850 10V 2.5l Wagon, late '96, 65k km, CH.
*****************************************

Very often I wish I had more torque at low rpm.
Therefore I played several times with the idea
of changing the actual 10-Valve-Head with a used 20er
from the scrapyard. Sounds easy, might be not.

Is it basically possible
(engines have same body, mountings, strength)?

What other changes does it imply (engine ECU)?

Can such a modification be recommended as to power/torque increase and is lifetime affected?

I hope the topic is not too difficult, to be treated here.
As to answers: I'm eager to get them, but due to the nature of the matter I'm not in a hurry...

Sincerely,
Marco

PS: Some people allready warned me this might be a rather difficult task.

marco,
Increasing the valves certainly yields more HP (moving more air/fuel)...and I'm guessing it's easily done as the engine block and accesories don't change. The ECU I would think would be different however, maybe someone else could varify...
--
Tony G. '94 850GLT, '82 240DL (mint) July '99 "Rolling" cover

If you are looking for low-rpm torque then you probably will be disappointed by the 20V. This cylinder head will give a difference in higher rpm's (4000+) where the 10V won't flow as good as the 20V and you get better volumetric efficiency with the 20V head and thus more power.

I actually find that many 2-valve-per-cylinder engines are more tractable and have better low down grunt than identical 4-valve-per-cylinder engines. Higher up in the rpm range this changes over.

At low rpm's there are not many 'tricks' you can use on a normally-aspirated engine to get more power, except trying to get more cubic inches (but I haven't heard of a stroker kit for the 'white' engines) or bumping up the compression. The last will require you to run 92 octane or better all the time though.

Higher in the rpm range you can get better volumetric efficiency and thus torque/HP by porting the head, maximizing exhaust scavenging by careful header tuning and playing with the cam types and timings. These don't 'do' much at low rpm's or may even lose some power there.

Bye, Arno.

Hy Arno

Thank you very much for your comprehensive and extensive reply.
So there's no necessity to go in any technical detail:
Not the overwhelming volume is the problem at low rpm
but the lack of it!
Convincing.

What I would like to know at this point - and I'm aware
that this question has many answers - how do smaller aspirated
engines manage to provide more torque (at given rpms) than my actual one?
Compression only?

By the way, what's a stroker kit?

Sincerely

marco
 

> that this question has many answers - how do smaller aspirated
> engines manage to provide more torque (at given rpms) than my actual
> one?
> Compression only?

Usually yes. And you can create a camshaft which will give good low-down power, but this often has the tradeoff that above 4500rpm there is 'nothing' anymore, which can be a bit bothersome on the highway.

Volvo did this with the 6-cylinder engine in the 960/S/V90 in the USA which got different cams to give them less peak HP (I think it dropped from 204hp to 180 or 190), but more low-rpm torque.

Sorry.. Didn't read your original message properly.. You're in switserland, right? If you increase the compression of the engine (eg. shave a little off the head) then you would need to use 98RON octane all the time to stop pinging/knocking.

Older engines which used to run on leaded fuel often have 11:1 compression or higher, but the current engines often only run at around 10:1 or 9.5:1.

To address your problem Volvo pretty much came out with the low-pressure turbo. It doesn't add that much HP at high rpm, but the torque at low rpm is much, much better.

> By the way, what's a stroker kit?

A different crankshaft, connecting rods and pistons which increase the stroke of the engine and thus the capacity. It's not really possible to increase the bore of these Volvo engines at a later time because of the way they are constructed.

Bye, Arno.

Hi Tony

Thank you too, for your opinion.

It does indedde look very simple but besides the electronic Engine Management there might be differences in manifolds, transmission and
who knows what else...

Sincerely,
Marco

Arno, as I can see you're really proficient.
And I also see, that I rather let the idea go.

To change head is easy, everything else
involves a lot more work.

Maybe I'll start getting interested in turbos,
whose fiability I've always mistrusted.

Greetings,
Marco