dvw
Well-Known Member
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
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.
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.
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.
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.
Update:
The car is now running on Sniper EFI with their electronic ignition. Distributor, coil, all changed. multiple sets of plugs and wires. No plug wires touching. 91oct fuel, even added octane booster, out of desperation.
The problem is still there. I've reduced timing, little by little and no luck. I took it to a knowledgeable shop which told me they found no problems and didn't hear anything. I didn't either, during our test drive. It started again on the way home.
I've tried all throttle positions, including full-throttle. More rattling and smoke out the back of the car.
I was seeing IATs at 140* and thought that was it, but after some cruising, it came down to the 120s and still did it.
The car USED to run just fine until all of this started and has done it since. The only thing I changed in between was removing a heat shield between the intake and carburetor. That's it. No apparent reason for all this, all of a sudden.
Today, I noticed the coolant temp sensor was reading 20*F higher than the IAT sensor, but that's all that seems out of line.
I still can't put any load on the engine. The car HATES driving up hills. I'm about to pull the engine and star tearing it down until I find something.
The car is now running on Sniper EFI with their electronic ignition. Distributor, coil, all changed. multiple sets of plugs and wires. No plug wires touching. 91oct fuel, even added octane booster, out of desperation.
The problem is still there. I've reduced timing, little by little and no luck. I took it to a knowledgeable shop which told me they found no problems and didn't hear anything. I didn't either, during our test drive. It started again on the way home.
I've tried all throttle positions, including full-throttle. More rattling and smoke out the back of the car.
I was seeing IATs at 140* and thought that was it, but after some cruising, it came down to the 120s and still did it.
The car USED to run just fine until all of this started and has done it since. The only thing I changed in between was removing a heat shield between the intake and carburetor. That's it. No apparent reason for all this, all of a sudden.
Today, I noticed the coolant temp sensor was reading 20*F higher than the IAT sensor, but that's all that seems out of line.
I still can't put any load on the engine. The car HATES driving up hills. I'm about to pull the engine and star tearing it down until I find something.
Some Car Guy
Well-Known Member
I don’t remember all the post and I’m not going back to read
I’d at this point get some race gas. At least ten gallons. Try to get it to run right. If you prove it wants higher grade fuel now, and didn’t before, I’m thinking you have carbon build up, something damaged that now creates a hot spot in the chamber, or a slipped balancer.
I’d at this point get some race gas. At least ten gallons. Try to get it to run right. If you prove it wants higher grade fuel now, and didn’t before, I’m thinking you have carbon build up, something damaged that now creates a hot spot in the chamber, or a slipped balancer.
BLK 68 R/T
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I’ve reread the whole thread. Detonation has been a common issue since the very beginning is what I gathered.
Time for a compression test.
List what you get for each cylinder.
Make sure you have a fully charged battery when you start.
Time for a compression test.
List what you get for each cylinder.
Make sure you have a fully charged battery when you start.
gtxrt
Well-Known Member
you need to go to 3800 rpms to check total timing with vacuum advance unhooked. 29* at 2000 rpms is a lot for a street car.
It only smoked when I started hearing the noise and gave it the beans, out of frustration. No smoke any other time.
I thought i posted the numbers. Will look them up and edit this and the original post.
I have no vacuum advance. I'll check my data log for timing at that RPM. With all the issues, I may not have a log that goes that high.
Update:
Drove the car last night. With coolant temp at 180, IAT 90, ambient temp approx 85-90°.
Zero noise. But it does this, some times.
Only change is a new coolant temp sensor.
Could I be hearing valvetrain noise? Oil supply issue? Oil pressure reads fine but maybe it's not getting to the lifters? Asking because I now notice lifter tick when starting the car. Stops after 2-3 sec. Kicker is I think I heard one continue to tick when pulling into the garage.
Lifters recently installed due to one ticking.
Just ran the car enough for break-in. Haven't changed oil so assly lube and extra zinc still in oil pan.
However, I did find paperwork from the original owner. He had it into a shop for detonation issues.
Who knows what kind of gremlin I'm chasing.
I can't even find information to prove that the degreed the cam, etc.
Jeff K
Member
That used cap you show in post 20 looks like you have high resistance in your secondary (high voltage) ignition circuit. You also mentioned that you lost your headlights and half of your dash lights. Those two symptoms taken together sounds like a bad ground somewhere. Check your battery cables. Clean and tighten both, then clean and tighten the negative cable where it bolts to the block or head. You should also have a ground strap from the back of the engine to the firewall. I think it bolts to the rear of the PS cylinder head or the rear of the intake manifold, and from there to the firewall. Clean and tighten both ends of this wire as well.
What are your plugs gapped to? What do the old ones look like?
What are your plugs gapped to? What do the old ones look like?
It's possible there are grounds missing. The guy I bought the car from wasn't much mechanically inclined. Easy miss.
Headlights going off and on turned out to be a loose wire in the bulkhead. Fixed.
Gauge cluster is still a mystery.
Plugs are kept to factory, I'll have to go back and look for the recent gap. I may have even went on the smaller end of the range to see if it helped, though it should be fine with the upgraded ignition.
I just tossed out the old plugs day before yesterday lol
Unfortunately I'm working 0700-1930 Sat-Thurs so won't be able to investigate further until about this upcoming Saturday. But then I'll have a solid seven days to check things out.
The grounding straps have been a concern of mine. I haven't been able to find out how many there should be.
Thanks! Glad to have some direction. Will report back ASAP. This is next on my to-do list.
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