Timing insanity, please help...

saudivette

Clueless In Sandland
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Mar 24, 2008
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Aussie expat in Saudi Arabia
*Disclaimer*
I bashed my head at work a few months ago and the resultant gash required a couple of stitches. I'm assuming now that I must also have suffered some brain damage. Read on...


I've been trying to tune the BOSS and after reading Lars' papers, had a go at it.


No go.


The car seemed to idle happily enough around 16* BTDC with the vacuum advance removed and plugged but there was almost no mechanical advance at all. I had a look around the distributor and finally saw where the flyweights had been contacting the inside of the rotor. I removed some plastic and kept trying it until the flyweights didn't leave a tell-tale mark on the rotor any more. Started the car again and no difference.


I looked at the distributor again and even though the flyweights look like they're mired in grease, they actually move very easily. However, they were able to move a long way before coming under spring tension, as you can see in this pic:
354bdd6ed804c24.jpg


When I pushed the reluctor (correct name??) around so the flyweights were at full extension and under full spring tension, they weights half cover the rotor screw holes. Given the thickness of the plastic of the rotor, there would have been very little flyweight movement from the sloppy pic above to them contacting the inside of the rotor:
354bdd6ed8ccf4c.jpg


WTF?


I had a look around the net and every single pic of an HEI distributor looked different to mine. I pulled mine apart a while ago but took pics during disassembly and reassembled it the way it was. So how the hell did my distributor get like that?


Anyway, I thought that I'd stumbled onto why the car was behaving like a POS and I couldn't tune it. I went into town this morning and bought a new cap and a second hand distributor. Side by side you can see my original (on the left) is around 90* out:
354bdd6c856fd37.jpg


I stripped the one I bought and put the shaft and flyweight assembly into my pretty red distributor. I lined it up and dropped it into the engine and when I tried to start it, it fired up straight away and ran lovely. The engine revved nice and quickly and the carb stumble I talked about in another thread, is almost gone!


I let it warm up and this is where the brain damage part comes in :huh:


The car was idling nicely and sounded better than it has since I've been trying to time it. I plugged my vacuum gauge into manifold vacuum and I'm getting around 11-12" Hg. I disconnected and plugged the vacuum advance and connected the timing light. According to my timing tape, the car's idling at 34* BTDC. If I dial in 36* on the timing light, idle now hovers around 0*. I revved the engine up and saw that the timing mark was moving but stabilized and pegged out around 2500 RPM but the timing shows around 12* BTDC. The timing tape's on the right way:
354bdd6c8643e26.jpg


Like I said before, WTF??


I thought I must have had the distributor a tooth out or something so I incinerated my hands and messed around realigning No. 1 TDC, dropped the distributor back in and it's exactly the same. I didn't double check that the TDC mark lines up with No. 1 cylinder at TDC though as it was too damn hot to pull the plug...


I disconnected everything and took it for a little drive around our compound. there's speed humps everywhere so I couldn't go fast but even with those odd readings, the car is running better than it ever has. The slightest goose on the throttle and there's some squealing from behind me. But, I want to set total timing and work out the advance curve.


Feel free to take the piss out of me if I've done something foolish or overlooked something, but please tell me what it is!
:withstupid:​
 
If I am reading this correctly, I surmise the springs are so bad, as soon as it starts, it is already running advanced.
Use two gold springs from a Mr Gasket 928G, and make sure the gear dimple aligns with the rotor point.
There just ain't much to the HEI dizzys
 
If I am reading this correctly, I surmise the springs are so bad, as soon as it starts, it is already running advanced.
Use two gold springs from a Mr Gasket 928G, and make sure the gear dimple aligns with the rotor point.
There just ain't much to the HEI dizzys
Well, I thought the springs were pretty good. These flyweights are under spring tension almost as soon as they move, compared to the sloppy setup of the first ones, and they seem pretty tight - they snap back into place quite nicely.
I bought a new gear this morning too, as they were pretty cheap. It has a dimple but it's not directly inline with the roll pin hole like the original ones are, it's slightly off to one side but I didn't think that meant anything :confused:

I thought your vette was a 82? Did you remove the CFI?
Yes, it is 82 but the Crossfire's been part of an artificial reef for some years now...
 
Will a slipped balancer do something like this? I'm going to physically check #1 TDC tomorrow.

Maybe it's the wrong timing cover, well, incorrect timing pointer on the cover?

This is the first time I've tried to tune it since I've had it. I replaced the timing cover as the other one was bashed all to shit but I took it with me when I got the new one. But after reading around the net, I guess the timing cover I replaced could have been incorrect...
 
Chevy changed the balancer and the keyway/timing mark relationship was different-- 10* IIRC? Somewhere around there anyway.

Your timing tab looks like a bolt on. There are also some adjustable ones out there so you can get it spot on.

(How's that for the Queen's english!!))
 
Maybe I read this too fast. Is the dizzy allowing a 20* change, or not?
Verifying TDC is always a good move anyhow.
 
I kinda remember timing my 82 through the back of the waterpump. If that is still an 82 engine I say the timing pointer is wrong.
 
The 82s timing pointer is off to the side, not behind the water pump. He has the correct one, or at least resembling the correct location.
 
Righto, the brain damage has been contained!

I still don't understand how the flyweights on my original shaft were orientated 90* different to every other distributor and from what I could see in various disassembly pics, the reluctor and flyweights can't be re-orientated :confused:

The springs were ratshit anyway and the flyweight posts were pretty worn, so money well spent on the replacement distributor.

Anyway, I thought I had checked #1 TDC ages ago but can't actually remember now if I did or not (the onset of dementia perhaps?). Ages ago, I replaced the timing cover and used the same bolt on timing pointer and the same harmonic balancer.

It took me a while working on my own, but I eventually ascertained that the timing mark is off by 30*. I moved the timing tape accordingly and hit it with the timing light.

But... it runs quite sweet now. With the vacuum removed and plugged, the timing pegs out at 2500 RPM and with total timing set to 36*, idle is 18*. Vacuum reconnected to manifold vacuum at idle is 12-13" Hg. There's the tiniest of stumbles if I mash the go pedal but I'll mess around with that later, after I've deciphered Lars' paper on vacuum advances - as in, which one do I need for my HEI?

Thanks for all the input guys :thumbs:
 
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With the vacuum removed and plugged, the timing pegs out at 2500 RPM and with total timing set to 36*, idle is 18*. Vacuum reconnected to manifold vacuum at idle is 12-13" Hg. There's the tiniest of stumbles if I mash the go pedal but I'll mess around with that later, after I've deciphered Lars' paper on vacuum advances - as in, which one do I need for my HEI?
It would be nice if you could just drop in a good dist from a non-computer chevy v8.
Is your vacuum advance working , take note if during all this parts swapping you have ended up with an Oldsmobile dist or the pickup coil from an Olds the vacuum advance will work backwards ? I don't have a dist with me to compare to your pics but it might explain things. Just a thought !
 
The only thing I swapped out was the center shaft and flyweight assembly as my original appeared to be arse about. There's no computer in the BOSS anymore and everything's running pretty sweet now :thumbs:
 
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