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Discussion Starter #1
Getting my car running after years of sitting. After dialing in idle (16 inches of vacuum) and float levels, she ran pretty good. She idles fine. Pushes you back in your seat. Only rough spot is that she surges when you're cruising with light throttle. (Thought maybe that was too much vacuum advance or lean.)

Then I checked the timing. With vacuum advance plugged, she showed 60 degrees advanced initial! Huh? Used a different timing light. Same thing. No knocking during idle or driving. I turned the distributor to take out some advance. It immediately ran worse. Couldn't get down to the teens or it would die. Hmm... Got a piston stop out and confirmed the dampner hasn't shifted. TDC on the timing tape is still TDC for #1 piston.

What am I missing?

65 GTO with 400. 6X heads. 770cfm Holley. Pertronix HEI. MSD. Only 1,000 miles on the build, but she has sat for years at a time.
 

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Unhook vac line & plug it off.

Find out what your TOTAL MECHANICAL ADVANCE is first. For most Pontiac engines it should be 34-36 degrees.

Check the rpm at which you reach TOTAL advance.

If that number is above 3500, you need to buy an advance curve kit, and substitute a weaker spring, til you get the total to stop advancing at between 3000 & 3500 rpm. Most want their curve to start advancing at about 1000 and increase to total, by 3000.

AFTER you have the MECHANICAL curve set correctly, then you can hook the vac line back up & see how much advance the vac can adds.

I've read that you don't won't it to reach above 50 degrees. Some say mid 40's is enuff. If your dist has an adjustable vac can, you can back it off all the way, and if that's too low, adjust it back up in small increments. If your vac can is not adjustable, you can buy a Pertronix adjustable. Or, you can buy a Crane vac advance kit, which comes with an adjustable vac can & weaker advance weight springs.

https://www.summitracing.com/parts/pnx-d9006?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-pertronix&gclid=CjwKEAjw_PfGBRDW_sutqMbQsmMSJAAMpUapllQcqaUyrsnLf21E_-Mbt_fmNQ4dvqC16lF9cJQpOBoCy1Tw_wcB

https://www.summitracing.com/parts/crn-99600-1
 

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Discussion Starter #3
Thanks bigD. I measured advance with vacuum advance disconnected and plugged. I know the targets to shoot for. Where I'm at a loss is that it shows 60 degrees initial and likes it! Throttle response isn't as great in the lower end of the rev range, but I thought for sure it would be knocking and pinging if I had several times more initial advance than anyone I know. No detonation that I can hear. And she starts right up every time. Something's up and I don't know what.
 

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I agree, something's not right here. If it really has 60 degrees in it I'd expect it wouldn't even start. Please forgive me "in advance" (lol) for asking a really dumb question, I'm not trying to insult your intelligence or anything, but you are connecting the light to the front cylinder on the driver's side, right?

Bear
 

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"...you are connecting the light to the front cylinder on the driver's side, right?..."


Yeah, you can hook it to either #1 or #6 wire, since the zero mark on the balancer will hit the zero mark on the timing tab when every time either #1 or #6 piston is at TDC of it's compression stroke. It's a bit easier to use #6 , on a Pontiac, since you point the light from the pass side.

The timing light doesn't know which wire it's hooked to. It just flashes when the charge comes thru the wire. So, you can hook it to each wire, to make sure every wire is firing. But, for timing purposes, you must hook it to either #1 or #6 wire.
 

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Discussion Starter #6
Thanks for the replies guys. No offense taken!

I know my light is on #1 wire. Driver side at the front closest to radiator. Two different guns got same reading. Neither gun of the dial back variety.

Plug order on cap is right. 1,2,3,4... Just kidding. : ) 18436572 counterclockwise.

I pulled distributor last night. Put #1 piston 12 degrees before TDC on the compression stroke (watched intake valve open and close to confirm that), then took off the distributor cap. You would expect rotor to be pointing right at #1 terminal. It was noticeably past #1 terminal. I think this confirms that indeed it has a LOT of initial advance. Rules out the gun and the tape being the problem I think.

