Yet Another Cam Thread - B20 Content

Hello, I'm sure we've all seen a ton of these threads but I can't seem to piece together the info I need...

I have what is supposedly a pretty hot B20, but as I'm digging into it more I'm not sure what has been swapped and what hasn't at this point. I have two cams, both of which I have no clue what/where/who they came from.

The specs of the one in the car are as follows (I measured):
Duration @ 0.050": 226 ----- @ 0.020": 247
Centerlines: 107
Overlap @ 0.050": 12 ------- @ 0.020": 26
LSA: 107
Installed lift at the valve: 0.429"

This cam made 120whp in this car, and broke up a little over 6k rpm.

The other cam I will measure fully once I'm back from this next race, but measuring the overall lobe height * 1.5 rocker - lash should put the true installed lift at ~0.566".

I don't know a ton about what makes power and doesn't in these motors, I'm coming from dorito land myself. But that first cam seems not very aggressive at all, and from my reading the second cam is massive and would require actual clearancing of the head to even fit.

So... does anyone have any clue what this first cam might actually be? Is the second cam probably something silly that I shouldn't even look into? What would be a good route to take to get this car making some real power, I'm more than willing to buy a cam and get this thing singing.

The valvetrain has double springs, and the chromoly pushrods and chevy lifters already, so I believe that won't be an issue. It currently revs to 7k happily (other than the break up just past 6 that you can push through).

Note: This is a 100% race motor, it will only see track time (NASA ST/TT5 and GLTC) so driveability and economy are of no concern, Ideal power would be in the ~160 range but I know that may be high to expect out of it.

That's cool! And positively massive!

First set of questions... can that cam be run without removing metal from the head? I'd prefer not to go that far down the rabbit hole right now. Also... how completely hamstrung would that be with DCOE40s on it?

Judging by the cam specs you provided it looks like you have a VV71 cam. 120 whp (~140 crank hp figuring 15% drive train loss) is actually pretty good for that cam.

For comparison Volvo's stage I engine made ~145 hp with an F cam, special head casting, 45 Solexs, tubular header @ 10.5:1.

This site has a ton of info on Volvo B20 cams.

http://www.1800philes.com/ianr/_superlist_grinds.html

How much port work was done and what size are the valves? Do you have flow numbers for the head? That will ultimately determine what the best cam for your engine will be. There's no point in opening the valve further if it doesn't flow any more.

The dynamic compression ratio calculator shows 7.7:1 with the U cam @ 11:1 static. I still think you'll need to mill the head.

To run the U cam you may need to machine the springs seats down like the stage II head or you might experience coil bind.

hiperfauto said:

Judging by the cam specs you provided it looks like you have a VV71 cam. 120 whp (~140 crank hp figuring 15% drive train loss) is actually pretty good for that cam.

For comparison Volvo's stage I engine made ~145 hp with an F cam, special head casting, 45 Solexs, tubular header @ 10.5:1.

Click to expand...

I think you may be correct, and I think the power level is appropriate for it (still researching all this stuff, my spinny engines don't have cams...)

hiperfauto said:

How much port work was done and what size are the valves? Do you have flow numbers for the head? That will ultimately determine what the best cam for your engine will be. There's no point in opening the valve further if it doesn't flow any more.

The dynamic compression ratio calculator shows 7.7:1 with the U cam @ 11:1 static. I still think you'll need to mill the head.

To run the U cam you may need to machine the springs seats down like the stage II head or you might experience coil bind.

Click to expand...

From the looks of it, I would say some cleaning up, maybe a little deshrouding of the valves, and port matching to the manifolds. But I don't have a stock one to compare to. Since the P.O. died, some of the info I have is shaky, but from emails his wife found the only reference to the head is "big valve canadian head" so I'd assume it's an FI head that's been adapted with the 44mm intakes? The same email also states that it has been milled 0.100" to bump to the 11.0:1 static. I do not have any flow numbers.

IF this car ever had the vv101 in it, it would have required the spring/guide modifications as well right?

Can you take a pic of it? Maybe with an exhaust valve taken out, showing the bowl/port?

I think I have a Stage 3 head (iirc) and the area just past the valve seat in the exhausts looks a lot different than my stock F head.

JohnMc said:

Can you take a pic of it? Maybe with an exhaust valve taken out, showing the bowl/port?

I think I have a Stage 3 head (iirc) and the area just past the valve seat in the exhausts looks a lot different than my stock F head.

Click to expand...

I can't do that for a few weeks. Racing next weekend and don't want to pull manifolds or anything, I wasn't planning on pulling the head anytime soon if it could be avoided. I can get photos of the bowls eventually though.