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After the next project
 
x98boardwell's Avatar
 
Join Date: Sep 2006
Location: Central Valley, CA
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How to break in rings on an 87-930... what do the experts say?

FYI: Also listed on the Engine Rebuilding Forum.

I own an 87-930 and recently did a top-end job including honing the cylinders and installing a new ring set. I did not touch the case in anyway during this top end other than installing new master link chains and ramps.

Here is the link from the build with pic's. Updates on engine top-end rebuild

I have heard a few things and am curious on what the experts think. I use the word experts because I would like feedback from the guys who have seen this in the real world... not someone who heard it from a buddy.

1) I was told to go easy for 1,000 miles with no boost.
2) Go easy for 1,000 miles and introduce boost occasionally (around 1 - 2 10ths bar) to help seat the rings with higher pressure.
3) start driving like normal... the boost will actually help seat the rings by forcing them to push against the cylinders under load... my buddy told me this, hence the reason for this thread.

I am using normal (non synthetic 20/50) oil for the first 1,000 miles and plan on changing once around 200 to make sure there are no metal chunks that I need to know about. Also, I realize that my car is a relatively low compression motor around 7:1 or 7.2:1 or something around there. I am guessing that when boost is introduced the compression rises to around 10 or 11. Now, an SC motor is around 9 or 10:1 and their compression is always that high. So, whats the difference if it is compression from boost or from the pistons normaly?

Lastly, when people purchased these cars back in the 80's the dealer or Porsche did not tell them to "baby" the car for the first 1,000 miles did they? I bet they left the lot sideways if they had LSD. This is what may have lead to short engine life but I am trying to figure out what is best based on experience.

Your input is appreciated.

Thanks,
Bryan

Old 01-26-2009, 11:51 AM
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Turbo Hooligan
 
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meh, get it up to temp, vary the rpms, and introduce some boost. let it cool down. and then full boost.
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Old 01-26-2009, 12:30 PM
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Cynical Misanthrope
 
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I had to do the cam break-in 20min at 2,500rpm.
Then I changed the oil and filter.
Then I took the car for a 1hr drive breaking in the rings just like I did on the racebike.
First 10min, alternate 50% throttle and overrun (vacuum coast-down), up to 5k. Yeah I felt like a dork hobby-horsing down the thoroughfare, screw 'em I was still driving a Turbo.
Next 10min, alternate 70% throttle and overrun.
After that, give'er the berries for successive pulls and make sure to let it coast down under full vacuum. I didn't rev it out all the way but I let it get several successive 3-5k 3rd gear pulls to get the pistons and rings good and hot.
I knew my rings were bedded in in 200 miles because I had lots of engine braking again, and cold startup only gave a puff of smoke. I passed CA smog 375 miles after rebuild.
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Old 01-26-2009, 12:38 PM
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Banned
 
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I'm curious about the "advise" of no boost for 1K miles . . . this is counter to any "wear in" proceedure I have ever performed, or heard about, on any engine . . .

A very accomplished and reputable race engine builder in the DFW area does it like this . . . three "stand still" heat cycles, followed by several 3/4 RPM pulls on a dyno, followed by "dropping the hammar" (on a dyno) . . .

AFM744's process sounds like an excellent, non-dyno method, however . . .

Ronnie
Old 01-26-2009, 03:58 PM
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You want to seat the rings as fast as possible and, yes, you want to boost it right away. Use a low gear and drive it up the rev band and then let off the gas and let the weight of the car do the rest of the work. You don't want a steady state; you want variable load. After it's warmed up good, start the boost as soon as possible. You want to load the rings, you see. Don't free rev it and don't think "gentle" with them else you could glaze the cylinders. Change the oil as soon as possible - and use non-detergent oil, or even cheap dyno oil. Don't use synthetic oil at all for the break in period; don't use a synthetic blend. Most people don't even consider the oil used with a break-in and think synthetic and the metal-to-metal contact that must happen briefly with rings and the cylinder walls never takes place and they become glazed. I use this process on my 700plus hp bmw motors and they seat nicely and hold up to hell or high water.
Old 01-26-2009, 04:28 PM
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Thanks

To all who responded. I have about 45 miles on the car and have done 4,000 + in rpm range with no boost. The next time I take it out... boost for sure.

I am running (as mentioned above) non-synthetic oil from Castrol. This oil is not a blend of any kind and normal 20/50 weight.

The car has not puffed a lick of smoke since I have adjusted the mixture on the initial start. My fuel distributor was rebuilt and the car was very rich on initial start. Other than that, she runs great.

I will do some hard pulls (3/4 throttle) and then let off and let the car/vacuum slow me down. After that... all hell is going to break loose. I'll let you know how the SC cams feel and a fresh motor.

Thanks again!

Bryan
Old 01-26-2009, 05:22 PM
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Can't wait to mash the pedal huh Bryan?
Your SC cams + Exhaust = Real Raspy as you left my house Sunday

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Old 01-26-2009, 06:06 PM
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