Custom Cams

[ky_infiniti2000]

Where would be the best place to have custom cams ground/made for out wonderful sr20's?

[P10DET]

Originally posted by ky_infiniti2000
Where would be the best place to have custom cams ground/made for out wonderful sr20's?

Why do you want custom ground cams? Do you think you know more about cam profiles than JWT or JUN?

[G-Forces]

You should probably read this first

[2002G20Racer]

Unless you out to kill your motor, I belive you should pick up a set of JWT S3 Cams. But then again if you want to distroy your motor go for it.

[ky_infiniti2000]

What are the specs on the S3 cam?

[P10DET]

Originally posted by ky_infiniti2000
What are the specs on the S3 cam?

They are proprietary of course. They may tell you the lift and duration, but that is far from the whole story.

Just know this...... +12 hp (or was that 16?).

[nis.k.a.]

A lot like head work, they only tell you a little bit or if any at all. Anyways, these are the specs given to SCC by JWT on their S3 cams. valve lift intake: .445" exhaust:.445", duration intake: 260deg. exhaust: 260deg., eff. lobe centerline intake: 111deg. ATDC, exhaust:117deg. BTDC, lobe seperation angle intake: 114deg.

[Group3J]

P10DET,

I looked into JUN cams but they are DAMN expensive....like $1200 Aust. It is but MHO, but I think that if you go to a reputable grinder with a good track record, that you shouldn't have anything to worry about.
Just my 2 cents.

2002G20RACER,

What makes you say that any cams other than the JWT S3's will kill the engine? My cams aren't JWT, my bottom end is standard, the head is still using HLA's, and the head mods are pretty much limited to porting and throttle bodies - no parts changes but for cams. My engine is fine and has spent the majority of it's life between 3600 & 7500rpm (it's in a circuit car). How come you think it's dangerous to use anthing but JWT cams? (Not trying to flame, it's a genuine question).


Unfortunately this probably won't help much as I'm in Aust, but:

I had some cams built up and reground for my SR by an organisation here in Australia called Ivan Tighe Engineering (http://www.tighecams.com.au/index.htm - although the site's playing funny buggers atm). They cost me $600 Aust.

Inlet duration: 290 degrees
Exhaust duration: 280 degrees
Lift (@ valve) Inlet and exhaust: 11mm
Effective rev range: 3500 to ~7500.
Lobe centres - can't remember.

My reason for listing the specs is to illustrate that you can get away with reasonably big cams will no ill effects on the engine, if that's what you want to do.

Hope that provides some constructive help.

Cheers

[P10DET]

Originally posted by Group3J
It is but MHO, but I think that if you go to a reputable grinder with a good track record, that you shouldn't have anything to worry about.

Well, this has been hashed out before, but.....

Reground cams alter the base circle. This puts undue stress on an already sensitive valvetrain.

You'll never find regrinds in my car if billets are available.

[Group3J]

Yep, true. But built and reground cams don't alter the base circle.

I wouldn't argue that reground cams are as good as billets in terms of longevity, but I would argue that reground cams can be a cost effective way for t.........then again, if it's already been discussed, then I won't start it again......

Incidentally, what specifically are you referring to when you say the valve train is "sensitive"? Which area of it is weak?

[P10DET]

Originally posted by Group3J
Incidentally, what specifically are you referring to when you say the valve train is "sensitive"? Which area of it is weak?

The valvetrain won't tolerate revs greater than 8k. The valves float and the rockers fly out. The GTi-R head has mechanical lash adjustment and that helps some.

Valve springs are one of the critical areas. Some folks just put in heavy springs, but that doesn't necessarily solve the problem. The problem with the SR20 valve train is the harmonics. JWT did some extensive R&D in this area. They now have some valve springs that are only slightly higher rate than OEM, but hey are significantly more effective and even more effective than heavy aftermarket springs. In fact, dyno testing have shown the valve springs along are worth 2 hp on a car with decent street cams (JWT S3 grind). There are only 2 companies in the entire world that are capable of producing these valve springs. They are made by a company that produces valve springs for F1 and CART cars (I don't know who the company is - that information is secret).

[Group3J]

Groovy, thanks for that.

