How to tell when detonation starts if you can't hear it?
07-15-2003, 07:02 PM
#1
Instructor
Thread Starter
How to tell when detonation starts if you can't hear it?
I was knocking during part-throttle acceleration a few weeks back, so i disconnected the vacuum advance and bumped the inital timing up a bit, lost a little omph but i didn't think much of it. Then the i installed my jet-hot headers/sidepipes. I must be running hotter than i thought because the coating has turned dull and i'm afraid the it will crack, plus Jet-Hot has "TIMING IS CRITICAL FOR MAINTAINING THE LIFE OF THE COATING" written about 3 times in the paperwork they give you. So i'd like to put as much timing back as possible, only with my sidepipes i can't hear exactly when detonation starts over the exhaust when accelerating. Any ideas?
07-15-2003, 09:42 PM
#2
Melting Slicks
Re: How to tell when detonation starts if you can't hear it? (Steve81)
Most HEI distributers have around 20 degrees mechanical advance ,so if you run 12-15 initial that would put the total at 32-35 degrees.Get yourself a Crane adjustable vacuum can and limit the vacuum to 10-12 and you should be in the ball park.Mine is set like that and not a trace of pinging with super unleaded.
You can do more damage running too much advance than th few extra ponies is worth.Best bet is run less than max advance,and don't risk the detonation. :yesnod:
You can do more damage running too much advance than th few extra ponies is worth.Best bet is run less than max advance,and don't risk the detonation. :yesnod:
07-15-2003, 10:21 PM
#3
Instructor
Thread Starter
Re: How to tell when detonation starts if you can't hear it? (The Money Pit)
Get yourself a Crane adjustable vacuum can and limit the vacuum to 10-12
That's pretty much what i planned on doing, i think my knocking was caused by too much vac advance at part throttle. Which springs did you use?
07-15-2003, 10:34 PM
#4
Safety Car
Re: How to tell when detonation starts if you can't hear it? (Steve81)
If you are not sure pull a few plugs, normally # 6 and 8 are the first to show signs of detonation. You are looking for little shiny specs on the porcelien (bits of your piston ) if you see this, you have problems.
07-15-2003, 10:39 PM
#5
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Re: How to tell when detonation starts if you can't hear it? (Steve81)
When the car is detonating, the spark plugs should have small brown dots on the ceramic insulator.
07-16-2003, 09:02 AM
#6
Melting Slicks
Re: How to tell when detonation starts if you can't hear it? (Steve81)
I tried a bunch of different springs and ended up with the Crane blue/silver combo they recommended.Baught a kit from Summit first and wasted about two weeks trying before I got the Crane kit,which worked perfectly.The PIA with the limiter plate is when you make a limit change it also affects the intial timing.I ended up setting mine so I was locking out most of the vacuum advance.
Remember,no two engines are alike,so your setup may end up being different than mine.
Remember,no two engines are alike,so your setup may end up being different than mine.
