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1300 problem diagnosis needed
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Stormc
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PostPosted: Fri Nov 04, 2016 8:44 pm    Post subject: 1300 problem diagnosis needed Reply with quote

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1300 engine, dual port, new 30pict 1 carb, mechanical advance dist with built in electronic ignition.

Running poorly. Idle speed wanders 750-850 RPM. Sometimes stalls on deceleration. Seems to be low on power. Also an oil leak on right side which doesn't appear to be pushrod tubes.

Spark plugs in picture shows left bank-3,4- a beautiful reddish brown. Right bank, 1 is pure white and 2 is pure black. Like 1 is running way too hot and 2 perhaps too rich. The plug is just black, not filled with gunk like burning oil.

Compression 1-90, 2-90, 3-100, 4-105
Vacuum gage oscillates 14-16
Max advance set at 28 BTC. Max is reached about 2300 RPM

Can anyone give me a clue what the problem could be?
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luvthemvws
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PostPosted: Sat Nov 05, 2016 12:45 pm    Post subject: Re: 1300 problem diagnosis needed Reply with quote

I think the intake valve on #1 is stuck open. The #1 cylinder thus force-feeds #2 and makes it appear too rich. Also, pushing cylinder pressure up the intake valve stem and leading to leaks.
Pull the 1-2 valve cover and turn the engine with a wrench (ignition off). Watch carefully the movement of all rockers and valves on that side for equal movement.
Rock on.
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Stormc
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PostPosted: Sun Nov 06, 2016 2:05 pm    Post subject: Re: 1300 problem diagnosis needed Reply with quote

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Thank you very much. I think you nailed it except that the problem seems to be a crack under the valve rather than a sticking valve. There is a crack from the intake to the exhaust valves where they are closest together. There is also a crack running down the spark plug threads. Anyway, a replacement head is in order.
Image may have been reduced in size. Click image to view fullscreen.

It looks like number 1 may have been leaking around the joint with the cylinder. At least, the top of the cylinder has wet oil on it which number 2 doesn't.
Image may have been reduced in size. Click image to view fullscreen.

They both appear to have been leaking at the crankcase end. That would likely be the source of the baby marking her spot when parked. I read elsewhere (Muir update) that blue silicone sealant is the best thing to use at the crankcase end as opposed to the paper gasket. Is it reasonable to apply a bead of sealant without removing the piston from the cylinder completely?

On the other hand, it would be nice to get the cylinders out to get them clean. If so, is it better to remove the pistons from the cylinder or to slide them out enough to pull the wrist pins? There isn't much ridge at the top, so I assume there isn't much at the bottom. I don't think there are many hours on the rebuild.
Image may have been reduced in size. Click image to view fullscreen.

And finally, any advice on finding a replacement head? There is a casting number in the top 113 101 375 A and 20. Is this sufficient for identifying a replacement head?
I really appreciate the help. I've never been this deep into a VW before.
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tobiasax
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PostPosted: Sun Nov 06, 2016 11:51 pm    Post subject: Re: 1300 problem diagnosis needed Reply with quote

These cracks are rather common. Many people have them on good running engines without knowing.

The cheap solution would be to re-tightsen the heads and see what happens.
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Stormc
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PostPosted: Mon Nov 07, 2016 8:11 am    Post subject: Re: 1300 problem diagnosis needed Reply with quote

But this isn't a "good running engine". Something is wrong.
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Stormc
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PostPosted: Sat Jun 03, 2017 3:40 pm    Post subject: Re: 1300 problem diagnosis needed Reply with quote

Followup. I installed a new head. In the process found that the previous rebuilder had a copper sealing ring under cylinder 2 but none under 1 which left one cylinder higher than the other! I removed the ring and sealed the bottoms with Formagasket 3. I ran it a bit and started a tuneup. Valves adjusted, check compression. #1 120, #2 118. Plugs look same as before. #1 white, #2 black! I guess I eliminated a lot of possibilities. I swapped plugs left to right, on the unreasonable chance it was a spark plug problem.

It seems that for some reason cyl 1 is getting a lean mix and 2 is getting a rich one. Beats me how this is happening. An air leak could cause the lean, but wouldn't explain the rich.

Anybody have a clue where to look? Thanks,
storm
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RolandD
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PostPosted: Sat Jun 03, 2017 8:14 pm    Post subject: Re: 1300 problem diagnosis needed Reply with quote

What exhaust are you running?

Crazy Roland
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Stormc
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PostPosted: Sun Jun 04, 2017 4:47 pm    Post subject: Re: 1300 problem diagnosis needed Reply with quote

Simple dual exhaust. The left bank-the good one- has started backfiring some on decelleration
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RolandD
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PostPosted: Sun Jun 04, 2017 7:53 pm    Post subject: Re: 1300 problem diagnosis needed Reply with quote

Like an old dune buggy? Not a 4 -into -1 and then a split into 2?

If like a dune buggy, what is the chance there is a restriction on the bad side?

Crazy Roland
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vwjetboat
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PostPosted: Sun Jun 04, 2017 7:59 pm    Post subject: Re: 1300 problem diagnosis needed Reply with quote

intake cracked between heat riser and intake part? only seen that once.. but there was a crack behind the intake between the tubes .. only found when off and had to look real hard..
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