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Discussion Starter #1
I just got done putting my engine back together but it was timed so bad at first that it backfired through the carb pretty good a couple times. it's a new 600 vacuum secondary. I bought it less than a month ago, does it have built in protection or do I still have to buy the seperate backfire valve? (in which case I probably also need to replace the power valve diaphragm
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Discussion Starter #3
awesome. I'm new to holleys and wasn't sure because I had heard they didn't before. I think I got everything working now (at least in the engine compartment). Just in time for the new engine, hehehe.
 

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I think the whole power valve blow out deal is over blown.
The valve is pretty tough, and the hole the backfire pressure would have to travel through is very small and leads into a chamber behind the valve.

Now, I have seen cars with a direct crosswire of the distributor wires where the backfire was like a gunshot! I'm suprised to see the carb still on the engine when THAT happens!

But an normal sneeze or cough hasn't failed a power valve on any holley I've used in the last 30 years.
But, the blown power valve deal is usually the FIRST thing someone brings up when a Holley carb runs bad.
I've found most often, plugging due to dried out fuel residue in the idle circuit or air bleeds, or bad power block gaskets to cause the trouble.

A periodic flushing out with carb cleaner works wonders.
David

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Check my web page for First Gen Camaro suspension info:
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First Gen Suspension Page
67 RS 327 Origonal owner. 69 Camaro Vintage Racer, 65 Lola T-70 Chev SB Can-Am Vintage Racer

[This message has been edited by davidpozzi (edited 02-28-2002).]
 

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Discussion Starter #5
haha, dave, I hear you, the first night I took out my car (seats with two bolts each, no hood, you get me) and I backfired a fireball through the carb. at night it would have been a beautiful awe inspiring site if it didn't scare the crap out of me
that didn't even really effect my edelbrock, so I had a hard time believing that holley's could be that much weaker in protection.
 

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I think the new fuels with all the ether in them is worse for backfire force.
David

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Check my web page for First Gen Camaro suspension info:
David's Motorsports page
First Gen Suspension Page
67 RS 327 Origonal owner. 69 Camaro Vintage Racer, 65 Lola T-70 Chev SB Can-Am Vintage Racer
 

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I havn't seen too many power valves "blown out" in the sense that the diaphram was ruptured (although I have seen a few that way)....I think that the little bit of heat that does make it through the passages actually damages or hardens the diaphram or somehow hurts the spring making the valve erradic....I've checked a few suspect ones with a checking tool that is used with a vacuum pump and the opening vacuum is never what it is supposed to be and sometimes the valve itself will not fully return to a seated position....and yes I have checked new ones and My guage is pretty close....these are just My findings/thoughts on this....another thing to consider is Holley FINALLY incorperated a checkvalve into their carbs........
 
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