Questions: L20/weber tune up Portland.
Questions: L20/weber tune up Portland.
Looking for some input or mechanic help in Ptld area.
I went with a local shop, in spite of their questionable reputation, because they have an exhaust analyzer and said they could really dial in my Weber. They told me if I wasn't totally happy they'd make it right.
When it was done it was much improved but still had a noticable flat spot when I tip into it from idle or cruise. It's especially irritating exiting a tight corner, right when you want it... nothing. The shop said to run good gas and that should clear it up. I ran the old gas almost out, then added over half a tank of the recommended Chevron Supreme. I've put some spirited miles on it but it still isn't carbureting totally clean and now the idle speed is being inconsistent. The shop owner's saying I should run 3 tanks of Chevron Super to clear it up. Sounds questionable to me.
After they'd worked on it, I took the shop owner for a ride and he said the flat spot was normal hesitation when the secondary kicks in (since when is that considered normal!). I now feel confident that the hesitation happens long before the secondary is called on and it happens no matter whether I have a light or heavy foot.
The car runs WAY better than before but I'm starting to think the shop doesn't intend to make me completely happy.
Anyone have suggestions or want to take a stab at getting it right?
Thanks
P.S. Browny points if you can name the shop.
I went with a local shop, in spite of their questionable reputation, because they have an exhaust analyzer and said they could really dial in my Weber. They told me if I wasn't totally happy they'd make it right.
When it was done it was much improved but still had a noticable flat spot when I tip into it from idle or cruise. It's especially irritating exiting a tight corner, right when you want it... nothing. The shop said to run good gas and that should clear it up. I ran the old gas almost out, then added over half a tank of the recommended Chevron Supreme. I've put some spirited miles on it but it still isn't carbureting totally clean and now the idle speed is being inconsistent. The shop owner's saying I should run 3 tanks of Chevron Super to clear it up. Sounds questionable to me.
After they'd worked on it, I took the shop owner for a ride and he said the flat spot was normal hesitation when the secondary kicks in (since when is that considered normal!). I now feel confident that the hesitation happens long before the secondary is called on and it happens no matter whether I have a light or heavy foot.
The car runs WAY better than before but I'm starting to think the shop doesn't intend to make me completely happy.
Anyone have suggestions or want to take a stab at getting it right?
Thanks
P.S. Browny points if you can name the shop.
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- Posts: 536
- Joined: 06 Sep 2010 15:10
- Location: Coquitlam
Re: Questions: L20/weber tune up Portland.
Bill's Datsun Shoppe??
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- Posts: 536
- Joined: 06 Sep 2010 15:10
- Location: Coquitlam
Re: Questions: L20/weber tune up Portland.
Post up ALL of your engine and carb specs, and I that means all of them.
Size of engine ( Stroker?)
Compression ratio of engine.
Any other engine modifications.
Carb model(s) and all jetting sizes. Low speed or transition Jets, main jet size, Air bleed , Emulsion tubes.
Choke sizes
Accelerator pump nozzle sizing
Ignition timing at idle and full mechanical advance.
Idle speed. ( And position of transition slot or holes to butterfly. Critical with big cams ).
Are you using Vacuum advance. Ported or Manifold source?
Cam specs including lift and duration.
Rear end ratio.
Size of engine ( Stroker?)
Compression ratio of engine.
Any other engine modifications.
Carb model(s) and all jetting sizes. Low speed or transition Jets, main jet size, Air bleed , Emulsion tubes.
Choke sizes
Accelerator pump nozzle sizing
Ignition timing at idle and full mechanical advance.
Idle speed. ( And position of transition slot or holes to butterfly. Critical with big cams ).
Are you using Vacuum advance. Ported or Manifold source?
Cam specs including lift and duration.
Rear end ratio.
Re: Questions: L20/weber tune up Portland.
Engine off, air cleaner off, flashlight on, look down the carb bores and actuate the throttle. You should see fuel spray in from the accelerator pump. If you don't, this is your problem.
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson
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- Posts: 536
- Joined: 06 Sep 2010 15:10
- Location: Coquitlam
Re: Questions: L20/weber tune up Portland.
^ Sure... go with the simple things first. Doh!!
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- Joined: 24 May 2006 12:40
- Location: Van. Isle.
Re: Questions: L20/weber tune up Portland.
Definitely 'look' into this first. At least the accelerator pump is on the outside of the weber.
Assume you have a 32/36 and not a 38/38 weber. The 32/36 is a progressive carb and the secondary will come in at about 3/4? throttle. At low speeds try punching it to 2/3 or 3/4 or just short of the secondary and allowing the revs to come up some before flooring it all the way.
Assume you have a 32/36 and not a 38/38 weber. The 32/36 is a progressive carb and the secondary will come in at about 3/4? throttle. At low speeds try punching it to 2/3 or 3/4 or just short of the secondary and allowing the revs to come up some before flooring it all the way.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs
- bertvorgon
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Re: Questions: L20/weber tune up Portland.
Also, make sure the "booster" venturis are NOT loose and rattling about. This is common on older 32/36's.
