We've had problems with my carb at WOT. The Primaries run great on it and the secondaries are decent. The Problem is at WOT the engine seems to cut in and out slightly. If you back off the throttle slightly the cutting off stops. My dad and i mentally noted the throttle position and while in the driveway we looked to see what the secondary throttle plates were doing when we back off. They are practically closed. So whats going on guys? He have a modded engine, headers, cam, intake, breakerless ignition ect ect. What have you guys had to do to your carb to take it up a notch for upgrades. We have the carb kit and have been messing around with different combinations. Wat have you guys done to fix this problem.
Assuming you're running a q-jet... If the secondary air valves - not throttle blades - are opening properly (you probably won't see this revving in park, they take a moment to open under WOT), then I suspect you may have a fuel delivery issue. Has anything been done to check or upgrade the fuel system? Devon
9 out of 10 times this problem is caused by not enough fuel. Remove the return line from your fuel pump and plug it. Then give it a go. :TU:
we will check thouse things. It feels like it takes way to long to wind up to redline. I've got a 3.9 gear so it should wind up real quick. It takes for ever to hit redline after 4,000 rpms
Another thing that helps with diagnosis is a fuel pressure gage...if you have unrestricted lines and at least 1-2 psi at WOT, you might end up looking for some other problem. Devon
i only have the line that goes into the carb and the one that comes from the gas tank. So what do you mean?
no we havents upgraded or check the fuel system. When i changed the manifold i had to put in a rubber line from the metal line to the carb to make up for the height difference.
maybe i need a new fuel pump, its the original un-rebuilt one still in there. We also have a high flow needle and seat. Would that help solve the fuel starvation?
Before we can say for sure, the pressure check should be done. That way you don't have to spend money guessing (or maybe you have a newer or hi-po fuel pump you can try?). Devon
i think these guys are steering you in the right direction i assume you dont have air cond sisnce you only have one line from tank to fuel pump? pull your gas filter and cut it open see if its got gunk in it.replace it anyways.eliminate that possibilty but it can tell you how much crap is in your tank/lines check your rubber hoses for cracks or being wet after engine was ran even by tank ,if so replace. if you can put a fuel gauge on it and check fuel pressure under load.it should be 4-5 under load .if not replace/ upgrade
Good advice, Andy, though I have to say I've not seen a stock pump hit such high pressure at full throttle on a healthy engine. o No: I did more digging; Doug Roe's "Rochester Carburetors" book says the q-jet can perform on 2 psi, but ideally should be no less than 4, no more than 6, for what it's worth. Jake, I hope the detail is of more help! Devon
Just FYI, a new pump might be good insurance anyway, had the original one let go on me 150 miles from home. A new one cost 13.95 and took me an hour to install without jack stands and me being an idiot and not putting the engine at TDC.
where did you find one for $13. TA sells that one for like 70. Im going to check the filter and what not. I'm gonna head up to murrays and get some valve cover gaskets (pos chrome valve covers :af: ). I'll ask them about fuel pumps and how much $$ they want. Im hoping that we can get this thing running good before i leave for bootcamp. I wana take it to the track at least once before i leave.
Doesn't look correct and probably isn't the same quality as the TA one but for insurance I say throw it on and keep your old one. If the new one craps out, throw the old one on and get another one. edit: I just checked, TA's is a high flow pump, more than you'd need. http://www.partsamerica.com/ProductDetail.aspx?mfrcode=MST&mfrpartnumber=41197&parttype=52&ptset=A
PROBLEM SOLVED! For anyone that has given me help in the last six months thanks. We've been working on getting this car running good for a long time and been very frustrated. We've gone through vacuum leaks, fuel lines and pumps, timing problems, and gone through the carb numerous times and now we got this baby singing. The final solution to our problem was changing over to a high flow high cap. needle and seat assembly. On the first trail run to an open house I brought the hammer down and she's back and more. That sucker really really flies. There is no more stumble or struggle at WOT, you can feel her take a big gulp as the secondaries flip open for a scream. We will be doing some fine tuning today and fiddling with a few more things but she is definitely hauling. Thanks again for every one that has helped me and my dad identify the numerous problems and things that needed to be changed. This site is priceless when it comes to this stuff. Our next goal is taking it to the strip and we will get you guys some time slips. Thanks again -Jake- :3gears:
