Pro Cams Or Pon Cams 260 9.15. Rb26

[jet.26r]

hey guys i bolted in some tomei cams i then did a compression to see the results and it was low at about 100psi over all 6.

i bolted the standard cams back in and compression went back up to a better 155psi.

all shims have been set and are 100%

i am being led to beleive that they are pro not pon.

the code on the inlet has been stamped: A2691N

EX: A2691X

[djr81]

hey guys i bolted in some tomei cams i then did a compression to see the results and it was low at about 100psi over all 6.

i bolted the standard cams back in and compression went back up to a better 155psi.

all shims have been set and are 100%

i am being led to beleive that they are pro not pon.

the code on the inlet has been stamped: A2691N

EX: A2691X

Tomei have taken to calling some of their Poncams Procams when sold as a single cam.

The difference inthe cams is simply that a low lift cam can be fitted without modification. A medium or higher lift cam cannot.

See here

NISSAN_RB26DETT.doc

[jet.26r]

Tomei have taken to calling some of their Poncams Procams when sold as a single cam.

The difference inthe cams is simply that a low lift cam can be fitted without modification. A medium or higher lift cam cannot.

See here

thanks for your reply but a pon cam with 260duration and 9.15 lift does not require any modification to the head but the pro cam with 260 duration and 9.15 lift does does anybody know why?

[djr81]

thanks for your reply but a pon cam with 260duration and 9.15 lift does not require any modification to the head but the pro cam with 260 duration and 9.15 lift does does anybody know why?

That is not correct. They are the SAME camshaft.

The old convention was that a Procam needed mods to fit. Now that Tomei call any cam a Procam you cannot make that distinction anymore.

From what I understand they are Poncams when sold as a pair (For an RB26 you get 260 inlet & either 252 or 260 exhaust all with 9.15 lift, ie a type A or B) & procams for the high lift versions & for single cams.

You can according to the Tomei listing buy inlet cams in 252, 256, 260, 270, 280 & 290 degree durations. All of which are called Procams. But the listing states "equal as Poncams" for the relevant ones.

Edited November 19, 2009 by djr81

[jet.26r]

thanks for your help i dont understand how i can get a significant variation in compression still between the tomei and standard cams

[djr81]

Have you confirmed what cam you have? Specifically the lift. The base circles & lifts are at the bottom of that sheet in the second post. Easy enough to measure to be sure.

[jet.26r]

i got them measured at cam tech sydney and they confirmed the specs of the cam.

[djr81]

thanks for your help i dont understand how i can get a significant variation in compression still between the tomei and standard cams

Because the Tomei cam has a longer duration - hence the inlet is open longer when the piston is on the compression stroke. So you get a lower compression test number at however many rpm it is done at.

The nature of longer duration cams is that the motor works less well at lower rpm.

The question is, other than the comrpession number, was there anything wrong with the motor with the 260 degree cams fitted? Reason being that the compression number may be perfectly normal for that duration cam (Assuming it is degreed properly, ofcourse).

[jet.26r]

i tested compression with a fully charged 12volt truck battery all spark plugs out the starter motor was cranking as fast as it can go no gearbox on either, my mate also bought the same identical cams as mine and he got 140psi with cam gears set at 0 as mine are set at 0 too. and timing marks are 100%

[NickR33]

thanks for your reply but a pon cam with 260duration and 9.15 lift does not require any modification to the head but the pro cam with 260 duration and 9.15 lift does does anybody know why?

the PRO cams are 10.8mm lift and require shims, springs etc... I have a set in my 26

I wouldn't worry about that small decrease in compression, as djr81 has stated if there is nothing wrong with the motor then this is just a symptom of the longer duration

Edit: Misread your first post... 55psi variance is pretty damn big!

[jet.26r]

the PRO cams are 10.8mm lift and require shims, springs etc... I have a set in my 26

I wouldn't worry about that small decrease in compression, as djr81 has stated if there is nothing wrong with the motor then this is just a symptom of the longer duration

Edit: Misread your first post... 55psi variance is pretty damn big!

ye its big alright and drop standard cams in back to good comp this problem has done my head in for quite some time now im ganna rage it soon!!!

[jet.26r]

bump