I've installed a newly rebuilt 428 I don't seem to have the power I should. it tuned up ok timing,rpm's,temp all look good.I don't know if I'am getting enough fuel to my qudrajet.It runs around 5.5psi at idle. at 40 mph if I try to accerate it goes down to around 2psi is this normal??any suggestions would be welcome to try to get my power.
Lots of variables. Kinked fuel line, gas tank sock clogged, fuel filter clogged, bad fuel pump, float not set correctly on carb, to lean, too rich, timing not right, ignition issues with coil, wires, plugs not gapped correctly. Need info on initial and total mechanical timing, vac reading at idle, what type of ignition (HEI or Points, etc), what type of plugs? What type of cam is in there, what heads, and what gear ratio?What do you mean by it has no power? Does it bog, misfire, or just won't shred the tires?
I have used the same gas lines & tank for 4 years with a small 400 it was ok, same hi end plug wires, new plugs gapped around .055, new generic HEI dist. (not to sure about that either)stock 46 heads, 15" steady vac at idle. rear end 355 with 2004r trans I have used for 2 years. Carb rebuilt quadrajet. timing set to 9 degrees @ approx 800rpm. Main problem is acceleration,it drives fine, i've had it upto around 60mph & engine runs smooth. I'am going to try a 750 edelbrock carb this weekend.
Only to help out, but why would trying another carburator increase fuel pressure? If the carb has a higher demand, it would drop pressure further, wouldn't it?
I don't think fuel pressure is the issue. One time when the jesus clip was hanging up in my quadrajet--listening to all these "experts"--I focused on fuel pressure being too great. I installed a fuel pressure regulator. Reagrdless to the setting, even down at 1 psi, the car had the same performance.
It can be a handfull of things that cause the problem, but I'd concentrate on timing, whether it be initial, advance, or cam. If there wasn't a hot start problem, the first thing I'd do is bump up the initial timing. Next, I'd play with the timing advance.
A while back, I remember reading something about manafacturers retarding the keyways in timing gears as an emission reduction. (You see, people could simply put older--more advanced--timed cam gears in emisson controlled cars and up the hp. I don't know if this still goes on, but if the gear application covers 55-81 Pontiac, something in the timming has to be chopped. Otherwise, these parts would be in volation of federal emission laws, something that manafactures don't want to do.
I have no clue as to how to degree a cam, or check it, so unless you know the cam's timing, it's dealer's choice as to its degree.
So you have 9 degrees initial mechanical (with the vac adv plugged) at idle. That may have been the factory setting, but with an after market HEI that setting is I'll bet way off. Do you have a dial back timing light? You need to check total mechanical advance and what RPMs it's all in by. I had my HEI recurved by this guy Sun Tuned on the CP web site. Not only did it come back all shiney new and a piece of art, but he curved it so I can have 14 initial mechanical and 36 total mechanical all in by 2800 RPMs. I then use a vac can with 8 degrees of adv that I use on ported vac source. Works very, very well on my 400. As a quick test, have you tried switching vac adv from full manifold to ported, etc? You also didn't mention what cam you have. Too radical and you will have no low end power enough to even spin the tires. Keep us posted - it took me many months to get my setup running the way I want it. If it's still a dog with the Edel 750 and timing changes, I learned a few tricks on how to set that carb up nice. (I have a model 1411).
What makes you think its a fuel problem. Is the car nose diving when you put it to the wood. The first thing that comes to mind for me is are the secondaris opening to slow or fast. Did you change to a richer needle and jet combo. If this is the same carb that was on your 400 it may be way to lean for you 428. My brother just dyno a 455 and we gained 40hp from jumping the jet sizes up 6 numbers both front and back. This was a demon not a quadrajet but same principle. I would think it would be normal for your pressure to go down with the car accelerating.
I don't Know if it a fuel problem, I do think it is a carb related problem. I have not used this carb before. I'am looking at the secondaries. Very good suggestion, I already have a edelbrock that I know works. I will end up with a quadrajet. I will probably be changing the jets and looking at the pulloff & secondary cam.
I changed the carb today not much of a difference between the quadrajet & the edelbrock, the car ran a little smoother at idle but power wasn't much better. I checked dist mechanical timing:idle set at 800rpm 9d, @1000=14d ,@1200=20d ,@1500=26d ,@2000=29d ,@2500=31d. I dont Know much about distributors or what the timing should be for this engine. I belive I have a crane cam #283951 288/458
Experiment with advancing the timing. Try it by ear. Advance it a small amount and listen to the throttle response. If you get it too advanced you will get spark knock and hard starting. Jim
Some quotes on that cam you are using from the CP web site regarding no low end power:
"If it has 288 degrees duration at .050" lift. That is your problem. You need at least 3.90:1 rear gears with that cam. It has no cylinder pressure at low RPM. That means it has NO low end torque and you need the low gears to bring the RPM up quickly to get the engine in cam range. Simple as that."
"Launching at a higher RPM won't help much. It will fall flat on it's face a few yard out of the hole. You need lower gears to sustain the high RPM launch down track with a long duration cam."
"That's a fairly aggressive cam. It's a little hotter than a "744" cam and just slightly less crazy than the "041" cam. It probably won't have a ton of bottom end without Rhoads or other bleed-down hydraulic lifters. You might need to attend to the primary circuit of the carburetor and ensure that the fuel delivery curve is adequate for the low vacuum and low RPM you're seeing off the line."
First adavnce your initial timing to 12, give it a try and then 14 if you still see no improvement. If still not much of a change put the pump shot arm on the carb at the top hole. If still no good you will need the edel calibration kit to change out jets/ rods and step up spring. What stall converter do you have with the tranny? I think you are going to need at least a 2500 stall with that cam. It's a failrly radical cam that is designed for power in the high RPM range - so down low it's going to be low on power.
