GTR1999

Using a XE268 cam what would be the best way to time it when first firing it up? Use the L-82 spec for the year(75) or something else.
Thanks,
Gary

Fevre

Best thing to do is to leave the dist just loose enough to rotate it by hand then once you get it fired and running at 2000+ rpm's rotate it slightly to get the best sound. Once the cam is broken in then do the real timing. During cam break in you want to let the eng run at the 2000+ rpm's for 20 to 30 minutes with no interuptions, also leave the vac adv unhooked during break in.

marshrat99

:iagree: with Fevre. If you've got the cam degreed OK, all you need to do is to bring #1 up to TDC and verify that your distributor rotor button is pointing approximately somewhere between 6-7 Oclock AND that this is approx. where your distributor cap has the #1 wire located. The sucker should fire right up ! Good luck... :cheers:

Vetterodder

If you mark the position of the rotor in realtion to the distributor housing and the position of the distributor in relation to the engine BEFORE you remove it your timing should be close to right. By doing it that way you'll spare yourself, and your engine, a lot of grief.

dewcustom

when you fire it you want to keep the rpm above 2000 but not steady the whole time you need t very it between 2000 and 3500 slowly back and forth for 20-30 min

GTR1999

Thanks guys, I do have the the engine @ TDC on #1. I had the top half off to replace the heads so I made sure the timing tab ws at true TDC with an indicator.
Comp said to start it at TDC@1 and run it like that for the 20-30 minutes. I was going to get it close to 8*BTC by setting the balancer @8* BTDC then aligning the dist to the #1 wire. I didn't know how much difference it will be running at TDC or 8* BTDC for the break in time?
Thanks,
Gary

marshrat99

Shouldn't make a whole lot of difference. Just keep an eye on your temps. :cheers:

Fevre

Plus make sure you use dino oil, not synthetic for the break in. Break in the cam, change the oil/filter, drive 500 miles, change oil/filter, then you can use syn if you like and change oil/filter at regular intervals.

7T9Shark

All good advice. I dispute the "must run 30 min. continuously" advice. How is shutting it down periodically going to have a negative effect? It's not a problem to do it in short 5 min bursts if you don't want to hold the accelerator for that long. In fact, my builder recommended shorter cycles rather than one 30 min. session.

Fevre

Oil drain off and temp cycling can have an adverse affect on the cam break in process. Better to do it at one time when the oil is nice and warm. Cycling the rpm's up and down is a good idea too. Some people even recomend an additive for cam break, don't recall any specific additive names/brands. Suppose there is more than one way to skin a cat but this is pretty much a tried and true method.

fauxrs

GM EOS (Engine Oil Supplement) is excellent for break in procedures - between this stuff and Red Line assembly lube, thats more or less all i use when building an engine. I agree break in with Dino oil - You can stop "If you have to" but if you dont have to ....dont.....

GTR1999

Thanks again for the info guys :seeya
gary

greg454

When I did mine I did it in 3 different bursts because of overheating issues. It worked just fine for me.
Greg.

Vetterodder

Greg, what turned out to be the overheating issues and what was needed to solve them? I ask because your experience might be helpful to others, including Gary, that are about to go through the same process.

7T9Shark

It actally was a mute point for me, too, because I had to stop to fix vacuum, coolant and oil leaks. Dang valve cover leaks filled the garage with smoke!

I also used a GM break in fluid that was recommended, but forgot what they called it. Drained it out after the cam break in.