Cam Lobes

[NeedForSpeed]

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"

[NeedForSpeed]

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.

[SilverSpear]

Originally Posted by NeedForSpeed

There are other lobes that look promising.

[mbtoloczko]

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.

[TomsSVX]

are you suggesting using 9mm of lift 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

[mbtoloczko]

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.

[NeedForSpeed]

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".

Originally Posted by mbtoloczko

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.

[NeedForSpeed]

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

[oab_au]

Originally Posted by NeedForSpeed

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"

Good work Ron, 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.

[dynomatt]

Not sure whether it's worth posting this in the other thread as well...or whether that's gotten too convoluted.

Anyhoo. Here's some random learnings.

Valve spring coil bind occurs at or about 9mm (no news there).

Using only a regrind profile (ie no welding as well), the most lift you'll get out of the cam is 9.6mm. This is a limitation of the cam journal size.

WRX valves are the same diameter (36mm/32mm) but have 104mm stems rather than our piddly 90mm.

Hydraulic buckets can have their centre bored out to make them solid. WRX buckets are solid and are also 33mm so "should fit"*

In theory* a complete WRX valve, spring, retainer and bucket should go in the same slot as the EG33...thereby rewarding us with more lift potential...for a reasonably low cost.

* - this will be tested when I get to have a play with some WRX valves in the next few days.

Matt

[SVXRide]

Originally Posted by dynomatt

Not sure whether it's worth posting this in the other thread as well...or whether that's gotten too convoluted.

Anyhoo. Here's some random learnings.

Valve spring coil bind occurs at or about 9mm (no news there).

Using only a regrind profile (ie no welding as well), the most lift you'll get out of the cam is 9.6mm. This is a limitation of the cam journal size.

WRX valves are the same diameter (36mm/32mm) but have 104mm stems rather than our piddly 90mm.

Hydraulic buckets can have their centre bored out to make them solid. WRX buckets are solid and are also 33mm so "should fit"*

In theory* a complete WRX valve, spring, retainer and bucket should go in the same slot as the EG33...thereby rewarding us with more lift potential...for a reasonably low cost.

* - this will be tested when I get to have a play with some WRX valves in the next few days.

Matt

Matt,
Good stuff! It would be nice if the springs work, as we're looking for springs that are ~10% stiffer to use with the new intakes and exhaust cams. Can you do a "stock-to-stock" spring stiffness comparison?
-Bill

[Trevor]

Matt,

You are now on my wavelength as a result of researching what is available, exists and what is practical. If you modify the lifters to solid, can you gain vital spring space ? Grinding/reducing the back of the cams will assist in this area.

Good thinking, Trevor.

[NeedForSpeed]

Matt,

Thanks for posting this info in this thread.

To add further, and please confirm if you can, I'm told that the hydraulic bucket can 'pump up' approximately .075" more [Harvey posted .75mm plus .50mm? in this thread, about .030"-.050"]. If true, the cam base can be reduced by that same amount adding .075" lift to the cams. .280"/.311" lift plus .075" gives .355"/.386" or 9mm/9.8mm lift without welding. [Matt, did you mean 9.6mm lift on the intake lobe?]

By not welding, most of the cost involved in modifying our cams is saved. If one is comfortable with a reduced cam base and one installs a valve spring with enough free travel before binding, a low-buck higher lift setup could be had. Grinding the intake lobes to exhaust specs without welding would not require a spring change, saving welding and spring costs. A true low-buck mod, perhaps $100 US per cam.

I really like the wrx parts idea and look forward to your findings. And if that set-up works as you expect, perhaps the larger diameter sti valve can be adapted? Do you know the stem length of that valve?

Originally Posted by dynomatt

Not sure whether it's worth posting this in the other thread as well...or whether that's gotten too convoluted.

Anyhoo. Here's some random learnings.

Valve spring coil bind occurs at or about 9mm (no news there).

Using only a regrind profile (ie no welding as well), the most lift you'll get out of the cam is 9.6mm. This is a limitation of the cam journal size.

WRX valves are the same diameter (36mm/32mm) but have 104mm stems rather than our piddly 90mm.

Hydraulic buckets can have their centre bored out to make them solid. WRX buckets are solid and are also 33mm so "should fit"*

In theory* a complete WRX valve, spring, retainer and bucket should go in the same slot as the EG33...thereby rewarding us with more lift potential...for a reasonably low cost.

* - this will be tested when I get to have a play with some WRX valves in the next few days.

Matt

[oab_au]

Originally Posted by NeedForSpeed

Matt,

Thanks for posting this info in this thread.

To add further, and please confirm if you can, I'm told that the hydraulic bucket can 'pump up' approximately .075" more [Harvey posted .75mm plus .50mm? in this thread, about .030"-.050"]. If true, the cam base can be reduced by that same amount adding .075" lift to the cams. .280"/.311" lift plus .075" gives .355"/.386" or 9mm/9.8mm lift without welding. [Matt, did you mean 9.6mm lift on the intake lobe?]

By not welding, most of the cost involved in modifying our cams is saved. If one is comfortable with a reduced cam base and one installs a valve spring with enough free travel before binding, a low-buck higher lift setup could be had. Grinding the intake lobes to exhaust specs without welding would not require a spring change, saving welding and spring costs. A true low-buck mod, perhaps $100 US per cam.

I really like the wrx parts idea and look forward to your findings. And if that set-up works as you expect, perhaps the larger diameter sti valve can be adapted? Do you know the stem length of that valve?

Gid'ay Mate, the extra lift that we got on the Nissan RG25, was done that way. The cam profile was reground, reducing the base circle by 0.75 mm. The Nissan lifters pumped up the extra 0.75 mm. So I would expect Eg33 would do the same.

You can only get an extra 0.75 mm lift this way, without building up the lobe. You could bring the lobe up to its maximum height, and reduce the base circle, to gain the extra 0.75 mm, to give a total of 9.75 mm, if needed.

Harvey.

[oab_au]

Originally Posted by dynomatt

Not sure whether it's worth posting this in the other thread as well...or whether that's gotten too convoluted.

Anyhoo. Here's some random learnings.

Valve spring coil bind occurs at or about 9mm (no news there).

Using only a regrind profile (ie no welding as well), the most lift you'll get out of the cam is 9.6mm. This is a limitation of the cam journal size.

WRX valves are the same diameter (36mm/32mm) but have 104mm stems rather than our piddly 90mm.

Hydraulic buckets can have their centre bored out to make them solid. WRX buckets are solid and are also 33mm so "should fit"*

In theory* a complete WRX valve, spring, retainer and bucket should go in the same slot as the EG33...thereby rewarding us with more lift potential...for a reasonably low cost.

* - this will be tested when I get to have a play with some WRX valves in the next few days.

Matt

Good info Matt, do you know if the difference in the WRX assembled valve length+ lifter, is the same as the Eg33 assembled valve length+hyd. lifter?
Could be the same? as the sodium exhaust valve would be useful.

Harvey.