Ok I was having a problem with a unsteady idle so I rebuilt my Carburetor ,( which had a bunch of crap in it ) BUT still have a problem. So I connected a Vacuum Gauge and the needle is really crazy at idle around 11in to 15in SHAKEN LIKE CRAZY if you rev it up the needle still shakes but the vacuum goes to 15in and 20 in . Vacuum leak at the Manifold??? or Valve train issue's . Overall the motor runs preety smooth you can hear a slight miss at idle but it sounds pretty good and smooth revved up , Open to any and all thoughts on this???? Danielle
Sounds like a burnt valve or a lousey tune...Have you thrown a tune up at it yet??? Plugs/wires/cap/rotor/fuel filter/points&condensor (if it has em).Set timing and adjust carburetor.Could be a simple vacuum leak too.
Danielle; check the vacuum modulator line. Make sure it is there, and that the rubber line is good, and the steel line isn't kinked, bent or rusted apart.
Thanks everyone Tomorrow i will get at it again , had to quit when the sun went down tonight . The link Thomas posted was great. The bad news is I may be looking at a burned valve .
Earl I have two lines that go to the tranny vacuum modulator one is hooked to the intake and the other is not hooked to any thing ,Any ideas where it should get hooked two . 1974 250cubicin straight 6 with a c-4 .
Danielle; check on the modulator and see if there are two ports. If not, plug off the one that is not hooked up. That will at least get the vacuum leak. On a '74, I think they all had one port. Let us know how it works out. Good luck!
Ok Sorry I am still bugging every one, But I have not yet figuried this one out . I still have a problem !! So here is what I have done ,Compression check 150,145,140,140,145,150 reset timing 8 degrees btc ,rebuilt carb, replaced plugs ,points, condensor, cap, rotor, plugwires, removed EGR and installed steel plate with gasket, Sympton's rough idle , runs good above idle . if I spray carb cleaner near front of the cyl head between intake runnels and valve cover. The idle speeds up ??? If you put a vacuum gauge on it reads 15 to 20in but it vibrates like crazy between the two readings like crazy, So are the intake manifold and head all one piece?? Is there a gasket between the two ? and do these 250 6cyl have a history of cracked Intakes? Any and all thoughts are welcome .
Sounds like a cracked intake runner or the soft plug at the end of it(round metal plug in end of intake)has a hole in it or is no longer sealing well. Make sure there arent any un plugged/un covered vacuum nipples in the vicinity where you sprayed.
WO HOO!!! PROBLEM SOLVED Yes I thought that the intake might have a crack in one of the runners too, so I steam cleaned it and was giving the manifold a very close inspection today, But it all looked very good, so I went to remove the EGR spacer that is between the manifold and Carb and there was my problem staring me in the face , the gasket between the manifold and spacer had a big piece missing out of it , about a one inch section was gone. Man am I glad thats over with, I was getting worried I might have to get a whole new cyl head , Thanks for all the help guys, it really helps to know you are all here to bounce ideas off of and get a new perspective on things when you hit a mental block on these type of problems , On the road again, Yee haw! ~ Danielle
