engine breakin

what is the best way to break in the '77 305 i rebuilt, it has a performance summit cam, new lifters, valves and all new rings and bearings

im going to preoil it with an old distributor first though

If you have a solid cam make sure you use 15-40 Diesel oil or GM EOS to help break in the cam. I run the engine at 1500-1800 for 15 minutes, make sure it is timed right primed and starts right up also. Then I drive it at varying loads IE: pull some grades in a higher gear to get some load on the engine, moderate speeds and rpms of course. Depending on the build technique, maybe for 500 miles.

so run the engine at 1500-1800 rpm with 15W-40 for 15 min

then change the oil and filter and run regular oil like 10W-30 or 5W-30

what brand of filter and oil would you recommend?

Purolator Pure One is one of the best in tests, also Wix premium. Again, hydraulic or flat tappet cam? Is the engine built to racing specs, stock? No info on what's what here.

its a stock engine with a hydraulic cam

why 15W-40 oil for breakin what does it do for the engine?

check out this sight.
http://minimopar.knizefamily.net/oilfilterstudy.html .
search the sight and you will find out what oil filters really are.
Wix is my preference.
as for oil, good question, why the 15w40.
never herd of that one. I would go with syn. oil. mobile1 5w30 is my choice.
As for the breakin,
fire it up, and get everything set. coolant, timming, gas, ect. and then get it out on the road. I took my camaro with a 400s.b. out on our interstate that runs 70mph and drove it just over 100 miles with no stops. and no hood I might add :evillol: . If you cant do that at least keep a higher rpm for a good half hour or so.
If there was a way for you to keep a load on the engine that is better too.
the harder you work the engine the better the outcome.
My humbel opinion only.

GM EOS no longer contains the zinc everyone is talking about. STP may be a better choice for intial break-in.

The primary reason for a "break-in period" is the flat tappet cam. Whether hydraulic or solid lifters, flat-tappet cams have very specific break-in requirements, to establish a wear pattern, preventing premature cam failure. That's where the revs are held at about 2,000-2,500 for a 15-20 minute period. Some like to vary the speed a bit during the process, but we've found that unnecssary. If the engine is equipped with a roller cam (hydraulic OR solid), just take it out and pound on it. We've found the best approach is to put the car in 2nd gear, and rev it hard to about 4,500, and back off, allowing "engine braking" to slow the car. Repeat the process three or four times, and the rings should be "seated". Keeping the revs down will prevent scorching the new rings.

I recommend against using synthetic oil during break-in. It can actually lubricate TOO well, preventing the necessary friction for wearing "in". Once you've established the engine is "healthy", with no leaks or smoke, THEN switch to synthetic.

The 15W-40 refered to is the rating of the various heavy duty "truck" oils, which offer better lube for the tappets. We use either Shell Rotella or Union HD.

Jim

I knew you'd jump in here MrP, my 4 bottles of EOS, list high Zinc/ZDP content, but they are a year old. Agreed on the Rotella, just finished a 331 Hemi, ran it in for 500 miles, did an oil analysyis and cut open the filter all looks good.

so what grade of oil do i use?
how long and at what rpm do i run the engine for?

so what grade of oil do i use?
how long and at what rpm do i run the engine for?

Flat tappet cam? The diesel oil (Shell Rotella-T and others) contains the proper amount of zinc phosphate (ZDDP) to ensure proper lubrication of the cam lobes. Flat tappet camshafts take a huge amount of stress. The zinc phosphate forms a 'sacrificial layer' of metal, preventing cam wear. Newer gasoline-rated oils such as SM grade do not contain any usable quantities of this necessary ingredient, so cam lobe failure is a common occurance.

The break-in phase of the camshaft on a flat tappet arrangement is absolutely critical to longevity. The camshaft receives its lubrication from oil slung off the crankshaft counterweights. During break-in, wear is accelerated and the camshaft must receive a copious amount of lubrication to ensure the lobes won't be wiped off. At engine speeds below 1800 RPM, oil from the crankshaft is insufficient for the camshaft break-in. This wear equalizes after a certain amount of time, at which the cam is considered 'broken in'. For me, the break-in time goes to 30 minutes, just because I like to be conservative on a flat-tappet cam break-in. You see, I don't like replacing a camshaft 20 days after installing it.

During the break-in phase, the camshaft will produce a good amount of metal, which will remain in suspension in the oil. For that reason, I like to change the oil and filter immediately following a break-in.

Again, a flat tappet cam will not live long without the proper amount of zinc in the oil. Racing oil provides this, as does diesel rated oil. You will find the Rotella costs about half of what Valvoline racing oil does. For diesel oil, you want CI-4 rated oil.

Roller camshafts do not need a certain break-in period, nor do they require the zinc additives.

My personal break-in procedure for a flat tappet cam is 25-30 minutes, varying engine RPM between 1800 and 2500 RPM.

thanks, that made everything make sense
:grinyes: