Cam break in

[John M.]

From the many posts on this subject it's pretty clear that this is critical to the health of your engine. Did GM do this in the 60s? After 2 years I'm ready to fire this thing up and have a couple of questions. The car has power steering so the system needs to be bled. The manual recommends starting the car, running it for a few seconds, refill reservoir, start and run a few seconds, etc til the fluid level is stable. I've filled the reservoir but am going to skip the start, stop bit. Will this harm any of the power steering parts? I can probably manually get the timing within about 5 degrees; it's a single wire electronic module, so I don't think I can rotate the distributor and get a static spark like with a points system. Can I quickly set the timing before the 20 minutes at 2000RPM? The engine has all the assembly lubes, etc and I'll reprime the oil pump before starting. I want to do this right and would appreciate any advice.
Thanks, John McRae 30025

[Rob A.]

Re: Cam break in

I just did this with my engine. I can't add much to all the tips regarding cam break-in, however, as in previous posts, the wheels can, and mine did, abruptly turn fully in one direction on startup if the control valve is new or rebuilt. Afterwards I balanced the valve, and it operates normally. If the timing was close enough to start the engine, at 2000rpm for cam break in, it really won't matter exactly where you have it set anyway, just in the ballpark. Don't worry about adjusting the timing per specs at idle until you are satisfied the cam has been broken in. Have your idle adjustment screw turned in all the way, so when the engine warms up and the choke releases, the idle will still be high enough to continue cam break in.

[Chuck S.]

Re: Cam break in

The top priority is to run the engine in without damaging the cam...forget about the power steering for now and remove the belt.

Don't be monkeying around with the PS and the timing when you should be concentrating on maintaining break-in rpm, checking oil pressure, coolant temperature, watching for oil/coolant/fuel leaks, and generally keeping an eye out. Methods for setting static timing have been covered often, and are in the archives.

Only one pulley HAS to turn during engine run-in and that is the water pump. If necessary, a fully charged battery can sustain the low power draw of the ignition system during the relatively short 20-30 minute run-in time.

[Roger Legge]

Re: Cam break in

Like Chuck said, forget the power steering for now. I've heard all kinds of reasons *why* the RPM is elevated for flat tappet (non-roller) cam break-in, but the one that makes the most sense to me is that they are not pressure oiled and get their oiling from oil flying off the crank. Elevated RPM supplies more oil during the critical surface mating period. Immediately bring it up to around 2200 to 2500 RPM, watch the oil pressure and watch the coolant temp. If something goes wrong (hot, leak, whatever), just shut it off, remedy the problem and restart it and bring the RPMs back up. Just make sure the total time is at least 20-25 minutes or so. Source for this break-in info, other than the personal comment on splash lubing the cam, is Ultradyne Cams. I carefully hook up a timing light and check the timing at the elevated RPM. Anywhere around, what, high 20s to mid 30s would be fine. Retarded timing can cause an engine to run hot and a new, tight engine tends to run a bit warm anyway.

The comment about the power steering turning is good advice. I installed a rebuilt control valve, did the centering adjustment best I could, but it still whipped the wheel full-lock one direction when I started the car.

Good luck!

Roger

[Duke W.]

Re: Cam break in

Flint did not go through any kind of cam break-in procedure, nor did St.Louis.

Flint hot fired the engines for 30-60 seconds, then shipped the them to St. Louis. At the end of the line a guy started them up and drove the car away.

The "cam break-in procedure" is critical if you have a racing cam with high rate valve springs, but is not critical for a OE cam and valvetrain.

Notwithstanding the above, I think it's good idea to do the cam break-in
procedure as it is cheap insurance. You can adjust the timing if necessary after the engine fires. Assuming you have a vacuum advance, leave it connected and use a dial back light to adjust the total timing to about 35-40 degrees with the engine running at about 2000-2500. Snug the distributor before you start the engine, but not so much that you can't rotate it with your hand.

Once the breakin is complete you can let the engine idle and go through the initial timing procedure.

As previously recommended, get a different belt or whatever you have to
do to bypass the power steering pump. All you really need is the water
pump and alternator.

Deal with the power steering fill and bleed later.

Duke

[John M.]

Re: Cam break in

Thank you all, very much.
John McRae

[frank mccracken]

Re: Cam break in

My experience is not to have the idle screw turned in to maintain hi idle. If you do need to shut down for any reason, with the throttle plates held open, when you turn off the key it can remain running by deiseling farting and popping for quite a while. It's far better to have a helper in charge of engine rpm only via the throttle while you watch for leaks, temp, oil press etc and possibly make ign timing adjustments. If you do it by yourself like I usually do, you can use a wedge, piece of folded cardboard etc, between the throttle stop and screw to keep the idle @ 2000 that can be pulled out easily so the engine will not deisel on once it gets hot.

[John H.]

Re: Cam break in

OEM GM flat-tappet cams were "Parkerized" on the lobe surfaces to reduce friction at initial start and to eliminate the need for any cam "break-in"; aftermarket cams are not, and require the break-in procedure.

[Mark H.]

Re: Cam break in

Don't forget to change the oil and filter when the cam break-in is complete. Then again after 500 miles, and then you're set.

[John M.]

Re: Cam break in

Thanks, John
That's something I've always wondered about as I'm sure others have. I can't see GM spending 25 minutes on any detail like this.