Wrong timing marks?

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Old Apr 10, 2025 | 03:51 PM
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calebsg's Avatar
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Wrong timing marks?

Hey, new here. I’m at a shop working on classic euros but we have a 68 cutlass S with a rocket350in right now. Working on timing it after I put in an HEI dizzy.

is this timing marker wrong? Every picture I see of the one for this car looks different. Is 0 degrees TDC at the leftmost edge? What should I set my advance to at max load/idle?

Old Apr 10, 2025 | 05:38 PM
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Pretty sure 0 is at the point of the V which the V points to, the next unnumbered V point is 5 degrees and the V point is 10 degrees.

What HEI was used a GM factory one? The HEI's need full battery voltage. That car left the factory with a pink resistance wire going to the coil from the bulkhead connector, it won't supply full battery voltage to the HEI.

Is it a factory 4bbl motor which means high compression or a 2bbl low compression?

What timing settings? Other forum members can give you better advice on that than me, wait for their response.

Old Apr 10, 2025 | 09:20 PM
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Originally Posted by calebsg
Hey, new here. I’m at a shop working on classic euros but we have a 68 cutlass S with a rocket350in right now. Working on timing it after I put in an HEI dizzy.

is this timing marker wrong? Every picture I see of the one for this car looks different. Is 0 degrees TDC at the leftmost edge? What should I set my advance to at max load/idle?
You are going to run into some other issues trying to time that with a factory calibrated Olds HEI. The factory spec with the points is somewhere between 6° BTDC and 10° BTDC. The HEI wants 20° BTDC with the 8:1 compression cars that it came in. That timing pointer might be at 15° off the top edge.
You need to find out how much mechanical advance is built into the distributor you installed and get your total mechanical advance to about 36° BTDC when all in. If there is too much initial advance with the HEI, the car will have a hard time starting.

Last edited by svnt442; Apr 10, 2025 at 09:20 PM. Reason: typo
Old Apr 10, 2025 | 09:43 PM
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Originally Posted by svnt442
You are going to run into some other issues trying to time that with a factory calibrated Olds HEI. The factory spec with the points is somewhere between 6° BTDC and 10° BTDC. The HEI wants 20° BTDC with the 8:1 compression cars that it came in. That timing pointer might be at 15° off the top edge.
You need to find out how much mechanical advance is built into the distributor you installed and get your total mechanical advance to about 36° BTDC when all in. If there is too much initial advance with the HEI, the car will have a hard time starting.
out parts team ordered the 6009 HEI from performance-world.com… and yes we have a sun distributor tester. I can figure all that out on my own. I just need to know where true 0 degrees is in reference to this poorly marked timing tab, and I guess I need to know what I should set base timing to with vacuum advance disconnected.

im using an edelbrock avs2 4 barrel carb.
Old Apr 10, 2025 | 09:46 PM
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Originally Posted by Sugar Bear
Pretty sure 0 is at the point of the V which the V points to, the next unnumbered V point is 5 degrees and the V point is 10 degrees.

What HEI was used a GM factory one? The HEI's need full battery voltage. That car left the factory with a pink resistance wire going to the coil from the bulkhead connector, it won't supply full battery voltage to the HEI.

Is it a factory 4bbl motor which means high compression or a 2bbl low compression?

What timing settings? Other forum members can give you better advice on that than me, wait for their response.
yea I’ve got full battery keyed voltsge to the dizzy. No issue there. I’m using a 4barrel edelbrock avs2. I just need to know what total advance should be for these cars, what the aftermarket hei needs at idle, and what those marks on my pulley tab mean. Any info appreciated
Old Apr 10, 2025 | 10:15 PM
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Think of the pointed end of the V that is at the rearmost part of the tab as pointing at the # as in:

>=10 BTDC
>=5 BTDC
>=0 TDC

The lower hole is a zero so that pointed V is 0 TDC, the next notch is 5 BTDC but the 5 isn't there it is implied and the notch closest to the top of the engine has a 1 and 0 next to it for 10 BTDC. As for the base timing and total advance rely on other forum members.

A Sun distributor machine...nice! A Sun scope too?
Old Apr 10, 2025 | 10:55 PM
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Originally Posted by Sugar Bear
Think of the pointed end of the V that is at the rearmost part of the tab as pointing at the # as in:

>=10 BTDC
>=5 BTDC
>=0 TDC

The lower hole is a zero so that pointed V is 0 TDC, the next notch is 5 BTDC but the 5 isn't there it is implied and the notch closest to the top of the engine has a 1 and 0 next to it for 10 BTDC. As for the base timing and total advance rely on other forum members.

A Sun distributor machine...nice! A Sun scope too?
thanks for the help! Wonderful. Yeah I’ll do my research on the actual timing for use with an HEI…
yes it’s a sun 504 distributor tester….. older than me haha I’m 22 years old. No scope but we might get one. All we do is older cars…

Old Apr 12, 2025 | 08:06 AM
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Old Apr 13, 2025 | 07:07 AM
  #9  
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Check the curve, you definitely have the machine to do it. My Chinese HEI had a points style curve. Factory timing would have worked with this 350. I have found about 5 different curves on factory HEI, aftermarket not sure. A dial back timing light let's you set whatever curve you want on this 350.

Last edited by olds 307 and 403; Apr 13, 2025 at 07:11 AM.
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