Detonation on startup
Thread Starter
Racer
Joined: Jul 2008
Posts: 323
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Detonation on startup
What causes just a small detonation knock at the startup moment on a chevy BB?
Is has 11 degrees timing at idle. 36 total. No detonation on idle or load, just a small ping at startup.
thank you
Is has 11 degrees timing at idle. 36 total. No detonation on idle or load, just a small ping at startup.
thank you
Last edited by 70rs/ss396; Jun 18, 2020 at 02:55 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
If it has 11 degrees advance at idle with vacuum advance still connected, you have the ignition timing WAAYYY retarded. 12-15 degrees advance with vacuum advance DISCONNECTED (and hose plugged off) would be where you want it.
Race Director
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From: Virginia
What is the total vacuum advance, and is it connected to ported or manifold vacuum? If you didn't buy the correct can, add a limiter, or put in an adjustable can, and measure the result, it may be too much.
Thread Starter
Racer
Joined: Jul 2008
Posts: 323
Likes: 18
Thread Starter
Racer
Joined: Jul 2008
Posts: 323
Likes: 18
The distributor has no vacuum.
Last edited by 70rs/ss396; Jun 18, 2020 at 11:55 PM.
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Thread Starter
Racer
Joined: Jul 2008
Posts: 323
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Im thinking this engine dont like my 870 Street avenger, its a vacuum carb and onley one acc pump. Think it want more fuel....dubble pumper...
Becasue its hard to start when cold to.....starts Easy when hot.
I have no choke, and with dual plane intake and Only fuel from one accpump, I think it wants more fuel...
Is my vette stock?? HAHA
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Sounds like your idle may be lean or your squirted are too small....if you don’t have ping anywhere else, then it’s a lean condition at startup. What rpm is it at when it pings. What’s your choke idle speed. You could also put more tension on your choke to fatten up the initial fuel charge
Thread Starter
Racer
Joined: Jul 2008
Posts: 323
Likes: 18
Sounds like your idle may be lean or your squirted are too small....if you don’t have ping anywhere else, then it’s a lean condition at startup. What rpm is it at when it pings. What’s your choke idle speed. You could also put more tension on your choke to fatten up the initial fuel charge
Thread Starter
Racer
Joined: Jul 2008
Posts: 323
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461 ci
10.0 comp.
comp hydraulic roller #11-451-8 0.547/0.547
LS6 intake
edelbrock performer rpm aluminium heads. Rec port.
holley 870 Street avenger.
Hmmm...I know the fuel in the car is atleast 3-4 years old. But it should ping under load if fuel was tooo old.
10.0 comp.
comp hydraulic roller #11-451-8 0.547/0.547
LS6 intake
edelbrock performer rpm aluminium heads. Rec port.
holley 870 Street avenger.
Hmmm...I know the fuel in the car is atleast 3-4 years old. But it should ping under load if fuel was tooo old.
Thread Starter
Racer
Joined: Jul 2008
Posts: 323
Likes: 18
Sounds like your idle may be lean or your squirted are too small....if you don’t have ping anywhere else, then it’s a lean condition at startup. What rpm is it at when it pings. What’s your choke idle speed. You could also put more tension on your choke to fatten up the initial fuel charge
cant say any rpm....its in the precise startup
Last edited by 70rs/ss396; Jun 19, 2020 at 11:04 AM.
Is my vette stock?? HAHA
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Unless you pump it 5 to 7 times risking flooding, I don’t know if there’s anything you can do
Thread Starter
Racer
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