B20 with 92mm bore ventil/port size.

[Miksa89]

Trying to figure out B20 optimal valve size with 92mm bore.

If using 46mm inlet valve port size should be pretty big if smallest area is 0.86 x 46mm.

If using original 44mm inlet there should be more safety margin not punching holes to port walls Imho.



Is there proven differences between "old-school" 46-38 vs 44-37/38?

Is there real benefits to use morelikely "tulip-shaped" exhaust valves instead flatter plate style?

E: One head wich i have does have 37mm seat-rings buy are those too small to 37mm valves?

Or is it better idea to use head with no hard seats and just cut seats to head or install hard seats?
Is there enough material to use hard seats that are big enough to use 38mm exhaust valves?
If using 46/38 valves seatring gets pretty close to inlet seat?

What size seatrings are good for 38mm valves?

[Miksa89]

https://ibb.co/7WCjSWW

https://ibb.co/pP4NLRB


Quick test with already ruined head. Port is now 41mm to inlet side and 38mm diameter other side of the conical milling where SSR starts to bend down.

Having technical issues with mill so need to continue some day when problema fixed.

[Erland Cox]

Porting like you do in the pictures works with cams up to 312 degrees advertized duration.
These days i use a straight port from the manifold flange and do all the expansion in the intake manifold.
I have made some 44-35 valved heads and they work as well or better than 46-38 heads.
The absolute maximum diameter you can port a B20 head to is 40mm if you follow the stock port routing.
Everything above 39mm:s is dangerously close to the water jackets.
If the port entry is 39mm with a radius in the flange if the manifold is 42 mm:s try to keep that diameter to the valve guide.
Then taper the port down to the throat under the valve seat to 38mm:s.
You must taper the port down through the bend.
With a 38mm throat a 44mm valve works fine but with a 92mm bore a 46 mm valve can also be used.
I have gotten 255 hp with 46-38 valves on 230 Volvo engines so 44-35 will be more than enough to support 220 hp.
Problem is that it is hard to make the port large enough for a 46 valve and on the exhaust 35mm is all that is needed.
35mm will give more hp before maximum hp than 38mm:s in a B20 and slightly more maximum hp with a cam with the same intake and exhaust duration.
The strongest B20 I have tested was a 2260cc with a 46-38 head that I mace, 231hp and 252Nm with 50 DCO carbs.
Another 2260cc with 45:s and an H3 cam with 46-35 gave 213 hp and 257Nm:s.

Erland

[Miksa89]

Porting like you do in the pictures works with cams up to 312 degrees advertized duration.
These days i use a straight port from the manifold flange and do all the expansion in the intake manifold.
I have made some 44-35 valved heads and they work as well or better than 46-38 heads.
The absolute maximum diameter you can port a B20 head to is 40mm if you follow the stock port routing.
Everything above 39mm:s is dangerously close to the water jackets.
If the port entry is 39mm with a radius in the flange if the manifold is 42 mm:s try to keep that diameter to the valve guide.
Then taper the port down to the throat under the valve seat to 38mm:s.
You must taper the port down through the bend.
With a 38mm throat a 44mm valve works fine but with a 92mm bore a 46 mm valve can also be used.
I have gotten 255 hp with 46-38 valves on 230 Volvo engines so 44-35 will be more than enough to support 220 hp.
Problem is that it is hard to make the port large enough for a 46 valve and on the exhaust 35mm is all that is needed.
35mm will give more hp before maximum hp than 38mm:s in a B20 and slightly more maximum hp with a cam with the same intake and exhaust duration.
The strongest B20 I have tested was a 2260cc with a 46-38 head that I mace, 231hp and 252Nm with 50 DCO carbs.
Another 2260cc with 45:s and an H3 cam with 46-35 gave 213 hp and 257Nm:s.

Erland

Thanks for your reply.

I have Agap F13.3 272 cam with 105 LSA.
And 48DCOE Fajs carbs and Kg type 3 header.


Maybe i should go with 44/38 this first attemp because exhaustvalve seats are so bad that larger valves or seatrings are only way to go? Or 44/35 with hard seats?


Do you have any good idea what size exhaust throat should be under the seat with example 35mm valve?

That conical port was just first test to shitty head. If you succest that way wich you descriped earlier maybe i should go that way too? Do yoy mean "straight port" in cylindrical meaning or not angled up or down or both?

E: I have one head with 44/35 valves with hard seats but it has some core shift. Here is picture,is that core shift bad way or good way? Its good canditate to use 44/35 valves?
https://ibb.co/TBTpLRW

One good point to use 44/35 valves is that its usable with original bore too

[Erland Cox]

Use a hard seat with 39mm OD, set it 6mm deep and use 31mm for ID.
You can use MIRA 4104C for the exhaust.
Make the inlet the size of the location rings OD 39mm in. KL racing has nice intakes with that dimension.
Port the intakeport so that you can draw a 38mm valve through it, you can follow the stock port.
I usually do not lower the port floor halfway in from the flange and instead make a long radius from the flange towards the short side radius.
Let the port taper down slightly from the ssr to the throat.
I will send you some pictures from another computer a little later.

Erland

[Erland Cox]

Here are some B20 pictures: http://www.topplocksverkstan.se/referenser2.html
The difference today is smaller opening at the intake flange.

Erland

[Miksa89]

Thank you!

Do you have some succestions where to buy valves?

[Erland Cox]

It is harder getting good valves these days but I will check it out and get back.
KG trimning still have some Intervalves left but more and more it is becoming Chinesium and some of them are terrible.

Erland