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202 timing issue

Hi all,

Firstly, i put a timing light on my motor again today because the mechanic told me to check my timing. It was at 6 degrees advance at idle but then at around 2500-3000rpm it had 40 in it. Which is obviously way to high. I backed off the timing to around 27-28 but then it didnt want to idle. I presume this means the dizzy needs some attention or a new one purchased. (By the way i'm running a Bosch HEI dizzy) I had another one fo the same dizzy out there which seemed in better condition so put that in but then it was trying to say it had around 25 in it at IDLE.

I thought I must have put it in 1 tooth advanced so pulled it out and turned it back a tooth and then it wouldnt start. From there it went downhill, i got the sh!ts with it so just pushed it back in the shed and thought i'd leave it till tomorow and start from scatch again getting TDC for cyl 1 etc.... Can anyone recommend how much timing it should have in it?

Also its still got a pop coming through the exhaust like I said in a previous post. I have readjusted all the rockers and that didnt fix it, i then even backed them all off a bit so they couldnt be to tight but it still had the pop.
For those that didnt see the original post, here is a video of the pop coming through the exhaust
http://www.youtube.c...

Any help much appreciated

Cheers
James

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" It was at 6 degrees advance at idle but then at around 2500-3000rpm it had 40 in it. Which is obviously way to high."

I would be happy with 40 deg Advance at 3000 RPM. I would make changes to the Distributor to get it if it wasn't manifesting.

"Also its still got a pop coming through the exhaust like I said in a previous post."
An Exhaust Valve may be riding. Look for any wear Marks where each Valve Stem meets its Rocker. If there is any sign of wear, the Lifter will be driven crazy trying to nill out the Lash. These surfaces *must* be unblemished to allow the Lifer to make a reliable measurement and adjust accordingly.

Otherwise the Lash will change each time the Valve cycles and the Lifter will have to recalculate. It will take at least 2 mins before it zeroes out any negative Lash.

"I had another one fo the same dizzy out there which seemed in better condition so put that in but then it was trying to say it had around 25 in it at IDLE. "

The Balance Weights may be sticking.

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T

My Shed

Holdenpaedia, they're the brakes Mate.

Hi T,

So 40 degrees at 2500-3000 seems about right to u? If that's the case would you recommend I just put that other dizzy back in and leave it how it was?

And I'll have a look at the top of the valve for any wear. If its not that, what else do u think it could be?

Cheers
James

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Hi James,

"So 40 degrees at 2500-3000 seems about right to u? If that's the case would you recommend I just put that other dizzy back in and leave it how it was? "

Yes.

"And I'll have a look at the top of the valve for any wear. If its not that, what else do u think it could be?"

Rocker/Valve Stem wear is a common cause of riding Valves when Hydraulic Lifters are used and has tricked a lot of people because Valve Lifters have a good reputation for taking up clearances. They are also very reluctant to release their hold if the Valve Train isn't reliable because it has constantly changing clearances.

Other causes may be a burnt Valve, burnt Valve Seat, something stuck under a Valve. A Valve Stem may be too long. A Rocker Stud may be bent. Excessive Carbon on a Valve Stem was a common cause or riding Valves in the US.

In a recent Post, Ben Simpson said he just polishes the Rocker Face smooth when he finds wear there and things work out OK.

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T

My Shed

Holdenpaedia, they're the brakes Mate.

Thanks T I will investigate it further Tomorow and let you know how I go. Hopefully it's just something minor and I dont need to pull the head off or anything major like that.

It's just strange because it didn't hae this pop before it went to the mechanic for the front end and then I got it back and it had the pop in the exhaust. They didn't touch the motor (well they weren't meant to) so shouldn't be anything they did. He just said I need to look at my timing because he said he thought it had to much advance in it and it should only have about 28 in it at 3000 and not to drive it until I get it sorted.

Correct me of I'm wrong but I was always under the impression that as long as its not pinging then it alright?

Cheers
James

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"Correct me of I'm wrong but I was always under the impression that as long as its not pinging then it alright?"

I Agree.

The Wedge Combustion Chambers Holden Sixes use can run a lot of Spark Advance. Much more than some other Combustion Chamber Designs. You can research the Ricardo designs to find out more about this if you want.

When I first had this Rocker Wear problem it took a little while to manifest because the sharp edges had to blunt down before the problem appeared.

I have some used Rockers in the Shed. I'll try to examine and photograph their Stem Faces soon unless another Member has some they can post up.

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T

My Shed

Holdenpaedia, they're the brakes Mate.

40 degrees is way too much advance. Most ting lights are not that accurate at 3000 rpm anyway. Send the dizzy off to get recurved, you want about 10-12 at idle and about 32-34 at about 2700 in a 202, may be little bit more if manual. This will make your car run way better, more responsive and economical, dosnt cost much either

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Anywhere in the 36 - 40 degree range at those revs is fine James. The earlier you can get that much advance the more torque you'll have (unless she pings...)

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Cheers...Dave

"Search more, Post less"

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Thanks guys, I really appreciate the help. Seems to me like the mechani might have been trying to get some extra work out of me then. I've now had you 2 on here and another 2 of my mates all tell me the same thing.

T those pictures would be a great help, I'll try get you some Tomorow aswell.

Cheers
James

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compression, camshaft and fuel used play a MASSIVE part in how much timing your motor can take. do you KNOW your cam specs and REAL compression ratio??

if yours has a decent size cam then you may be wise to have the dissy recurved, as the larger camshaft could want as much as 20-25 degrees at idle and 40 or so at max rpm.

my hq race engines with small cam like 40+ degrees at 4500rpm on 98 octane and 11:1 compression. but only 25 or so degrees at 3000rpm. the curve is where a LOT of power is hiding that many people leave on the table.

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I know my cam specs but not the compression ratio. I would like to get the dizzy sorted when I get the money but at the moment the main focus is to just get it running so I can drive it once registered without doing any damage.

Am I going to do any damage to the motor with the timing set the way I had it as stated above? That's my main concern at the moment. Can always hunt for power a bit later on if you know what I mean. Fuel wise it's got 95 in it at the moment.

Cheers
James

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check/adjust the mixture at idle, also turn the dissy at idle with motor running, sometimes excess (and insufficient) advance causes popping and what not.

once your motor is modified the factory 6 degrees is out the window.

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sounds like a bent push rod or a lobe off the cam. is it a fresh build? if the cam was not run in correctly with a zinc additive in the oil the cam will be rooted. easy way to check. remove rocker cover. cut piece of cardboard to sit down the side of the head (tappet cover gasket sealing area) this will catch most of the oil.start it up and look closely at the rockers. are they all moving the same amount?

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Hey mate, yes it's a fresh rebuild but the cam was already in it when it was running before I rebuilt it. The cam was run in properly.
Thanks for the advice will look into it Tomorow.

Cheers
James

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"It was at 6 degrees advance at idle but then at around 2500-3000rpm it had 40 in it."
--------------------------
Is that with the vacuum hose on or off? You should measure it with the hose off and plugged.

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