OT:(non Ford)Explain my detonation issue.
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Cargo Master
Joined: May 2008
Posts: 2,486
Likes: 336
From: Bakersfield, CA
OT:(non Ford)Explain my detonation issue.
I run 87 octane. I have a stock used caddy 500ci in a project car and the factory service manual calls for 10º BTDC. I set it there and it pinged like it was about to explode. I set it back to ~6-7º and it pinged way too much, so I threw it all out the window and said screw it, I set it at like 1º BTDC.
Yep.One.
One Degree.
She still pings blatantly going up slight inclines at even the lightest throttle.
The distributor (the whole thing) is a rebuilt unit from rockauto. Should I be worried about the advance mechanism?
This pathetic smog-era engine can't possibly have a higher compression ratio than 8.5:1
I see no reason why 87 Octane won't suffice.
A little pinging under extreme acceleration? Sure I get it.
But I should not be worried when I hear "a thousand hornets" when I'm barely going 22 mph, engine at 1900rpm and I'm trying to gently accelerate up a hill to a reasonable 35mph. This can't be how they ran at the factory. Engine is well used but shows no signs of doomed health.
Yep.One.
One Degree.
She still pings blatantly going up slight inclines at even the lightest throttle.
The distributor (the whole thing) is a rebuilt unit from rockauto. Should I be worried about the advance mechanism?
This pathetic smog-era engine can't possibly have a higher compression ratio than 8.5:1
I see no reason why 87 Octane won't suffice.
A little pinging under extreme acceleration? Sure I get it.
But I should not be worried when I hear "a thousand hornets" when I'm barely going 22 mph, engine at 1900rpm and I'm trying to gently accelerate up a hill to a reasonable 35mph. This can't be how they ran at the factory. Engine is well used but shows no signs of doomed health.
Last edited by mOROTBREATH; May 20, 2026 at 06:28 PM.
Hotshot
Joined: Oct 2009
Posts: 16,165
Likes: 4,765
From: Burbank, WA
Unless the cam timing is way off, or there's an issue with the chain not on correctly, something internally incorrect, I'd say you're right in suspecting the distributor is not advancing like it should and is defective. I'd recommend finding someone local with a distributor machine that can check it and correct it. There's really no point in truing to fight Rock Auto over this, there is no winning with those folks. Just fix what you have, put it behind you and get back on the road. That's my 2c.
Laughing Gas
Joined: Mar 2002
Posts: 946
Likes: 342
From: Newton Illinois
as @ALBUQ F-1 said those rubber mounted harmonic balancers can slip, I have worked on more than 1 ford that would barely run if the timing was set with a light. Usually the timing is way slow though
You should be able to get a good idea about the centrifugal advance by just revving the engine with a timing light.
How does it start? to much advance usually makes for hard cranking.
Are you 100% sure you have the pickup on #1 cilinder?
Also on a old engine is there a chance that the timing pointer is not in the correct position?
You may just have to forget the timing marks and time it to where it will run
You should be able to get a good idea about the centrifugal advance by just revving the engine with a timing light.
How does it start? to much advance usually makes for hard cranking.
Are you 100% sure you have the pickup on #1 cilinder?
Also on a old engine is there a chance that the timing pointer is not in the correct position?
You may just have to forget the timing marks and time it to where it will run
Last edited by lshort; May 20, 2026 at 06:58 PM.
Logistics Pro
Joined: Nov 2006
Posts: 3,671
Likes: 367
From: Fallon,NV & Bainbridge OH
There are several things to look at here.
1) is it timed with or W/O vacuum advanced hooked up
2) how does it run at 1 degree (Ross probably hit the nail on the head)
3) how is usually driven (lugging around can build carbon on the pistons and chambers raising static CR)
4) what distributor (you didn't give a year, could be a point dist or could be an HEI)
5) have you looked at the advance weights to verify they are still in place and not frozen
6) if your advance was coming on to soon it would ping worse
7) CR for Caddy 500's varied from 10.25:1 down to 8.25:1 depending on year
8) lower elevation requires more octane, as do higher air temperatures, than higher elevations, cool air, air density/atmospheric pressure issues (Bakersfield is listed as 404', and is HOT)
9) is this a new problem or something that recently occured
1) is it timed with or W/O vacuum advanced hooked up
2) how does it run at 1 degree (Ross probably hit the nail on the head)
3) how is usually driven (lugging around can build carbon on the pistons and chambers raising static CR)
4) what distributor (you didn't give a year, could be a point dist or could be an HEI)
5) have you looked at the advance weights to verify they are still in place and not frozen
6) if your advance was coming on to soon it would ping worse
7) CR for Caddy 500's varied from 10.25:1 down to 8.25:1 depending on year
8) lower elevation requires more octane, as do higher air temperatures, than higher elevations, cool air, air density/atmospheric pressure issues (Bakersfield is listed as 404', and is HOT)
9) is this a new problem or something that recently occured
Thread Starter
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Cargo Master
Joined: May 2008
Posts: 2,486
Likes: 336
From: Bakersfield, CA
I can't believe I forgot to mention I'm working with an HEI dist.
