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Back pressure

Discussion in 'Chevy Trucks' started by 79GmcBigRed, Sep 7, 2003.

  1. 79GmcBigRed

    79GmcBigRed Junior Member
    from dsghsd
    Messages: 6

    Alrighty i got a few questions here. On my 79 the guy i had bought it from put straight pipe from the headers to glasspacks. And if im not mistakeing back pressure is not good on the engine. There are no cats on this truck just completely straight 3" pipe and i was curious if that is bad or if it woul produce to much back pressure? Also another thing. My truck runs like Poo in the mornings pretty much until it hits about 210 degrees and it will choke itself if it is gassed to much. it has an electric choke. it wouldnt be so bad if it didnt take foever until it heated up. I live in alaska and we've already had the frost hit us and i was wondering if there are any accesories i can put on my truck to possibly get the engine warmed up faster other than a heater block?

    Last edited: Sep 7, 2003
  2. wyldman

    wyldman Member
    Messages: 3,265

    The problem with it running poorly when cold,is probably the choke pull-off.Pass side front of carb,it has a little arm to pull the choke open slightly when the engine starts.

    A good quality block heater will work fine.I have them on our small blocks,and they warm up very quickly,almost heat out the vent from the get go.

    Headers,3" pipes,glasspacks and no cats will have very little backpressure.You do need some backpressure.The glass packs are not the most effecient muffler,so if you want to change something,get rid of them.
  3. snowjoker

    snowjoker Senior Member
    Messages: 283

    I've got cherry bombs / glasspacks on my 84 but have 2 inch tailpipes 10 feet long on each side:cool: Man talk about nice sound i love the rapping when cruising i also have a saying "If it cant look good it better sound good " the truck is a rust bucket but the pipes take away from that :eek:
  4. Rondo

    Rondo Member
    from 54166
    Messages: 52

    Hmmm....see if I can help

    As far as back pressure goes. Low or no pressure is good if you're going drag racing. :nono: For a plow truck you need some. The 3" pipes are OK but you need a muffler that's not straight through. And run the tailpipes to the back of the truck. Longer is better.
    You said you have headers so my guess is that you no longer have the heat tube to the air cleaner. This would give warm air to the air cleaner immediately. Open [aftermarket] air clearners are bad in the cold. Stock ones are better in winter.
    Then, the other dude is right. You probably need a choke pull off. [IF you have a Rochester carb!!!] If you have something else this doesn't' apply and then maybe you just need to adjust the choke setting.
    Next, under the carb, inside the intake is a crossover passage which directs hot exhaust though it to warm the carb. Almost all old Chevy motor are clogged up. If you have an after market intake, these do not even have the crossover. [cold carbs are best for performance] If your's is stock, you might have to pull it to clean it out. Also, Rochester carb are notorious for leaking internally while they sit. That would cause hard starting and rough idle until it warms up.
    Of coarse, plugging in an engine heater will always help in the cold!
    A good tune up is a must for winter too!
    Good luck! :cool: