Having difficulties getting engine timing and idle screws set for basic running around. I cannot currently use a timing light as the dampner has spun so the marks are useless. I am just trying to get timing and idle in the ballpark. I can get the car to start up and idle okay but if I hit the gas pedal while in park the engine will backfire from the exhaust. I have read that it's the timing. I have read that it's the idle mixture. I have read that it's is idling rich or lean. Can someone give me a simple way to set the timing so that it does not backfire. I either need to advance it a little or retard it but no matter which I do, it will still backfire. Anyone had similar issues?
Need some basics on timing and idle setting.
- Thread starter Riggins44
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You are really going to need some kind of timing mark. In my case, what I did was remove the #1 spark plug and stick a rod in there that rested on the piston top. I then turned the engine over by hand (socket on the crank nut) until the rod stopped moving in the upward direction, and used a sharpie pen to mark the damper next to the TDC indicator. I then rotated the engine one complete turn in the other direction, and made a mark. The "real" TDC should be halfway between the two marks on the damper (in my case, this was 15 degrees advanced from the groove on the damper) — I marked this with a dab of white paint. Then use that to set the timing to the factory setting as your starting point.
4spdragtop
Well-Known Member
If your dampner/balancer has spun you need to replace that 1st.
Replace the damper for sure. FIRST. Also, it would help to know what we're workin on here.
You know what I mean.
How about a vacuum gauge. Ah, if he doesn't have a timing light he probably wouldn't have a vacuum gauge.
If I said replace the damper first would that be redundant? I hope not because that’s the first move IMO.
For now, the stick/rod in the #1 hole and mark your old pulley, will get you close. Then replace your pulley.
Sorry. It's a 383.
Indeed, yes.
Year 383? 71 was the last year with a cast crank and the engine was externally balanced. See where we're goin here?
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Take the carb off, flip it upside down and drain it.
Find the transfer slots.
Close the throttles , making sure the choke fast idle-cam is not engaged.
Using the speed screw, adjust the the throttle opening until the transfer slots appear as tiny little squares to a little taller than wide.
Flip the carb over, topside up.
Reset the mixture screws to 2.5 turns out.
If you have a 4bbl.
Make sure the secondaries are completely closed but not sticking.
Adjust your accelerator pump slop to zero.
Reinstall the carb and put some gas in the bowl thru the vent.
Now
Before you start it, I'm assuming that the WET fuel level is doggone close; and that the PCV system is fully functional, that all the air that the intake sees is coming thru the carb, ie ; NOT thru the brake booster, not thru a ruptured VA diaphragm, and not thru manifold leaks.
Next
from this point on,
DO NOT ADJUST THE SPEED SCREW.
Ok start the engine. Set the idle speed with Ignition timing. More timing will make it idle faster, less timing will be slower. Remember;
DO NOT TOUCH THE SPEEDSCREW.
How fast?
Put the trans in gear. If she stalls, it's too slow. If it lurches the whole car, and clangs the trans, that would be too fast. Remember,
DO NOT TOUCH THE SPEEDSCREW.
This will get your idle-timing almost perfect.
Finally, very lightly tip the throttles in;
If she bogs, hesitates, stumbles, or stalls, she wants a little more fuel from the transfers; NOW is the time to adjust the speed screw maybe a half a turn.
Post Idle-timing adjustment;
Warm the engine up. Idle it up to in the window of 1800 to 2200 and fix it on the nearest fast-isle step. Make sure the choke blade is fully off. Twiddle the mixture screws for highest or smoothest rpm.
Idle the engine down then shut it off. Now Open the screws an additional 1/8 turn; then check the new screw setting.
It should be 2.5 turns out. If they are less than 2 or more than three, then most likely your wet float level is not correct, or the engine is sucking air, or the airbleeds need work. Where ever they are, leave them there, both the same.
Ok now, start it up again. Go look for a tip-in sag. Correct as before; now she's as perfect as it gets with the current timing curve.
This is your starter tune.
I cannot help you with Power-Timing nor Stall-timing until you get your balancer fixed and TDC is found. So, If this setting I just gave you, results in detonation at WOT, and you rattle your piston skirts into the pan, that's gunna be on you, cuz you asked;
BTWs
>If you have a 2-bbl carb, everything I said still holds true except obviously you cannot adjust the secondaries, lol.
> make sure your KD system is not holding the throttle open.
>If your VA has a ruptured diaphragm, replace it!
> the VA needs to be on the spark-port.
**
Oh yeah, if you still have after-fires.
on closed throttle;
make sure your exhaust gaskets are 100% not leaking
On smacking the throttle open,
check your accelerator pump-shot.
**
>If you just cannot get rid of it;
check your ignition system, I'm suspecting missfires. or
check your valvesprings for insufficient seat pressure, or check the valve seat seal
Happy HotRodding
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