camaroracer016

I have a 305 computer controlled carb system on my 350 for now. Seems like top end power isnt there. Is this why? what problems should i run into with this 305 carb on my 350?

--steve

ljnowell

The top end power is probably lacking because of the heads and cam, IMO, if it is stock. Otherwise you have some tuning issues.

Air_Adam

When you used the CC carb, you also used the CC distributor too right? You need both for the system to work properly.

Did you change the knock sensor? You will need a knock sensor for a 350 for the computer to work properly. If you used the sensor for the 305 in the 350, it will not work properly. You need to use a knock sensor for a 5.7 TPI engine. They aren't expensive, and it goes in the coolant drain hole in the block just above the starter.

Did the carb come from a regular 305, or a 305 HO engine? If its from the regular 305, it may be running to lean if set up to original specs. If you recalibrate it to 305 HO specs, it will perform much better for you.

camaroracer016

Its off a regular 305. It never had a knock sensor. So i dunno... I have the complete system installed. No Trouble codes or anything.. Runs fine, jsut the top end.. it like stops making power.. like the car jsut stops revving. What do you think that is?

five7kid

iTrader: (14)

Fuel delivery.

Fuel filter and/or pump, most likely.

camaroracer016

new pump and new filter. Both stock replacements!

Air_Adam

If its still set up like stock for the regular 305, then the secondaries are way too lean for a 350. Try setting up to the 305 HO specs on the secondaries. The HO had the secondary side alot richer for improved WOT performance, and it worked well on my 350.

camaroracer016

cant i buy rods for this CC quardajet? Which ones should i buy? Also, there is a kink in my fuel line, maybe thats wny im not running too good up top.

naf

iTrader: (7)

The ecm won't really affect WOT throttle fuel mixture other than going full rich on the primaries. The secondaries are managed solely by the rods/hangers/air valve tension. There's a tech article on this site that gives some recommendations.

The ecm does, however, control ignition timing which could affect WOT performance. The wrong knock sensor could cause the ecm to pull timing out thinking it's experiencing detonation.

If you installed a stock-type fuel filter did you remove the small check valve in it? I've had these check valves cause enough restriction to cause the carb to starve under WOT.

camaroracer016

This setup never had a knock sensor. I didnt take the check valve out. Should i? What would be the disadvantaeg of this?

naf

iTrader: (7)

On the check valve, just remove the small spring and check ball inside. I suppose without it fuel could be allowed to drain back from the filter causing the pump to have to work a little harder on start ups. Many people ditch the stock type filter in favor of a better in-line filter which would have the same effect though.

Vader

The check valves in the pump should take care of any fuel reversion.

The instructions you have been given are correct. A different hanger, secondary metering rods, and adjustment of the secondary AV spring windup should solve most of the heavy throttle problems. You may have to slightly adjust the lean- and rich-stops on the primaries for the 15% larger displacement, but if it was properly tuned for the 305, it should at least run you fairly close with just a slight lean tendency. Given that the secondaries can be tuned to compensate, it might not make a huge difference.

I'm a bit confused that there is no detonation sensor. Was this an export model?

camaroracer016

What Rods/ hangers should i use? I dont think this is an export model, but there in no knock sensor. What does the pulg look like? how man wires go to it? I really needa get this thing tuned up!

naf

iTrader: (7)

Knock sensor should be below the pass side headers, middle of the block with a one-wire connector. It may be there and not connected/wire missing maybe.

99Hawk120

Early LG4s did not have knock sensors. I believe pre-85. They got them when the compression was boosted, I think.

camaroracer016

Do you think the kink in my fuel line is the problem in the top end? not flowing enough fuel? This just started when i took ym car outa storage, And the fuel line got bent. Would that cause that?

naf

iTrader: (7)

Yes it could cause it. Hit a JY and pick up a replacement if you can.

naf

iTrader: (7)

Keep in mind that fuel starvation will cause the motor to "fall flat on it's face" under full throttle. The motor will noticeably stumble and rpm's will sharply drop. I'm not sure if you're experiencing this or not. If you're just seeing a lack of the power you'd normally expect in the top end (but no stumble) you can try:

1) check that full ignition advance is coming in with a timing light. This won't tell you whether the ecm is pulling timing due to knock sensor issues but will let you know the ccc dist and ecm is working properly.
2) Connect a voltmeter to the O2 sensor (explained in one of the tech articles) and observe the readings under WOT while driving. This will let you know if you're running lean under heavy throttle and a rod/hanger change is in order.

camaroracer016

how can i check if full timing is coming in. What should full timing be? I know its not that the motor stops making power, because last year, the thing would fishtail shifting into second. I dunno if its the fuel System, Or the ignition system. I really want to get this figgered out. Thanks for all your help guys!

