How Much Of A Difference Higher Lift Makes ? + Camshaft Duration

[r33_racer]

Also if you are building a new head and wanted to use big duration cams with big overlap you can sink the exhaust valves into the head a few millimetres to help stop intake flow passing straight out the exhaust valve during overlap. If you can achieve the ideal inlet to exhaust pressure ratio then you could make benefit out of the overlap without losing too much of the fresh intake charge blowing straight out the exhaust and being wasted. Should still get good blow down to clear out residual exhaust but keep as much of the fresh charge in the chamber for more bang!

[GTSBoy]

Sounds like they are mismatching the intake lobe centres so they are phased differently to each other in each cylinder grouping. So they are basically opening one valve earlier or later then the other (depending on which way you look at it lol).

A quick and easy way to change the mixture motion going into the chamber. Trying to induce more swirl into the airflow pattern entering the chamber which will increase efficiency and torque through better air/fuel atomisation and more complete burning of the mixture.

Actually if you didn't want to use their cams you could achieve a similar effect by mismatching the valve lash on your intake valves. Set 1 valve at say 0.010" and then its mate at say 0.020". I have no idea what that difference might achieve in terms of valve opening degrees though. You would have to try it and dummy assemble and then use degree wheel & dial indicator to measure the difference in actual valve timing.

Pretty much this. ^ 4 valve heads create very little swirl. All the motion is pretty much tumble. Swirl is a better. It takes a lot of effort to create useful swirl through with split timing on the inlet lobes.

There was an outfit in the US (I think it was thought up by David Vizard) reworking heads somewhat radically - with quite different cam lobes and different porting in each pair to create a lot of swirl and apparently it worked really well. But it all went quiet over the last couple of years. Dunno why. I wouldn't think that Kelford's tech would be a massive difference. It's probably good, and measurably better, but not by big margins. I would like to see what it can offer though.

As to the idea of setting the valve clearances different to try to achieve the same goal......not gunna happen. Too little range of available clearances that will work (without breaking shit) and no real measurable change in valve timing.

[GTSBoy]

A quick google found what I was thinking of.

https://www.google.com.au/?gws_rd=ssl#q=david+vizard+polyquad

[cobrAA]

Pretty much this. ^ 4 valve heads create very little swirl. All the motion is pretty much tumble. Swirl is a better. It takes a lot of effort to create useful swirl through with split timing on the inlet lobes.

There was an outfit in the US (I think it was thought up by David Vizard) reworking heads somewhat radically - with quite different cam lobes and different porting in each pair to create a lot of swirl and apparently it worked really well. But it all went quiet over the last couple of years. Dunno why. I wouldn't think that Kelford's tech would be a massive difference. It's probably good, and measurably better, but not by big margins. I would like to see what it can offer though.

As to the idea of setting the valve clearances different to try to achieve the same goal......not gunna happen. Too little range of available clearances that will work (without breaking shit) and no real measurable change in valve timing.

Thanks guys, I will email the tech again to know what's their definition of this split technology. However, considering my budget is not unlimited, maybe that extra 500-600$ would be better spent on head porting or put toward a front lsd Vs. tomei 252 9.15mm. Just a thought

[Piggaz]

Front LSD should be a mod VERY high up on the modding tree. DO NOT put that engine back in the car without one. You're crazy if you do.

[Piggaz]

Big Mike. What cam would you suggest for the OP's engine?

[cobrAA]

Front LSD should be a mod VERY high up on the modding tree. DO NOT put that engine back in the car without one. You're crazy if you do.

I wanted to go quaiffe ( i know you have high respect with the quaife), but I can have a brand new nismo for 400$ less than the quaife and i spotted a cusco MZ ( scared it might be too harsh for daily since its rated for track) for 600$ less..

I'M already sorted with the rear, i will be using a 1.5 ats ''regular''

[GTSBoy]

Quaife at the front end or go home.

[Piggaz]

Don't be a tight ass.

As above.

