LostX

iTrader: (1)

I have and small block 350 which i thought had a holley 650 but after running the numbers it is a holley 390 4 barrel vacuum secondary. Is it worth it to tune the 390 to work for my 5.7L? or go to a 650 or 700. Can it be made to work?

Right now the car wont idle below 1300 or so at running temp. any lower than that and the idle will slowly trail off until it dies. The choke has been milled off.

I replaced the accelerator pump squirter from a 25 to 31 and it took away the hesitation starting from a complete stop. I put a new diaphram and lighter spring in the vacuum secondaries and WOT now screams and sounds nice. But i still cant get a lower idle Should i try a power valve or mess with the timing?

sofakingdom

iTrader: (1)

How much improvement did following the Holley tuning sticky at the top of this forum make, after the complete rebuild you did but forgot to mention?

LostX

iTrader: (1)

not sure what this means. That tuning thread says nothing about making a tiny carb on a big engine run correctly. and i did not rebuild this carb

sofakingdom

iTrader: (1)

No, of course that thread talks about nothing of the kind... why should it? What's so "special" about that?

It talks about how to get a HOLLEY to run on AN ENGINE. It makes not the slightest difference what size either one is; the techniques work the same. It's all about fuel and air, neither one cares how big the metal pieces are.

Oh I thought, being as how it's the most sensible thing any sensible person would have done, that you would have rebuilt your carb and rendered it GUARANTEED non-defective, before even beginning to consider getting around to playing with the notion of "tuning" it. Oh well, silly me.... goes to show how little I know about humans...

Rebuild the carb, so it's KNOWN TO BE free of defects; then follow the Holley tuning sticky.

LostX

iTrader: (1)

sorry, but its hard to take you're posts seriously with that attitude.

im not posting on this forum to be belittled. just looking for sensible answers

sofakingdom

iTrader: (1)

Not sure about "belittled"; I'm giving you credit for being a sensible person and doing sensible things, and if I'm "belittling" ANYONE, it's myself, for not understanding humans any better than I do (which is pretty frickin LITTLE I can assure you). What's wrong with that?

It's hard to take people who ask for help seriously when they come across with some holier-than-thou attitude like that.

You seem to be expecting that someone is going to hand you a list of jet sizes or something. While someone may do that, that approach is DESTINED TO FAIL. The ONLY way to get a carb dialed in to a specific motor, is to dial it in to THAT specific motor. WHich is what the sticky is all about. It works a little like the way you "isloate" muscle groups at the gym, and then "target" them with particular exercises: it "isolates" the behavior of each system in the carb, allowing you to then tune that particular system of YOUR carb to match YOUR engine as perfectly as possible.

So, how did it work out after you tried it?

pancherj

What is the timing at idle with and without the vacuum advance plugged in (I assume you are running a vacuum advance distributer)? Not wanting to idle is most often (in my experience) caused by too little timing advance at idle. The band aide that most people apply to this timing situation is to open the throttle blades of the carb a ton, which fuly exposes the transition slots and leads to all kinds of trouble. This COULD be your problem. It could also be something as simple as a clogged air bleed or clogged transfer slot. A good cleaning would solve that issue

midias

Yes 390 is small for a 350 grab a 650

LostX

iTrader: (1)

i have a timing light and my timing is very far advanced. Im assuming because my idle is at about 1400. Its advanced past the last marker on my harmonic balancer (the last mark is 12 degrees) but i seem to be at 20-25 degrees with the vacuum advaance unplugged. If i try to retard the timing any it dies.

I was told the car had a 480 lift cam and thats all i was told. So i cant verify that. But i probably have a low vacuum at idle.

i have this with the choke milled off. It also has no fast idle cam or anything else that was a part of the choke
http://www.holley.com/0-8007.asp

pancherj

I'll try to help you, but I think you are about to start your first semester in "bought someone else's puss case".

1) Verify that the timing marker is correct. How? Get a piston stop, rotate to TDC number one (according to balancer and firing order), insert stop, rotate engine (BY HAND!) in both directions and mark the ZERO position (per the tab) on the balancer. Do this in both directions and the spot in the middle of your two marks is TDC. That is confusing to write, but if you try it you will quickly see what I mean.

2) With TDC verified, now set your timing (with idle speed turned WAY DOWN and the vacuum advance unplugged) to 14* advance. Get a timing light with a dial back feature. That and a vacuum gauge will be invaluable.

3) Make sure the rockers are adjusted correctly.

4) Start tuning the carb. However, if you can spare the cash, dump that carb and get a new (or used) known carb. The one you have sounds butchered and it may never run right.

Fast355

iTrader: (2)

Actually if you are never going to go to the track a 390 is perfect for a smog 350 or a low RPM 350 for that matter.

Damon

You have a mismatch between the balancer and the timing tab, I bet. Very common when somebody takes the balancer off the orignal 305 and sticks it on a 350. The original 305 in your car had the timing tab in the 12:00 position (straight down behind the water pump). The timing line on the balancer is made to match that position. If you try to use that balancer with a common 1:30 postion timing tab (under the driver's side leg of the water pump) your timing will read off by about 30* from where it actually is.

Does any of this make you smack your forehead and say "Of course! It's so obvious!"

Your symptoms fit this problem perfectly and since it's got a 350 in it we know it's not the original engine. So...... you know.

LostX

iTrader: (1)

I stuck a feeler probe into the #1 cylinder to feel exactly when the piston reaches the top. The line on the balancer it right on (give or take 2 degrees) from the deepest V in the marker. From this point I had to flip the wires 180 degrees for it to run. I did not set the rotor to position #1 instead i set it to the cylinder on the oposite side of the distributor

pancherj

I'm not sure I follow your description...is it running okay now?? You can pick whichever post you want on the distributor and mark it #1. Then, from there, follow the firing order (1,8,4,3,6,5,7,2).

The piston comes to TDC two times...once for firing and once on exhaust. Are you sure you found TDC on the firing stroke? It seems like you did.

LostX

iTrader: (1)

it runs ok it just idles very high, which defeats the purpose of having a 390 for good gas mileage if im idleing all of the gas away.