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Old 07-22-2010, 12:38 PM
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Correct timing vs what works question

I know this has been brow beat some so I'll keep it short. As I've said before my builder is up my wazzoo every time we talk about NO MORE THAN 36 DEGREES TOTAL!!!! OK thats where its set. Then today I finally get a replacement light for the one that croaked and guess what. Either a lights advance wheel was out, something got moved or whatever I've had a total of 40-41. So quik fast I reset to 36. Go out and do a WOT. Anyone with me may have thought it good if they didnt know the car but I was less than impressed. So aside from what my vac is set at does a fellow leave it at 36 and some how tune other stuff to smarten it up again(If thats even possible)? or does he go back to the 40?compression is 9.75

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Old 07-22-2010, 02:07 PM
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More info on the complete setup ie; engine, tranny, gears, weight of car etc would help if this thread goes further but...If your motor ran well before and did not ping, started easy, idle quality was good, good power etc etc then leave it were it was. The 36 is a number that falls within the bench marks for the SBC total timing without vac advance added in, with the vac added yours could be around 52 total...not bad, so it is not like the motor is going to self destruct at anything over 36, is your builder concerned about warranty or something? and how did you get to the 36 by adjusting the base down or limiting the mechanical advance? what is the base set for?
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Old 07-22-2010, 02:36 PM
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Quote:
Originally Posted by Custom10
More info on the complete setup ie; engine, tranny, gears, weight of car etc would help if this thread goes further but...If your motor ran well before and did not ping, started easy, idle quality was good, good power etc etc then leave it were it was. The 36 is a number that falls within the bench marks for the SBC total timing without vac advance added in, with the vac added yours could be around 52 total...not bad, so it is not like the motor is going to self destruct at anything over 36, is your builder concerned about warranty or something? and how did you get to the 36 by adjusting the base down or limiting the mechanical advance? what is the base set for?
I'm sure the guys here are getting sick of this BUT
383 SBC
air gap RPM intake
650 AVS edelbrock carb
edelbrock 70cc heads
hypereutectic slugs
comp 270 HR cam
Hedman 1 3/4 headers out to straight 2 1/2
3700 pound car with th350 built by me and 373 gears
Ya its the builder barking that if I come back with a defunked engine I'm on the hook if it was more than 36. God I honestly think sometimes I'm going to put a notch on the intake and distributor at 36. Drive it at 40 and if anything happens for any reason just get my 9/16 out of the glove box and set it to 36.

Oh gee says me to builder, it was on 36 the whole time.I dont have a clue what could have happened.
To answer your question,NO it never pinged,it just went like a frikin hurricane. You wouldnt think that 4or5 degrees would make that much of a difference but man does it ever in mine
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Old 07-22-2010, 02:55 PM
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Thanks for posting specs again, was not sure about the "big picture". Well if the only condition to his honoring the build is the 36 degree limit then you have it made, at the risk of playing devils advocate here IMHO set it back to what ever it needs to effectively feed the hurricane without detonation and drive it like you stole it
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Old 07-22-2010, 04:15 PM
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Quote:
Originally Posted by Custom10
Thanks for posting specs again, was not sure about the "big picture". Well if the only condition to his honoring the build is the 36 degree limit then you have it made, at the risk of playing devils advocate here IMHO set it back to what ever it needs to effectively feed the hurricane without detonation and drive it like you stole it

Just came in from that exact deed. I did notice one thing however, that the vac was a bit stronger on the skinny side of 40, actually around 39 so thats where its at. I struck a comprimise between the overall degrees it wanted and picking up a hair more idle vac which may take away the tiny hair of a lul that I had if I punched it from a stand still. I got er marked at 36 and by gum thats where she'll go back to if sh1t hits the fan. See he had this one guy he built the same deal for accept in a 6200 pound truck hauling a 5000 pound trailer with the timing set at 40 and another full point of compression over me and an engine that ran 20-30 degrees hotter than mine take up a 45 degree hill with that whole mess and go into melt down mode,so now the builders all squirelly when he hears big timing numbers. Builder is very compitant at putting the stuff together but admits that after its together his tuning abilities are strictly race and not street. Thanks for being a sounding board Custom10
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Old 07-22-2010, 04:20 PM
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Did the balancer ring slip?

With 11:1 compression and old bowtie heads on race gas, we used to routinely run 40-43 degrees locked total, and that was determined on an engine dyno. Some new heads are as little as 28 degrees for peak power.
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Old 07-22-2010, 04:33 PM
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Some chamber shapes will like more timing, some(like the Vortec)will like less. You will find that most engine dyno operators will start around 32-36, and then let the engine and the dyno #'s tell you what the engine likes by testing. You are by no means out in left field at 39-40, the aluminum heads have a little more tolerance and may prefer to be a little higher.

Let the engine tell you what it wants rather than trying to bend the engine to your preset notion of what it needs.

It is very common for two different timing lights to read differently, especially the dial back types. Pick one light and use it exclusively, don't borrow a light at the races, it could bite you.
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Old 07-22-2010, 04:41 PM
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Quote:
Originally Posted by lmsport
Did the balancer ring slip?
You're thinkin' what I'm thinkin'. I'm bettin' that what the OP is seein' as 40 degrees is actually somethin' less.
http://www.crankshaftcoalition.com/w...op_dead_center
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Old 07-22-2010, 05:09 PM
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Quote:
Originally Posted by techinspector1
You're thinkin' what I'm thinkin'. I'm bettin' that what the OP is seein' as 40 degrees is actually somethin' less.
http://www.crankshaftcoalition.com/w...op_dead_center
How does one detect balancer slip?any way other than the whole tdc bit?guess not huh
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Old 07-22-2010, 05:26 PM
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Quote:
Originally Posted by sooper
How does one detect balancer slip?any way other than the whole tdc bit?guess not huh
If it was easy, everybody would be doing it.
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Old 07-22-2010, 05:27 PM
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Quote:
Originally Posted by sooper
How does one detect balancer slip?any way other than the whole tdc bit?guess not huh
Paint a line from the hub to the outer ring, if it moves more you will be able to see it down the road.
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Old 07-22-2010, 05:48 PM
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Quote:
Originally Posted by sooper
How does one detect balancer slip?any way other than the whole tdc bit?guess not huh
I try to remember to index mark the hub to the ring, but i forget sometimes. The balancer people out to do that!

Most engines I build use an ATI.
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Old 07-22-2010, 06:50 PM
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Quote:
Originally Posted by sooper
How does one detect balancer slip?any way other than the whole tdc bit?guess not huh
If it is a lot of slip, just comparing the location of the inner damper keyway to the outer camper ring TDC mark will tell you.

Depending on what damper/tab you have, the difference between the keyway and the TDC line will be 2, 10 or 40 degrees. Having the damper off would be the easiest way to see things clearly for measurement.

Another way to look at it, is if the damper mark and tab are aligned at TDC, the keyway should be @ 2 o'clock.
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Old 07-22-2010, 06:51 PM
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more than 36deg (on this motor) indicates the balancer/timing tab is off, the light is wacked, or the mechanical timing curve is wrong.

If you give it more than what the motor really needs for max power you will not go faster and risk engine damage.

Get a clue and find out why your motor is different than the other 4,000000 built and run since 1955.

Do not go by race motors using domed pistons and old school leaded race gas. This fuel slowed the fuel burn speed requiring more max power timing.

If the carb jetting is too rich or too lean the motor will want more timing than usual. (cause the fuel burn speed is slowed) If the ignition amplifier is crap or the timing chain is slack the timing will retard as you rev it up.

If the engine timing curve is lazy wit low inital and a slow timing curve , you will be fouled by jacking up the timing. The added inital and mid rpm timing will feel more impressive, but the top rpm WOT timing will be excessive. You really need to recurve the distributor. Stock out of the box distributors are never set up right for high perf motors with non stock cams.

Start by verifying true TDC on the balancer timing tab and correct as nessessary. All aftermarket tabs are out, many factory tabs are out.
Balancers do slip.

Your builder is right 40deg total max mechanical advance is too much. And its more than you need to go fastest, make the most possible horsepower.
Fix it.
Then work on the timing curve etc.

To find 36deg without using the advance dial on the timing light first verify true TDC using a piston stop and then measure (one tenth) 1/10th around the balancer. one 1/10th the circumference is 36deg.

Wrap masking tape around the balancer. Mark the 0 TDC point, yank it off and lay it out straight. measure the length and divide by 10. Mark the tape accordingly at 36deg and reinstall it realigning the 0tdc points. mark the balancer at 36deg BTDC.
If you are going to play around with the motor and seek max timing put good gas in the tank. Busting a piston won't make your builder happy. Sunoco 94 is the best pump gas stuff sold in Canada for street motors.
ya it makes a difference.

Last edited by F-BIRD'88; 07-22-2010 at 11:34 PM.
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Old 07-22-2010, 07:14 PM
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Many street motors using pump gas actually make the most horsepower with less than 36deg total. The better job of optimizing the combustion chamber and fuel mix quality, the less timing required to burn the fuel.
All modern unleaded pump gas is fast burning. The old school rules don.t apply. Excessive timing advance will bust your motor and will not make you go faster.
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