Cam Lobes
 

Now that a few have installed intake cams with good success, it seems appropriate to find and compare hard data on these lobes, as well as other lobes that could be used. Driving impressions of different cammed engines should also be included in the thread.

The problem in comparing svx-stock lobes with other lobes is that no standard was used to compare. I asked Delta Cams to find the lift that the svx 236* intake duration and 244* exhaust duration spec was based on. This was measured to be .006" lift. The lift that 'advertised' duration is measured varies from manufacturer to manufacturer. Advertised duration is generally referred to as 'seat to seat' duration.

Once this spec was determined, I asked for the duration on the Nissan lobe, measured the same way. Now, we are much closer to apples for apples comparison.

The Nissan lobe is Delta tool #F327. This is the lobe profile installed by TomsSVX and Chiketkd.

Measured cam specs:
SVX intake lift: .280" Duration: 236*@ .006" lift/ 184*@ .050"
SVX exhaust: .311" Duration: 244*@ .006" lift/ 194*@ .050"
Nissan lobe: .314" Duration: 256*@ .006" lift/ 194*@ .050"

more lobes
 

We have comparative measurements on two more Nissan KA24 dohc cams. The Cam Doctor would not provide a consistant measurement at .006".

So, let's compare the duration at .010" lift.

Measured cam specs:
SVX intake lift: .280" Duration: 219*@ .010" lift/ 184*@ .050"
SVX exh. lift: . 311" Duration: 226*@ .010" lift/ 194*@ .050"
Nissan lift: .342"/.350" Duration: 282*@ .010" lift/ 206*@ .050"

There are other lobes that look promising.

:rolleyes: :) :D ;) :cool:

Good work Ron,:cool: Bin hoping somebody would get the guts on the cam profile.

Looking at the figures, the cam we have been using is a slow opening cam. You can see that it takes an extra 10* to get the valve open. This type of cam is not the best for creating a strong sonic wave. The SVX exhaust profile would work better. Same lift faster opening.

Harvey.;)

Hi Ron,

I just got off the phone with Scott @ Delta Cam, and the second set of KA24DE cams that I sent to him have very promising profiles for the SVX intake (and exhaust). Here are the stats:

S14 KA24DE motor (late model 240SX)
intake profile: 0.350" lift, 206 deg @ 0.050" (a bit too much duration)
exhaust profile: 0.350" lift, 200 deg @ 0.050" (almost too much duration, but probably ok).

He says that he's going to do some search for other profiles that may work, but I'm leaning towards using that S14 exhaust profile. In comparison to Chike's and Tom's intake cam profile, this profile will have 4 deg more duration, and another 0.040" (1 mm) of lift.

are you suggesting using 9mm of lift:eek: :eek: I think we will go coilbound with that. Unless you are just suggesting 1mm over stock. Either way, let me know because come this weekend my set of cams will be shipped out. Whether I use a new profile or stick to the old one is still up in the air but I need to replace my front seals badly and have been waiting for this to do them. So if there is any good info by friday please post what u know

Tom

Bill (SVXRide) has a few items to check with his bench cylinder head:

1) Amount of valve lift required to cause valve collision during overlap.

2) Clearance between intake cam lobe and rim of the lifter bore

3) Amount of intake valve lift before going coil bound.

I have been in touch with Bill on this, and I will also confirm these numbers.

As for valve collision during overlap, cams with .480" lift and 266* at .050" have been used. That's huge lift and the valves are open a long time. We shouldn't have any problem in this area.

Nice. Sounds like 9 mm of lift should be no prob. I'd still like to get some confirmation from Bill just to get a 2nd confirmation. :-)

Even if the valve springs don't bind, isn't there a risk of valve float in the upper rpms with that much lift over stock?

-Chike

Yes, I posted rough specs on those new Nissan lobes above. It seems that many cam profiles were used on KA24s.

You are comparing duration of the two Nissan lobes at .050" and making a decision only on that. As Harvey pointed out, once more data was available, lobes can have virtually the same total lift and the same duration at .050", but have very different opening rates, which on non-boosted eg33s can make a big difference in our sonic wave. The Nissan lobes have very lazy opening rates, perhaps to prevent the 31mm top shim for kicking off the follower. The Nissan doesn't have our intake system, so the lazy opening is not critical to the Nissan engine. Perhaps the Nissan lobes are a better profile for our supercharged engines and very acceptable for our higher rpm 6mt cars.

What Scott didn't tell you is equally important in our cam choices. He only provided the duration @ .050" which looks to be 6* more on the .350" lift cam than on the .314" [Tom/Chike] cam. This is not enough information to make a comparison. With only this information, it looks like a good choice, but remember, we know now that Nissan lobes are slow opening. More lift further multiplies the lazy opening.

Look at my posts again, and compare these two sets of Nissan lobes.

Nissan [Chike/Tom] Lift: .314 Duration 256*@.006/ 194*@.050
Nissan [2nd set] Lift: .350 Duration 282*@.010/ 206*@.050

The second lobe is not the 200* lobe you mentioned, I don't have specs on it. But I have specs on four different KA lobes with lifts of .342"/.350"/.367".

Nissan lobe durations at .050" lift: 204*/206*/208*/216*
Nissan lobe durations at .010" lift: 272*/276*/282*/284*/292*

For comparison, the SVX intake duration @.010 is 219*/ exhaust 226*
Extrapolating, a Nissan lobe with 200*@.050 could be 262* at .010".

Nissan lobes of .350" lift are not as close to the .314" lobes as you would expect with only 4-6* difference at .050".

The Nissan lobes are slow to open because those lobes are designed for solid buckets, to take up the lash.

I did a little more searching for possible cam profiles. The Nissan VG30DE motor ('90-'95 300ZX) may have a worthwhile profile. Its a DOHC engine with direct acting cams and hydraulic lifters. Factory spec on the cams are 0.335" lift and 248 deg total duration for both the intake and exhaust. Scott @ Delta Cam says that he has a few pairs in his storage room, and he's going to get them out tonight and measure the cam profiles.

Great,

Get duration at .006"/.010/.020/.050/.100/.200/.250/.300

What is the lifter diameter of the ZX?

Scott says his profiling machine still isn't functioning properly at low lift. He's going to try to fix it before taking measurements.

The lifter diameter is 31 mm.