2V High lift cams

There are no negatives to higher lift as long as the valves don't hit the pistons, or the valve springs bind. High lift, short duration, makes excellent low speed torque,and good high speed power, that is why I like roller tappet cams,a s you can use aggressive ramps. If you could figure out how to turn Fcar heads into roller DOHC, you could really wake these motors up

If the lift it too high/ramp too aggressive on non roller applications, you get extra stresses on the lifter shims,and a different lifter shim retaining method may be needed.


Doug

 

When I read the title I thought you were talking about high lift cams

 

hah! I guess high is a relative term Mark

Melissa at webcams gave us two really solid options.

grind 226: .383 lift and 253 dur @ .050

grind 1002: .374 lift and 248 dur @ .050


They both sound like they will work well with stock springs as it is my understanding that P6 is .374 lift which also used stock springs.

 

Take 1002 then if that is the highest known good lift with stock springs and shims and I think you'll find that less duration is better, particularly if you are running carbs.

Both these options still have pretty mild ramps it appears..... with 248 degrees the lobes I pick are making .452 lift. You can see how much steeper the ramps are compared to stock.
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Dave,

Are you going with a shim under bucket system or will you keep it stock?

At which point does a positive location of the shim become compromised?

This is nice stuff, I'll take a drive to you in the coming week.

 

I think he was shim under with that cam.

 

I don't think you really need or want the extra duration and there should be no need to go over 250 degrees at .050".

You can have .395 lift with only 242 degreees with their 483 master, it pops the valve open quickly giving lot of flow time without the reversion problem you get from long duration. With .010 lash that is .385 valve lift and that should be fine if your coil bind is .435.

I don't know...I just hate duration lately

 

After thinking this over a bit, it appears the difference between each is going to be maybe 5 flywheel bhp, but the higher duration cam is going to decrease driveability raising the power band a few hundred rpm. I am rooting for grind 1002.

 

Guys, great discussion! I’ve been going back and forth with "lvferraripilot" on a cam design for a set of 10.1:1 high compression pistons (web cam’s 1001 grind, 248 dur @ .050 with .370 lift : with intake @ 104, exhaust @ 106). I’ve been going through my workshop manual and I can’t find any kind of designator for my ’75 GT-4 cams. I’ve heard a lot of guys use the designator “P6” for a cam, but don’t know what year/engine code these belong to. Is there a thread out there that explains all the designators for 308 cams? Sorry for the novice question, my 308 addiction in a relatively new vice. ....Chris

 

P6 is an old Ferrari racing cam. Too extreme for street use without injection. A modern grind which yields driveability is a little less extreme and yields close to the same bhp.

 

Guess I should have given specs! P6 intake. 266 due @ .050 and .374 lift. Strangely the early Porsche 911s uses a nearly identical cam stock, but they are mechanically injected.

 

Dave,

I don't have much to add to what has been said already. Together with the other modifications it will be one sweet engine.

Once you have decided on a cam profile, consider the effect it'll have on the shim and base your configuration based on what you find. It would be a pity if it starts tossing shims.
Shim under is of course more work when you want to adjust your clearances, but it is the safer option (and the shims are a lot lighter!)

 

Dave,

What will it look like before we get to the valve: stock head with carbs? I'm sure that Mark has flow numbers for this, maybe he can feed some of these into his magical box?

 

Here you go

Stock v 1002
Stok v 483
1002 v 483
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here is 1002 v 226. 226 makes a LITTLE more hp on top but cost you quite a bit everywhere else. Duration is bad.
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Thanks Mark, that was quick!

Which cams are the stock cams you fed in, the early ones? And what CR's?

Puts things a little more in perspective, doesn't it? I'm not sure if the 15hp or so gain is worth the loss of low-end torque; you'd basically be driving around at 500rpm+ higher for the same grunt, and the gain only kicks in at close to 7k rpm.

There must be a better solution.

 

OK,
Stock v 1002 intake and stock exhasut
1002 intake v 1002 both
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That last sheet is very interesting to me as it shows all four being the 1002 style cams to be hindering performance when compared to using stock intakes as exhausts. These are all assuming 10.5:1 cpr Mark?? Thanks so much for plugging these in