Need tips for controlling detonation through heat reduction
Drifting
Joined: Sep 2004
Posts: 1,959
Likes: 1
From: North Bend Ohio
You need to slow the advance curve a little more. Be careful with colder plugs, they may foul at cruising speeds.
What is happening is that the advance curve is too fast for the intake density. If you can delay the advance curve the engine may have a chance to make it to higher speeds where it can use it without rattling.
BigBlockk
Later.....
What is happening is that the advance curve is too fast for the intake density. If you can delay the advance curve the engine may have a chance to make it to higher speeds where it can use it without rattling.
BigBlockk
Later.....
Pro
Joined: Jun 2005
Posts: 725
Likes: 1
From: FL.
If your bottom end is OK you wont have to change pistons to solve your problem. 11:1 Is too Much with Iron heads and Pump gas (I Wouldnt rely on Octane boost). As said above Aluminum heads with 74cc chambers and a .030 thick gasket will get your compression down. Try that with your 222 duration cam and 93 octane and I think your problem would be solved. Your engine wont be making as much power but you wont destroy it either!
Also you may have carbon buildup on the piston tops and chambers. That will also add to the detonation potentials.
Also you may have carbon buildup on the piston tops and chambers. That will also add to the detonation potentials.
Advanced
Joined: Nov 2007
Posts: 82
Likes: 0
From: Central Texas
As stated the curve is coming in too early. I'd try pushing it out to all in around 2800 - 3000.
If you are willing to get new heads, aluminum with larger chambers will help a bunch and with some careful consideration will make more power even with the drop in compression. Save the stock heads for nostalgia as you have said - for the guy that wants a museum peice, not a driver.
I also do not like octane boosters and the junk they leave behind.
If you are willing to get new heads, aluminum with larger chambers will help a bunch and with some careful consideration will make more power even with the drop in compression. Save the stock heads for nostalgia as you have said - for the guy that wants a museum peice, not a driver.
I also do not like octane boosters and the junk they leave behind.
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
The only way to run over 11 to 1 compression, iron heads and a 222 duration cam is with race fuel or detune it to the point you have noticably less power. No other options. You have to change something. Cam, heads, pistons. You have to reduce compression, increase octane, or increase cam duration big time. New heads are really your best choice.
Last edited by 63mako; Mar 9, 2008 at 11:55 PM.
Thread Starter
Pro
Joined: Apr 2005
Posts: 618
Likes: 0
The only way to run over 11 to 1 compression, iron heads and a 222 duration cam is with race fuel or detune it to the point you have noticably less power. No other options. You have to change something. Cam, heads, pistons. You have to reduce compression, increase octane, or increase cam duration big time. New heads are really your best choice.
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Instructor
Joined: Oct 2005
Posts: 187
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From: TRAILER RENTALS - Florence Twp. NJ
It sounds like the motor wants better fuel....try either 100 (unleaded) or C112 (leaded)......Race fuel - no octane boosters....34 degrees and pinging may also suggest a higher (actual) compression ratio.....we have run 42+ degrees -iron heads- 12 to 1 ....
Last edited by J.K. Cooley; Mar 10, 2008 at 08:43 AM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Have you tried any octane additives to see what happens? If you boost the octane and your pinging stops, you have some choices: to keep the engine in "stock" condition, you can put in some fuel additives [add some racing or aircraft fuel to your tank] when you want to "use" the engine; or your engine might be a candidate for water injection. I know that last one sounds wierd, but I believe it cools the air/fuel charge somewhat to reduce pinging and boost the HP in the process. Here's some basic overview information from Wikipedia: http://en.wikipedia.org/wiki/Water_injection_(engines) . I'm sure you can find additional info on it and some products that would serve your purpose.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Here's another site I found that has more information on water injection.
http://www.rallycars.com/Cars/WaterInjection.html
Good luck with your problem.
http://www.rallycars.com/Cars/WaterInjection.html
Good luck with your problem.
Thread Starter
Pro
Joined: Apr 2005
Posts: 618
Likes: 0
Have you tried any octane additives to see what happens? If you boost the octane and your pinging stops, you have some choices: to keep the engine in "stock" condition, you can put in some fuel additives [add some racing or aircraft fuel to your tank] when you want to "use" the engine; or your engine might be a candidate for water injection. I know that last one sounds wierd, but I believe it cools the air/fuel charge somewhat to reduce pinging and boost the HP in the process. Here's some basic overview information from Wikipedia: http://en.wikipedia.org/wiki/Water_injection_(engines) . I'm sure you can find additional info on it and some products that would serve your purpose.
I am using Max Lead 2000 right now, and it helps a lot. It's about $11 more per fill-up to use it, so it's not too terribly expensive. It's tetraethyl lead, just like the engine used to run on in 1970. I add a quart, which supposedly raises the 93 octane up to just over 101 octane. That HAS to be enough!
