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Hi Everyone,

Has anyone here had any first hand experience with the Chinese Knock Off Weber 45 DCOE carbs. I would like to hear from someone who has them fitted to a 260Z L28 engine. Preferably anyone who has them running well. I have a set on my L28 but they will not idle correctly. This is a fully reconditioned L28 with a 60 thou overbore. Standard cam, reconditioned N42 standard head head and block. Flat top pistons. All new timing chain, gears, guides, and tensioner. Set on position 1.

1. I have checked and rechecked the timing several times and it is absolutely correct. Currently set at 12 degrees advance.

2. Checked and rechecked the valve clearances and they are absolutely correct as per the book. 

3. New points correctly set. New condenser.

4. Mixture set using a Colourtune spark Plug (nice blue flames in the chamber)

5. Re-Jetted the idle jets from 55F8 to 50F8. Made slight improvement but still wont idle below 1850 rpm. This is with the butterflies fully closed.

6.Some backfiring through the carbys. Re-jeting improved this but not fully sorted.

7. Engine starts dieseling when ignition switched off.

8. Fuel pump is Carter P4070. Fuel Regulator set at 2.5 psi. Any more and the carbs flood. I've tried to check the actual pressure but it will not read on the 0-15 psi gauge. Is running a fuel return line to the tank.

9. Float levels are set at 12mm. Checked and rechecked.

If anyone can suggest what else I can try short of chucking the JASF Weber knock offs and fitting genuine Webers help would be greatly appreciated. 

Best Regardsw,

Champ 54

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1 hour ago, Champ54 said:

This is with the butterflies fully closed.

With the engine not running, if you remove the screw covering the progression holes can you see the edge of the butterfly/throttle plate ?

The edge of the plate should be covering the first progression hole.

1 hour ago, Champ54 said:

.Some backfiring through the carbys. Re-jeting improved this but not fully sorted.

So idle mixture is too lean?

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Thanks for the reply and the suggestions. These carbs came with 5 progression holes. ( lord only knows why)I've had the butterfly plates fully closed and have been creeping them open by 1/4 turns on the adjustment screw but I'll try your suggestion and see what happens.

we have also set the mixture using a Gunson colourtune spark plug. Colourtune plugs  have a clear glass window around the ceramic so you can see the colour of the flame inside the cylinder. Excellent invention. A yellow flame indicates mixture is too rich, blue flame indicates correct mixture, and whitish blue flame mixture is too lean. According to colourtune If the flame is Whiteish blue misfiring may occur. When I adjusted all the mixture screw to get a nice blue flame it improved substantially but still kept popping some.

In my L28 the flame is a nice blue colour. Tried adjusting the mixture to both excess rich and excess lean but the best results seem to be with the blue flame but still getting the popping back in the carbs. 

Nothing seens to correct the high idle.

Thanks.

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Do you have these issues when the accelerator linkages are disconnected from the individual carbs?

Have you checked that you have a good air tight seal for the intake manifold mounts on both the carbs and the head?

Have you synced the individual carbs to ensure they all have the same airflow when idling?

If all this is fine then (if they were Webers) you should get a good idle with the mixture screws 2 turns out.

Maybe post some photos of what your spark plugs look like?

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5 hours ago, Champ54 said:

If anyone can suggest what else I can try short of chucking the JASF Weber knock offs and fitting genuine Webers help would be greatly appreciated. 

Hmmm this is why I run the Mikuni/Solex carbs.

But sounds like a vacuum leak to me.

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2 hours ago, AndBir said:

Do you have these issues when the accelerator linkages are disconnected from the individual carbs?

Have you checked that you have a good air tight seal for the intake manifold mounts on both the carbs and the head?

Have you synced the individual carbs to ensure they all have the same airflow when idling?

If all this is fine then (if they were Webers) you should get a good idle with the mixture screws 2 turns out.

Maybe post some photos of what your spark plugs look like?

 

2 hours ago, AndBir said:

Do you have these issues when the accelerator linkages are disconnected from the individual carbs?

