7a cams-intake retard!?

[ADP]

Hello fellas,aim think to fit my 7a cams,but they have a lot overlap!So according by me i must to retard the intake with 1 theet on cams chain!?What is your oppinion and practise advice?
many thanks in advance!

[GazzaG60]

sounds a lot 3 teeth.

id run stock cams unless you are gt35 or above.

I run the 7a ex cam. helps up top a bit. not as punchy down

[ADP]

GT 3788 R is the turbocharger

[jsws3]

Get I touch with jonus-racing in Norway he has 5 different sets of cams for power levels of 400hp to 1300hp

[Thuppu]

I use 7A cams with stock clocks, works nice. I havn't measured them, but there shouldn't be much overlap. Tried to retard both ex and in by two degrees on dyno and got 46 hp less power in top end.

[ADP]

Thanks for replys guys,when i plot the cams degrees of adu and 7a i think that i beter way to retard inlet cam only!For this reason i wish to ask someone who have any practical expirience with this setup!
Thupu my opinion is not to retard both cams ,the problem with overlap will come worse!
But this I cant prove with dynografs, still don’t have a dyno in my garage!:))

[Thuppu]

So you wan't earlier spool and torque? Hmm, I'm not 100% sure but in my setup the cams clocked to factory markings did sure look like there was close to zero overlap. How much overlap have you measured? 1 teeth is quite much, you would need a adjustable cam sprocket so you can mix more accurate.

[prj]

There is no overlap on 7A cams on stock marks!

[A1QSHIP]

Here is an interesting read about camshafts & cam timing.

http://www.s2forum.com/forum/showthread.php?t=34945

HTH, Chris

[JP]

Advance intake using a adjustable wheel if you want to increase lobe seperation

[JP]

Forgot to say 1 tooth is way too much

[ADP]

prj is quiet precised and maybe right-im not make mesuring with the AAN cams wheel,i make with original 7A wheel,soon i will make measurment with both to investigate what is the diferents!

[ADP]

after measurments OVERLAP exist-9 degr!

[prj]

after measurments OVERLAP exist-9 degr!

7A intake:
Opens: 6 Degrees ATDC
Closes: 38 Degrees ABDC
Duration: 212 degrees

7A exhaust:
Opens: 42 Degrees BBDC
Closes: 3 Degrees BTDC
Duration: 219 degrees

So where is the overlap?
Exhaust is long closed (3 deg BTDC) when intake opens (6 deg ATDC).
9 degrees is the time when both the intake and exhaust valves are closed (theoretically speaking, not accounting for the fact that the valve is on a spring and not instant).

From another perspective - 7A cams always make more top-end power than stock cams. If there was overlap, then top-end power would drop off, due to backpressure on smaller exhaust housings.

If you are really measuring something, then your camshafts are not timed correctly.

[JariP]

PRJ's degree numbers are for 1mm lift at the valve and ADP has measured seat to seat timing, hence the difference?