Solex P40 ii idle problem

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Steve Hatfield
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Re: Solex P40 ii idle problem

#16 Post by Steve Hatfield » Mon Sep 09, 2019 9:43 pm

Joseph,
FWIW, I had this issue a few years ago on a similar 912/Solex set up. What I discovered was old paper gaskets were fused onto both sides of the used phenolic insulators on all four pieces. They gave no hint of leakage but failing all other corrections, I replaced all four insulators and all eight gaskets with new and the problem disappeared! Insidious.
Steve Hatfield
Fort Walton Beach, FL
'63 S90 Sunroof Coupe
'06 997S Coupe

joseph rossi
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Re: Solex P40 ii idle problem

#17 Post by joseph rossi » Tue Sep 10, 2019 12:29 am

Steve, I used new blocks. The original set up for a 69 912 used steel spacers with vacuum lines.

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Phil Planck
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Re: Solex P40 ii idle problem

#18 Post by Phil Planck » Tue Sep 10, 2019 3:38 pm

"Tried disconnecting the throttle linkage and creeping up on a higher RPM. The minute I reved the engine up after the adjustment, it still stuck at a high RPM, only higher than before."
Did you get to 850rpm idle with links off, without the problem? Did you rev afterward with links on or off?
Phil Planck

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Richard Shilling
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Re: Solex P40 ii idle problem

#19 Post by Richard Shilling » Tue Sep 10, 2019 4:26 pm

Phil beat me to it. Disconnect the down links and start from there. Have you measured the air intake on all 4 carb throats? Split shafts were a blessing when they were new as it was easy to get airflow in all four carbs by adjusting the screw. But that was 50 years ago. The phonetic piece can fall out, the screw can rust in place, the spring can break, etc. All 4 carb throats have to suck the same
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1965 356C dolphingrey 

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Re: Solex P40 ii idle problem

#20 Post by Robert Vaughan » Tue Sep 10, 2019 6:17 pm

And then after you do that, set your 4 individual idle mixture screws on the rich side of the rpm peak.

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Re: Solex P40 ii idle problem

#21 Post by joseph rossi » Tue Sep 10, 2019 9:02 pm

Phil, I could not get to 850 RPM. It gets to about 800 and anything higher will put it into an over idle mode of 1500 Rpm. I made all the adjustments with the carb linkage disconnected.
Richard, the split shaft blocks are in excellent condition. There is absolutely no play between throats. During all of my adjustments, lm constantly checking the balance between all the throats. I check them at idle, what little there is, and at higher rpms (1500 to 2000).

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Re: Solex P40 ii idle problem

#22 Post by Phil Planck » Tue Sep 10, 2019 10:04 pm

Seems like mechanical advance is kicking in too soon. Have you checked maximum advance? Usually 33-35 at crank pulley. Need some more expert input here. Im not an expert, just tying to help based on my limited experience.
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Re: Solex P40 ii idle problem

#23 Post by joseph rossi » Tue Sep 10, 2019 10:18 pm

Phil, static timing is 3 degrees btdc.. All in advance is 32 degrees at the pulley. I just had work performed on the distributor by John Jenkins. Advance begins at 1100 rpm to make sure it won’t advance in the typical idle range. I’ve tried two distributors so far. I might try another tomorrow in a final attempt to at least rule out the distributor.

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Re: Solex P40 ii idle problem

#24 Post by Martin Benade » Tue Sep 10, 2019 10:42 pm

If both distributors acted the same they are probably not the cause.

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Steve Hatfield
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Re: Solex P40 ii idle problem

#25 Post by Steve Hatfield » Tue Sep 10, 2019 10:58 pm

Time to send the carbs back to the rebuilder for testing on a known functioning engine.
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Re: Solex P40 ii idle problem

#26 Post by Robert Vaughan » Wed Sep 11, 2019 8:03 am

Can you swear that the distributors advance curves are proper? Did anybody change the distributor fly-weight return springs and un-knowingly put in weaker springs?

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Ronald I. Maciejewski
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Re: Solex P40 ii idle problem

#27 Post by Ronald I. Maciejewski » Wed Sep 11, 2019 1:20 pm

Joseph et al,

My problem is very similar and I have tried 99% of the diagnostic suggestions graciously recommended by Members above plus more. I will try to summarize as my log on this problem is approaching 14 pages.

In my ’58 356A, I’m running C spec Zeniths, Arias 9.0 CR P&C set, mild cam, Bosch 022. Total engine rebuild years ago but only 4K miles since then.

RTNI (Return to Normal Idle): After running near perfectly for 8 years, I experienced a sudden slow RTNI with frequent sticking between 2,500 to 1,500 rpm.The frequent sticking went away mysteriously with 022 #2.

It will idle all day without fluctuation. Rev to 4K rpm and it takes up to 12 seconds to RTNI.

Vacuum leaks, carb linkages, dirty carbs, etc. checked ad infinitum - have shown no problems.

Different distributors:
022 #1 when problem started.
009 swapped in: RTNI improved but still 7-8 seconds with obvious performance degradation.
022 #2 purchased from Registry Vendor – Same problem
022 #2 adjusted twice by same Registry Vendor (tightened the spring tensioning plate to retard the onset of advance) – Same
problem
123 Ignition installed – Same problem

Since the same problem exists with the 123 that would seem to eliminate the distributor as the culprit.

Fuel pump refurbished by Registry Vendor and eventually replaced by a second refurbished fuel pump. Problem persists.

Fuels: Usually use Sunoco 93 octane but tried different brands including non-ethanol. Problem persists.

Due to a sticking valve problem in the middle of this, heads were refurbished professionally and carbs were cleaned, kitted, and adjusted. Therefore valves were adjusted and necessary gaskets were replaced so vacuum leaks should not exist?? Problem persists.

Need to try 022 in another 356 and see if the problem follows.

Interesting conundrum, is it not? Any and all help is sincerely appreciated.
Ron

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Juha Vane
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Re: Solex P40 ii idle problem

#28 Post by Juha Vane » Thu Sep 12, 2019 2:28 am

Interesting that such simple? mechanical device can produce such complex problems.
My car has Webers and had misfiring problems. Checked everything, changed parts and so on.
As last resort changed the brand new, according to manufacturer, premium quality ignition cables to standard and problem disappeared.
More about these cables later in separate topic.

Tedious but one way is to change one thing and see if it help, if not return back and change next thing until problem disappear.
But if your Solex idle goes way up if you just crack the idle screw open, have you verified that the idle screws are correct?
Have a pair of unused split shaft Soles P40 II and took enclosed photo of the idle screw. Does your look similar?
If so, perhaps the screw seat is "screwed" up?
solex-idle.jpg
solex-idle.jpg (83.81 KiB) Viewed 70 times
KTF,

Juha Vane
Finland

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Re: Solex P40 ii idle problem

#29 Post by joseph rossi » Thu Sep 12, 2019 3:44 pm

The idle screws are correct and they respond to adjustment.

To definitively rule out the distributor, I swapped a known good 022 unit from my C. The idle problem persisted. It's definitely associated with the carbs. I just sent another set of carbs to be refurbished. I'll try those on the car. Can't think of anything else to try!

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Steve Hatfield
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Re: Solex P40 ii idle problem

#30 Post by Steve Hatfield » Thu Sep 12, 2019 3:47 pm

There’ya go!
Good luck.
Steve Hatfield
Fort Walton Beach, FL
'63 S90 Sunroof Coupe
'06 997S Coupe

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