Working out cam lift - GT-R Register - Official Nissan Skyline and GTR Owners Club forum

Madden · 17th June 2008, 06:07 PM

Hello

I have been donated a brand new Tomei cam. The markings re A2691N. So i guess its a 270d cam?

I have been working out the lift.

42.02mm fully open and 33.20mm fully closed. The stock cams have a fully shut of 32.15.

So would this make the cam a 9.87mm lift compared to the stock cam?

Any help ?

Listerofsmeg · 17th June 2008, 06:09 PM

it may be the lobe that you have problems with mate, the combination of the bucket and lobe will increase the lift.

Jonne · 17th June 2008, 06:28 PM

The easiest way to work out the lift is to measure the lobe height. You can do this by measuring the lobe and the base circel. Then you take the base circel AND the valve clearance from the total lobe height and you have the lift.

NISFAN · 17th June 2008, 06:36 PM

I presume the 33.2mm is when you measure the base of the cam? Almost impossible to do it this way on higher duration cams, as there isn't 2 opposite points you can pick up with a vernier that aren't already ramping into the lobe. Most accurate way is to install cam into a head (or v blocks), and clock the base circle lobe difference.

Tomei type B cams usually have 1mm smaller base circle than stock, so IIRC that would be 31mm. Stock 32????.
Which makes that 11mm lift. Deffo need new springs and head work for it to work.

SamuraiSam · 18th June 2008, 02:41 AM

You guys are making this way harder than necessary.

Get a magnetic base dial indicator, put it on the lobe, zero it out, and spin the cam. The highest point the gauge registers is the lift of the cam.

Madden · 18th June 2008, 10:46 AM

The base circle is visibly bigger on the tomei cam. I have spoken a RB and they say the same thing that they are meant to be 1mm smaller but only on the large lift cams. So this cam could be an 9.7mm lift?

NISFAN · 18th June 2008, 11:39 AM

Correction to above statement, getting manufacturers nomenclature confused. Tomei reduced base circle cams are PROCAM. 30mm

Stock and PONCAM is 32mm

From Tomei web site they don't list a 269 degree. You sure it is Tomei?

Listerofsmeg · 18th June 2008, 01:15 PM

yep im sure its a Tomei

unless Tomei have started shipping out other peoples cams!!

Madden · 18th June 2008, 04:30 PM

Yea its a tomei but it really weird. Do they do custom made cams?

Also when i was on they phone to RB they checked the part number with another tomei cam. Theres was a A2692N. That was a 270 with big lift.

It must be a poncam then?

tweenierob · 20th June 2008, 08:52 PM

It is a type b poncam, part number matches perfectly.
The cam has been cut wrong by tomei, the only explanation i could come up for this when i had the cam in my hand is that maybe it would work with some naprec valves or something to that effect that are 1mm shorter.
When you compare it to another Poncam or stock you can see the base circle is much bigger.
Get the grinder out

Rob

Madden · 21st June 2008, 12:58 AM

Nice one Rob. Cheers for that i knew something was odd.. Do you reckon is was a mistake?

What should i take the grinder to? The valves or base circle? or the whole car

SamuraiSam · 21st June 2008, 08:44 AM

Take the cam back to Tomei or a distributor and have it replaced if it is actually somehow at fault.

17th June 2008, 06:07 PM	#1 (permalink)
Madden New Users Join Date: Nov 2004 Location: Berkshire Posts: 2,078	Working out cam lift Hello I have been donated a brand new Tomei cam. The markings re A2691N. So i guess its a 270d cam? I have been working out the lift. 42.02mm fully open and 33.20mm fully closed. The stock cams have a fully shut of 32.15. So would this make the cam a 9.87mm lift compared to the stock cam? Any help ?

17th June 2008, 06:09 PM	#2 (permalink)
Listerofsmeg GTROC Member Join Date: Jul 2006 Location: Shefford, Beds Posts: 1,719	it may be the lobe that you have problems with mate, the combination of the bucket and lobe will increase the lift. __________________ White R33 GTR Its working!! 10.908 @ 128mph on pump fuel and full trim!

