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302 problems

Discussion in 'Ford Trucks' started by Grshppr, Jan 20, 2003.

  1. Grshppr

    Grshppr Senior Member
    Messages: 268

    I've got a 302 in a 86 F150 SB 4X4. The engine I have in it was apparently rebuilt a couple of years ago. It runs beatiful, idles nice, doesn't use oil, and has never let me down. It has very bad gas mileage. (about 4mpg) It has 1/4 the power of my 76 blazer with a 350. Ive had different mechanics put different carbs on it, and it makes absolutely no difference. They say the carb is tuned perfectly. No opinions from them as to what it could be. I was wondering, could it be the cam? What about gearing, the truck was a stick shift origionally, and someone converted it to an automatic. Any opinions would be greatly appreciated. :confused:
  2. wyldman

    wyldman Member
    Messages: 3,265

    It could be the cam,or cam timing,or ign timing,or weak coil,etc,etc

    I would start by checking the exhaust,for a plugged cat,muffler etc.If you bang on the cat and it rattles it may have come apart inside.Go to a muffler shop and get them to put a test pipe on it,to bypass the cat.If power improves,then replace the cat.If the cat has come apart,have them check the muffler for pieces of the cat stuck in it as well.

    Next I would check the basics like compression,plugs,wires,cap,coil,etc.See if you can borrow or swap a coil and just try it.Also check the EGR system,EGR valve may be leaking internally or stuck open.

    Next I would try ignition timing.You can do this yourself.Loosen the dist assy and advance the timing a bit.Does it ping ?If not go a little more.What your trying to do is find the max timing without pinging.Once it pings,back it off just a bit.

    If that doesn't fix it then either your carb is too big for that motor,or you may have a bad timing chain,which retards the cam timing.
  3. Grshppr

    Grshppr Senior Member
    Messages: 268

    Thanks for the relpy. I think I will focus on the cam or cam timing. Those things I haven't checked out yet. The card is a 650 edlebrock, so it should be good for the 302. New coil/plugs/egr /mufflers/ and has no cat. The ignition timing has been advanced as far as it can. Thanks again, I think I'll check the cam and timing chain in March once the snow is gone, as the truck has works fine right now and has for 4 years now, but it sure would be nice to get more power and gas mileage. Good thing it isn't my daily driver or I'd be working for Petro Canada.:D
  4. wyldman

    wyldman Member
    Messages: 3,265

    Sounds like you have a handle on it so far.If your going to replace the cam,go small,and with something that makes lots of low end power,especially in a truck.Will help in the mileage dept too.
  5. mike9497

    mike9497 Senior Member
    Messages: 466

    being a mustang mod builder.the first thing i always did with them was the cats and mufflers.get rid of them and put high flow units in.second if its an EFI change the intake.i've done that on some f150 and 250 both with 302 and 4.6 281 i installed alot of GT-40 intakes on the 150s and some custom intakes for 4.6L.but check the little things like air filter,vac lines,plugs,coil.when these items are not 100% the gas mileage will stink.air filter and exhaust seems to be the problem areas when this happens
  6. Pelican

    Pelican 2000 Club Member
    Messages: 2,075

    Another thing to check is that your vacuum advance line is going to the right port. I had made a swap and used the wrong port, the truck was a dog and acted like you describe. I took it to 3 different shops who didn't find it, finally a friend who's real sharp looked it over and spotted it.

    I've got the same carb on a 351, I'll look tomorrow and see where it is.

    CARDOCTOR PlowSite.com Addict
    Messages: 1,304




  8. Grshppr

    Grshppr Senior Member
    Messages: 268

    Thanks for the info guys! As the truck is working half decent now, I will wait until spring to try these suggestions. I'll post the results once its fixed.

    Chris V