1800: P1800e 1971 Running Twin HS6 SU's

[powen1]

Hi all, Advice please

I have a p1800e 1971 running twin SU HS6 Carbs. The PCV set up Is correct but happy to be corrected see Pic :-) Reducer at inlet manifold to about 2mm
I have tuned the carbs but car running rough, hunting also pinking on high revs, under load, The PCV pipes are all connected at one end of the Inlet manifold (wondered if this is an issue as false Air all one ended, but after reading Ron kwas feed maybe not an issue, reviewed Doc by Ron also re set up of PCV good info.
In addition I have a Bosch Distr 0231 163 021 with a vacuum advance but no pipe running to either Carb or manifold - does this matter ?
Timing set at 8' Btdc

Much appreciated to get the car running smooth
Thanks
Paul

[142 Guy]

The PCV set up looks correct. The only issue I see is that it looks like the hose connected to the oil filler cap is kinked which could reduce the effectiveness of the PCV system. That would not cause your rough running problem. Having the restricting orifice on one end of the manifold should not be causing operational problems.

The Bosch part number is the distributor that was originally installed on the B20E; but, I think there may have been variants. It looks like an original D jet distributor because I think I see the plug for the contacts in the base of the distributor. The engine should run fine with the vacuum servo disconnected. The distributor should have a mechanical advance system which provides a total of 25 deg of advance (measured at the crankshaft) that tops out at around 3000 RPM . I am assuming that your 8 deg of advance is static advance? If you have access to a timing light check the operation of the advance mechanism on the operating engine. You probably want to set the ignition timing so that it tops out around 32 deg total advance at 3000 RPM. Your static advance of 8 deg plus the mechanical advance of 25 deg should provide 8 + 25 = 33 deg which is in the ball park.

This presumes that you are using fuel with R+M = 92-92 which I think is about RON 98. If you are running a lower octane rating you will have to retard the ignition slightly to avoid pinking. If the engine is older and has some carbon build up in the combustion chambers this can also contribute to pinking which may require that you retard the ignition. Finally, has the engine had the head off for maintenance in the last 10 years? If it has and the head gasket was replaced using a fuel injected head top end gasket kit you most likely installed a head gasket meant for the B20F which is slightly thicker than the correct B20E head gasket. The thicker head gasket increases the clearance area in the quench zone of the combustion chamber reducing the effectiveness of the quench zone making the engine more prone to pinking. Again, you may need to retard the timing slightly to eliminate the problem.

What brand sparkplugs and heat range are you running in the engine?

Before you can accurately set fuel mixture, the ignition timing has to be good and the valve clearances must be accurately set (very important). Have you done a cranking compression test on the engine? If the compression is poor this will make it difficult to get a good carb tune completed.

I am not knowledgeable about SU carbs. That said, have you removed the sparkplugs to check the color of the insulator around the center electrode. This may give you some clue as to whether your fuel mixture is rich (very dark brown to black insulators) or lean (white insulators to almost looking like glazed sugar - very bad). Does the engine suffer from misfires? That can be a sign of a lean fuel mixture.

Finally, does the engine still have a Volvo D camshaft which would have been the original B20E camshaft? The D camshaft has a fair amount of overlap which makes for a variable idle speed even on my Megasquirt equipped B20E. I recall watching an Amazon Cars YouTube post and they made a comment about the problems with SU carbs and high overlap camshafts. I can't remember whether they said the D cam represented the upper limit for overlap on an SU equipped car or whether the D cam had too much overlap for an SU equipped car. If you have a D camshaft or a camshaft with even more overlap you may never have a smooth idle. SU carbs require a good manifold vacuum to idle smoothly and a D cam does not provide a good vacuum. At an idle speed of around 850 RPM my manifold pressure is running about 55 kpA (absolute) which is around 6.6 psi or 14 inches mercury (gauge). You can improve the vacuum by upping the idle speed; but, at some point that stops being an idle .

[Ron Kwas]

Paul;

Not much info to symptoms, but good general info from 142G...I agree...first check and assure Ign at idle and advance...not having vac advance connected wont hurt anything, but means that input to timing curve is obviously out of the picture.

For troubleshooting, disconnect PCV and plug manifold connection to take it out of the picture also.

Good Hunting!

[c1800]

If thats an original B20E distributor it has a vacuum retard, not advance. Some run with it disconnected from the manifold (and plugged at the manifold) and not plugged at the distributor.

Purportedly was designed to reduce emissions and improves performance when disconnected.

