All in at 1500 rpm. Is this bad? - Chevelle Tech
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post #1 of 9 (permalink) Old Apr 22nd, 14, 1:44 PM Thread Starter
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tom
 
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All in at 1500 rpm. Is this bad?

I wanted to see what my initial would be if I set my total timing to 36 at 3000 rpm. I noticed right away that 36 was reached at 1500 rpm and stayed there all the way up to 3000 rpm. By the way, my initial was at 19. I have an original 283 with HEI distributor and the vacuum advance was disconnected while the carb port was plugged.
Do you think I have a problem? I don't have any major engine issues, just a slight stumble from a dead stop.
thanks,
tm
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post #2 of 9 (permalink) Old Apr 22nd, 14, 2:23 PM
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Re: All in at 1500 rpm. Is this bad?

Sounds to me like you need to put stiffer mechanical advance springs on the distributor. That said, if the engine isn't pinging then perhaps you don't have an issue. Still and all, that's a lot of timing at 1500 RPM on a heavy car like a Chevelle. What's your driveline? Eng/trans/differential?
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post #3 of 9 (permalink) Old Apr 22nd, 14, 2:26 PM
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Re: All in at 1500 rpm. Is this bad?

Quote:
Originally Posted by tm66 View Post
I wanted to see what my initial would be if I set my total timing to 36 at 3000 rpm. I noticed right away that 36 was reached at 1500 rpm and stayed there all the way up to 3000 rpm. By the way, my initial was at 19. I have an original 283 with HEI distributor and the vacuum advance was disconnected while the carb port was plugged.
Do you think I have a problem? I don't have any major engine issues, just a slight stumble from a dead stop.
thanks,
tm
Did you go beyond 3000 rpm? Many distributors don't reach full centrifugal advance until 4000 rpm or beyond.

Was this done on the engine or in a distributor machine? A distributor machine reads distributor RPM which is half of engine RPM.

Full centrifugal advance at 1500 engine RPM is probably WAY too early. Depending on vehicle weight and gearing, full centrifugal at 2500--3000 could be more reasonable AND allow for more vacuum advance which might improve part-throttle response and economy.

Excess initial advance is often used to "crutch" a deficient idle/transfer fuel curve. Less initial timing and perhaps more idle fuel could yield improvements in throttle response off-idle.

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post #4 of 9 (permalink) Old Apr 22nd, 14, 4:07 PM Thread Starter
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Re: All in at 1500 rpm. Is this bad?

I don't know the driveline specs. The car is an all original 283 Malibu with a powerglide tranny.

I did not go much over 3000 rpm and the timing was checked on the engine, not a distributor machine. The distributor is the $99 unit from Summit Racing and no alterations done to it.
tm
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post #5 of 9 (permalink) Old Apr 22nd, 14, 5:13 PM
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Re: All in at 1500 rpm. Is this bad?

If the timing is truly all in @1500 rpm and the engine doesn't ping, run on, or the starter is OK cranking...go for it.
I ran my 540 all over town for years with the timing locked out @38 degrees. Started, idled, and ran great. Ran cooler too.

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post #6 of 9 (permalink) Old Apr 23rd, 14, 11:34 AM
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Re: All in at 1500 rpm. Is this bad?

Every car is unique, factory specs are a compromise. My 67 327 likes the timing all in w/38* total at 1800rpm...

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post #7 of 9 (permalink) Old Apr 23rd, 14, 1:50 PM Thread Starter
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Re: All in at 1500 rpm. Is this bad?

Thanks for the responses.

Should I advance all in from 36 to 38*?
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post #8 of 9 (permalink) Old Apr 24th, 14, 8:18 AM
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Re: All in at 1500 rpm. Is this bad?

The total timing truly does depend on the particular engine. But with old skool heads and the like, it is LIKELY ( but not certain) it will like more advance. Eg my bbc prefers 35. My buddy's LT-1 ( old skool) prefers 40.

The other issue is how accurate the reference on the balancer is.

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post #9 of 9 (permalink) Old Apr 24th, 14, 1:06 PM
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Re: All in at 1500 rpm. Is this bad?

Checked on a dist machine is that dist rpm or engine rpm ???...........most machines read dist rpm pbly 3000 engine rpm even thats fast for a stock dist
and yes run it to at least 5k if a stock dist and advance mech not sticking etc it pbly will advance more with vacuum advance hooked up and 19* initial it should ping if its all stock at cruise tip in .......... I have never seen a stock GM dist that give 19* in initial unless of course its been modified even that is alot
I would recheck your numbers ................OOOPS I see Shurkey posted same thing

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