Brand new 302 question

KEOliver · 01-24-2010, 05:05 PM

My 67 has a newly rebuilt 302 in it. The guy that built it up said to run conventional oil for the first 3000 miles or so and switch to a good synthetic. He said that this was "best" but he did not say why. Just curious, does anyone know why he would say this?? Is it reasonable advice?

Kev

slim · 01-24-2010, 05:21 PM

Quote:

Originally Posted by KEOliver

My 67 has a newly rebuilt 302 in it. The guy that built it up said to run conventional oil for the first 3000 miles or so and switch to a good synthetic. He said that this was "best" but he did not say why. Just curious, does anyone know why he would say this?? Is it reasonable advice?

Kev

Not to be a wise a** but you trusted him to build the engine why not ask why he said that? I agree with asking a second opinion by the way.

shaneh · 01-24-2010, 05:25 PM

That is the old school way to break one in on conventional oil. Grumpy Jenkins used to say an engine was broken in by the 3rd full throttle pass and then you can beat on it and do what you want with it. Nowdays, if we break an engine in in the car, we'll put it in high gear and do a full throttle run up the road for a bit and then let the engine coast down against itself. Then repeat 3 times. The engine is broken in at that point and you can put any oil you want in it. If it's not broken in by that time, it's not going to be broken in. What I've found is that a lot of engine builders prescribe to the 1000-3000 mile breakin while most of the engine tuners think along the lines of what I've noted here.

KEOliver · 01-24-2010, 05:42 PM

Quote:

Originally Posted by slim

Not to be a wise a** but you trusted him to build the engine why not ask why he said that? I agree with asking a second opinion by the way.

Right, but I did not mention that I bought the car with 500 miles on the rebuild and the quoted advice was reported by the p.o. I would asked, and the collective wisdom of this forum is more accessible that the dude who built the motor. Thanks for the input .

slim · 01-24-2010, 08:24 PM

Quote:

Originally Posted by KEOliver

Right, but I did not mention that I bought the car with 500 miles on the rebuild and the quoted advice was reported by the p.o. I would asked, and the collective wisdom of this forum is more accessible that the dude who built the motor. Thanks for the input .

Good move! By the way years ago I bought a "rebuilt engine", turned out it was degreased
and painted. Fortunately the seller had believed the guy he bought it from.
He had no intention of deceiving me. He refunded my money.

jsm0372 · 01-25-2010, 11:45 AM

I believe the thought on conventional versus synthetic during break-in is the conventional oil allows for 'normal wear' during the break-in period and that synthetic is too slippery for this to actually occur. I ran conventional through my crate motor for the first 1500 miles, then changed both the oil and filter to make sure any contaminants (metal, dirt, shipping oil, etc.) from break-in were out. I agree with some of the other posts regarding how to break-in and have also heard that if you baby the car too much during break-in that the engine won't perform optimally. The main thing during break-in is to vary speed and RPM....in other words, don't just cruise around at 60 mph on the highway the entire time.

tubo3 · 01-25-2010, 02:08 PM

What jsm0372 said.
Here's a link to an engine breakin site, is worded for motocycles. The principals & methods still apply to SBF's

Break In Secrets--How To Break In New Motorcycle and Car Engines For More Power

6t9mach1 · 01-25-2010, 02:25 PM

The reason is for proper ring seating to occur. The length of time for the rings to seat depends on the ring material and how the cylinders were honed. If you are using rebuilder special cast iron rings it may take 1500-3000 miles for them to seat. Moly rings usually take 500 miles if the cylinders were honed properly. As others have said, a day at the track with several hard passes will usually seat the rings. If you dont run it hard and it has cast iron rings I'd wait at least 1500 miles to go to synthetic.

greenstang2003 · 01-26-2010, 02:17 AM

I dont know his reasoning, some of the other postings had good explanations but i do the same thing when breaking in a motor. When i break in my engine after a rebuild i use regular oil for the first 1000 miles then change the oil to full synthetic. My reason is because immediately after breaking in the engine, you need the change the oil. So why waist $40 on Synthetic when your only going to use it for 1k miles when you can spend $10 but regular. Anyway, that's why i do that.

supershifter2 · 01-26-2010, 03:08 AM

using straight 30w non-synthetic oil on a new engine allows for a tad bit of friction so the rings can wear-in(seat) and a new flat tappet cam and lifters can do the same. there is not any break-in period on the bearings or roller cam. i run a new engine at about 2000 rpm for about 20 minutes to seat the rings and change the oil to valvoline 10w30 non-synthetic racing oil. i use JE J100F8-4000-5 chrome ring set.

bryancobb · 01-26-2010, 05:35 AM

When aircraft engines are reringed, you run straight mineral oil for the first 25 hours and run the engine HARD, for the reasons stated above: to wear the rings to the contours of the new cylinders they live in. This makes them seal better which raies the compression and gives more power. There is also another important benefit. Low oil consumption for the next 1500 hours.

kenash · 01-26-2010, 08:48 AM

Quote:

Originally Posted by KEOliver

My 67 has a newly rebuilt 302 in it. The guy that built it up said to run conventional oil for the first 3000 miles or so and switch to a good synthetic. He said that this was "best" but he did not say why. Just curious, does anyone know why he would say this?? Is it reasonable advice?

Kev

Hi Kev,

I'm assuming the guy who built your engine "said that this was "best", but did not say why" is referring to: "in his opinion", using synthetic oil is better than conventional oils.
What the others have stated about the break-in cycle is all good information. But, I read your comment as asking whether synthetic is better over conventional oils?
This point can be argued until the cows come home. It has been my experience, having built a number of engines, having participated in organization road racing events, having flogged the crap out of my "spirited built engines", and having driven all of my daily drivers well over 100K miles with no engine repairs due to "worn or damaged bearings", that using synthetic oils would have made any difference. (sorry for the run-on)
In my opinion, I think it far more important to recognize when to change the oil and filter based on your driving habits that makes the difference. As an example. I once bought 1982 Cadillac from a "little old lady" who only drove it to church on Sundays, nearby. This was confirmed, by way of the fact, her son had given me all of the invoices during her ownership. There were numerous invoices for oil "leaks". As soon as I bought it, I changed the oil and filter as a matter of record. When I added oil, it backed up out of the VC. I pulled the VC and found the rocker covered with "gook" to the point "all" of the oil return holes were blocked to the extent that I had to research the head to determine where the oil return holes were located to ream them clean.
Enough said, on the importance of frequent oil changes.
Maybe, in her case though, synthetic would have been the better choice??
Maybe the moral of the story is "if you don't want to change your oil, then, use synthetic!