LilJayV10

iTrader: (5)

I have a Holley 600cfm carb part# 80457-S
http://www.summitracing.com/parts/hly-0-80457s

on my 89 T/A w/ a stock 305 w/ professional products low rise dual plane, 1 3/4 headers and 4inch exhaust(long story, car had a 406 in it but the stock 305 was put back in)

I was going to do sofa's holley tuning tonight but realized that the smallest jet in my jet kit is a 64, it has 65's in it now. I have no idea if I will actually need a smaller jet or not but that's the direction I was going to start. Before I go out and buy a bunch of jets that I don't need what's a ball park jet size where I might end up? I'm not asking "please tune my carb" just an idea of what I need to buy.

The car has several issues and I'm finally fed up to where I'm going to work on it. I spend anywhere from 60-90 hours a week fixing other peoples cars. I am going to take an afternoon and work on my stuff.

1. The car misses and runs bad when cold w/ the choke on. I have tried adjusting the choke but it hasn't made any difference. It also revs to about 1600 on a cold start and will slowly creep up to 2000rpms.

2. It can be 90 degrees outside and when I start it the car still goes to a fast idle if it has been sitting for a while.

3. The car runs great on the highway(where I do 80% of my driving)with light throttle input at 65mph@2100rpms. When I go to pass another vehicle the car falls on its face, bucks and has no power. If I floor it, it clears up. I can't tell if its going rich and me opening the throttle all the way is helping it clear out or it's going lean and when the secondaries finally open its adding more fuel. After reading sofa's sticky I'm going to change my PV after I get the jetting sorted out.

4. When accelerating through 1st gear at 1/2 throttle or so when it shifts into second gear the car lays down, starts bucking and has no power.

I have an intake walbro 210 pump(from the 406)w/ the mallory regulator and fuel pressure is at 7psi. This carb has non adjustable floats so I have no idea if they are set correctly. I took the bowl off and turned it upside down and the float is about level, maybe a tad on the low(as is low fuel level)side.

Timing is 34 degree's total with 14 initial. I'm going to pull the plugs in the morning and probably replace them.

This turned into more than just a simple jet question.

J

LilJayV10

iTrader: (5)

I ended up rebuilding the carb tonight. I found several air bleeds stopped up. The secondary diaphram was tore in half so the secondaries were never working. Found a couple other ports/holes blocked. It idles much better. 21in of vacuum, 3/4 turn on the idle mixture screws. Fast idle with the choke on seemed much smoother and more stable and the engine wasn't missing like it did before.

I'm going to try and find a 10.5 PV tomorrow. Hopefully that will take care of the huge lean spot I have.

It still misses and stumbles when it shifts into 2nd gear at 2500 rpms. Does the PV come into play then?

I still need to pull the plugs but I definitely think I'm headed in the right direction.

JaBoT

If the 10.5 pv doesn't fix the lean spot under part throttle highway passing you might need to up the front jets and see if that helps.

The only way the pv would cause the issue at 2500 rpm at wot is if the engine was making more vacuum than the pv rating which is probably 6.5. I doubt a 600 cfm carb on a basically stock 305 is pulling that much vacuum at wot unless maybe the secondarys aren't opening up and causing vacuum above 6.5 at wot. Put a vacuum gauge on it and see what it reads.

LilJayV10

iTrader: (5)

Thanks for the reply. I am going to put a vacuum gauge on it before I leave work and watch it on the way home.

Even though I replaced the secondary diaphram it doesn't feel like they are opening. It has a gold or silver spring in it. A friend gave me the carb a while back I don't know if he has done anything to it.

A few quick questions. When I rebuilt it last night I noticed it only has a metering block and it seals to the big blue gasket to the carb. Others I have seen have a gasket, a plate, another gasket then the metering block. Is it suppose to have the plate and extra gaskets?

Also when I took the squirter off there wasn't a check ball of a needle valve under it. I looked down the hole and it looks like it has a fixed orifice of some kind. Fuel does shoot out of the squirters when I open the throttle.