I can play with weights and springs, but what has me stumped is why would it want 60 degrees? Doesn't make sense.

If cam and crank gear were out of whack it wouldn't want THAT much advance would it? Timing chain and engine build only has about 1,000 miles on it. (And I've timed it before since the build!) Also, why would it run reasonably well if cam and crank were way off.

When I degreed in the cam, I remember talking with a builder about advancing or retarding the cam itself. I remember he was asking if I had a crank offset key. I can't remember what I did on that if anything. But if the cam was a little advanced or retarded, it wouldn't dramatically change my ignition timing, right? 60 degrees at idle isn't a tweak.

I really appreciate all ideas and help.
 

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Discussion Starter #7
Just checked my timing tape. Measured the circumference. Then measured the distance of 40 degrees worth of marks. It's the right one. Still scratching my head.
 

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Hey, maybe it's just playing a April Fool's joke on you. I'm pretty sure an engine will not idle @ 60 degrees advanced.

Hey, just for kicks, humor me and hook a light up to #6 wire. It should read exactly the same as when on #1 .
 

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65Poncho....That surging and bucking at light throttle cruise too much timing advance...

if your centrifigal and base is high, adding in 16 more from vac is way too high....

that said I have had guys say their car runs pretty good, when we pull dizzy and put it on the machine it has so much adavnce cannot believe they drive it like that!

some will have 40 in the weights and adding more on the base......then another 22 from vac....

what usuaslly saves them is heavy springs nd it keeps all that advance from coming in until way up in the rpm range.....

60 at idle....seems like it would be awful hard to start that....

you want 36 total Mechanical and 46 to 48 with vac....

hot cams can take a little more base and a little less cetrifigal....

the vac can add ten more:nerd:

sometimes the worse knocking is the knocks that you don't or can't hear!
 

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PS....double check for a crossed plug wire...as was mentioned ....

be double sure that you are not just clipped on the wire at the No 1 plug but that that plug wire is actually at the corresponding place on the cap''''

sorry, if you already verified, but this can happen easy...
 

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It's sure a head scratcher.... I'm wondering if the timing chain is "off a tooth" or so but I haven't thought that all the way through yet to decide if that would have anything to do with the price of frijoles in Tijuana... or if an extreme amount of ignition lead could otherwise "make up" for that such that it could run reasonably well.

Bear
 

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distributor gear must be oriented right as well, with dimple matching rotor tip. Slipped balancer ring,

stuck Dizzy weights...stuck open;.... will pull the advance out at lower RPMs..

don't know his idle RPM but could be high say 1000 or higher...

stuck or springs off will send timing soaring....

vacumn leaks that create an extra lean idle and therefore allow it to fire earlier.......

from a recent reassembly....or crossed plug wires or crossed ignition module wires should all be checked.
 

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It's sure a head scratcher.... I'm wondering if the timing chain is "off a tooth" or so but I haven't thought that all the way through yet to decide if that would have anything to do with the price of frijoles in Tijuana... or if an extreme amount of ignition lead could otherwise "make up" for that such that it could run reasonably well.

Bear
Now this jogs my memory. Back in around 1971, I had a '69 GTO, which I'd bought new, in early '69. At somewhere around 40k miles, the timing chain jumped, because of the plastic teeth which came on the cam gear, back then. Those teeth were almost guaranteed to fail by 50k miles.

The engine would not start. A guy I knew, moved the dist around, as I tried to crank it. Well, it finally cranked. But it had no power at all. Would not even get up to 50 mph. But, I did make it home, less than 10 miles away. At that time I knew almost nothing about the insides of an engine. So, I got a neighborhood mechanic to take a look. He discovered the jumped chain. Also had a couple of bent pushrods, since the valves were open at the wrong time.

Apparently, there was no valve or piston damage, since I drove it passed 60k miles, then successfully raced it for 2 seasons, without any internal changes at all.

Therefore, I assume that it may be possible to have the timing only 1 tooth off, and still have at least reasonable power, considering. ?????
 

