Mark305TBI

I've been having trouble with my carbureted 305. No matter what the pump nozzle and cam size are, it can't get enough fuel on rapid throttle openings. If you want to hear more about my problem and combo, go here.

With the largest pump cams and largest shooters with hollow screws, I still can't get enough gas off idle. The fuel pressure is at 7 psi, the floats are set correctly, idle is good, 14 degrees of advance at idle, .052 shooters, biggest pump cams. I can't find any vacuum leaks.

I don't know anything else to do, except change the intake to a dual plane. I'll probably change to a Crane 2032HR camshaft at the same time I change the intake. It'll have to deal with the stock convertor for a while, until I get the cash to get a new one. It would be better if it fits under the stock hood, though that's not an absolute requirement (I've always wanted an aircleaner that stuck out of a hole in the hood ). Any recommendations not listed are more than welcome.

Pablo

iTrader: (1)

its not going to make a difference.. you have a problem somewhere else i bet your timing is retarded

Pablo

iTrader: (1)

and that combo is nowhere near horribly mismatched... mismatched combos dont run as well or fast as they were intended... they dont NOt run at all.. thats damn near impossible to pull off even for an idiot

I have that same manifold, crappier heads, and a larger cam yet my car runs fine. All those things would exascerbate your percieved problem. A smaller cam is going to give better vacuum signal at idle and better heads the same provided the port volumes are similar.

I wonder how mine even runs, with a carter no less, and the smallest stock shooter (it needs more but it runs fine)

like i said, did you check your timing? retarded timing will do the same thing

you even said it ran OK with the tbi, that says it all.. if you cant get it to run OK with the carb then its something you are doing tuning wise.. its not that a carb is that much worse at dealing with what you call your "mismatched combo"

why do you habitually want the problem to be larger than it is?

fast_broker

iTrader: (1)

I'm with Pablo. probably timing, or possibly fuel delivery.

What distributor you rinning and EXACTLY how is your distributor set up?

-intial advance (with vac disc) at idle
-total mech advance.
-total possible advance, including full vacuum advance
-is the vac canister active at idle? (ported or FV connected?)
-are you sure your balancer is timed correctly (slipped ring?)

RB83L69

1. What list # carb?

2. What have you done with the jets?

3. What power valve is in it?

No amount of twiddling the distributor is going to fix a lean-out. It's fuel delivery. A single-plane intake is going to have that tendency on a small motor, no matter what; but it should be possible to get it to run at least OK if not great.

That's a terrible intake anyway, no matter how you slice it. The car will go faster with almost anything else on it. I would strongly urge you to get rid of it before you do anything else to the carb, and then see where you end up.

A Performer RPM will give you better top end than the T2 without murdering the low end like the T2 does. Or, another way to go would be a ZZ4 intake, which are easy to find used or new take-offs, there's a couple on the classifieds right now. It depends on what your goals for the car are. Sounds to me, if you're at all happy with the stock peanut cam and you're looking at a 2032, you don't need a single plane intake - or a Perf RPM either - you're not looking for that kind of a motor at all.

I'd suggest a Comp XR264HR cam; 1.6 rockers if your heads have been cut for larger springs or 1.5s if you're stuck with the stock diameter ones, in which case put new ones on (part # 981); and the ZZ4 intake. I think that will give you the all-around best combo.

Mark305TBI

RB83L69
It's a 4777 650cfm double pumper.
Factory installed jets
Factory installed power valve

I've already got the 2032HR cam, I got it after I installed the heads and intake and haven't got in there to install the cam yet. I've just been trying to get it to run okay, first. It's got ported Al L98 heads with 1.25" springs that are supposed to be good to .530" lift.

fast_broker
I'm at work right now, so I can't check on all the specifics. I'll let you know what I know right off the top of my head, thought.

