My brother went with a Seam Murphpy Induction quadrajet on his ZZ4.
He said the idle cleaned up but misses his Holley as far as how the motor sounds idle lumpy and throaty at cruise speeds.
I have a 355 with 225 duration cam, headers, and Tko 600. I currently run a Holley 600 vac secoundarys and think that the motor needs more air. Seems to run better without an aircleaner.
Also I thought maybe getting anougther Holley with 4 idle screws would help me with my rich idle condition.

Can you tell me what carb I should be looking to purchase?
thanks in advance for any help.

i always say go with the double pumper with a stick & leave the the vac. carbs to the automatics.

it sounds like your running rich problem could be a blown power valve????????????

maybe a bigger vac.secondary carb sized @ 750-770 cfm would work for you with a dual line in, OR

maybe a mechanical secondary carb sized @ 650-700-750 would work for you with your engine/trans combo............

I like the 770 Street Avengers, it would be a good combination.

Dave

i definitely wouldn't run a dp with a stick unless you have it geared down real low, at least 4.10's for a 350 in a heavy car. otherwise a vac sec carb is going to work better, imo.

I run a double pumper 600 cfm on my 350 with an auto and it works well. If you go with a double pumper dont go too big!! A 650 cfm DP max.

I have a 454 and a TKO w/3.90's and the 770 is the carb to beat...stick shift and all! I have a 800 DP only the shelf, and that d#mn 770 just runs superb!

I have 3:07 gears but plan on going to 3:73's
So I guess the 770 avenger is the way to go?
Are these avengers still have the metering blocks like the old holleys that can be modified?
I was reading a post a couple days ago that someone was going to come up with a how to set up your carb (drill and installing brass set screws to be drilled)
Did anything ever come of that?

>> "Did anything ever come of that?"

Not that I know of. Truth is, you shouldn't need it on a reasonably standard type combination anyway.

Rich idle? why don't you just lean it out with the idle mix screws? adding 4 corner idle is going to make it richer, not leaner. Those are not needed unless you have a really big cam, so big it won't idle idle under 1000RPM.

A 600 moves enough air to keep a 355 happy to 6500RPM, are you running more than that every run?

Double pumper on a small block in a heavy car is a well-known bad move.

A vacuum gauge installed and monitored at WOT in high gear will help you decide on your induction system.A buddy riding shot gun can help you qauntify the numbers while you keep your eyes on the road/track.Any time a restriction at wot in the intake manifold falls out of known parameters..the carb MAY be suspect.The manifold may not be optimal or the exhaust may be restrictive.My advice..borrow some carbs for testing that give you max idle vacuum..part throttle crisp and minimal wot vacuum under load at max rpm.IMHO..without tons of testing and tuning,the classic 3310 vac secondary is a tough nut to beat out of the box these days.It is not like the old 780,pig rich over a smallblock and will only be as big as reqd when called upon.

ok, after reading everyones replys, I decided to try to work on my 600.
I have about 10-11 inches vac at idle.
I put a 4.5 power valve in and put a .040 dia wire in the idle restrictors. The restircters originally measure about .056 dia.(so I thought I would be restricting the flow of fuel at idle quite a bit)
Put it all back together and adjusted the mixture screws. Still very stinky at idle.
Also I noticed on the metering block by the idle feed restricters there is a angle hole adjacent to the brass hole.(Is this normal?)

If it runs better without an aircleaner find out why.

I was the one talking about the 770.I have someone on here that is going to help me dial in my 770 as far as light cruise AFR.He gave me a list of parts and tools I would need to get it done.I have everything I need so I will be doing this in a few weeks.He told me I should be able to go from 12MPG now to atleast 18MPG and also get my WOT balanced out.I also have the innovate AFR and O2 sensor and have the 770 working good at idle and part throttle but need to dial in the cruise and WOT.Whats ironic is that after all the tuning with the innovate Im back with the stock jetting which is 72-75.So for an out of the box carb for my application it works good.

I will be doing all of the tuning via PMs so after Im done maybe we can get a post together with pics and info.

>> "Did anything ever come of that?"

Not that I know of. Truth is, you shouldn't need it on a reasonably standard type combination anyway.

Rich idle? why don't you just lean it out with the idle mix screws? adding 4 corner idle is going to make it richer, not leaner. Those are not needed unless you have a really big cam, so big it won't idle idle under 1000RPM.

A 600 moves enough air to keep a 355 happy to 6500RPM, are you running more than that every run?

Double pumper on a small block in a heavy car is a well-known bad move.

Also with the 770 I was able to get the Idle AFR as lean as 17.0 with it still running fine so its posible with no mods to get that.I have even got as lean as 15 without vaccum advance hooked up at 18* initial.

>> "Also with the 770 I was able to get the Idle AFR as lean as 17.0...."

If you're using the version of WBO2 that hangs on the end of the exhaust pipe you may need to adjust the procedure a little. At idle the pulsing in the exhaust will cause lean readings. Find an old towel or something to wrap around the end of the pipe, then read the gauge. You might find it quickly richens up to around 13.5:1 from the 17 or 18 you were seeing. This same deals causes lean mix readings while coasting against the engine. High manifold vacuum causes fresh air pulsing in the pipes. Decel is actually rich.

No Tom this is the O2 thats about 6" back of the collector.

ok, after reading everyones replys, I decided to try to work on my 600.
I have about 10-11 inches vac at idle.
I put a 4.5 power valve in and put a .040 dia wire in the idle restrictors. The restircters originally measure about .056 dia.(so I thought I would be restricting the flow of fuel at idle quite a bit)
Put it all back together and adjusted the mixture screws. Still very stinky at idle.
Also I noticed on the metering block by the idle feed restricters there is a angle hole adjacent to the brass hole.(Is this normal?)


The powervalve has absolutely no effect on idle quality unless it is leaking/ruptured. You should base your powervalve selection on what your vacume reading is at cruize speed not idle vacume. What is your current timing curve and where are the idle mixture screws adjusted?

If the initial timing is retartded being less the 18 deg for a perf cam that will cause you to have to set the idle speed too high which in turn forces the prim throttle plates past the idle circut into the mains at idle resulting in rich mixture at idle so adv the initial if its not already at 18 for a non stock perf cam.

Also,if dbl pump carb ensure the secodary throttle blades are closign all the way and not partially off seated position partially activating the secondary fuel circut at idle.

For power vakve make sure initial timing is at 18 deg for perf cam then take an idle vac reading at idle (auto trans in gear) to get idle vacuum reding.

If its 10 " @ idle then a 6.5 is fine,they often recommend 2-3" below idle vac for p/valve but that activates the p/valve a little on the early side IMHO andi like to be more like 3-4" below idle vacuum because holley's are rich enough as is.

As already meantioned getting vacuum reading at cruise is a better way to go about it for a better more accurate p/valve choice but most of the time working off an accurate idle vacuum reading for p/valve choice will work out close enough.

Scott