Help, 302 with bad (?) idle..
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Fleet Mechanic
Joined: Apr 2004
Posts: 1,443
Likes: 5
From: Willamette Valley, Oregon
Help, 302 with bad (?) idle..
I have a 302 from the early 70's in my 56 F-100, has a C4. 2 Bbl carb, stock ignition, new points, plugs, wires, cap, rotor, condenser. When I bought it I was told "it has a bit of a cam in it" I do not know if that is true or not. Had a rough idle before a tune up, still has it after all that. At an idle it sounds like a miss, the whole truck shakes, it is set at the factory specs for idle level. Runs well over all, however shakes a bit at idle. I have no experience with this engine so I am relying on you folks for a hand here. What should it "feel" like and "sound" like at an idle, and how can I smooth it out? Or should I?
Thanks..
Thanks..
Junior User
Joined: Apr 2004
Posts: 99
Likes: 0
From: Wausau.WI
You might want to look into your vacuum, it's hard to say but I would think with a 2 Bbl and an auto trans the cams not real big, but who knows. Ive got a summit cam in a 70 302 the cam runs 2000-45000 RPM that is smooth at idle. The other mods are .30 over, 10.5:1 comp, 650 holly vac sec, stelth intake, headers. One more thing to look at is the dwell of your points. When the dwell slips on my points the 302 will idle rough.
Hope this helps
Hope this helps
Junior User
Joined: Apr 2004
Posts: 99
Likes: 0
From: Wausau.WI
For the vacuum test you will need a vacuum gauge. warm up your motor and hook it up to a intake fiting, the reading should be around 12 to 16 at idle I think. Most gauge's have a normal scale on them. Of corse your vacuum reading will very by cam size and such. When your in there look for and hose's that might be off, cracked or lose. Also a bad carb base gasket or intake gasket could be a leaker. Dont forget the vacuum hook up at the tranny for the modulator.
Keep me posted if you like
If it's not vacuum there are some other things we can look into.
Keep me posted if you like
If it's not vacuum there are some other things we can look into.
No problem. I hope it helped.