Lo-tec

84 LG4, no knock sensor and no timing (24 or 26 total wag). If you have an LG4, you'll probably need to bump the timing for starters.

What's in this 350? Heads, cam, exhaust, etc etc etc???
All stock??

camaroracer016

Motor is completely stock for now. With Stock manifolds. I know i need to get this changed.. but just saving up money! Im Just stumped tho, because it was crazy fast last year, now the upper end sucks!

naf

iTrader: (7)

If it worked fine before, replace the possible restrictions in the fuel line. If it started after your fuel line got bent, fix that first.

As a test, you could replace the bent section with some rubber fuel line. Just don't leave the rubber line on as a permanent fix.

camaroracer016

Well i just took her out for a drive. And if im rolling at like 30 Mph, and i smash the gas, the rpms jump up, then i hear like a crackle/pop in the carb. What is that?

camaroracer016

Any idea what that crackle/pop is?

camaroracer016

Any idea what that crackle/pop is?

Lo-tec

Does the engine miss, stumble or bog down when this happens?

camaroracer016

yeah stumbles, and slightly bogs down.

Lo-tec

It could be the vacuum break for the secondaries. Round canister on the right front of the carb by the choke. Remove the vacuum line from the carb (leave it on the vacuum brake), push the rod coming out of the brake all the way in, and cap the vacuum line with your finger. If the rod shoots out, the piece is bad.

camaroracer016

ill try that. But that just opens the secondary air valve doesnt it? My secondaries open. The car revs up, but when it gets to 4500 kinda stops revving, and popping through carb. But im gonan go try that right now! Thanks for the tip.

camaroracer016

well i tried it. It didnt pop out. Just fine. but i ran the car, and if i ease into high rpms, itl get there.. but if i smash the gas, it revs up, gets to 4000 and starts shaking, and smokes. Man.. i wanna get this figgered out!

camaroracer016

Any Ideas??

Fast355

iTrader: (2)

It sounds starved for fuel. Have you tried changing the metering rods out yet? Just go to the Junkyard, look in an 80s van, it will have a Q-Jet carbed 305 or 350. Grab the rods, they will probably be either DRs or DAs, might grab the hanger as well (probably a F) That will make your 350 plenty rich, much more than the crummy DD rods that came in some LG4/LV2s.

Also check the cam/ecentric that sits under the secondary hanger. They tend to crack, break, and deteriorate over time. That will cause the secondary metering rods to only be partially lifted, limiting fuel flow..

I also have another though, I wonder if it is just the engine doesn't have any power left untapped up there. No mention of anything done other than a 305 swapped for a 350. Does it still have the stock intake, air cleaner, exhaust, Cat, Y-pipe, stock cam, stock 350 heads, etc. If so, don't expect much more power than the 305 that came out.

camaroracer016

It has an edelbrock performer intake, accel high output coil, edelbrock proflo airfilter. It ran good lastyear, would pull all the way up to about 5600. So i should go get the rods out of an 80's van? cant i just go to summit and buy some new ones?

Fast355

iTrader: (2)

I believe you can still get them from Edelbrock, but there selection is very limited, and they are like $7.00 a pair plus shipping.

I have a local yard that will just give them to me.

The reason I suggest a Van, is they have the richest calibration I have seen in the smog years. They are calibrated rich so the engine doesn't burn up when you run WOT for extended periods of time. Put 8 people in one, add a 5,000 lbs trailer, a hill, and a head wind, guess where you are, WOT.

naf

iTrader: (7)

I'd look at fuel/air problems in your secondaries, like Lo-tec was suggesting. Either fuel delivery or air valve/secondaries not functioning correctly. The air valve won't open unless the demand is there (engine load) so you can't rev it in the driveway and check for proper operation.

Check all your linkage, look for vaccuum leaks and clear any fuel restrictions. Do the things that don't cost money first.

Many carb problems turn out to be electrical. When it bogs/stumbles does the tach jump around? Did you put a timing light on it and check for full advance?

camaroracer016

Lemme get this straight. The airvalve are the flaps ontop of the carb right? or are they the ones on the bottom? They have to be opening, because i cah hear them, they nice sound of a 4 barrel.. the whooooooooommppp when they open. But if i smash the gas, it smokes. If it were running lean, would it smoke?

camaroracer016

is this correct? And how do i check for full advance?

naf

iTrader: (7)

Have you fixed the kink in the fuel line yet?

camaroracer016

not yet.. too freakin coooooold! lol im gonig to do ti wednesday tho.

camaroracer016

Well, i fixed the fuel line, seems a lil better, but it still runs weird at upper rpms, like stumples a lil bit. And if i brake touque it it hesitates, but then eventually goes up to upper rpms. I think it is still a fuel problem. Im gonna buy me some new secondary rods, and hangers. Any suggestions?

naf

iTrader: (7)

Got mine from summit. B hanger but don't remember the rod size. Raining out or I'd check. Tech article recommends CK's (available from Summit). Stock LG4 rods appear to be CH.