"Racing makes heroin addiction look like a vague wish for something salty" - Peter Egan
Keith Law
1973 2 Door Slalom/hill climb/road race / canyon carver /Giant Killer 510
1971 Vintage 13' BOLER trailer
Keith Law
1973 2 Door Slalom/hill climb/road race / canyon carver /Giant Killer 510
1971 Vintage 13' BOLER trailer
Re: Questions: L20/weber tune up Portland.
Thanks for the inputs,
Chickenman,
Bingo!
You win the browny points free beer!
Engine size - Stock L20 as far as I know.
Mods - Long tube header and Weber.
Weber - 32/36 manual choke (bought from Redline 3-4 years ago). Don't know the jetting specifics. According to Ye Olde Shoppe's exhaust analizer I think they put in a #10 main jet. Does that sound right? Whatever it was it definitely improved things. I can't find my receipt.
Accel. Pump - The mechanic commented that it was pumping strong. Maybe too much?
Timing - The shoppe checked the timing but only at idle.
Idle speed - The shoppe set it fairly high but now it's settled too slow, kind of lumpy and has to clear it's throat when I rev it. I'm pretty sure it's got a stock cam.
Vacuum advance - Stock vacuum adv. I think.
Rear end - 510 wagon so pretty sure it's 3.9:1.
Except for the Weber and header the engine is how I got it. Wish I knew more. Most of my time is spent prepping our ground and keeping our farm equipment functioning.
Datzenmike - That's pretty much the way I drive anyway. I don't ever remember flooring it before it's spinning. My old SSS 1800 had the SUs. This is my first car with the secondary action. I have to say I like the progressive character of the SUs rather than having to push it hard to feel some torque.
Anybody in the Portland area available to look at it?
Thanks guys,
Chickenman,
Bingo!
You win the browny points free beer!
Engine size - Stock L20 as far as I know.
Mods - Long tube header and Weber.
Weber - 32/36 manual choke (bought from Redline 3-4 years ago). Don't know the jetting specifics. According to Ye Olde Shoppe's exhaust analizer I think they put in a #10 main jet. Does that sound right? Whatever it was it definitely improved things. I can't find my receipt.
Accel. Pump - The mechanic commented that it was pumping strong. Maybe too much?
Timing - The shoppe checked the timing but only at idle.
Idle speed - The shoppe set it fairly high but now it's settled too slow, kind of lumpy and has to clear it's throat when I rev it. I'm pretty sure it's got a stock cam.
Vacuum advance - Stock vacuum adv. I think.
Rear end - 510 wagon so pretty sure it's 3.9:1.
Except for the Weber and header the engine is how I got it. Wish I knew more. Most of my time is spent prepping our ground and keeping our farm equipment functioning.
Datzenmike - That's pretty much the way I drive anyway. I don't ever remember flooring it before it's spinning. My old SSS 1800 had the SUs. This is my first car with the secondary action. I have to say I like the progressive character of the SUs rather than having to push it hard to feel some torque.
Anybody in the Portland area available to look at it?
Thanks guys,
-
- Supporter
- Posts: 6080
- Joined: 24 May 2006 12:40
- Location: Van. Isle.
Re: Questions: L20/weber tune up Portland.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs
Re: Questions: L20/weber tune up Portland.
Step 1 - verify that your engine's valve clearance is set correctly.
Step 2 - all of these other suggestions...
If (for whatever reason) the valve clearance is set incorrectly on one cylinder, then you can sometimes end up with an unworkable imbalance between cylinders that will render any carb-related twiddles a total waste of time.
Step 2 - all of these other suggestions...
If (for whatever reason) the valve clearance is set incorrectly on one cylinder, then you can sometimes end up with an unworkable imbalance between cylinders that will render any carb-related twiddles a total waste of time.
Re: Questions: L20/weber tune up Portland.
First check fuel pressure should be around 3.5, than make sure your fuel filter is good and check the filter in the carb. If all is good, your main jets are too small causing a lean condition.. go 2 sizes bigger. It will take cure the problem. I had the same issue and after replacing emulsion tubes,air corrector jets,idle jets, I found the main jets were the culprit that controls the fuel mixture once throttle plate is starting to crack open. This was all verified test driving the vehicle using a wide band o2 sensor. I have the carb dialed in now and the air /fuel ratio is around 12.6-14.4 from idle-WOT. Also put in a f6 or f3 emulsion tube on primary side. You will like it more.
Re: Questions: L20/weber tune up Portland.
Sorry for the delay,
Thanks guys for the input (hopefully you'll see this). I haven't had a chance to dig into it yet but today I took it for a spin in this nice, warmer weather and it was driving pretty well except for the lumpy, slow to slower idle.
I really appreciate you all sharing your knowledge.
Thanks guys for the input (hopefully you'll see this). I haven't had a chance to dig into it yet but today I took it for a spin in this nice, warmer weather and it was driving pretty well except for the lumpy, slow to slower idle.
I really appreciate you all sharing your knowledge.