This page will help with understanding what is needed to break-in your new GMPP crate engine.
This is one of our information documents.
Updated 05-11-2006.
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Print this page out and check off boxes below (in the printed copy) when each step is completed.
Step Box
1) Safety first! If the car is on the ground, be sure the emergency brake is set, the wheels are chocked, and the transmission cannot fall into gear. Next verify that all hoses are tight and that both the radiator and radiator over flow jar/tank are full and have been filled with the proper anti-freeze and water mix.  
2) Before starting your engine for the first time, add one pint of engine oil supplement ( EOS¹) to the crankcase oil and then check the oil level. Once this has been done, prime the oil system with an oil pump primer tool. Make sure number 1 cylinder is on TDC compression stroke, and install the distributor.  
3) Adjust the distributor timing roughly by hand for a quick start up and smoothest idle possible.  
4) When the engine first starts, verify that the engine rpm is at a safe level and that the timing is set near or at 30° before top dead center (BTDC). Run the engine speed between 1,500 and 2,500 RPM’s, varying the engine speed up and down with-in this range, to prevent overheating of the exhaust valves and the exhaust system. This should be done with no-load on the engine and for the first 30 minutes of operation.  
5) After the first 30 minutes of the engine running, set the ignition timing according to the timing specifications. Now would be a good time to check thoroughly for leaks.  
6) Adjust the carburetor settings, if necessary.  
7) Drive the vehicle with varying speeds and loads on the engine for the first 30 miles. Be sure not to use a lot of throttle or high RPM.  
8) Run five or six medium-throttle accelerations to about 3,800 RPM (55 to 60 MPH), then letting off in gear and coasting back down to 20 MPH.  
9) Run a couple hard-throttle accelerations up to about 3,800 RPM (55 to 60 MPH), then letting off in gear and coasting back down to 20 MPH.  
10) Change the oil and filter with recommended oil (10w30SG in most cases) and filter.  
11) Drive the next 500 miles normally, without high RPM’s (below 3,800 RPM), hard use, or extended periods of high loading.  
12) Change oil and filter again.  
13) Your engine is now ready for many happy cruising miles!  
Note¹: EOS P/N 1052367 can be used any time during the life of the engine.
Technical Note: This procedure has been corrected and improved from the original GMPP procedure by GILBERT CHEVROLET.