Does It Hurt a Motor to Retard the Timing to Run in a Slower ET Class? - Chevelle Tech
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post #1 of 14 (permalink) Old Sep 23rd, 10, 2:59 PM Thread Starter
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Bart
 
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Does It Hurt a Motor to Retard the Timing to Run in a Slower ET Class?

The season is almost over and on one race date I can run two classes if one is faster than 14 seconds, and a second if its slower than 14 seconds. This car runs 13.5 without NOS, and 11.90's with a 125 shot. I can retard the timing without NOS to run low 14's. This engine likes 47 degrees total timing.

Does this do any harm to the engine - running it intentionally retarded - by taking out 10-15 degrees? I might be able to go some extra rounds with the slower cars. I'm just having some end-of-the season fun as my primary car finally popped the motor - after six seasons of bracket-race blower abuse and I'm trying to reignite some interest to rebuild the other motor (and the finances) after my inevitable mishap with the remaining race season.

'70 Chevelle, 496, Vortech V-7
Turbo 400, 3.90 12 Bolt, 3,200 Stall, Gearvendors, Performer RPM Heads, Victor Jr., Jesel Rockers
10.42 @132 best w/ 3,980 Race Weight
9-10,000 Routine Local Air Density
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post #2 of 14 (permalink) Old Sep 23rd, 10, 3:12 PM
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Dan
 
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Re: Does It Hurt a Motor to Retard the Timing to Run in a Slower ET Cl

IMO the 47* total is doing more damage than backing it down to 34-36*.

47? YIKES!!!

I used to run way too fast for my class for a few years & what I did to slow down was to lower my shift points to accommodate the class.

It may take a few runs to figure out the new shift points for the ET you want but your engine will last forever.

ex: my old 400 sbc shifted @ 7200 would run 11 flat ALL day...but to stay in the 12.00 class I had to shift it @ 5500. That motor was raced for 10+ years & is street raced by the new owner to this day! thats 20+ years on that 400sb.

He even runs a good size shot of spray on it too! Runs deep 10's.

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Last edited by dreis454; Sep 23rd, 10 at 3:40 PM.
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post #3 of 14 (permalink) Old Sep 23rd, 10, 3:39 PM
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Mike
 
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Re: Does It Hurt a Motor to Retard the Timing to Run in a Slower ET Cl

X2...you'd be amazed how much lowering the shift points will slow you down.
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post #4 of 14 (permalink) Old Sep 23rd, 10, 4:39 PM
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Marshall
 
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Re: Does It Hurt a Motor to Retard the Timing to Run in a Slower ET Cl

Leave the engine alone, adjust the throttle linkage so the secondaries don't fully open, and or leave the shifter in drive, leave the line at idle, etc.
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post #5 of 14 (permalink) Old Sep 23rd, 10, 5:41 PM Thread Starter
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Bart
 
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Re: Does It Hurt a Motor to Retard the Timing to Run in a Slower ET Cl

Doesn't seem like I could go much lower on the shift point - its already at 5,000 and isn't a high RPM motor. Suppose I could go to 4,000 and see the difference. I've talked to a guy with a 598 who tried to slow down his son's camaro to run 11.70 for the high school class by limiting throttle travel, but couldn't do it consistently.

I have a timing retard knob for the 6AL box, so thats why I was leaning towards that, as it can be changed from the drivers seat, even if still in - in both quicker and slower classes. Part of the reason for the advanced timing is that the Air Density is usually 9-10000 ft, though a little better in the fall.

It wouldn't seem that anything mechancial would be hurt by retarding the timing, as long as done consistently. Wouldn't have to raise the hood, just reach for the dial-in for the window.

'70 Chevelle, 496, Vortech V-7
Turbo 400, 3.90 12 Bolt, 3,200 Stall, Gearvendors, Performer RPM Heads, Victor Jr., Jesel Rockers
10.42 @132 best w/ 3,980 Race Weight
9-10,000 Routine Local Air Density
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post #6 of 14 (permalink) Old Sep 23rd, 10, 9:28 PM
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Re: Does It Hurt a Motor to Retard the Timing to Run in a Slower ET Cl

I think it may just make it run hotter.

