Jump right in:
1) theres a little bit of a lope at 600-700 rpm idle
2) standing on brake and transmission set in drive with accelerating to high RPM the engine starts missing spray starter fluid over carb it smooths out
3) driving it varies performance with light acceleration the engine seems ok til about 50 mph or so then feels like its surging. Especially above 60 mph when trying to climb grades or pass there is pulsing and lag in performance.
4) at times the engine will pulse or lag just in city driving with mild acceleration to 35 mph
Things that have been checked or changed: plugs, points, timing
The carb is a Rochester QJ that was rebuilt "professionally" supposedly to spec. What do I look for? All input is welcome... Thanks in advance TD
Secondary seems to kick in and there is down shift
Check the Vacuum advance and if that is okay, check the adjustment on the spring controlling the secondary air door.
Greg Surfas
Along with the above---especially the vacuum advance that is very oftened overlooked and very easy to diagnose, I'd look at fuel delivery- there is the fuel pump, there is the fuel line--- a pin hole in metal (sometimes in the tank pick up--)or crack in rubber hose(s), then there are filters-- one in fuel tank, and on some fuel pumps ( at the input of the fuel pump housing), and then, of course, one just before the carburetor, and one on the carburetor input. There are several ways to "cut to the chase" regarding fuel flow, (a fuel pressure gauge), but the one approach I use is potentially very dangerous and requires some technical knowledge . Any minor debris build up in these filters or a small pin hole or crack in a fuel delivery pipe will cause your engine to "starve" for fuel--- which causes "surging," stalling, and loss of power during acceleration. Because well functioning fuel pump will work to supply fuel in spite of clogs and vacuum leaks in the lines, there is no reliable way to diagnose the issue without digging in to and eliminating each potential clog or break or mechanical issue with the pump. Hope this helps, James
vacuum advance is good. Regarding the fuel supply. There is the original glass bowl fuel filter just before the carb. Filter is clean. The rubber lines coming off tank to metal have been replaced recently. However, I was told that using regular fuel line hose would not work. That the hose was too soft and would suck itself shutting off fuel. I have a hard time believing that the would be enough draw from fuel pump to actually collapse the line. Number two isn't there enough fuel both in filter and carb that if that would not be an issue?
As mentioned have you checked the filter in the carb inlet fitting?
I agree with Dave, and, you're the best assessor of your tech knowledge, mechanical skills, and concerns for safety, so if you are comfortable taking off the line coming off the filter and into the carburetor, and that can be a real chore, as it's easy to damage the carburetor threads at this juncture. So with the fuel line off the filter outlet, another length of flexible hose sufficiently long enough to be away from the engine, and with a containment cup to catch the fuel, having some one crank the engine while you observe the output from the pipe will provide you with some evidence as to the condition of the plumbing and filters as well as, perhaps, your fuel pump (or, you could purchase a fuel pressure gauge). If you attempt this, PLEASE be very cautious, make certain that you're only cranking the engine, and have a fire extinguisher handy. If the gasoline piping, associated filters and fuel pump are in good working order, you'll get a pulsing flow of fuel of considerable quantity, and if that's the case, then take off the fuel filter at the carburetor inlet. If that's clean, then you've all but eliminated fuel delivery and fuel pressure issues... but so much can be even slightly amiss with fuel delivery on these pld cars, that simple issues can create the kinds of failures you're experiencing. Hope this helps, but please don't attempt this diagnosis unless you're very comfortable and experienced and be very careful. James
Ok understood regarding the fuel line test. I will also double check the carb filter. thanks for all input
In regard to the supply line collapsing, it can and will very easily. Even with new fuel line hose. Use hose rated for fuel injection. The Deathanol in todays fuel won't deteriorate the rubber in that type of hose. I chased that same problem in my Eldorado. Replaced all of the rubber lines with fuel injection rated hose and the problem was solved.
I now only use Deathanol free fuel in my classics.