Advance/retard timing chain?
Thread Starter
Safety Car
Joined: Oct 1999
Posts: 4,101
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From: NorCal
Advance/retard timing chain?
Like the title says, anyone done this? I build lots of engines, but I've never been brave enough to change the basic timing on the double roller sets I typically use. I get that retarding the chain 4 degrees generally adds low end torque, and 4 degrees advanced adds mid and top end horsepower. I worry about detonation with an advanced cam, but anything else that folks have experienced? I'm currently building a 327/350 HP clone with a Lunati 00210 Hydraulic flat tappet cam with 10.5 - 1 Keith Black pistons, 461 heads, good dual plane intake and long tube headers. I'll use better fuel in this in a 3200 pound car, just asking about real world experiences. Thanks in advance!
Hans
Hans
Thread Starter
Safety Car
Joined: Oct 1999
Posts: 4,101
Likes: 10
From: NorCal
OK, learn something new every day. Any personal experience, sort of seat of pants feel? I'm especially curious regarding the effect on pre ignition ("pinging"). I would expect worse detonation with an advanced cam? Thanks for the response!
Hans
Hans
Last edited by Wrencher; Feb 24, 2021 at 08:20 PM. Reason: add text
Had a 1976 L-82, 4-sp
Joined: Mar 2011
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From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
Yes, advancing the cam timing is the wrong direction in preventing the onset of detonation. Retarding the timing will bleed off pressure due to the intake valve closing later.
Last edited by resdoggie; Feb 24, 2021 at 08:31 PM.
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
The advance and retard features available on many timing chain sets can be used for 2 purposes:
Lars
- When you "degree" a cam and find that the parts tolerance stack-up of your particular engine results in the cam not being "at spec," you can use the + and - degree feature to correct the out-of-spec issue to get the cam to it's "in-spec" degree specification.
- When you have your engine on an engine dyno and you have firm dyno data and curves with engine torque and power, you can advance and retard the cam to see the shift in the torque & power curve, thus tailoring the cam to your most desirable power curve. You have to have actual dyno data to see if either shift is desirable or not.
Lars
Last edited by lars; Feb 25, 2021 at 12:28 AM.
Team Owner
Joined: Apr 1999
Posts: 21,953
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
You must have quite a dome to get 10.5 out of a 327. The majority of my custom cams were ground 4 degrees retarded compared to equivalent comp cams extreme line of off the shelf cams valve events.
I've played around with DCR VS Static Compression ratio calculators. You can input the valve event numbers with + or - 4 degrees and see where you are at.
I've only built one total detonation motor. I had everything to detonation proof my I think it was 10.8 383 . .038 quench -7 cc forged flat tops Swain tech ceramic thermal barrier pistons. Aluminum heads . Crane adjustable vacuum advance set to under 8 degrees additional. 32 degrees max mech timing just like the afr heads said. All in at 3000 rpm. going down a freeway at 65 mph it would just rattle away on california 91 octane. I ran octane boosters.......... The solid roller 232/238 cam was the problem. I just went up to 236/242 and the motor ran like a champ for many years.
I've played around with DCR VS Static Compression ratio calculators. You can input the valve event numbers with + or - 4 degrees and see where you are at.
I've only built one total detonation motor. I had everything to detonation proof my I think it was 10.8 383 . .038 quench -7 cc forged flat tops Swain tech ceramic thermal barrier pistons. Aluminum heads . Crane adjustable vacuum advance set to under 8 degrees additional. 32 degrees max mech timing just like the afr heads said. All in at 3000 rpm. going down a freeway at 65 mph it would just rattle away on california 91 octane. I ran octane boosters.......... The solid roller 232/238 cam was the problem. I just went up to 236/242 and the motor ran like a champ for many years.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
You will never notice the difference.......don't waste time, money or energy on it.....
A third reason to move the cam around is if you are very close on piston to valve.....moving the cam + or - 4 degrees can get you in spec if you have already installed the pistons and fly cutting valve pockets is not an option....not really the right way, but if you are out of time and have to get to the track tomorrow....it can save your ***.
Jebby
A third reason to move the cam around is if you are very close on piston to valve.....moving the cam + or - 4 degrees can get you in spec if you have already installed the pistons and fly cutting valve pockets is not an option....not really the right way, but if you are out of time and have to get to the track tomorrow....it can save your ***.
Jebby
