Timing, too far advanced maybe?
Thread Starter
Safety Car
Joined: Dec 2004
Posts: 4,071
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From: San Diego CA
Timing, too far advanced maybe?
I adjusted my timing a bit this afternoon after I changed the oil as I noticed my new harmonic balancer has timing marks all the way up to 60 degrees. I put a divit in the 30 degree mark and busted out the timing light. Put total timing around 36 degrees, or so I hope. I was already close but I made a tad adjustment.
Anyways now I'm wondering if it could be too far advanced as when I floor it or even give it a good shove of the gas it bogs down then comes up, almost like a lean surge. I haven't tried it once it's warmed up all the way, yet, but it seems to bog worse now than it did before. So perhaps I should retard the timing a tad or maybe try a slightly stiffer advance spring?
Anyways now I'm wondering if it could be too far advanced as when I floor it or even give it a good shove of the gas it bogs down then comes up, almost like a lean surge. I haven't tried it once it's warmed up all the way, yet, but it seems to bog worse now than it did before. So perhaps I should retard the timing a tad or maybe try a slightly stiffer advance spring?
Thread Starter
Safety Car
Joined: Dec 2004
Posts: 4,071
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From: San Diego CA
Geez where is everyone?
Well I tested it out on a bit of straight road and was going ~20 mph then floored it. It hesitated for almost 2 whole seconds before it went like a bat out of hell. Should I try retarding it a tad?
Edit: Talked to Top flight corvette and to them it sounds like it's more likely that it's dumping fuel in to the intake and not getting enough air. So possibly a choke issue or maybe the jets a tad too big? (q-jet by the way) It's not pinging or detonating so I would assume the timing isn't too far advanced.
Well I tested it out on a bit of straight road and was going ~20 mph then floored it. It hesitated for almost 2 whole seconds before it went like a bat out of hell. Should I try retarding it a tad?
Edit: Talked to Top flight corvette and to them it sounds like it's more likely that it's dumping fuel in to the intake and not getting enough air. So possibly a choke issue or maybe the jets a tad too big? (q-jet by the way) It's not pinging or detonating so I would assume the timing isn't too far advanced.
Last edited by Kalway; May 28, 2007 at 01:50 PM.
Le Mans Master
Joined: Apr 2004
Posts: 7,106
Likes: 38
From: Newark DE
if it doesn't pink or knock it shouldn't be the timing.
if mechanical timing is too high is when detonation is evident. if it surges or chuggs during a steady cruising it's usually too much vacuum advance.
the hesitation or bogging down as you describe sounds like a carb adjustment issue
if mechanical timing is too high is when detonation is evident. if it surges or chuggs during a steady cruising it's usually too much vacuum advance.
the hesitation or bogging down as you describe sounds like a carb adjustment issue
Le Mans Master
Joined: May 2002
Posts: 5,086
Likes: 786
From: Lebanon Township New Jersey
I don't think its a timing issue either. Could be that the top flap on your secondaries is set too loose. There is a spring that you can tighten to adjust it and make it open more slowly.
Thread Starter
Safety Car
Joined: Dec 2004
Posts: 4,071
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From: San Diego CA
The airhorn has been taken off several times since lars last touched it. 
Here's something I'm noticing. In park, if I hit it WOT from idle the secondaries will open a tad, when it gets to probably ~4000 rpm. I thought the secondaries were supposed to never open when there's no load on the engine.
Here's something I'm noticing. In park, if I hit it WOT from idle the secondaries will open a tad, when it gets to probably ~4000 rpm. I thought the secondaries were supposed to never open when there's no load on the engine.
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Race Director
Joined: Mar 2006
Posts: 14,112
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From: Florida
That can be normal. Most people just don't rev it high enough or long enough for that to happen in neutral. I can get mine to open about 1/3 of the way.
I recommend not revving that long though.
If you've had the top off, double check the pull off and sec airvalve operation.
Your timing is probably good.
Check for your sec air valve opening too fast or the accel pump squirt or float level.
I recommend not revving that long though.
If you've had the top off, double check the pull off and sec airvalve operation.
Your timing is probably good.
Check for your sec air valve opening too fast or the accel pump squirt or float level.
Thread Starter
Safety Car
Joined: Dec 2004
Posts: 4,071
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From: San Diego CA
Well I know the accelerator pump gives a good squirt and we recently adjusted the secondary air valve screw to the right tension. So I'll check the float next. Never thought about that maybe getting low.
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
You can test your sec air valve by setting the spring tighter than spec and seeing if that eliminated the bog. The tension is correct when it opens smoothly with no bog. Check the pull off spec for opening time.
