What advantages would I gain in swapping out the Secondary Metering Plate for a secondary metering block to my 454? (4160 to 4150) The carb is a Holley 750 with Vacuum Secondaries, model 80508. (Not interested in purchasing a new model at the time, doesn't seem to be cost effective since I allready have the carb.)

Also, how difficult is the swap and tuning process?

I am well versed in most modifications and tuning but never had to do the modification to the secondary plate to block.

It's easy... and you don't need a book to do it... but it's good to have.

THIS BOOK (http://www.amazon.com/exec/obidos/tg/detail/-/093147227X/qid=1090877226/sr=1-1/ref=sr_1_1/103-0632856-2323055?v=glance&s=books) is the only book I every use for 4160/4150 carbs.

It's real easy and I didn't use a book as it is real straigt forward. I pretty much am a rookie on carbuerators so if I could do I believe you will have no problems. The hardest part was getting the original gaskets cleaned off.

I would like to know what effect on performance will this have (going from metering plate to metering block)? I have a 600 cfm 4160 carb and I thought of upgrading it as well. Thanks.

It allows you to have jets in the seondary side of the carb. After installing the plate you can tune and screw around with secondary mixture ratios till ya cannot stand it any longer.

Plenty of opportunity for getting headaches from the gas fumes, possibly a fire if you mess up the gaskets or a float setting / needle. Opens up tremendous potential for fun as well as greatly increasing the number of potential combos of primary and secondary jetting selections.

Unless you are a real dyed in the wool racer who has his foot in the secondaries all the time I doubt you will find this mod. worth the aggravation but some folks are just into pain so to each his own.

sam454ss, I just recent converted my vac secondary over to this new proform metering plate that allow you to run standard jets on your secondary side. I have a tunnel ram set up and this allowed me to run the standard float bowls and not have any clearance issues without turning the carbs sideways. I had no tuning issus with my idle circuits (they are adjustable too with the new metering plate) You might want to check them out. Its sold @ jegs for 42$ or 52$ depending on your setup. :D http://www.jegs.com/photos/793342.gif

That's a cool idea, especially for a model with a fuel transfer tube/side hung float bowls. How is the secondary side idle mixture adjusted with this jet plate? Bob

Bob, the secondary metering plate has screw in bleeds for the fuel metering for the idle circuit. I restricted them on my setup to allow a leaner idle circuit, since I have 2 600's on my engine. Most people dont know that holleys use the secondary floats to help feed fuel for the idle circuits ;)

its a very easy swap. Get the Holley conversion kit, so that you can use 4150 fuel rail systems.

I bought a quick fuel kit, and it fits inside the bowl, so i need to change over the fuel rail intermediate peice when switching to a 4150.

You'll understand when you get the kit.

Thanks for the feedback everyone!

I'm thinking I'll go with the modification after all...

Sam

The block I got came with #76 jets. Are those comparable to what the metering plate has in it?
3310 Holley 750 vacuum