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Dave in MN · 06-04-2020, 10:14 AM

Observation: I have rebuilt 190 engines using insert bearings. About 15 are full pressure, another 15 have unfiltered oil direct to the center main and the rest are gravity fed. Of these engines I have had 6 engines come back to date with damage from running the engine with too much advance. In all 6 cases, the crankshaft was not damaged. The main bearings were the first to fail with the center main being the worst, the front journal following closely. The rear main had the least damage.

When the bearings failed, the bearing material was at the worst, pulverized, at the least shattered into course chunks.
The rod bearings in these failures all showed high pressure marking on the bearing surfaces. A couple of them had some early bearing material fractures.
The repairs to the main bearings were easy and not expensive to make. Change the inserts and thoroughly clean the engine. As a precaution, the rod bearings, also all inserted, were replaced even if they showed no distress.

All of the engines that returned for repair were fitted with High Compression heads. Most of the guys thought they were running their engines with the proper advance but when I checked their timing they were all over 30 degrees advance with one hard-of-hearing gent over 40 degrees. One gent ruined his bearings during a 6 hour run and less than 2 tanks of gas. Yes, It can happen that fast!

My point and advice: Too much advance will shorten bearing life. Back the timing advance down when using a head with higher compression than Ford's stock head. In most cases with heads of 6:1 compression, the advance should not be over 26 degrees before top dead center at full advance.

More concern: A new 7:1 head I dyno tested early this year, produced phenomenal power but started to noticeably knock at 22 degrees advance. No significant power was gained over 19-20 degrees advance. The owner brought the car back to me saying the engine "will just not run without knocking" and would I check it over. I immediately checked the timing and found he had the timing set at 28 degrees. I set his timing at full advance to 19 degrees and sent the car back with him. He reports: "It goes like stink but sure requires fiddlin with the timing to keep her from knockin". So don't assume by the book normal timing will work with anything but a standard head.
Good Day!
www.durableperformance.net

06-04-2020, 10:14 AM	#21
Dave in MN Senior Member Join Date: May 2010 Location: Jordan, MN Posts: 1,416	Re: Spark advance Observation: I have rebuilt 190 engines using insert bearings. About 15 are full pressure, another 15 have unfiltered oil direct to the center main and the rest are gravity fed. Of these engines I have had 6 engines come back to date with damage from running the engine with too much advance. In all 6 cases, the crankshaft was not damaged. The main bearings were the first to fail with the center main being the worst, the front journal following closely. The rear main had the least damage. When the bearings failed, the bearing material was at the worst, pulverized, at the least shattered into course chunks. The rod bearings in these failures all showed high pressure marking on the bearing surfaces. A couple of them had some early bearing material fractures. The repairs to the main bearings were easy and not expensive to make. Change the inserts and thoroughly clean the engine. As a precaution, the rod bearings, also all inserted, were replaced even if they showed no distress. All of the engines that returned for repair were fitted with High Compression heads. Most of the guys thought they were running their engines with the proper advance but when I checked their timing they were all over 30 degrees advance with one hard-of-hearing gent over 40 degrees. One gent ruined his bearings during a 6 hour run and less than 2 tanks of gas. Yes, It can happen that fast! My point and advice: Too much advance will shorten bearing life. Back the timing advance down when using a head with higher compression than Ford's stock head. In most cases with heads of 6:1 compression, the advance should not be over 26 degrees before top dead center at full advance. More concern: A new 7:1 head I dyno tested early this year, produced phenomenal power but started to noticeably knock at 22 degrees advance. No significant power was gained over 19-20 degrees advance. The owner brought the car back to me saying the engine "will just not run without knocking" and would I check it over. I immediately checked the timing and found he had the timing set at 28 degrees. I set his timing at full advance to 19 degrees and sent the car back with him. He reports: "It goes like stink but sure requires fiddlin with the timing to keep her from knockin". So don't assume by the book normal timing will work with anything but a standard head. Good Day! www.durableperformance.net Last edited by Dave in MN; 06-04-2020 at 01:52 PM.