Valve seating force

Do you mean the spring poundage or something more subtle?

But the V8 forum is probably the best place for this sort of info.

Fitted load approx 75 lbs. Full lift load over the cam nose approx 170 lbs.

Now where else on the planet could you get a _knowledgeable_ answer to a question like that in so quick a time? Usenet rocks!

JB

a quick google would tell you, such as:

In this day of the internet age I can't help but wonder at people that work on engines/cars/bikes without the factory workshop manual.

By learning to use google? "rover v8 workshop manual"

engine manuals

3.5L, 3.9L and 4.2L http:/ and 4.6L 3.5L, 3.9L and 4.2L data Valve springs Free length 48.30 mm Fitted length 40.40 mm Load at fitted length 339 ± 10 N

4.0L and 4.6L data Valve springs Free length 48.30 mm 1.90 in Fitted length 40.40 mm 1.60 in Load - valve open 736 ± 10 N 165 ± 2 lbf Load - valve closed 339 ± 10 N 76 ± 2 lbf

Thanks Dave that's about the same as "the better googler than I" found at 339 N. From the top of your head?

Not enough to resist a high boost pressure though ;-)

AJH

How do you work that out? I suspect the inlet valve staying seated during exhaust stroke is the least of your issues for a "high" boost Rover V8.

Nah. From actual poundage measurements in my database of valve springs I've measured on my spring tester when doing development work on different engines.

In message , Dave Baker writes

You need to get out more ;)

It's his day job, not his hobby.

Only trouble doing this is if you strip a head and it's got springs that have a set or are weak or someones been in there already and fitted uprated ones. It's not until you do the next one that you find a discrepancy.

Yes I know that..... hence the smiley.

For a 40mm inlet valve with an 8mm stem I reckon it would lift off during the exhaust stroke at 3 bar.

Whilst doing these calculations it seems that at 5000 rpm, and assuming similar, 11mm, lift and force for the exhaust, the springs consume 8kW, which is only 4% of likely full power but more significant at cruising power so with wear being significantly lower than 40 years ago why no engines with desmodromic or slide valves?

AJH

On Saturday, January 5, 2013 7:47:21 AM UTC-5, snipped-for-privacy@sylva.icuklive.co.uk w rote:

The entire valvetrain of a V8 push rod engine takes no where near 8 Kw to s pin at 5000 rpm, and that is including the camshaft bearings, rocker arms, push rods, and lifters. The vast majority of the work required to open the valve against the spring is returned when the valve closes (the spring pus hes back as the valve closes). Total valvetrain friction will be on the or der of 1% of engine output at rated power, of which the contribution of the valve spring is relatively small.

On 11/11/2013 03:33, Oldcastiron wrote: > On Saturday, January 5, 2013 7:47:21 AM UTC-5, snipped-for-privacy@sylva.icuklive.co.uk wrote: >> On Fri, 04 Jan 2013 01:03:10 +0000, Peter Hill >> >> wrote: >> >> >> >>> On 03/01/2013 22:18, snipped-for-privacy@sylva.icuklive.co.uk wrote: >> >> >> >>>> Not enough to resist a high boost pressure though >> >>> >> >>> How do you work that out? I suspect the inlet valve staying seated >> >>> during exhaust stroke is the least of your issues for a "high" boost >> >>> Rover V8. >> >> >> >> For a 40mm inlet valve with an 8mm stem I reckon it would lift off >> >> during the exhaust stroke at 3 bar. >> >> >> >> Whilst doing these calculations it seems that at 5000 rpm, and >> >> assuming similar, 11mm, lift and force for the exhaust, the springs >> >> consume 8kW, which is only 4% of likely full power but more >> >> significant at cruising power so with wear being significantly lower >> >> than 40 years ago why no engines with desmodromic or slide valves? >> >> >> >> AJH > > The entire valvetrain of a V8 push rod engine takes no where near 8 Kw to spin at 5000 rpm, and that is including the camshaft bearings, rocker arms, push rods, and lifters. The vast majority of the work required to open the valve against the spring is returned when the valve closes (the spring pushes back as the valve closes). Total valvetrain friction will be on the order of 1% of engine output at rated power, of which the contribution of the valve spring is relatively small. >

Your right.

That is the instantaneous peak power demand. The spring stores much of the energy and gives it back. The power used to accelerate the valve becomes kinetic energy at 1/2 lift, that can be recovered during deceleration to stationary at full lift and seated.

Th actual drive losses are friction and oil film shear.

They quote losses as BAR. Power = Pressure x Volume x Events / sec. For a 4L V12 0.37 bar at 1000 rpm is about 1.2Kw (370000 x (4 / 1000) x 1000 / (2x60).

1000rpm 0.36bar 1.2Kw 2000rpm 0.32bar 2.2Kw 3000rpm 0.29bar 2.9Kw 4000rpm 0.26bar 3.5Kw 5000rpm 0.24bar 3.9Kw 6000rpm 0.22bar 4.3Kw 7000rpm 0.205bar 4.8Kw 8000rpm 0.2bar 5.3Kw The valve train becomes nearly twice as efficient at redline but as there are 8x more valve events it demands about 4x power than at 1000rpm.

That is for 4 valve DOHC flat tappet followers which suffer quite high friction, has lots of bearings with oil film drag.

5 valve quad cam V8 Ferrari Fig 7 shows inlet cam torque at 1800rpm. The average is 5.4Nm, that requires 4Kw at 1800rpm to drive 4 cams. For a OHV V8 there will be a large reduction as it has far fewer cam journals (5/6) and 1/2 the number of tappets for each cylinder. There is an additional loss from rocker arm pivot and the sliding motion at rocker / valve. With roller followers in a single cam OHV V8 there will be reduction in drag offset by the tappet drag. As the cam approaches and leaves the roller tappet there is a large axial offset in the contact point on the roller. That drives the tappet onto the tappet bore wall. A roller rocker on OHC either pushes or pulls the rocker harder on to it's spindle.

Only way to find out for sure is to get a heated oil supply and drive the cam with an electric motor to measure your valve train power demand.