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Re: Intake Backfiring

To: Michael Graziano <mgrazian@ltcm.com>
Subject: Re: Intake Backfiring
From: John Trindle <johnt@tsquare.com>
Date: Mon, 5 Apr 1999 14:49:21 -0400 (EDT)
On Mon, 5 Apr 1999, Michael Graziano wrote:

> Hey folks.  The Midget (1500) has been backfiring through the carb lately.
> I haven't gotten to check the valves yet,  but before I do, I thought I
> might ask if that could be the problem.
> 
> What things _could_ cause the engine to backfire through the carb.  I find
> dark black sooty deposits on the inside of my air filter, and it happens on
> acceleration (often) and deceleration (once or twice)

Others have pointed out that lean running causes backfire through the
carb...

I'm going to go a step further and guess that the reversion on
*deceleration* is indicative of an air leak between throttle plate and
cylinder.  On deceleration with closed throttle you have the highest
manifold vacuum you get, introducing the most air for a small amount of
fuel going in through the "closed" throttle butterfly.  

Anywho, check the manifold-to-head gasket for gaps and the manifold studs
for looseness.  If you have a vacuum advance/retard attached to the
manifold, check the hose and the advance/retard "can" on the distributor.

-- 
John M. Trindle | johnt@tsquare.com    | Tidewater Sports Car Club
'73 MGB DSP     | '69 Spitfire H Stock | '88 RX-7 C Stock




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