might have to try it out.
If you could help me understand this thing, it would be appreciated.
Holley choke #
LIST-7397 (next line down) 3356
There are numbers stamped on the metering block
8675 (next line down) 7397

 

[az66]

Try www.holley.com web site

 

[Scotch]

You've got a 'reverse idle' system on that carb. It's not that unusual, but it's good to know about it. (Don't take the sticker off- it will remind you which way to turn the idle enrichment screws).

In a 'normal' Holley, that idle screw controls fuel flow at idle. On yours, it controls air flow, and fuel flow is not adjustable.

Holley developed this setup for improved emissions in the late '70s. It shouldn't affect anything- just don't pull the sticker off so you remember which way to turn the screws.

 

[dauber65]

You've got a 'reverse idle' system on that carb. It's not that unusual, but it's good to know about it. (Don't take the sticker off- it will remind you which way to turn the idle enrichment screws).

In a 'normal' Holley, that idle screw controls fuel flow at idle. On yours, it controls air flow, and fuel flow is not adjustable.

Holley developed this setup for improved emissions in the late '70s. It shouldn't affect anything- just don't pull the sticker off so you remember which way to turn the screws.

I've heard about these set ups before, but I'm not sure how to start the initial tune with them. On the standard set up you screw the mixture screws in untill they gently bottom out them back them out a 1 1/2. Then turn them equally untill max vacum/best idle.
How do you start the initial adjustment with these?

 

[lg1969]

Be aware if you install a performance cam in the motor, you may experience off line hesitation or bogging. That carb was design for engines with high manifold vacuum, because the way the idle circuit is design for low emission.

 

[dauber65]

I did some research on my own and found this....
http://www.holley.com/data/Products/Technical/199R9881.pdf

Look at page 7 and 8.

Apparently those plastic caps are "emmision control limiters" of some sort.
Very interesting.

 

[dauber65]

Be aware if you install a performance cam in the motor, you may experience off line hesitation or bogging. That carb was design for engines with high manifold vacuum, because the way the idle circuit is design for low emission.

How much of a performance cam are we talking? I've got a XE262 cam. It still pulls pretty good vacuum at idle.

 

[lg1969]

Trail and error. just install it. I had used it in my chevelle, switch to a performance cam in my small block and that where my problem started, bogging and hesitation. Difficulty adjusting air/fuel mixture screws.

 

[dauber65]

Anyone else have more luck than me at IDing this carb? I've scoured the internet and really can't find anything......... and yes I've searched the "holley" website.
Personally I think the Holley's website sucks for finding stuff, but that is because the past two Holley carbs I have had I can't find ANYTHING on them on their site.