Engine is 327 with 30-30 cam (variant). True 10.85 - 11.15 measured/calculated SCR. Pump high test 93 PON. Vac advance disconnected, initial 10 degrees, centrifugal add 21 degrees, all in at 2500, total 31 degrees.
Detonation at cruise, tip-in. Occurs between 3000 and 5000 RPM.
Idle speed 900 RPM.
Idle vacuum 7 in-hg @ 900 RPM.

Crap/old fuel?
Try dosing it with that 104 stuff & see what happens.

Try this:
http://torcoracefuel.net/pro-accelerator.html

you have a CR way to high for the octane
What sort of dizzy do u have, If pionts or HEI there is no way you can have all in at 2500 without having the weights bouncing around ....about an intial of 12 deg total 30/32 all in around 28 to 30 is about as light as one can go with the springs.

I would say you have not one issue but a combo of the above and most problerly an issue with the carb Powervalve and/or jetting.

I disagree with step's on this one. I run near the same comp with a shorter cam, with no detonation.

I don't like your tune. Your advance is all in before the detonation rpm, notice that?
Go to 16 degree's initial, 18 mech, and delay the mechanical so it's all in at 3500-4000.

Also, you're probably going lean at tipin. what's your cruise vacuum? Get a power valve 2" higher than your cruise vacuum, this will kill the tip in ping completely.

Your DCR is around 7.06 :1
I used an altitude of 1,200 feet and ABDC of 82*, I don't know if that is correct for the 30/30 but I think it is, or very close.
8.2 is ideal and 8.5 is getting there for pump gas, that being said, your compression ratio is not the problem here.
I run a cc286H-10 in a .040" 327 with 10.85+ and don't have any detonation.
I run vacuum advance, 16-20 initial, and close to 60* total with vacuum (I know it's high, but it works) timing is all in at or around 3,500rpm, it's hard to tell, HEI distributor with silver springs.
I agree with JimM, shoot for all in at 3,500rpm, that is where mine is and there isn't any detonation at cruise and up to 7k
I tried to get the timing in sooner with the light copper springs, the initial was all over the place, weights were slapping around, and it ran like crap.
After you get this sorted out, you may want to switch to full vacuum advance, your mpg will increase, better streetability and more hp.

You don't need race gas, or even 93 for that matter, you will just be wasting money, the problem isn't the fuel, it is your tune.

Your not running an edelbrock carb are you? They run very lean in the upper rpm, mine does, and I have seen a friend with a buick motor go crazy lean on a dyno with an edelbrock 800.

you have a CR way to high for the octane
What sort of dizzy do u have, If pionts or HEI there is no way you can have all in at 2500 without having the weights bouncing around ....about an intial of 12 deg total 30/32 all in around 28 to 30 is about as light as one can go with the springs.

I would say you have not one issue but a combo of the above and most problerly an issue with the carb Powervalve and/or jetting.

93 RON.. yes..
93 (R+M)/2.. No, the comp ratio should be fine.

you have a CR way to high for the octane
What sort of dizzy do u have, If pionts or HEI there is no way you can have all in at 2500 without having the weights bouncing around ....about an intial of 12 deg total 30/32 all in around 28 to 30 is about as light as one can go with the springs.

I would say you have not one issue but a combo of the above and most problerly an issue with the carb Powervalve and/or jetting.

It is an original distributor from a 1965 327/365 engine. The points have been removed and converted to Breakerless SE.

This is a fresh rebuild. Before the rebuild the dist was never an issue, I ran blasts up to 7000 RPM no problem.

I disagree with step's on this one. I run near the same comp with a shorter cam, with no detonation.

I don't like your tune. Your advance is all in before the detonation rpm, notice that?
Go to 16 degree's initial, 18 mech, and delay the mechanical so it's all in at 3500-4000.

Also, you're probably going lean at tipin. what's your cruise vacuum? Get a power valve 2" higher than your cruise vacuum, this will kill the tip in ping completely.

Jim,

I sure hope you're right! Yes, I noticed that right quick..........so I removed the VAC. My flyweights are heavy, and still deploy fully, early, with heavy springs on them.
The carb is a Holley 2818 from the original engine. It is on temporarily because I have to sort out hood clearance issues with the Quick Fuel 750 DP that will end up on the DZ intake manifold. I also still have the iron manifolds installed, until next spring when I'll install the headers and low restriction mufflers that I bought last year.
The setup now is temporary, until I flatbed the car to Mufflex, who is going to fab the exhaust system for me.
I didn't realize that detonation would be an issue at this time..................only want to break-in/test the new rebuild before winter sets in.
I obviously did too good of a job in building in compression/sealing.
Maybe I should let you know what the cranking compression is.
The rings are Total Seal gapless top ring set.
The valve seals are positive type teflon.
The block was honed with a torque plate.
The water jacket was 3/4 filled, so the bores are rigid as hell.
The 870 Corvette block sonic tested better than .250 at its thickest and .140 at its thinnest before the .030 overbore/hone.

Cruise vacuum is about 14 in-hg@ 65. PV installed in the stock Holley 2818, is 6.5.
How does the cruise vacuum sound?
How about the idle vacuum? Is it low at only 7 in-hg @ 900?

