1800: Valve adjustment

[powen1]

Hi,

Can anyone advise the best OHV adjustment figures for my engine.
Volvo P1800 - Its a b20E engine K cam, running twin HS6 SU's
I've looked through the hand books and have found 0.40mm stated but nothing for a mix of B20E with twin SU's mongrel !
Amazon cars quoted different values for Inlet and Exhaust although maybe for a different Cam.

What is everyone else running ?
Thanks
Paul

Car appeared in this months Classic car Monthly

[packers1712]

Hi Paul,

I run mine as per the book, which from memory are the same inlet and exhaust possibly as per the values you've quoted, however when I was at the rolling road Neil suggested that as my engine has a high lift cam (D or K spec I which haven't managed to establish which yet) that I might need to adjust the values.
He said he would try and find out for me but I haven't heard anything from him yet, its probably slipped his mind!
I did some research myself and came up with nothing, so at book values it has stayed, and appears to be ok, none of them go tight, with the engine up to running temp!
No doubt someone will have an opinion and hopefully validate it!

Doug.

[csm22]

Paul,

My Amazon's running a K grind cam in my B18D with head decked to 3.390", .08mm head gasket, SU HS6 w/ KD needles. Inlet/Exhaust settings are 0.40/0.45mm, based on what I could find for the K. Seems to work well so far.

Cheers,

Chris

[142 Guy]

The correct clearance for the B20E with the D cam is 0.40 - 0.45 mm. However, the B20A with the lower lift and duration A cam also gets the same clearance spec so I expect that the clearance recommendation is not completely related to the camshaft. The 1971 B20B engine with the C cam gets a 0.50 - 0.55mm clearance recommendation.

A characteristic of the D cam is that if you set the idle speed up normally (850 RPM) the manifold vacuum is poor. That isn't much of a problem for the D jet; but, SU carbs don't work so well with low manifold vacuum. Setting up the idling speed will fix the low vacuum problem; but, at some point high idle speed ceases to the idle . Opening up the clearance on the valves actually reduces the effective valve duration and may improve manifold vacuum which might be why the twin carb B20B got the higher clearances. Of course, all of that is speculation because Volvo never explains the 'why'.

If you are running the 0.40 - 0.45 mm clearances and are happy with the way the engine idles then I would stick with that. If the idle is less than ideal, you could try the higher clearances used on the B20B; but, I would not expect a huge change. If you have poor idle performance the K cam which has the same lift; but, a nudge less duration will run with a higher manifold vacuum which may make for happier SU carbs.

When setting up clearances, if the rocker shoes have not been reprofiled make sure to use a narrow Vee feeler gauge inserted at 90 deg to the center line of the rocker shaft. Over time, a groove wears in the rocker shoe where it contacts the valve tip and a fat feeler gauge will bridge the groove meaning that you are not getting an accurate clearance measurement between the valve tip and the contact area on the rocker shoe.

[Derek UK]

Regardless of the engine spec the valve clearances are what is specified for that cam. In this case the Volvo K cam. VP Autoparts have this on the K cam in their catalogue.
The K-cam was original for the B20E from 1974.
Made for sporty driving with good traction even at low revs.
Camspec.
Lobeseparation: 110°
Duration SAE.
Intake: 260°. Exhaust: 260°.
Valvelift.
Intake: 10,76 mm. Exhaust: 10,76 mm.
Valve lash.
Intake: 0,43 mm. Exhaust: 0,43 mm.