Have you checked that you have a good air tight seal for the intake manifold mounts on both the carbs and the head?

Have you synced the individual carbs to ensure they all have the same airflow when idling?

If all this is fine then (if they were Webers) you should get a good idle with the mixture screws 2 turns out.

Maybe post some photos of what your spark plugs look like?

Hi guys, thanks for the assistance. I do have the linkages disconnected. The readings on the balance meter have all 3 carbs at around 8 which I think may be too high. I have tested thoroughly for vacuum leaks spraying all the connections and joints with carbs cleaner. No change. Also tried with the vacuum advance disconnected and connected. No change. I think the idling at around 1850 rpm causes issues with both vacuum and mechanical advance but I cannot get it any lower.

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1 hour ago, Champ54 said:

balance meter have all 3 carbs at around 8 which I think may be too high

Not sure what sync meter you are using but on my L28 the STE Sync meter gives a reading of 5 with the Weber 45s at an idle of 1000rpm. - not sure what it would show at your high rpm.

What size choke was supplied with your carbs - 34mm?

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20 hours ago, Champ54 said:

7. Engine starts dieseling when ignition switched off

What octane fuel are you using, as you will have a higher compression ratio with flat top pistons?

L28 w/N42, dished pistons and OEM gasket = 8.29:1

L28 w/N42, flat top pistons and OEM gasket = 9.82:1

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Thanks again everyone for the suggestions and I wish I could post photos but unfortunately we cant. These carbs came with 5 progression holes (lord only knows why) and with the throttle butterflies fully closed the brass disc is covering the the second and 1/2 the 3rd hole. the first and second holes are small holes and the 3rd is the larger hole and the 4th and 5th are smaller holes. I'm beginning to think that these are the problem and maybe letting too much fuel through. 

 

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23 minutes ago, AndBir said:

Hopefully you bought these via PayPal less than 6 months ago.

If so, use the buyer protection resolution process to say these are not fit for purpose and get a refund!

Unfortunately no. I bought these in 2015 and shortly after I suffered an illness that prevented me from doing anything on the car for several years. I spent a few years in and out of hospitals. I thought what I was getting was at the time was the genuine Weber carbs but it was only in 2020 that I was well enough and able to resume work on the vehicle and then realized that what I had was the cheap chinese knock offs. I tried contacting the company that sold them (and they still do) but they just ignored me. Got no reply at all. I am inclined to agree with the post from 260DET that I should just junk them and bite the bullet and buy genuine. The manifold I have should be OK as it is a Redline although the linkages do leave a bit to be desired.

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On 2/14/2021 at 5:50 PM, AndBir said:

Sorry to hear that.

Unless you are happy experimenting with them by maybe blocking off the first progression hole etc. then going genuine Weber DCOE seems the way to go.

Yes, I totally agree. Thats why I've now ordered a set of new genuine Webers. I also found that 1 of the accelerator pump jets was not working. Pulled everything apart no visible contamination. Swapped the jet to the other side but the first side still not working. Seems to be a blockage within the casting. Definately not the jet itself.

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  • 2 weeks later...

Hi everyone. Thanks for all the suggestions. I finally bit the bullet and bought 3 new 40 DCOE Genuine Webers and they work just great. Got them tuned in very easily. Also I may have discovered some of the problems with the JASF junk. 

1. the throttle stops were very poorly made and required slight modification to get the butterflies to close fully.

2. these carbs have 5 progression holes and when the butterflies are fully closed 1 progression hole is still fully exposed. I didn't try plugging it up but that possibly would have helped.With the poorly made throttle stops 1 1/2 progression holes are exposed.

3. I think the 45mm with 36mm chokes may be a bit large for my basically standard L28

4. In one carb the throttle pump jet in one side was not working. Switched it to the other side where it worked so the blockagewas not in the jet but somewhere else in the carb possibly the casting.I didn't investigate further.

Thanks again for everyones tips. The L28 is now purring like a kitten.

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