440 initial timing and spark knock

[Sonny]

My newly rebuilt 440 is running great but getting a little spark knock under load. My initial timing is about 18 adv and all in around 38. My total timing is pre set in my Summit electronic dizzy. What do you guys run (initial and total)?
Specs:
1970 Belvedere
-440 30 over
-Keith Black raised pistons
-Comp cam (mild) 110 and .48 lift
-Quick Fuel 650 brawler carb
-Spread bore to square 3/4” spacer
-Stock intake and 452 heads
-Long tube headers
-will add ported vac advance after tuning

 

[PRHeads]

More than likely, you’re going to need to slow the curve down.

 

[Sonny]

More than likely, you’re going to need to slow the curve down.

Like try and get to 18/34 or use a stiffer spring?

 

[69 GTX]

What octane gas are you running, my guess is you'll need to run 93 at a min.

 

[khryslerkid]

Try backing it down to 16* and see how it acts.

 

[Sonny]

What octane gas are you running, my guess is you'll need to run 93 at a min.

running 93

 

[Sonny]

Try backing it down to 16* and see how it acts.

I just did just that at lunch and WOW! Less knock but the power gain was nice!

 

[khryslerkid]

I just did just that at lunch and WOW! Less knock but the power gain was nice!

Are you saying you have more power at 16* ?

 

[Bill Monk]

I just did just that at lunch and WOW! Less knock but the power gain was nice!

Mine is at 14 initial and 34 all in. If it liked 16, you might try to back it off a hair more and see what you have. I agree that you may need 93 octane fuel depending on your compression. You said ported advance on the vacuum advance, that is sure to cause more knock at light to mid throttle. I recommend you read this article: http://4secondsflat.com/Ported Vs Constant Manifold Vacuum.htm
Good luck!

 

[Sonny]

Mine is at 14 initial and 34 all in. If it liked 16, you might try to back it off a hair more and see what you have. I agree that you may need 93 octane fuel depending on your compression. You said ported advance on the vacuum advance, that is sure to cause more knock at light to mid throttle. I recommend you read this article: http://4secondsflat.com/Ported Vs Constant Manifold Vacuum.htm
Good luck!

Thanks Bill. Was holding off on vac advance until I got the base tune down. May only just use the va on Power Tour highway stretches

 

[Sonny]

Are you saying you have more power at 16* ?

Sure seems like it. Maybe my foot was just heavier without the spark knocking

 

[khryslerkid]

Sure seems like it. Maybe my foot was just heavier without the spark knocking

I'm useing the 452 heads also, with flat tops so there is no quench. I haven't had any spark knock but did experience some lean conditions which was creating higher temps. Reading my plugs, the timing mark on the plug straps told me I needed less timing. I also try to run E-free 90+ octane. Theres been occasions when I used 10% 93 octane and noticed the engine ran 5 to 10 degrees warmer. Performance is good with either. Reading your plugs can tell you just what you need for final tuning.

 

[Sonny]

I'm useing the 452 heads also, with flat tops so there is no quench. I haven't had any spark knock but did experience some lean conditions which was creating higher temps. Reading my plugs, the timing mark on the plug straps told me I needed less timing. I also try to run E-free 90+ octane. Theres been occasions when I used 10% 93 octane and noticed the engine ran 5 to 10 degrees warmer. Performance is good with either. Reading your plugs can tell you just what you need for final tuning.

“Timing marks on plug straps”? Do tell or point me to information on that please! That’s new to me. Thanks!

 

[khryslerkid]

“Timing marks on plug straps”? Do tell or point me to information on that please! That’s new to me. Thanks!

Another good article from "4secondsflat"
http://www.4secondsflat.com/Spark_plug_reading.html

 

[Bill Monk]

“Timing marks on plug straps”? Do tell or point me to information on that please! That’s new to me. Thanks!

Straps. Going to again refer you to 4secondsflat. They know their stuff!
http://4secondsflat.com/Spark_plug_reading.html

 

[Bill Monk]

Another good article from "4secondsflat"
http://www.4secondsflat.com/Spark_plug_reading.html

Man!!! You beat me to it by a second....good job

 

[Sonny]

Straps. Going to again refer you to 4secondsflat. They know their stuff!
http://4secondsflat.com/Spark_plug_reading.html

Wow I had no clue. Will be popping out some plugs tonight.

 

[Bill Monk]

Wow I had no clue. Will be popping out some plugs tonight.

If you don't have many miles on the engine, the results may not be conclusive but should give you a starting point. You want at least several hundred miles on plugs for a true reading

 

[Bee1971]

383/432 Stroker - 440 Source Kit

10.5 - 1 / 200 psi cold cranking compression on all eight

Edelbrock E Street 75cc Heads

93 Octane - Slight ping under light throttle this summer

18 initial - 18 mechanical = 36 Total / Spark Plug Pictures posted



Currently before winter storage did some fine tuning

Running 15 initial - 18 mechanical = 33 Total

Zero pinging , ran awesome , will pull spark plugs in spring and compare

 

[BSB67]

More than likely, you’re going to need to slow the curve down.

This. Yes, stiffer springs

And, run a cooler plug, 160° thermostat, make sure your not lean, or just richen it up a bit, and block the heat crossover.

You don't want to necessaryly reduce total timing. I don't know if I have ever seen a factory iron head motor not perform best with at least 36° total.