2V High lift cams

I'm busy trying to decide on an inlet camshaft profile . lvferraripilot and I have been comparing a number of cams . Noteably one that has 9,73mm of lift . I'm interested to know if there are any negatives with the extra lift . All the cams we are looking at are around 250@040 .
I am busy doing a dry build at the moment to check valve to piston clearance as the piston valve pocket were done for P6 cams which have around 9,3mm lift if I recall correctly ?
I know luckydyne ran cams with 10.5mm lift , but had a problem that was oil related . At what lift do the std springs coil bind ?
Somewhere I read something about to much lift hurting the flow , but I think that was related to 4V heads ?

 

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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Mark is the 009" realy going to make a difference as that cam has a little more duration ? Obviousely I will have to check valve to piston clearance .

 

Mark those cams are pretty impressive !!
I've been searching through old threads and found luckydyne saying the inner spring binds at .435 " that's just over 11mm . So 9,7mm seems safe from a coil bind point of view .

 

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.

 

Hi Jack good to hear from you , come visit anytime .
Std shim arrangement , I think it's the 4V motors that have the issue of flipping the shim . The 2V motor have quite a big diameter shims .
What do you think of the extra lift ?

 

Luckydyne was running std shims with over 10mm (040"+) lift ??

 

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!)

 

The Carubo " Daytona " which we have a dyno sheet for and makes close to 280HP has 0,360 lift and 246@050 . Then there is 1002 which has 0.374 lift and 248@050 . The extreme one is 0.383 and 253@050 .
So do we go with a known quantity or push the boundaries a tiny bit ?? What does the extra lift do ? Help the bottom end ?? If so is m ke suggestion worth considering which is 0.395 with 242@050 ?
The Norwood rebuild article suggests around 250@050 for 280 HP ??
If I can get somewhere around 280Hp I will be more than happy . So possibly the 1002 grind is the way to go ??
It would be great if luckydyne could comment

 

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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Basic motor spec : original 2V drysump motor with carbs (40mm )
New st/st valves , abronze guides , head rebuild with 3 angle seats and port matching , possible inlet manifold ceramic coating ,
10,5:1 JE pistons , 355 Ti rods , lightend flywheel as per " Chrismorses " post and pic's , Ceramic coated headers .
I'll sart with the original points ignition , but want to upgrade to possibly a Motec computer .
My idea re cams is to use the Web 1002 grind for the inlet and use my early carb inlet cams as the exhausts ( must just check valve lift and clearance )
If I can get somewhere around 270/280 HP I'll be very happy .

 

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