18th June 2008, 01:15 PM	#8 (permalink)
Listerofsmeg GTROC Member Join Date: Jul 2006 Location: Shefford, Beds Posts: 1,719	yep im sure its a Tomei unless Tomei have started shipping out other peoples cams!! __________________ White R33 GTR Its working!! 10.908 @ 128mph on pump fuel and full trim!

20th June 2008, 08:52 PM	#10 (permalink)
tweenierob GTROC Member Join Date: Aug 2003 Location: herts Posts: 1,738	It is a type b poncam, part number matches perfectly. The cam has been cut wrong by tomei, the only explanation i could come up for this when i had the cam in my hand is that maybe it would work with some naprec valves or something to that effect that are 1mm shorter. When you compare it to another Poncam or stock you can see the base circle is much bigger. Get the grinder out Rob __________________ Off to Dubai to map some R35's, 599.3hp and counting www.trracing.co.uk OSGiken 3.0l T51 back on... 3 track days before christmas

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17th June 2008, 06:28 PM	#3 (permalink)
Jonne GTR Register Member Join Date: Nov 2006 Location: Holland Posts: 140	The easiest way to work out the lift is to measure the lobe height. You can do this by measuring the lobe and the base circel. Then you take the base circel AND the valve clearance from the total lobe height and you have the lift.

17th June 2008, 06:36 PM	#4 (permalink)
NISFAN GTR Register Member Join Date: Oct 2003 Location: Herts Posts: 1,696	I presume the 33.2mm is when you measure the base of the cam? Almost impossible to do it this way on higher duration cams, as there isn't 2 opposite points you can pick up with a vernier that aren't already ramping into the lobe. Most accurate way is to install cam into a head (or v blocks), and clock the base circle lobe difference. Tomei type B cams usually have 1mm smaller base circle than stock, so IIRC that would be 31mm. Stock 32????. Which makes that 11mm lift. Deffo need new springs and head work for it to work.

18th June 2008, 02:41 AM	#5 (permalink)
SamuraiSam GTR Register Member Join Date: Oct 2007 Posts: 390	You guys are making this way harder than necessary. Get a magnetic base dial indicator, put it on the lobe, zero it out, and spin the cam. The highest point the gauge registers is the lift of the cam.

18th June 2008, 10:46 AM	#6 (permalink)
Madden New Users Join Date: Nov 2004 Location: Berkshire Posts: 2,078	The base circle is visibly bigger on the tomei cam. I have spoken a RB and they say the same thing that they are meant to be 1mm smaller but only on the large lift cams. So this cam could be an 9.7mm lift?

18th June 2008, 11:39 AM	#7 (permalink)
NISFAN GTR Register Member Join Date: Oct 2003 Location: Herts Posts: 1,696	Correction to above statement, getting manufacturers nomenclature confused. Tomei reduced base circle cams are PROCAM. 30mm Stock and PONCAM is 32mm From Tomei web site they don't list a 269 degree. You sure it is Tomei?

18th June 2008, 04:30 PM	#9 (permalink)
Madden New Users Join Date: Nov 2004 Location: Berkshire Posts: 2,078	Yea its a tomei but it really weird. Do they do custom made cams? Also when i was on they phone to RB they checked the part number with another tomei cam. Theres was a A2692N. That was a 270 with big lift. It must be a poncam then?

21st June 2008, 12:58 AM	#11 (permalink)
Madden New Users Join Date: Nov 2004 Location: Berkshire Posts: 2,078	Nice one Rob. Cheers for that i knew something was odd.. Do you reckon is was a mistake? What should i take the grinder to? The valves or base circle? or the whole car

21st June 2008, 08:44 AM	#12 (permalink)
SamuraiSam GTR Register Member Join Date: Oct 2007 Posts: 390	Take the cam back to Tomei or a distributor and have it replaced if it is actually somehow at fault.