I was aware of the tappet problem. I was chatting to a guy here in Aust who build touring car engines, and he's apparently got a solution for it - although it sounds a bit.......agricultural? He seems to think it's a combination of revs and big lift, which cause the problem because the geometry of the valve train get's all out of wack.

The valves "float"? Float meaning bounce?

Yeah, I was looking at using GTiR posts in place of my HLA's, but it's a money and time thing. The recesses in the DE head for the HLA's is bigger than the GTiR recesses, hence I was considering making up sleeves. Problem is that it's pretty expensive to buy all the gear and I couldn't find anyone else who had done it. I didn't want to spend big $$'s to be a guinee pig, so I had the cams ground for the HLA's. I'm planning a full house grunter for 18 months from now or so, so I'll need to sort it out.

[P10DET]

Originally posted by Group3J
Groovy, thanks for that.

My pleasure.

Originally posted by Group3J
I was aware of the tappet problem. I was chatting to a guy here in Aust who build touring car engines, and he's apparently got a solution for it - although it sounds a bit.......agricultural? He seems to think it's a combination of revs and big lift, which cause the problem because the geometry of the valve train get's all out of wack.

Lift has nothing to do with it. You can blow out the rockers with stock cams. Happens all too often.

Originally posted by Group3J
The valves "float"? Float meaning bounce?

Yes. The valve springs reach a point where they cannot keep the rockers in contact with the cam lobes. This is due to the valvetrain harmonics more than anything else.

Originally posted by Group3J
Yeah, I was looking at using GTiR posts in place of my HLA's, but it's a money and time thing. The recesses in the DE head for the HLA's is bigger than the GTiR recesses, hence I was considering making up sleeves. Problem is that it's pretty expensive to buy all the gear and I couldn't find anyone else who had done it. I didn't want to spend big $$'s to be a guinee pig, so I had the cams ground for the HLA's. I'm planning a full house grunter for 18 months from now or so, so I'll need to sort it out.

Tomei makes a kit to convert from HLAs to mechanical. You might want to look into that. They also make something called a "lash killer" kit that helps keep the rockers in place.

[Group3J]

Hmmmm....that would make sense. I must admit that I find it a constant annoyance having to decipher the rubbish from the truth, when it comes to cars and specifically engines. I won't criticise the guy who told me these things, but I will say that yet again, it would appear that someone's reputation exceeds their expertise. Just need to keep that BS filter working......

JUN also make a lash killer kit, which gets rid of the HLA's and replaces them with a solid arrangement. It was $1200 Aust, last time I looked into importing it (from JUN, who seem to have a good customer service department I might add). I was considering billet cams ($1200) and the lash killer kit (another $1200). Given this is only an interim motor, it just wasn't worth the investment......

Are you able to explain how the harmonics work to me, by any chance.....pretty please? *searching for an on the knees smiley icon *

[P10DET]

Originally posted by Group3J
Are you able to explain how the harmonics work to me, by any chance.....pretty please? *searching for an on the knees smiley icon *

Here is where my knowledge starts running out. I don't have the first hand knowledge of this, but I get the information from a friend of mine who was involved with the R&D of JWT's cams and much of the other stuff they make for the SR20.

For more information you will be better served searching the SE-R Mailing List archives here:

http://www.se-r-list.org/archives/

I certainly wish I could explain more, but I cannot. I suggest searching on: Kojima JWT cams harmonics

You could also try some combinations using: valve springs

Mike Kojima is an engineer for Nissan. He also does consulting and writes for a major magazine here. He used to build engines for Toyota's GTP program. He's a pretty no bullshit guy. He'll tell you the reasons behind things, and if he can't because it's proprietary, he'll tell you that as well. If he can't tell you the details, he will usually tell you enough to make decisions on.

More importantly, Mike has never lied to me to either deceive me or to answer something he didn't know the real answer to. If he is guessing about anything, he'll tell you that as well. On the rare times he gets something wrong, he will acknowledge it and also learn as much as he can about it.

You can trust him on this cam and valvetrain stuff. Pretty heady stuff. I know a bit of the background behind it, but I don't know what I can share and what I cannot.