I will check the front pulley in the morning but I'm pretty sure they are internally balanced and it's one piece of steel.
I'll check the timing @1500rpm and other rpm ranges ASAP.
Hard cranking and deiseling upon shutoff was a serious issue but the dieseling went away after setting it at 1º. It still gets a little stuck cranking when engine is hot but the battery is tiny and out of my little honda.
I'm sure its set at cyl #1
Timing pointer being incorrect is definitely a possibility I honestly haven't considered, and these engines apparently are notorious for having 3-4 different timing setups(and as many pulley setups which really make things interesting)
Always been a problem since first time I drove it and I tried adjusting timing lower and lower and it made a difference but it still seems to ping too much for such a low compression ratio and low performance.
I'm gonna mess with things and check out the front pulley tomorrow and I'll be back with some info to update.
Thank you everyone for the guidance.
I will check the front pulley in the morning but I'm pretty sure they are internally balanced and it's one piece of steel.
I'll check the timing @1500rpm and other rpm ranges ASAP.
as @ALBUQ F-1 said those rubber mounted harmonic balancers can slip, I have worked on more than 1 ford that would barely run if the timing was set with a light. Usually the timing is way slow though
You should be able to get a good idea about the centrifugal advance by just revving the engine with a timing light.
How does it start? to much advance usually makes for hard cranking.
Are you 100% sure you have the pickup on #1 cilinder?
Also on a old engine is there a chance that the timing pointer is not in the correct position?
You may just have to forget the timing marks and time it to where it will run
You should be able to get a good idea about the centrifugal advance by just revving the engine with a timing light.
How does it start? to much advance usually makes for hard cranking.
Are you 100% sure you have the pickup on #1 cilinder?
Also on a old engine is there a chance that the timing pointer is not in the correct position?
You may just have to forget the timing marks and time it to where it will run
I'm sure its set at cyl #1
Timing pointer being incorrect is definitely a possibility I honestly haven't considered, and these engines apparently are notorious for having 3-4 different timing setups(and as many pulley setups which really make things interesting)
There are several things to look at here.
1) is it timed with or W/O vacuum advanced hooked up Without and plugged off.
2) how does it run at 1 degree (Ross probably hit the nail on the head)
3) how is usually driven (lugging around can build carbon on the pistons and chambers raising static CR) 1/2 city and hwy, TH400 trans, not a whole lotta lugging can take place
4) what distributor (you didn't give a year, could be a point dist or could be an HEI) Sorrry, HEI
5) have you looked at the advance weights to verify they are still in place and not frozen I did quite a few months ago and they were free, but I'm not experienced enough to know anything else
6) if your advance was coming on to soon it would ping worse
7) CR for Caddy 500's varied from 10.25:1 down to 8.25:1 depending on year Engine is stamped for 1976
8) lower elevation requires more octane, as do higher air temperatures, than higher elevations, cool air, air density/atmospheric pressure issues (Bakersfield is listed as 404', and is HOT)
9) is this a new problem or something that recently occured
1) is it timed with or W/O vacuum advanced hooked up Without and plugged off.
2) how does it run at 1 degree (Ross probably hit the nail on the head)
3) how is usually driven (lugging around can build carbon on the pistons and chambers raising static CR) 1/2 city and hwy, TH400 trans, not a whole lotta lugging can take place
4) what distributor (you didn't give a year, could be a point dist or could be an HEI) Sorrry, HEI
5) have you looked at the advance weights to verify they are still in place and not frozen I did quite a few months ago and they were free, but I'm not experienced enough to know anything else
6) if your advance was coming on to soon it would ping worse
7) CR for Caddy 500's varied from 10.25:1 down to 8.25:1 depending on year Engine is stamped for 1976
8) lower elevation requires more octane, as do higher air temperatures, than higher elevations, cool air, air density/atmospheric pressure issues (Bakersfield is listed as 404', and is HOT)
9) is this a new problem or something that recently occured
I'm gonna mess with things and check out the front pulley tomorrow and I'll be back with some info to update.
Thank you everyone for the guidance.
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