How much ignition timing does it have now? If it never detonated before and it does now it has more timing now than it did.
Doug
Detonation after distributor cap install.
- Thread starter kaj750
- Start date
Doug
kaj750
Well-Known Member
I have it where it was. Could just swapping out bad wires create a situation where I need to reduce timing further? I have no problem, giving it a shot, of course.
You would think. I'll finish swapping the spark plugs tomorrow and see what happens. The plugs in there now are NGK, cross-referenced from a catalog. Confirmed by physically being no different than the autolite plugs that came out before. Throwing in another set of 58s. At this point, the spark plugs are the only, actual change from before.
1 Wild R/T
Well-Known Member
Like I stated back in post 24...
Your old cap was junk... I've seen caps like that before where the engine ran like crap... Adding timing made the engine run better... Putting a new cap on means you need to pull timing out in order to run right...
So there's actually a pretty good chance that cap was bad when you bought the car... The erosion of the plastic around the center electrode didn't happen overnight...
Your old cap was junk... I've seen caps like that before where the engine ran like crap... Adding timing made the engine run better... Putting a new cap on means you need to pull timing out in order to run right...
So there's actually a pretty good chance that cap was bad when you bought the car... The erosion of the plastic around the center electrode didn't happen overnight...
Geoff 2
Well-Known Member
Another possibility for the detonation.
The dist will have an internal centrifugal curve that advances the timing. Done with weights & springs. Spring could have stretched or come off, allowing timing to advance more than it should.
The dist will have an internal centrifugal curve that advances the timing. Done with weights & springs. Spring could have stretched or come off, allowing timing to advance more than it should.
Some Car Guy
Well-Known Member
Set total to 34. I’d do that before changing plugs. NGK 5s are what you want.
Some Car Guy
Well-Known Member
Since we don’t know what his timing is at, getting the total under control is first priority. If he’s pinging at 34, then we can get into the curve.
LowBikeMike
Well-Known Member
Under what conditions does it detonate? Normal driving, heavy acceleration? I run a Unilite and get detonation in 4th gear mid to full throttle or heavy load.
kaj750
Well-Known Member
New post because I'm still dealing with this. Is it possible what I think is detonation, beginning at 2k RPM could be valvetrain noise? Loose lifter(s)? I just got done driving the car and the AFRs are in the 11s with timing at 29* at 2k RPM. It's rattling like nobody's business as soon as I hit 2k RPM, which is why I assumed it was detonation. But... it's pretty loud and starting to sound mechanical, possibly getting louder (I haven't driven the car in a while, so maybe it's noisier because I haven't heard it for some time).
I marked the balancer when the piston hit the stop, in both directions, and noticed the OEM timing mark is not in the middle. I have a paint spot next to the timing mark on the block. The paint and OEM mark are about the same distance away from each other as the balancer mark is from where it should be, if that makes sense. So... whomever built the engine looks to have made the paint mark the "new" TDC. I set the timing mark on the balancer to that paint spot.
I have a Mallory distributor. The "eye" lined up perfectly with one of the gaps in the rotor, per instructions. The rotor was pointed at my #1 plug wire.
All seems to be correct.
Timing at idle is 10* with 29* at 2k RPM.
I do not believe the car is running out-of-the-ordinary compression and is using 87oct pump gas (same as I've always run).
Fueling is a Sniper 2 (which is working perfectly).
Car never had this problem until I swapped from an OEM coil to an Accel (I didn't know they weren't compatible). Since then, I've had this problem, even after swapping back to the OEM coil.
If this is valvetrain, then that's a hilarious coincidence, that's sent me down this rabbit hole.
To reiterate: engine is a 440 of unknown year, stock heads. Mallory Unilite dist.
I marked the balancer when the piston hit the stop, in both directions, and noticed the OEM timing mark is not in the middle. I have a paint spot next to the timing mark on the block. The paint and OEM mark are about the same distance away from each other as the balancer mark is from where it should be, if that makes sense. So... whomever built the engine looks to have made the paint mark the "new" TDC. I set the timing mark on the balancer to that paint spot.
I have a Mallory distributor. The "eye" lined up perfectly with one of the gaps in the rotor, per instructions. The rotor was pointed at my #1 plug wire.
All seems to be correct.
Timing at idle is 10* with 29* at 2k RPM.
I do not believe the car is running out-of-the-ordinary compression and is using 87oct pump gas (same as I've always run).
Fueling is a Sniper 2 (which is working perfectly).
Car never had this problem until I swapped from an OEM coil to an Accel (I didn't know they weren't compatible). Since then, I've had this problem, even after swapping back to the OEM coil.
If this is valvetrain, then that's a hilarious coincidence, that's sent me down this rabbit hole.
To reiterate: engine is a 440 of unknown year, stock heads. Mallory Unilite dist.
kaj750
Well-Known Member
Just saw your post, sorry so late. It's pretty much any throttle condition as soon as I hit 2k RPM. My timing at 2k RPM is 29*. As noisy as the car is.... I'm thinking maybe it isn't detonation.
kaj750
Well-Known Member
Figured if it really were, I'd hear it all the time.
I'm going to try a different distributor. Maybe the advance springs on mine are bad.
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