Ray

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post #7 of 14 (permalink) Old Sep 24th, 10, 12:37 AM Thread Starter
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Bart
 
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Re: Does It Hurt a Motor to Retard the Timing to Run in a Slower ET Cl

I think I'll try lowering the shift point. Been told by a local source that retarding the timing can make a motor detonate just as having it too far advanced can. The shift point can be changed easily enough, and then back for the quicker class.

I've received some responses of disblief from local racers as many can't imagine trying to make a car run slower instead of the reverse.

thanks for the input.

'70 Chevelle, 496, Vortech V-7
Turbo 400, 3.90 12 Bolt, 3,200 Stall, Gearvendors, Performer RPM Heads, Victor Jr., Jesel Rockers
10.42 @132 best w/ 3,980 Race Weight
9-10,000 Routine Local Air Density
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post #8 of 14 (permalink) Old Sep 24th, 10, 12:58 AM
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Re: Does It Hurt a Motor to Retard the Timing to Run in a Slower ET Cl

can't hurt the motor running retarded timing. u have the knob in ur car so it's not like you have to wrench at all. i think thats the easiest thing to do.
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post #9 of 14 (permalink) Old Sep 24th, 10, 11:07 AM
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Re: Does It Hurt a Motor to Retard the Timing to Run in a Slower ET Cl

Excessively retarded timing will cook your headers and burn up your high temp coating.

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post #10 of 14 (permalink) Old Sep 24th, 10, 2:35 PM
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Re: Does It Hurt a Motor to Retard the Timing to Run in a Slower ET Cl

I'd fab a simple adjustable throttle stop for your carb.

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post #11 of 14 (permalink) Old Sep 24th, 10, 3:12 PM
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Re: Does It Hurt a Motor to Retard the Timing to Run in a Slower ET Cl

move your throttle bracket forward a little so you don't have WOT
That'll slow you down

ooops...just noticed Marshall already suggested that
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post #12 of 14 (permalink) Old Sep 25th, 10, 12:31 AM Thread Starter
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Bart
 
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Re: Does It Hurt a Motor to Retard the Timing to Run in a Slower ET Cl

Went out to run in both classes tonite, and left the nitrous at home as I didn't want run 2 seconds apart between classes. Went 13.5's with 47 degrees timing and 14.1's with 40 degrees - shows how sensitive the BBC is to timing. Won two rounds in the quicker class, and three rounds in the slower class.

Just dialed the timing back and forth with the adjustable knob from the drivers seat. I was still in, in the slower class and decided to call it a night. Car seems to run more consistently without the nitrous, but not as interesting. I told the gal at the time shack to polish up a trophy for me anyway.

Thanks for the help on this. I'd call it an overall success, especially if I"d run the number one more time in the quicker class.

'70 Chevelle, 496, Vortech V-7
Turbo 400, 3.90 12 Bolt, 3,200 Stall, Gearvendors, Performer RPM Heads, Victor Jr., Jesel Rockers
10.42 @132 best w/ 3,980 Race Weight
9-10,000 Routine Local Air Density
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post #13 of 14 (permalink) Old Sep 25th, 10, 12:13 PM
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Re: Does It Hurt a Motor to Retard the Timing to Run in a Slower ET Cl

Quote:
Originally Posted by dreis454 View Post
IMO the 47* total is doing more damage than backing it down to 34-36*.

47? YIKES!!!

I used to run way too fast for my class for a few years & what I did to slow down was to lower my shift points to accommodate the class.

It may take a few runs to figure out the new shift points for the ET you want but your engine will last forever.

ex: my old 400 sbc shifted @ 7200 would run 11 flat ALL day...but to stay in the 12.00 class I had to shift it @ 5500. That motor was raced for 10+ years & is street raced by the new owner to this day! thats 20+ years on that 400sb.

He even runs a good size shot of spray on it too! Runs deep 10's.
================================================== ========

2x,Dans right on,no need to detune to run slower.

Or as suggestion to change throttle bracket position or to fab an adjustable throttle stop.

Scott

SCOTT
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post #14 of 14 (permalink) Old Sep 25th, 10, 6:26 PM
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Re: Does It Hurt a Motor to Retard the Timing to Run in a Slower ET Cl

Retarding the timing will make your headers turn cherry red and may burn the exhaust valves. 34 to 36 should be normal and retarded should be less than 28.

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