Forum Discussion

john_engel's avatar
john_engel
Explorer
Jul 14, 2016

Header Installation - Abandon EGR Tube? - Acetone?

Hello all,
I just installed a set of Thorley headers on a Chevy 454 7.4L to fix leaky stock manifolds, great solution! Performance is awesome!!

My only issue is that the new headers don't have a fitting/port for the EGR tube that runs back to the manifold. Is it ok to abandon/block off the tube? Performance is great right now and it isn't throwing a code. Will it affect gas mileage?

I called a custom shop that is pretty reputable here and the guy said it wouldn't affect mileage and just to leave it capped. He DID suggest however to add 1 0z acetone to every 20L of fuel to increase gas mileage.

Any input on both of these issues?
Class A
  • Dannyabear1's avatar
    Dannyabear1
    Explorer
    Jul 14, 2016
    One once of acetone will evaporate long before it makes it into the engine
  • RLS7201's avatar
    RLS7201
    Explorer II
    Jul 14, 2016
    The EGR valve was installed to lower combustion chamber temperatures, which reduced the formation of NoX. Then the ignition timing was advanced to help compensate for reduced performance. With NO EGR and advanced timing, there is a chance of burning a hole in a piston.

    Richard
  • DavidP's avatar
    DavidP
    Explorer
    Jul 14, 2016
    Remove it completely and block the hole left on the intake manifold with a set of block-off plates. Easy to make but can also be purchased. You can also reuse the factory nuts. This will have no effect on emission testing. No reason to use acetone. Acetone can actually make the fuel worse if the fuel is laden with ethanol. If you really want a good additive for cleaning, stabilizing and helping with ethanol (if present in your fuel) look at PRI-G.
  • llr's avatar
    llr
    Explorer
    Jul 14, 2016
    i suspect the acetone is to clean the fuel system which would help. not sure if I would try it but if you trust the shop try it.

    I added headers and free flow intake to a 1977 class C many years ago, performance increased and mileage went up by 1.5MPG which was even better
  • sailor_lou's avatar
    sailor_lou
    Explorer
    Jul 14, 2016
    I don't see a problem leaving the EGR capped provided you don't have an issue with DMV inspections (provided you even have inspections). The acetone is a new one on me and it's difficult to believe 1 oz. in all that fuel would make any difference in MPG.

    Lou
    05 Travel Supreme Envoy

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