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Re: Popping back through Carb

To: "Olson, Mark W" <mark.w.olson@intel.com>
Subject: Re: Popping back through Carb
From: Steve Laifman <SLaifman@socal.rr.com>
Date: Mon, 23 Dec 2002 10:12:58 -0800

I guess your lifter was stuck full up, rather than full down.

On the power valve blow-out on backfire. This was a big problem with 
Holley's design, but an after market firm is marketing a blow-back 
relief valve kit. You take the carb body off the base plate, use the 
included special size small drill to put a hole in the base plate, push 
in the little valve, and the system is protected.  Holley thought so 
much of the idea that all their later designs already include one.  The 
item is available from places like Summit for about $6-$7  (see 
TigersUnited Online Resources, Performance Parts Suppliers) for a number 
of such providers (including Holley)


Olson, Mark W wrote:

>I used to have a '72 GMC pickup w/ a straight 6 that had exactly the same 
>symptoms.  It had a VERY sticky lifter that I surmised was not letting an 
>intake valve close completely, although I was amazed at that idea, given the 
>strength of valve springs.  But I was desperate, so I replaced the lifters and 
>the problem went away completely.
>If you are running a Holley, and you get a backfire through it, you are 
>running a big risk that you'll blow out your power valve.  Maybe someone else 
>can explain that.
>BTW, with my pickup, it would get real exciting.  When it would backfire, the 
>choke butterfly would bend and stick shut.  This would happen usually when I 
>really needed some acceleration to get onto a crowded freeway.  So I'd find 
>myself on the shoulder of a crowded freeway at the end of an onramp with a 
>stalled truck.  I kept a large bolt on the dash, so I could get out, take off 
>the air cleaner, whack the butterfly valve with the bolt to open it up and 
>then try to figure out how to get onto a crowded 75mph freeway with no runway 
>and try not to do it all over again.  It was exciting.
>Good luck.


Steve Laifman

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