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Static-time it. Put the engine on #1 TDC compression, and verify that the rotor is pointed directly at #1 on the cap. You're balancer should be at TDC, or 0 degrees. This is with the engine not running. IF your car was actually base-timed at 60 degrees initial, it would not start or even crank...if it did, it would kick back so hard it would probably break the starter or the ring gear.
 

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Yes I agree with GeeTee and BigD great points as well......

I went back to your description of the rotor being way advanced when you pulled the cap.....

I don't know if you are sure,.... but the bottom gear dimple must match the rotor tip and if it does not it throws the timing off 13 degrees....if in addition it was dropped in a gear off,.....you can get off quite a bit.....

so back to the beginning, pull the dizzy, check the gear, make sure the module wires are on correct weights turn freely, dizzy shimmed properly at bottom,...timing can mess up there as well...

then as GeeTee said starting points on engine TDC etc and re-drop the dizzy...

nothing fancy try the drop at TDC, pointing at #1 , which of course you double verified...

you will get it!:nerd::nerd::nerd:
 

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Seems others have experienced this thing as well. Many ideas and things to check, but ultimately, the reason was never found. A few comments point to the HEI/MSD with one mentioning the wires reversed internally. A big cam with a lot of overlap and low/dished compression was another thought because the engine needed more advance to work correctly with this combo. Check out this post: Timing way off, but runs great? | The H.A.M.B.
 

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yeah, when I have revesed the module wires accidentaly on the distributor machine it gives an erratic spark reading, so that is worth checking....

but it does feel like the timing light is just reading the wrong cylinder,,,,

no 3 maybe, and therefore it seems to run good and when you turn it down it does not, but you aew actually running at 30 BTDC not 60 and turning it down to past 0 and it stalls

all the while your light showing you 60 to 30....just something to really verify.....

but lots to check, if it starts easy just cannot see it really being 60....
 

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Discussion Starter #18
Thanks for all the input. Still trying to figure this out.

Pulled and went through the distributor. It is a Pertronix HEI unit. Weights felt a little "grabby." Cleaned them up. Put the quickest opening copper springs in. Turned vacuum advance down to 12. Confirmed with mityvac it does open with vacuum.

Put it back in. Checked and double checked order. #1 piston was confirmed to be 12 degrees before TDC on compression stroke. Pointed rotor at #1 . Wouldn't start. Turned dist both directions all the way. Wouldn't start. (Sigh)

Pulled the dist, advanced it about 45 degrees and put it back in. Starts right up! Put the light on it. 50 degrees. Take timing out, she stumbles. Add it, she likes it. Can only turn it to 60 so I do.

BigD, I took your suggestion. Switched timing light to #6 wire. (I want this to be operator error more than anyone) It also reads 60 degrees!

Idles smooth. Starts up first turn of the key. Will push you back in your seat.

Questions:
The dimple on the distributor. I don't know anything about that. Is that just for stock HEI's or would it effect my Pertronix unit?

Can someone tell me how to shim my distributor? Currently it just sits down on the block.

How do you tune your timing without a timing tape? Advance it until you hear spark knock then dial it back?

Guess I'll check for vacuum leaks. That sounds fun. I've watched some YouTube videos. Neither propane or starting fluid sound overly safe. : )

And now, the SUPER dumb questions because I feel like I'm losing my mind with this. When looking at the crank pully, it turns clockwise, right? So timing tape should wrap around it clockwise, right? Rotor spins counterclockwise, right? Twisting distributor counterclockwise advances timing, right? How far do I need to separate my plug wires (they are newer, performance oriented wires)?

I really appreciate the help guys.
 

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Crank does turn clockwise when viewed from the front -- the top of it spins towards the drivers side.
So... looking down at the Zero on your timing tape from the top, the markings that read advance should extend towards the right/drivers side as they increase. If you're looking up at zero from underneath the car (Zero on the bottom of the balancer) they should extend towards the passenger side.

You're making all your measurements with the vacuum advance disconnected and the hose plugged, right?

This is too weird....


Bear
 
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