[cobrAA]

Some people are hard lol!! This build wasn't expected ( engine was rebuilt 10k ago, timing belt skipped and im back to square one.. already put 6k toward the EFR combo, considering i gotta pay labour + all new valvetrain component), I'm getting close to my budget lol Sometimes I tell myself, better to have a nismo, than nothing ( in the case of the front lsd, for instance)

I still love you aussies

[Piggaz]

The way of the GTR .

Pick a budget... The double it, Atleast .

[djr81]

Ah budgets. I remember them. Now it just goes into the just fix it some more bucket.

Be interested to see how this all goes. For my 10 cents worth I reckon that cam is on the too large size.

[bigmikespec]

Also if you are building a new head and wanted to use big duration cams with big overlap you can sink the exhaust valves into the head a few millimetres to help stop intake flow passing straight out the exhaust valve during overlap. If you can achieve the ideal inlet to exhaust pressure ratio then you could make benefit out of the overlap without losing too much of the fresh intake charge blowing straight out the exhaust and being wasted. Should still get good blow down to clear out residual exhaust but keep as much of the fresh charge in the chamber for more bang!

Good words bro.

Swirl and tumble in a 4-valve sounds good too from Kelford.

[bigmikespec]

Big Mike. What cam would you suggest for the OP's engine?

I don't really know what he wants to achieve?

But if I was doing a street engine 500hp I would keep the duration close to stock and make sure there was no overlap (as there would be high back pressure relative to boost), go higher on lift without going silly and make sure the profile opened the cam fairly aggressively.

I might just choose the top spec Mines cams to be honest...

If you could get the above with Kelfords little offset trick then sounds good.

PS: Quaife front and rear or go home! If you own a GTR, you can't be a tight a$$, lol.

[cobrAA]

I don't really know what he wants to achieve?

But if I was doing a street engine 500hp I would keep the duration close to stock and make sure there was no overlap (as there would be high back pressure relative to boost), go higher on lift without going silly and make sure the profile opened the cam fairly aggressively.

I might just choose the top spec Mines cams to be honest...

If you could get the above with Kelfords little offset trick then sounds good.

PS: Quaife front and rear or go home! If you own a GTR, you can't be a tight a$$, lol.

a great all-around GTR focusing toward response OR, in other word, I want to be able to keep up with my friends 's R35 when we go for a little cruise ( I went from stock, to gt-ss, to -5s in the last 4 years). I'm not a dyno-queen. I'm sure the EFR 83/74 can get me to 600-650whp (dynapack 2wd) territories easily. which is enough for me, now I wish to make my setup as responsive as possible.

I think the 252, 9.15mm will be the choice. selling my type-B shouldn't be too hard.

Off topic : on my to-do list, I still wish to replace my ts3b for a Coppermix Comp, my sard 700cc for ID1000, spline gear for my oem n1 gear, front lsd, 3.5 inch catback for my 3 inch catback, mechman 170amp for the oem one. type R for my type-B. Surely, I'm forgetting stuff lol

Edited October 10, 2014 by cobrAA

[Piggaz]

Thought about a gearbox yet?

That will be next on the "to do" list.

[KING87]

So where do the Unigroup 260 10.8 cams that everyone has been talking about fit into this? Are they a custom grind from kelford?

[Piggaz]

They're an Alfa Romeo NA lobe which uses a 32 mm base circle (stock lifters). Camtech grind them up.

I'll get the specs one day and post them up. But what we wanted was short duration and biggish lift with an agro ramp rate. HKS step 2 springs wernt enough to keep the bucket on the lobe with anything more than 19 psi and 5700 rpm iirc.

After spinning up a JUN 264 at 10.5 and Tomei 270 at 10.25, Yavuz located this lobe and used it.

There is another set. 262 at 11.3 iirc, once again with an agro rate.

I'll get the finer details next time I'm out there (if he is ok with making the info public).

[KING87]

Yeah right. Thank you

262 11.3 sounds crazy lol

[Piggaz]

They have also put the 260 lobe on 2J sticks with very promising results.