cam timing

[justinburnett]

recently while rebuilding a 400 small block, I ran into a situation where the old timing gear was 4 degrees advanced. I was told that I should set it back to 0 when I put everything back together. I never thought to ask why, so I though maybe someone could explain it to me. What would happen if you had +4 cam timing? what does that cause to happen? valves open earlier on the stroke? What does this mean as far as power and such? I can't see why it would be a benefit.
Just have time to be curious at the moment whereas before I was scrambling to get the project done. Thanks.

[78 Chevyrado]

The degree marks on the crank gear are for further tuning purposes. Like if the cam you have isnt just right.

If you have picked out the correct cam, set it to 0.

[wyattglock]

If you are wanting to max out the power potential of the cam, +4 degrees advanced is a good start. But then you could run into other tuning problems. If the timing set had to be installed at -4 degrees, then there are other issues with the way the motor was setup that should be addressed. 0 degrees with the right cam is the easiest and quickest way to insure a good start without burning up the valves or causing detonation. If youre living life a quarter mile at a time, +4 is the way to go with a hot setup.

[justinburnett]

So then would that be what you would want to do with a large lobe cam running high rpms?

I just got an RV torque cam. Set it at 0. I'll be surprised if my engine ever sees 3500rpm so I'm not terribly worried about performance. Just wanna be able to haul loads to the dump, pull my car down to the shop, pick up rocks 'n hay, etc.

[3r!c84]

Originally Posted by justinburnett

So then would that be what you would want to do with a large lobe cam running high rpms?

I just got an RV torque cam. Set it at 0. I'll be surprised if my engine ever sees 3500rpm so I'm not terribly worried about performance. Just wanna be able to haul loads to the dump, pull my car down to the shop, pick up rocks 'n hay, etc.

mines sees 5k right before it shifts. but thats what my cam allows. not anything from a stock build. but they can be spun up higher then then that. just keep it under 4500. to be on the safe side

[wyattglock]

Depending on the heads, intake, and carb setup yes. Advancing the timing in a high performance setup would also require higher octane fuel to help reduce detonation. An MSD ignition or close equivalent would greatly help with spark control also. Honestly, with almost every car I have worked on, 0 degrees has been fine for the street.

[wyattglock]

BTW, that RV cam will be great for what you are describing. That is definitely the way I would have gone with the setup of the cam.

[justinburnett]

sounds good to me. Should have it running today. I've run into all sorts of snags, mostly with the transmission shop I used (if you saw the thread, you know). Everything's in now and I'm just doing some wiring and bolting on accessories. Looking forward to turning that key, but at the same time dreading that I'll find out the trans guy screwed me again or I forgot to install a rod bearing or something (I did that once and this time I counted probably 8 times and checked every rod probably 3 times to make sure both sides were in). Probably just paranoid.

The one thing I regret was I wasn't able to either have the carb re-built or replaced. I like the idea of the q-jets, but no one seems to know how to work on them. All I get is "those are really complicated carbs, just switch to an edelbrock". Getting that taken care of is on my list of things to do in the future, along with a HEI distributor and some other stuff but I just ran out of cash and couldn't do any more. Getting back to work now..