Originally Posted by Little Mouse

no the holes in the throttle blades wo
nt cause any issues. how much initial timing do you have. Good amount there is a good place to start. You are right the fuel enrichment valves dont play any part in anything till the carb gets into the main booster operation.

Originally Posted by knodty

Originally Posted by Jebbysan

I believe that is your issue right there.......that is a lot of controlled leak. And it appears the secondaries are open a smidge but could be just from the way you are holding it as the secondary linkage is resting on your hand.
Sucks that you are across the pond as I have an HP plate on the wall I could send you.

Jebby

Originally Posted by chevymans 77

The power valves open at idle will add no fuel to the idle, they add fuel through the main circuit so only after the main circuit is flowing will they add fuel.

With a 9" idle vacuum and a 3.5" power valve your power valves are not open at idle.

I would look for a vacuum leak and I agree that 4 - 3/16" holes, one in each throttle plate is a lot.

Neal

Originally Posted by Jebbysan

The timing is good.....may need a little more depending on what cylinder head you are running but you are in the ballpark. Your initial should be a touch higher at 16-18.
Most likely, this is your cam:
https://www.summitracing.com/parts/cca-11-213-3

This is not terribly big for a 460 inch BBC........you should have more than 7 inches vacuum at idle. I have the small block version of that cam in my 406 and it pulls 10-11 inches.
I feel this is where the problem lies.......I feel you have a vacuum leak somewhere.
Also....could you post a pic of the holes in the plates? 3/16" is huge.....and this in itself could be the issue. If they are actually .1875 in diameter.....you need to solder them up. Four .1875 holes is a LOT of air to pass at idle.....I have built plenty of setups that had that much cam and ran standard plates with no issues.
I just do not feel that that cam needs holes in the plates.......factory L-88's had more cam in them stock and they idled with no holes in the plates......if you had a solid roller with, say, 260 @ .050...then yes....that would work.
Easy thing to do would be to buy a new throttle plate and try it......or solder them up.....soldering them up is easy and free...the cost of a gasket to remove the throttle plate.
Another thing......very few carbs have two power valves in them anymore and they are usually for boat applications.....or road course where you are modulating more than 1/2 throttle to WOT in and out.....which is rare. If it was mine I would block the rear one off and add 8 jet sizes. One less thing to fail....and not needed once the engine is on the cam and accelerating.

Jebby

Originally Posted by chevymans 77

The carb has some mods that somewhat tell a story about its use, not sure if you made the changes or the PO,

the bowl vents have been cut short, the bracket on the throttle lever looks to be for a OD trans (TV cable), the rather large holes drilled in the throttle plates.

Have you looked up the list number chart and verified the air bleeds and jets for the carb?

Neal

Originally Posted by Little Mouse

I had a 310/320 mechanical in a 454 with an 850 dp and I did not have any holes drilled in the throttle blades so maybe im wrong and you need to get rid of the holes.

Originally Posted by tsw71

I saw several posters recommend drilling holes in the throttle plates. Drilling holes in the throttle blades is NOT the way to fix a carb. The idle air bleeds in the metering blocks are too large by design, which is why Holleys always run rich and require you to open the throllte blades up just to get it to idle. The better way to do this is to cut and strip a piece stranded wire. Bend 4 strands (one for each idle air bleed hole/2 holes per metering block) into an "L" shape and put a single strand (these should be roughly .010"-.012" dia.) in the idle air bleed holes. With them bent like an L, the gasket will hold them in place after assembly. Doing this allows the idle screws to become functional and highly tunable. Preferably, use of a wideband A/F gauge will allow you to set it up right.

Originally Posted by 427Hotrod

Think through what you wrote a little bit.... idle AIR bleeds that are too large will LEAN the mixture. Restricting them will just fatten it up.

Now you CAN restrict the idle FUEL feed orifices in the metering block and do what you're saying.

You've got the right idea....but just leave out the "air" part.

JIM

Originally Posted by cuisinartvette

drilling holes is old school thinking...for carbs that never had iab etc.
If you log onto speedtalk.com and post in the engine tech section a guy by the name of jmarkaudio can striaghten you up...or send it to him. It will be perfect the first time the guy is a holley wiz.


So many are quick to tel you to put a smaller PV in, change jets when it has nothing to do wiht that. PV opens when your engine dips to that vacuum level. So it wont enrich til you see 2.5 inches not sure thats the answer. Sometimes going higher or just leaving it stock is the answer. I get about 7ish inches at 1100 rpm idle, no smaller than a 5.5