Thread Starter
Pro
Joined: Apr 2005
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I've seen carbs go lean as u describe it(makes it ping).
.
Anyway, i'd start with 25 total timing on an 11:1 iron. Reduce from 34 by the stop on the weights. Then if it runs good, increase it 2 degrees a week unil it pings on a hot day, then go back 2.
.
BB hood, lots of work for cold air, but effective.
Must block heat riser and use carb heat isolator.
.
Anyway, i'd start with 25 total timing on an 11:1 iron. Reduce from 34 by the stop on the weights. Then if it runs good, increase it 2 degrees a week unil it pings on a hot day, then go back 2.
.
BB hood, lots of work for cold air, but effective.
Must block heat riser and use carb heat isolator.
I tried backing it off to 28 a few months back, and that really dropped the power; too much imo. I'm going to continue to try and mitigate the heat on the fuel charge: aluminum manifold with no crossover. Lifter valley oil shield. Colder plugs. 160 thermostat. Carb. insulator gasket. I might also try a later-style air cleaner housing. Somewhere in late '70, the L46 engine went from having an open element chrome air cleaner (mine), to one with a black base and the two inlets. Perhaps that might help a minute amount, by grabbing more air from the direction of the front of the motor, as compared to the surrounding engine air? Dunno...
Melting Slicks
Joined: Mar 2002
Posts: 2,164
Likes: 7
From: Beringen
From what i've read from your discription, the pinging is associated and audible with 100% filling of the cylinders of a specific rpm range. You could reduce timing like has been said and improve cooling here and there but you definatly will keep the pinging.
You could also try water/methanol injection as this would cool the intake charge far enough, but it would be difficult and expensive.
I would suggest using either a big cam and using a thich head gasket to reduce CR.
You could also try water/methanol injection as this would cool the intake charge far enough, but it would be difficult and expensive.
I would suggest using either a big cam and using a thich head gasket to reduce CR.
Race Director
Joined: Oct 2000
Posts: 15,102
Likes: 79
From: central FL, near the beach.
I tried backing it off to 28 a few months back, and that really dropped the power; too much imo. I'm going to continue to try and mitigate the heat on the fuel charge: aluminum manifold with no crossover. Lifter valley oil shield. Colder plugs. 160 thermostat. Carb. insulator gasket. I might also try a later-style air cleaner housing. Somewhere in late '70, the L46 engine went from having an open element chrome air cleaner (mine), to one with a black base and the two inlets. Perhaps that might help a minute amount, by grabbing more air from the direction of the front of the motor, as compared to the surrounding engine air? Dunno...
when u backed it off to 28, did u turn the dist? that's how newbies do it, and power drops. this is a BAD way to do it. Guaranteed to lose power! Don't do this!
But your plan sounds good, not sure on the air cleaner, however
Last edited by Matt Gruber; Mar 10, 2008 at 12:08 PM.
Drifting
Joined: Aug 2005
Posts: 1,682
Likes: 3
From: League City TX
You will have a hard time dropping dynamic compression via a cam change because dynamic compression uses advertised duration numbers. The factory cam already has huge advertised numbers.
Something that hasnt been mentioned, that you might try if you want to keep your engine all original, is to have your combustion chambers polished. The smooth finish of the chambers is supposed to be good for detonation resistance all by itself, plus it would make your chambers a few CCs larger so your compression ratio would drop a little. You may pick up a little flow too if they are able to reduce valve shrouding.
I dont know that this is the solution all by itself, but is one idea that would likely not hurt power while helping the problem.
Something that hasnt been mentioned, that you might try if you want to keep your engine all original, is to have your combustion chambers polished. The smooth finish of the chambers is supposed to be good for detonation resistance all by itself, plus it would make your chambers a few CCs larger so your compression ratio would drop a little. You may pick up a little flow too if they are able to reduce valve shrouding.
I dont know that this is the solution all by itself, but is one idea that would likely not hurt power while helping the problem.
Thread Starter
Pro
Joined: Apr 2005
Posts: 618
Likes: 0
Please elaborate and advise how to back it off "correctly". Thanks
Race Director
Joined: Oct 2000
Posts: 15,102
Likes: 79
From: central FL, near the beach.
when it doesnt
1st i tie the weights so they are locked(10min test only)
2nd i establish 0-10 maybe 20 mph launch, easy & hard. (base timing) usually 12-17, find max no ping HOT.
I.E. IF it is 14, and i want 29 total, i pull the dist, unlock it, remove bushing stop and put larger bushing on pin to limit dist advance to 15. Then
it goes back in base 14, max 29.
u still have to find the best curve springs.
that is the basics, but by no means the whole story. Most can't even change the bushing, so i'll stop now.
Last edited by Matt Gruber; Mar 12, 2008 at 02:13 PM.