L20B Weber 32/36 idle problem and cam timing question

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akara
Posts: 103
Joined: 19 Mar 2011 18:15
Location: San Diego, California

L20B Weber 32/36 idle problem and cam timing question

Post by akara »

Hey guys I am trying to help a friend of mine with his first project car, a 510 of course.

I cant seem to get this car to idle on the idle circuit of the new Weber 32/36. Idle mixture screw and choke changes have no effect. I have installed a couple of these carbs and I have never had a problem like this, I told my friend to get this carb because of how trouble free they have been so I am at a bit of a loss.

The car will idle and drive fine if I turn the idle speed screw in 3+ turns. I understand this means it is idling off fuel coming through the small enrichment circuit holes that have been uncovered.
The engine seems to run rich but well everywhere but at idle.
I have taken the idle jets out of the side and blew them out (I could even see some fuel in it still) I have also blown out the idle mixture screw passage. None of this has helped.
I took the top off the carb and checked the float height, blew out the main and air jets, everything was clean and clear, this is a new carb.
I have sprayed ether and carb cleaner everwhere with no effect on the idle. Ive blocked off all vac ports and PCV valve with no change. I cannot hear any vac leaks and have checked for what feels like hours.
The car drives great on the street and doesnt drive like it has a vac leak. I have checked the base gaskets and manifold to head gaskets.
Here is a little video of how the car runs.
https://www.youtube.com/watch?v=6uBt37HIcJU
I was thinking maybe the camshaft timing could be off? The only problem is that I am not sure what mark on the crankshaft pulley is TDC as the pulley itself is a mystery spare and I dont have a dial gauge to check it. It seems like the first mark is TDC when i look at the piston through the #1 cylinder with a flashlight but I cant be sure.
Here is two photos of the crank pulley timing marks and the corresponding camshaft timing marks. The cam sprocket is set to #2
Image
Image
It looks like the cam might be off a tooth? Could this even cause this type of idle issues or do I have two separate issues?

I know this is a big wall of text and I appreciate anyone willing to read through it and post up their thoughts!
Andrew
Last edited by akara on 20 Jul 2014 20:41, edited 1 time in total.
KoHeartsGPA
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Joined: 15 Oct 2006 12:03
Location: Eugene,Oregon

Re: L20B Weber 32/36 idle problem and cam timing question

Post by KoHeartsGPA »

I can't see your pics, but this is what the timing marks should look like...
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Can & Chain link alignment.
Can & Chain link alignment.
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Bottom end alignment.
Bottom end alignment.
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Diego.
akara
Posts: 103
Joined: 19 Mar 2011 18:15
Location: San Diego, California

Re: L20B Weber 32/36 idle problem and cam timing question

Post by akara »

fixed the photos
datzenmike
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Re: L20B Weber 32/36 idle problem and cam timing question

Post by datzenmike »

KoHeartsGPA wrote:I can't see your pics, but this is what the timing marks should look like...
Image
This is only true if installing the chain. Once the engine has been turned this bright link position become random. Besides this does not take into account chain wear or stretch. Regardless of bright links or stretch, or what hole position you are using, when the engine is at TDC you should have the horizontal etch line on the cam thrust plate just above or slightly to the left of the Vee notch in the back of the cam sprocket. Nothing matters but this relationship.

This cam is perfectly timed...
Image


These are close enough. The etch line is 4 degrees of cam so at the most you are within 2 degrees. Each notch on the pulley is 5? degrees so half that is 2.5 cam degrees. Close enough if not a race car.
Image
Image
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs
akara
Posts: 103
Joined: 19 Mar 2011 18:15
Location: San Diego, California

Re: L20B Weber 32/36 idle problem and cam timing question

Post by akara »

Thanks for the input datzenmike, now at least I know to focus on a carburetion issue. I am getting a new gasket set for the adapter plate and I will swap a different carb on to see if that fixes it but I really dont want to take parts from my daily driver just to put on my friends car :cry: :cry:
KoHeartsGPA
Posts: 513
Joined: 15 Oct 2006 12:03
Location: Eugene,Oregon

Re: L20B Weber 32/36 idle problem and cam timing question

Post by KoHeartsGPA »

Great info, Mike, ya I have new chain on mine and everything in lining up, hopefully she will be smooth and painless when final tuning while running happens :-)

akara, did you check for cracks in the manifold?, I just thought about that now
Diego.
akara
Posts: 103
Joined: 19 Mar 2011 18:15
Location: San Diego, California

Re: L20B Weber 32/36 idle problem and cam timing question

Post by akara »

no cracks in adapter plate or manifold. I'm thinking the carb might've defective and have the idle passage blocked in the carb or something
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butters68
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Re: L20B Weber 32/36 idle problem and cam timing question

Post by butters68 »

did you try moving the dizzy ?
ding ding dong dong all night long long.
akara
Posts: 103
Joined: 19 Mar 2011 18:15
Location: San Diego, California

Re: L20B Weber 32/36 idle problem and cam timing question

Post by akara »

have tried advancing it as far as 20 degrees with the vacuum port disconnected, helped a little but still needs the speed screw 3 turns in. By contrast my daily driver 510 with the same carb and camshaft idles great at about 2 turns in. it has an 620 EL dizzy. This weekend I will check the ignition timing again and swap the carb. Will report my findings
Three B's Racing
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Re: L20B Weber 32/36 idle problem and cam timing question

Post by Three B's Racing »

Choke pulled has no effect sounds like your idle circuit has bleed by because it should over richen and stall the engine. Try running your hand over the top of the carb while idling slowly choking it off. If the idle increases you have a vac leak, no change take the carb back. One thing I used to do was rev the engine then block off the carb creating super vacuum in the hopes it'll clear whatever obstruction may be in any of the feed circuits. If you have a stock carb run it to see if it's better. Obviousely if it idles great your carb is shit!! if no change ouch!!! Have you checked your valve settings?
"Lastnight the wife said oh boy when your dead you can't take nothing with you but your soul oh "Think"
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