I know different carbs have/don't have different parts I just want to make sure I'm not missing anything.

Any ideas where you think I should be at jetting wise? I am holding off buying jets.

Thanks.

Jason

LilJayV10

iTrader: (5)

I put a vacuum gauge on the car on the way home. Cruising vacuum is around 15in. Slight tip in puts be about 9.5. WOT is 0 or close to it.

When taking off from a stop at a little less than 1/2 throttle, when it gets to about 3000rpm the car starts accelerating much faster on its own with no added throttle input. It doesn't feel that way in other gears.

My 10.5 PV should be here tomorrow. I'm going to put that in and go ahead and change the plugs. I'm interested in seeing how the car reacts.

JaBoT

10.5 should do the trick.

What distributor and springs are you running?

LilJayV10

iTrader: (5)

Stock HEI w/ re curve kit. I'm pretty sure I'm running the lightest springs. It's been a while I can't remember for sure.

LilJayV10

iTrader: (5)

I pulled a plug out last night to see what it looked like. It looks like it has never had fuel on it. I raised the jet size from 64 to 67. It runs much better. It doesn't stumble after it goes into 2nd gear like it did. On the way to work this morning I found myself speeding driving the same way I always have. I'm guessing since it's not running as lean.

I'm going to mess with the jetting some more tonight. Once I get that lined out I will throw the 10.5 PV in.

JaBoT

I would suggest richening up the front jets to like 70 to start and follow sofa's holley tuning sticky exactly.
reading plugs is tricky since if you were idling for say 30 seconds after cruising, the plug are showing idle not cruise. You can pull a plug out of your engine and it's black, but what's rich? wot, cruise, idle? Not really useful on a street engine. Race cars can do it because they shut the car down right after the pull.

LilJayV10

iTrader: (5)

I agree 100% with you on reading plugs as you are absolutely correct. I know what a "normal" spark plug looks like after several thosand miles. My plugs looked brand new except for a tan stripe down the side. Thanks for the jetting suggestion.

I'm a little confused on when sofa says lean it out till it cuts out when you give it throttle. How much throttle are we talking about? Since I "think" the car is running lean now I don't have anything to compare it too. Once I jet it up some more and the car feels different maybe it will make more sense. Thanks again for your time and input.

Jason

LilJayV10

iTrader: (5)

I put some 70 jets in tonight to see how the car would react. It didn't like it all. So I decided to go to 73's. I did this out of curiosity more than anything, not that I felt it was going to improve anything. It didn't. The car would cut out and miss going up a hill at part throttle. I went back to 67's I had in it last night and put the 10.5 PV. The car runs much better. Throttle response is good and doesn't cut out going up a hill.

I went ahead and changed the plugs. I pulled a few more out and some of them where white, almost like an ash. Is that from too much timing?

Another thing that I can't figure out is the choke. The car can be completely warmed up and when I start it the car goes to fast idle and it takes about a minute before it will come off fast idle no matter how many times I jab the gas pedal.

JaBoT

basically when the jets get to lean when you give it a little extra throttle like when slowly passing on the highway or going up a hill at highway speeds and u need to give it more gas to maintain speed.

The 67 are probably the right jet for where you need to be. Also do you have a vacuum advance and if so is it hooked up? It will help you burn a leaner mixture at cruise and give you better fuel mileage with no adverse affects.

As far as the plugs it depends on how much white. Could be anything from normal to oil burning.
http://www.ngksparkplugs.com/tech_su...qs/faqread.asp

To adjust the choke just turn the choke adjustment down a little. It usually has a + and - on it. Turn it towards the - a little at a time till it's where you want it.

hamaf

This is definietely one problem. I tested all the springs holley has to offer. On my gmpp 350ho engine with 600cfm holley carb, only the white (lightest) short yellow (second lightest) and yellow (third lightest) allow the secondaries to open completely.

camarito

I'm running 68's on my 355 and I'm in the low 14:1 afr.
Running a carb bigger that what you engine can use (vacuum secondary) your secondary's might not open properly like they should, mine works fine with the stock spring and they open all the way at full throttle