I remember being somewhat taken aback when I ordered from Summit and wound up paying +20$ with shipping, though.

If the car's not running the way it was, I'd look elsewhere before swapping rods/hangers.

MilehighBird

iTrader: (1)

Was the original 305 an LG4? You said that you replaced the fuel pump with a stock replacement. If it was an LG4 replacement pump I was under the impression that that pump could barely keep up with the fuel needs for a 305 let alone a 350. Mayby naf or five7 could chime in if they upgraded the fuel pump to keep up with a 350. I know the GM ZZ4 conversion kit came with an in tank TBI pump and a fuel pressure regulator to feed that 350.

Lo-tec

A stock replacement pump (ala trash auto) can't keep up. I had this problem on two cars, and upgraded one with a better carter unit, the other the same setup as the TBI pump in the GM conversion. Both ways solved the problem (fell on it's face 2/3 way down the track).

naf

iTrader: (7)

Don't know, never tried the stock pump on the 350. I suspect it would be fine though.

"Was crazy fast last year, now the upper end sucks"

What has changed?

Fuel starvation will cause it to fall flat on its face under wot then pick back up as the carb has time to refill, at lower rpms. It won't buck, stumble, hesitate and then run fine. There should be enough fuel in the bowl to sustain wot for at least a second or two.

What bothers me is that it ran fine before. Sounds like a transition problem in the carb. Lo-tec brought it up first. Secondaries not coming in correctly...airvalve, vaccuum break, float level, etc.

Camaroracer: When it stumbles and recovers, does it "scream"? Can it sustain wot at load?

camaroracer016

welll, i think the problem may be with the electronics, maybe the dist. It doesnt run consistent at all. Soemtime the idle is rough, sometimes it is really smooth. Im not getting any codes at all. But when i floor it, itl throw you back, but when it gets up to 4000-5000 RPM's, it just doesnt pull, and the RPM's stop going up. If i let off the gas, RPM's drop, and itl run fine. Maybe something is wrong with the secondaries? But honestly, i think the prolem is electrical. I really wish i could get it running right! You guys are a great help!

camaroracer016

Oh yeah, and another thing, after the secondaries open, and then close, Ive noticed that fuel gets on top of the flaps, is this normal?

naf

iTrader: (7)

If it will sustain 4000-5000 rpm's then the problem is probably not fuel starvation. Fuel starvation will cause the rpm's to drastically drop even with the throttle open.

Do you have a timing light? Dwell meter? Voltmeter?

This carb ever been rebuilt?

Fuel on the outside of the carb is not normal, usually indicating a float level, needle/seat problem (unless it's leaking at the inlet).

Problems like this are difficult to diagnose long-distance, but if you have some of the tools above I can give you some things to look at.

camaroracer016

Yes, i have a timing light, and a vlot meter, but i can go pickup a dwell meter. The carb is a Ream. From AutoZone. only been used for about 6-8 months. But the fuel on the secondaries is kinda strange. If you are looking at the carb, and u move the linkage with your hand, to where the secondaries will open, and then after they close, a little bit of fuel get up on top of the flaps, right before they close all the way.

naf

iTrader: (7)

Connect your timing light to the number one plug and verify that you're getting ignition advance as you rev the engine. The exact amount is not important, but you should see plus 20 degrees of advance as the engine is revved with the gun pointed at the timing marks. Do not unplug anything at the dist when doing this. This will let us know that the ecm is bringing in ignition advance.

Get a dwell meter and connect its positive lead to the green diagnostic lead near the pass side firewall and negative to body/engine ground. With the engine warm and idling you should get a dwell reading that fluctuates around 50% (or 30 degrees on the V6 scale). It should slowly drift +/- 5 degrees or so. As you rev the engine or cover the air horn the reading should change then slowly narrow to a new position in a pendulum motion. This will tell us if the ecm is controlling the carb correctly.

The flaps on top of your secondaries are the air valve. The butterfly flaps on the bottom of your secondaries are the secondary throttle blades. The blades will open with throttle but the air valves will only open under load. Where do you see the fuel?

Did the problems start with the reman carb install? Was the reman carb properly set up and adjusted for this motor? It is the ccc-qjet for this application? Two electrical connections in front, top pass side and forward driver's side?

camaroracer016

OK. Ill G get a dwell meter. Last year, before i put the car in storage, it ran fine, runs rev all the way up to 5500 with no problems. I didnt change anything. The fuel on the secondary air horn is on the top of the flap, close to the firewall. All the electronics are connected. I noticed that when i rev the engine high, i get alot of exhaust fumes. And when i floor it for about 15 seconds, my gas gauge goes down by about 2 gallons! I dont think that is normal!