Thermoreactor to Cat Coverters on 308 GT4

Discussion in 'Technical Q&A' started by rickjaffe, Mar 23, 2005.

  1. rickjaffe

    rickjaffe Formula Junior

    Mar 6, 2005
    Full Name:
    richard jaffe
    In my paperwork for my 75 gt4 I have a statement from a ferrari shop that

    "the exhaust system also has been improved by replacing the non-available (failed) themoreactor with 2 catalytic converters."

    what exactly does that mean?
    1. was the thermoreactor the original emmission control equipment which was replaced by regular catalytic converters?

    2. Is that the same set up as what was put in the late 70's gt4 and other 308s?

    3. If so does that mean I've got the same downgraded performance as those later models?

    4. If so, given that there are no emmision control requirements on classics, can I just get rid of the cat coverters and regain my lost power, or do I have to add/replace some expensive other parts?
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  3. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    Full Name:
    Steve Magnusson
    #2 Steve Magnusson, Mar 23, 2005
    Last edited by a moderator: Sep 7, 2017
    1. the '73 thru '77 US-version 308s came with the thermoreactor muffler

    2. the '78-'79 US-version 308s had the 2 cats + a different muffler

    3. You've still got the better cams, so, if you assume that your existing exhaust set-up is a little more restrictive than the stock thermoreactor set-up, you're somewhere in-between the two.

    4. You've mis-stated this a little -- while the practical matter may be that, on the older cars, without inspection you can get away with most anything, I believe the law is "no modifications" (although it would be a little ironic if they forced you to remove the cats and go back to the thermoreactor muffler). I wouldn't worry about it either way -- it's not a big HP difference. If your air injection system is disabled, you could swap in any muffler (but it's a little silly to leave the air injector nozzles in-place), but if the air injection is still functioning you probably do want a fairly well-insulated muffler.

    For reference, the upper jpeg shows the thermoreactor muffler and the lower jpeg shows the later 2-cat set-up. Is your existing exhaust the stock 2-cat set-up or an "aftermarket" collection of parts?
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  4. robertgarven

    robertgarven F1 Veteran
    Rossa Subscribed Owner

    Feb 24, 2002
    Ventura, California
    Full Name:
    Robert Garven
    Get a tubi. In CA I even passed a smog with it, now The car does not need inspection. The tubi is the best thing i ever did for the car and my drivng pleasure!

    Rob Garven
  5. rickjaffe

    rickjaffe Formula Junior

    Mar 6, 2005
    Full Name:
    richard jaffe
    the car is already pretty loud; how much louder would a tubi make it? also how many thousands of dollars are we talking? (remember this is a 20k car).
    saw on the site some guy with an enzo (what is that 800 to 1.5 million) complaining about spending a 5 or 6 k for tubi's; (guy you would think that if you could spend a mill for a car; why worry about 6k);

    also remember seeing some other options from other companies. wouldn't mind getting some of the hp back but I don't think I'd spend alot of money trying to do it. the guy who sold me the car gave me some sagacious advice to the effect of not putting 40k into a car worth 20k.. I'll try to follow that advice, (if I can).

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