[powen1]

Thanks 142G Guy, Some answers to your questions that may help ?
The Bosch part number is the distributor that was originally installed on the B20E; Correct but, I think there may have been variants. It looks like an original D jet distributor because I think I see the plug for the contacts in the base of the distributor. Your Correct The engine should run fine with the vacuum servo disconnected. Great Thanks The distributor should have a mechanical advance system which provides a total of 25 deg of advance (measured at the crankshaft) that tops out at around 3000 RPM . I am assuming that your 8 deg of advance is static advance? I set this using a timing light at about 850-1000RPM Idle If you have access to a timing light check the operation of the advance mechanism on the operating engine. You probably want to set the ignition timing so that it tops out around 32 deg total advance at 3000 RPM. Ok can check that Your static advance of 8 deg plus the mechanical advance of 25 deg should provide 8 + 25 = 33 deg which is in the ball park. So this looks ok

This presumes that you are using fuel with R+M = 92-92 which I think is about RON 98. Im Using Super Unleaded (97 / 98 RON)
If you are running a lower octane rating you will have to retard the ignition slightly to avoid pinking. I use Premium If the engine is older and has some carbon build up in the combustion chambers this can also contribute to pinking which may require that you retard the ignition. Finally, has the engine had the head off for maintenance in the last 10 years? Yes Last year new Head gasket replaced with B20E gasket set If it has and the head gasket was replaced using a fuel injected head top end gasket kit you most likely installed a head gasket meant for the B20F which is slightly thicker than the correct B20E head gasket. The thicker head gasket increases the clearance area in the quench zone of the combustion chamber reducing the effectiveness
What brand sparkplugs and heat range are you running in the engine?
Using NGK BP6HS

Before you can accurately set fuel mixture, the ignition timing has to be good and the valve clearances must be accurately set (very important).yep 0.40-45

Finally, does the engine still have a Volvo D camshaft which would have been the original B20E camshaft? Yes original D Cam fitted

[c1800]

“ the valve clearances must be accurately set (very important).yep 0.40-45 ”

Valve clearance specs for B20E are .016 - .018 , for the B20B they are .020 - .022

That could be your problem.

[142 Guy]

The B20E gasket 'set' will almost assuredly give you a B20F head gasket. If you want a head gasket of the correct compressed thickness for a B20E (0.028") you need to order a 0.028" Cometic gasket or purchase a separate B20B head gasket from Elring which is the correct thickness for the B20E. The B20F head gasket works, you just need to run slightly less ignition advance to avoid pinking because of the reduced quench effectiveness.

The plugs should be OK.

I am assuming 0.4 is mm which would be about 0.016" - I thought Britain was still using Imperial measurements!

If you have the D cam, getting a good idle with SU carbs is probably not in the cards. You may just have to accept some hunting.

When you say original D cam fitted, do you mean the actual cam that the engine left the factory with or a new D cam just like the original? The reason I ask is that Volvo camshafts and lifters of that vintage are notorious for material failure / severe wear on the cam to lifter interface. I rebuilt my 1971 B20E about 8 - 9 years ago and the cam and lifters were severely worn. The lifters had severe spalling on the wear surface that contacted the cam lobe and the lobes were worn down. A perverse outcome of this is that the cam duration would be reduced which might help with idle; but, your dynamic compression ratio would increase because of the shorter duration which would aggravate the pinking problem. The engine would definitely be down in power. If you have a new D camshaft and lifters, then this clearly is not an issue.

[Burdekin]

Originally Posted by c1800

“ the valve clearances must be accurately set (very important).yep 0.40-45 ”

Valve clearance specs for B20E are .016 - .018 , for the B20B they are .020 - .022

That could be your problem.

That’s mm.

[Derek UK]

Swap the pipes. Oil cap to carb to allow clean air into the engine. Flame trap to manifold. You should have a PCV valve vertically just above the flame trap.
8º static. It will be higher at 1000 rpm, maybe 15º. At about 3000rpm it should be about 33º. Carbs might be set a bit weak.

Interesting to see the fuel supply hose at the bulkhead end. What sort of pump are you using?

[Burdekin]

Originally Posted by Derek UK

Swap the pipes. Oil cap to carb to allow clean air into the engine. Flame trap to manifold. You should have a PCV valve vertically just above the flame trap.
8º static. It will be higher at 1000 rpm, maybe 15º. At about 3000rpm it should be about 33º. Carbs might be set a bit weak.

Interesting to see the fuel supply hose at the bulkhead end. What sort of pump are you using?

It’s a B20E I assume Derek.