New cam and tappet break in

Harleygaz · Post by **Harleygaz** » Sat Aug 15, 2020 10:53 am

Getting ready to build my engine with new camshaft and tappets and I’ve read on some general engine build pages that the new cam for a flat tappet engine should be run at minimum 2000 rpm for 10 to 20 minutes as soon as the engine is started to break in the cam and tappets and ensure sufficient splash lubrication of the cam lobes. I’ll use z paste and assembly lube in the build and straight 30 break in oil for the first 500 miles. I’ve read the break in instructions in TM 9-8012 and it says nothing about this requirement. Is this required for an L134? I was thinking maybe Willys ran the engines for this cam break in period before delivery so it didn’t need to be in the TM.

Post by **wesk** » Sat Aug 15, 2020 11:34 am

It would help us offer up comments if you posted the source of this statement so we can review it in the context it was originally presented in before we offered our opinions. Out of context one or two liners can mean several different things depending on the original associated commentary.

Harleygaz · Post by **Harleygaz** » Sat Aug 15, 2020 12:54 pm

I just googled flat tappet cam break in and saw similar comments on a number of pages. I don’t recall which ones. Perhaps I could rephrase this and ask is there a requirement to run a rebuilt L134 with a NOS camshaft and NOS tappets at a specified rpm for a specified length of time to ensure the cam and tappets break in properly in addition to and prior to following the TM 9-8012 break in instructions?

Post by **wesk** » Sat Aug 15, 2020 3:14 pm

Nice of you to not expect us to go searching for your unknown sites. To answer your more direct question I could ask if you have read the applicable manuals? TM 9-1804A for the engine has some very detailed steps listed for the initial run in. Just review pages 98 & 99. This is the rare case where the military manual offers more guidance then the Willys civvy factory CJ manual SM-1002.

Harleygaz · Post by **Harleygaz** » Sat Aug 15, 2020 8:51 pm

I have read that section Wes but since I don’t have a dynamometer it doesn’t really help me much which is why I went back to 8012. I know 1804A says run for 15 minutes at 1,000 rpm but that is to warm up. So back to my question - should the engine be run in a specific way on first start up to specially break in a new cam and tappets?

Post by **wesk** » Sat Aug 15, 2020 10:54 pm

No. The hardened steel cam and tappits can hardly benefit from a special short runup 10-20 minute 2,000 RPM runup. Just how much hardened steel do you expect to do any yielding. I strongly suspect none. Perhaps you are reading racing engine maintenance jargon where hi-lift cams and much stronger valve springs are working a lot harder than any L134 ever will.

That very thorough run-in schedule in TM 9-1804A has a purpose far beyond reading the resulting BHP readings on a dynamometer and should not be ignored. Notice the RPM increase & decrease and the amount of time spent at each setting. Having worked both vehicle and aircraft applications of these run-ins I am well aware of what is done and why. Note the system operating parameters that must be observed and their limits. 10 areas must be monitored. I believe if one follows this run-in procedure precisely they will have no issues with any new steel parts.

Larger file is here: http://willysmjeeps.com/v2/modules/gall ... _in_sm.jpg

Harleygaz · Post by **Harleygaz** » Tue Sep 08, 2020 2:46 pm

I have read that section Wes but since I don’t have a dynamometer it doesn’t really help me much which is why I went back to 8012. I know 1804A says run for 15 minutes at 1,000 rpm but that is to warm up. So back to my question - should the engine be run in a specific way on first start up to specially break in a new cam and tappets?

RonD2 · Post by **RonD2** » Thu Sep 10, 2020 10:15 am

Following this post with interest.

Even though I'll have about $3500 in my L134 rebuild when done, and even if I could find a local shop with a dyno, I doubt I could afford 4 hours time on it just to comply with the Army TM. I wonder if Willys put new or rebuilt replacement engines on a dyno for 4 hours before selling them?

Could be wrong, but I always thought the initial start and warm-up to operating temp (maybe 30 minutes run time) was primarily to make sure everything sounds good, check for leaks, get good oil pressure and temp readings on the gauges, and dial-in the timing and carb settings. Some say don't let the motor idle much longer than it takes to adjust timing and carb --- then keep it moving around a bit --- but not racing. Then shut down and get the important re-torque of the head done. Then drive it asap to get the rings seating properly.

Everything I read says to be sure to use break-in oil with ZDDP at the correct concentration (too much isn't better). Some folks recommend immediate oil and filter change after initial start, some say after 100 miles, others say after 500 miles. Never read anything in the manuals specifically about cam and tappet break-in for the L134 and mine are new too.

Post by **wesk** » Thu Sep 10, 2020 10:23 am

Since you have almost twice the normal cost in you 134 overhaul I suggest that you start communicating with quality engine overhaul facilities for a technical explanation of what the incremental run up periods are for and how to do them. In the mean time why don’t you contact Ryan & Keith Buckley for a presentation of what foundry and production run ups were used during that period.