Your DCR is around 7.06 :1
I used an altitude of 1,200 feet and ABDC of 82*, I don't know if that is correct for the 30/30 but I think it is, or very close.
8.2 is ideal and 8.5 is getting there for pump gas, that being said, your compression ratio is not the problem here.
I run a cc286H-10 in a .040" 327 with 10.85+ and don't have any detonation.
I run vacuum advance, 16-20 initial, and close to 60* total with vacuum (I know it's high, but it works) timing is all in at or around 3,500rpm, it's hard to tell, HEI distributor with silver springs.
I agree with JimM, shoot for all in at 3,500rpm, that is where mine is and there isn't any detonation at cruise and up to 7k
I tried to get the timing in sooner with the light copper springs, the initial was all over the place, weights were slapping around, and it ran like crap.
After you get this sorted out, you may want to switch to full vacuum advance, your mpg will increase, better streetability and more hp.

You don't need race gas, or even 93 for that matter, you will just be wasting money, the problem isn't the fuel, it is your tune.

Your not running an edelbrock carb are you? They run very lean in the upper rpm, mine does, and I have seen a friend with a buick motor go crazy lean on a dyno with an edelbrock 800.

I'm on the East Coast, at sea level, and the cam is a Comp N+30-30S. Inlet valve closes @ 70 ABDC installed 4 degrees advanced.
Duration @ .006 284/291
Advertised 247/254
Carb is a Holley 2818 (585 CFM) see above post!

Stock manifolds and a 3/4 filled block will retain a lot of heat in the motor. No vacuum advance can heat it up even more. Try an 8.5 PV, cooler thermostat, stiffer mech advance springs. Float levels ok? Exhaust heat crossover blocked?

I'd go to 10.5 on the PV.

Use LIGHTER wieghts in the hei to slow the curve.

What sort of dizzy do u have, If pionts or HEI there is no way you can have all in at 2500 without having the weights bouncing around ....about an intial of 12 deg total 30/32 all in around 28 to 30 is about as light as one can go with the springs.

I would say you have not one issue but a combo of the above and most problerly an issue with the carb Powervalve and/or jetting.

JimM
I disagree with step's on this one.

LoL m8 we are saying the same thing...advance to fast and PV and jetting.

Do the HEI conversion on points dizzys come with heavier weights?
lighter (stock weights) and or heavier springs

With the higher intial and all in you vac will come up at idle /cruise of cruise so it is very likely JimMzs 10 pv could be high, but it is better to start high then go down if need be.
Once you have the cent advance sorted, know you cruise/idle and off cruise vacs you can then set your VA advance vac range it works in.

What are your rpms at highway cruise?

I road tested the car with 100LL avgas doped 93 octane, which gives me about 96-97 PON.
No WOT detonation, no tip in detonation.......no run-on.
That's all she needed!
I have the timing at 15 initial, plus 23 all in @ 2500, no vac advance....for now.

Rule of thumb
increase CR decrease advance
increase octane increase advance

Now if you do what Jim says above you will most prob do the same on pump gas.

LPG is over 105 ocatane and ideally requies min 10.5 cr (depending on cam...dcr)
Given this the curve in around a 45 deg angle when ploted on a graph
ie 1500 rpm/15 deg 2500/ 25 deg and all in around the 2800/3000 around 30 to 32 deg then VA maxing the curve to somwhere in the 36 to 38 deg range.

LPG has a way faster curve than the equivilent petrol engine, even on race gas

Your curve is steeper than even this....
Even thu you think u seemed to have 'fixed' the issue STILL follow Jims advice.

Engine is 327 with 30-30 cam (variant). True 10.85 - 11.15 measured/calculated SCR. Pump high test 93 PON. Vac advance disconnected, initial 10 degrees, centrifugal add 21 degrees, all in at 2500, total 31 degrees.
Detonation at cruise, tip-in. Occurs between 3000 and 5000 RPM.
Idle speed 900 RPM.
Idle vacuum 7 in-hg @ 900 RPM.

If the cam is a true 30-30 profile (346/346 adv.) your total timing is too low. A 302 with the same cam has about 9" vacuum at 900 RPM. You should be able to handle 18 degrees initial and 36 total with 15 degrees vacuum at idle. I do. That would help get the vacuum up. The 30-30 loves a lot of advance. Not sure what is going on here.

Stock manifolds and a 3/4 filled block will retain a lot of heat in the motor. No vacuum advance can heat it up even more. Try an 8.5 PV, cooler thermostat, stiffer mech advance springs. Float levels ok? Exhaust heat crossover blocked?

Vacuum advance works only at idle and cruise. At those conditions (lean mixtures) vacuum advance brings temperatures down.

Rule of thumb
increase CR decrease advance
increase octane increase advance

Now if you do what Jim says above you will most prob do the same on pump gas.

LPG is over 105 ocatane and ideally requies min 10.5 cr (depending on cam...dcr)
Given this the curve in around a 45 deg angle when ploted on a graph
ie 1500 rpm/15 deg 2500/ 25 deg and all in around the 2800/3000 around 30 to 32 deg then VA maxing the curve to somwhere in the 36 to 38 deg range.

LPG has a way faster curve than the equivilent petrol engine, even on race gas

Your curve is steeper than even this....
Even thu you think u seemed to have 'fixed' the issue STILL follow Jims advice.

wait, am I missing something here? LPG? He said 100LL av gas... like the stuff you can get at small airfields. it is 100 low-lead aviation gas, not LPG, which indeed does have a high octane etc etc... just wanted to clarify this!

still, sounds like the timing was a little too advanced in that area and the higher octane mix helped it out... so I guess that should be good, unless you want to save some $ and just take some timing out of it and go back to the 93.

wait, am I missing something here? LPG? He said 100LL av gas

yep
LPG has a way faster curve than the equivilent petrol engine, even on race gas
And his curve is faster than a LPG curve....thats how far out it is.