It's an Accel vacuum advance HEI distributor with the in-cap coil. Timing at idle was 14 degrees advanced with the vacuum line hooked up to the vac canister. I think the vacuum line is active at idle, I can't be sure though without looking at it. I hope the balancer hasn't slipped. I'll have to check on total timing, don't have that number off the top of my head.

pablo
You should swim to Decatur and fix this damn thing.

RB83L69

Don't waste your time trying to get it to run right, if you're going to change something that will affect it that drastically. Even if you get it perfect like it is, after you change the cam, you'll have to start all over again. What you're doing when you work on the carb, is matching its characteristics to the engine's reuirements; change the engine, you change what the carb has to do.

That cam is pretty mild even though it has 20° more .050" duration than your peanut cam, in fact it's mild enough to have a CARB number (accepted as a legal California modification). So it's still totally inappropriate for a single-plane intake. In addition to not wasting any more time on the carb until you change the cam, go ahead and put a more nearly matched intake on it at the same time, and then go to work on the carb.

The way to calibrate a Holley carb is to first get it to cruise correctly. Lean the main jets in 2-size increments until it starts to surge at cruise, then go back up 2 sizes. If your car already surges at cruise (probably does), increase the main jets in 2-size increments until it runs right.

Then, get the power valve right. Measure your idle vacuum, in gear if it's an auto trans. Put in a PV with a number at least half of the idle vacuum, but at most about 3 lower than your vacuum. With your stock cam you'd need the highest PV number they make; with the other, it will probably be a 8.5 or 9.5.

Then, go to work on the pump shot.

I'd still suggest the ZZ4 intake.

Pablo

iTrader: (1)

I disagree with your RB. Ive had the same exact situation as him,
I also have a 305
I also have a torker II
and what you would call a small cam (214/224)

How does he know for sure his car is leaning out? He doesnt.. he doesnt even know what his timing is set at. I have had my car accidentally set to have very little advance and the SAME thing happens.
Ive run a holley 1850 on it
Ive run 1 11/16 tbi on it
ive run 2" holley TBI on it
and finally ive run and currently have an edelbrock 1405 on it.

I think there is alot of left over dislike for the Torker I which was an X manifold which is why it was so terrible. The Torker II is not an X manifold and while it may not be the best out there its certainly not terrible. I know of people picking up mph in the quarter with one over a performer rpm. It also didnt "murder" low end torque on my car in fact its faster all around. But that is neither here nor there.

His problem lies not with his combo but with his tuning.

once again lets go over the facts

he does not know where his timing is
It ran "ok" in his words with the TBI on a mail order chip
he doesnt know a hell of alot about tuning

I know mark, have known him for awhile, and i know he has a tendency to get a little hysterical

Pony Killer

Im with RB83L69

If your going to change the whole setup, don't monkey with it. Change it to something more closely matched, then have another go at it.

If a stock cam, stock converter, single plane intake and low compression doesn't scream mismatch.. i don't know what does.

The stock converter may have a fair part in it, just being inherently tight, and with the motor with little low end torque being out of tune it just magnifies the problem.

so if your going to work around what you've got, keep that in mind.

Damon

How the he11 do you know if it's not just a weak ignition coil or something simple like that???

Have you checked the timing and the advance?

Here's a simple rule that applys to this situation is spades:

99% of the time it's not the carburetor.

You've crawled all over the carb. You've checked everything in it. It's probably NOT the carb, OK? Stop looking there and look elsewere!

It's also not your combination of parts. It's not mismatched that badly.

Pablo

iTrader: (1)

Thank you Damon.

I agree of course.

SSC

LOL, a single plain intake and a double pumper on a 305, not a bad mismatch????? :lala: It could be somthing else but really start with what you know, these parts do not match and were never ment for a 305. The double pumper is just pouring fuel, the single plain intake is directing all that fuel straight into the cylinders. I highly doubt theres is any lean problem off idle its a rich problem. Change the carb try a standard vacuum secondary 600cfm, I bet it helps out alot even with the single palin intake I bet the difference will be like night and day.