[Tom Vaught]

I have converted many carbs back to the "Lower Position" IFRs.

People always seem to have tuning issues with any carb that has the higher IFR position.

Simplest way is to just install a basic 1850 (600 cfm) or 3310 (780 cfm) metering block
on the primary side of the carb.

But it is your carb. In the time when Holley went to the high mount afr position they
were trying to get the carbs to pass emissions in some states who had idle emissions rules.
You also do not need the 3 emulsion holes on each side of the metering block.

Ask yourself, why did Holley go from a 2 hole per side Emulsion strategy, to a 3 hole, then a 4 hole, then a 5 hole emulsion block"
Because they did not understand how the emulsion circuits worked.

Buy a used Primary Metering Block (at a swap meet), 600 cfm #1850 or 780 cfm #3310, and install it on the Primary Side
if you are afraid to mess with modifying the metering block you have.

The engine will be a lot happier with that simple modification.

Tom V.

[chiphead]

Yup, the carb is worlds better than when I started, thanks to all the great input. The car will cold start cleanly, idle in traffic and performs pretty well overall. It still needs a little help with the transition, but it's very drivable now. The high stall converter really helps a double pumper work on a street engine with steep gears. Otherwise it would be bog city.

I agree that it now needs a wideband. Once you get a carb close , the butt dyno can fool you. It's hard to tell if its rich or lean if it's not surging or smoking or fouling plugs.

What do you guys think of the BLP fully adjustable metering blocks? I like the idea of building a block for it.

[1968GTO421]

Originally Posted by chiphead

Yup, the carb is worlds better than when I started, thanks to all the great input. The car will cold start cleanly, idle in traffic and performs pretty well overall. It still needs a little help with the transition, but it's very drivable now. The high stall converter really helps a double pumper work on a street engine with steep gears. Otherwise it would be bog city.

I agree that it now needs a wideband. Once you get a carb close , the butt dyno can fool you. It's hard to tell if its rich or lean if it's not surging or smoking or fouling plugs.

What do you guys think of the BLP fully adjustable metering blocks? I like the idea of building a block for it.

I checked out their web site and the adjustable metering block looks like a great solution to incorperating Tom's advice in the previous post. I need to look at my old Holley and see if this may solve some issues with it. By the way, great thread, thanks for starting it.

https://blp.com/cart/index.php?main_...ath=65_107_263

[1968GTO421]

Originally Posted by Tom Vaught

I have converted many carbs back to the "Lower Position" IFRs.

People always seem to have tuning issues with any carb that has the higher IFR position.

Simplest way is to just install a basic 1850 (600 cfm) or 3310 (780 cfm) metering block
on the primary side of the carb.

But it is your carb. In the time when Holley went to the high mount afr position they
were trying to get the carbs to pass emissions in some states who had idle emissions rules.
You also do not need the 3 emulsion holes on each side of the metering block.

Ask yourself, why did Holley go from a 2 hole per side Emulsion strategy, to a 3 hole, then a 4 hole, then a 5 hole emulsion block"
Because they did not understand how the emulsion circuits worked.

Buy a used Primary Metering Block (at a swap meet), 600 cfm #1850 or 780 cfm #3310, and install it on the Primary Side
if you are afraid to mess with modifying the metering block you have.

The engine will be a lot happier with that simple modification.

Tom V.

I agree that I would rather use a 3310 metering block but most of the 3310 Holleys my brother and I have found at swap meets had been damaged with problems like stripped theads for the jets and/or power valves. We've found carbs with jets held in with blue locktite. I could just get a new primary metering block from Holley for 3310 carbs:

https://www.holley.com/products/fuel.../parts/134-131

It costs more than the BLP but then chances of a F-U are much less