timing chain question

[pagilman]

I am at the point now to install my timing chain and need some advise. The cam sprocket has 3 key ways A. O. and R. Can you tell me what would be the advantages to advance,. on center or retard? Why would you retard the valves? My son in law installed his 350 chevy at -O- with 12 to 1 pistons and it runs on pump gas and he said for me to do it also, but I have heard that advancing really makes a differance in performance. I have comp xe268 H cam , flat tops +(pos) decked, X heads. Any advise will be appreciated. thanks Walt :thumbup:

 

[66dartgt]

The main reason for the different positions is to centerline the cam according to the cam makers specs, some cams are in need of correction and these positions allow for this.

I have heard though that if you want more torque at lower rpm's you retard the cam off its centerline, and if you want more horsepower at higher rpms you advance it. I may be mistaken about that relationship but its either the way I described it or exactly the reverse. Maybe someone else will know better than I. Normally most people install their cams at the recommended centerline of the cam maker.

 

[rumblefish360]

As per the chains instructions, use the straight up "Zero" mark. This will avoid possible valve to piston contact. I bent P-rods this way once.

 

[moper]

66, You're close, but got it backwards. The advancing of the cam timing will add cylinder pressure earlier in the rpm band. So it lowers the peak torque rpm. Retarding it does the opposite. The HP number may drop when you advance it, but you have more torque in most engines. On the XE268, you dont need to advance it. Run it "staight up".

 

[Dusterb318]

IMO if you are building an engine that is using an aftermarket cam you should be degreeing it in to the cam manufacturer's specs. I have never seen a timing set and cam that matched up 100% correct. I've always had to use the offest keys to get the cam timing dead on. I suggest you degree the cam in and use the offset keys to get it installed exactly as Comp Cams suggests then you will be getting the most out of your cam.

 

[ElephantKiller]

Not to highjack the thread, but I'm wanting to degree my cam and I seem to have misplaced the cam data sheet. Is there a place that I can look up the specs for the cam and where it should be set at? I'm using the MP Purple shaft 284/284 0.484 lift (PN P4120231).

 

[Dusteriduu]

Not to highjack the thread, but I'm wanting to degree my cam and I seem to have misplaced the cam data sheet. Is there a place that I can look up the specs for the cam and where it should be set at? I'm using the MP Purple shaft 284/284 0.484 lift (PN P4120231).

Here you have .pdf-file:
http://www.mopar.com/Tables/37.pdf

Centerline should be 108º.

 

[pagilman]

Thanks to all who responded, since it will be used to go for a sunday cruise I think I will align staight up. I bought the cam used and have no info on it. thanks again to all. :wav: