| Index Home About Search for Google's copy of this article Index Home About From: jgd (John De Armond) X-Source: The Hotrod Mailing list Date: Apr 1992 Subject: Re: Breaking in is hard to do? >I've built a lot of motors over the years, sometimes with all new parts >and sometimes not. What I try to do is apply a liberal coating of moly- >disulfide grease (cam lube) to the lobes and the bottoms of the lifters. I use a mix of Dow Moly 77 dry moly disulphide and STP mixed to a thick paste. Much cheaper than cam lube and seems to protect better. >I install the lifters cylinder by cylinder according to the firing order >and adjust them as I go. If you start at TDC of the power stroke for the >first cylinder, you'll only need to go thru two revolutions of the crank >to do all cylinders. Of course, this wipes some of the grease from the >first lobes, but not enough to hurt. > >The main thing you should try to avoid is excessive cranking to get the >engine started the first time. I pre-oil with a modified distributor, >prime the fuel system all the way to the carbs with an electric pump and >make sure my timing is close by lining up the rotor with the cap. With >any luck, the engine will fire almost immediately. Bring the rpm up to >about 2000 with the idle adjust and let it cook for about 15 minutes, all >the while keeping an eye on oil pressure, water temp, leaks and etc. A >buddy is real valuable at this point! This is what I call hairy edge engineering. My perspective is that if an assembly is that close to the edge, something should be changed in order to provide some margin for error. All these techniques are good ideas, don't get me wrong. It's just that I'd never be comfortable knowing that serveral hundred dollars worth of cam and lifters is riding on me getting it just right. The one thing I've not seen mentioned in this thread that I thought was common practice is the use of breakin springs for assembly, setup and runin. These are very weak springs (I make my own on my spring winder but they are available from various sources) that exert maybe 50 lbs of closed pressure. They provide enough tension to hold the valves shut at low speed. Just assemble the engine normally except use these springs, run the motor in as described above and then change the springs using a head-on spring tool and compressed air in the cylinders to hold the valves in place. I always run my engines on the stand before installation so it is fairly easy to change springs after runin. Another technique I use is vacuum to get oil up through the system the first time. I take an oil filter, cut the can off and braze a SAE flare fitting so that it connects to the oil inlet. Then I connect my refrigeration vacuum pump to the fitting and suck until oil comes out. This ensures there is oil in the oil pump and all the galleys up to and including the oil filter. If the oil filter is then filled with oil before installation, oil pressure is immediate. This works even on engines where it is hard to get to the oil drive - japanese engines, for example. John From: jgd (John De Armond) X-Source: The Hotrod Mailing list Date: Apr 1992 Subject: Re: Breaking in is hard to do? >> Another technique I use is vacuum to get oil up through the system >> the first time. I take an oil filter, cut the can off and braze a >> SAE flare fitting so that it connects to the oil inlet. >Most of us don't have access to such things as $300 and up vacume pumps. Having access to the proper tools is as simple as buying or borrowing the tools. Not being willing to do that is no excuse for not doing it right. >What I do to prime and engine (since none of the engines i work on can >be primed by the internal oil pump: 911, Datsun L,VW air and water...) >is just take a bottle with a pointed squirt end. Like the ones that >gear lube comes in. Fill it with oil, remove the oil pressure sender, >insert and squeeze. It works great! I make shure oil comes from the >cam squirters, crank, etc. It's low cost, and very affective. This does NOT prime the oil pump. This fills the relatively low volume galleys downstream of the oil filter. The oil follows the path of least resistance which is out through the rod and mains and to the cam towers. It does NOT flow back against the considerable resistance of the oil filter and the close tolerance pump. I have tried this technique with more sophisticated apparatus in the form of a small tank pressurized with shop air. Even with this high pressure system, I found little oil upstream of the filter. >Why reinvent the wheel? One reinvents the wheel when the original one is broken. My use of vacuum is not an idle decision. Here are some reason: * Vacuum expands air bubbles, allowing oil to displace them when the vacuum is broken. * It actually primes the suction path to the pump and removes all air from the pump. * There is no risk of accidently introducing foreign materials into the engine, particularly downstream of the filter. One plastic shaving from that squeeze bottle is all it takes to trash a bearing. * Any debris that may be in the oil galleys will be flushed OUT of the system and into the vacuum system. This method does NOT charge the galleys downstream of the filter. In practice this volume is small enough that oil can be seen at the cam within a couple of revolutions during cranking and usually before the engine fires. If for some reason the downstream volume is high, such as with an external oil cooler, then I turn the engine slowly (break in springs on the valves, remember?) until oil flows from the bearings. A variable speed 1/2" drill fitted with an adaptor to the crank works well for this. John From: jgd (John De Armond) X-Source: The Hotrod Mailing list Date: Apr 1992 Subject: Re: Cam break-in >set of springs and lifters. In general, for all but the most agressive >cam designs, the recommended springs have moderate rates. For cam profiles >designed for the street, I've never encountered a spring with enough >pressure to shear the oil/lube film and cause failure during run-in. I'm >not saying it couldn't happen, but if it did, I can't say I'd feel real >comfortable the second time around with lighter springs as the "fix". Why would that be? Why would you be uncomfortable giving the surfaces a chance to mate before subjecting them to working pressures. This is little different than the well known fact that newly fitted pistons will often seize if fully loaded before being broken in. >You also mentioned the use of STP as one of the ingredients in "Dr. John's >Fantasmagloric Cam Paste". I try to refrain from knocking products (see >the Slick 50 flame wars in r.a.t.), but I wouldn't use that stuff if Andy >Granitelli was my dear old dad. The only cam I ever saw "go flat" during >break-in had the lifters dipped in STP prior to installation. Two motors >were built side by side using identical components in the same shop, one >used moly-disulfide, the other STP. The one with the moly lube ran all >season (circle track), and so did the other as soon as the cam and lifters >were replaced and run in with moly lube. You are aware, I hope, that Dow Corning Moly 77 IS PURE powdered moly disulphide? I would not trust STP - or any other liquid - alone on high shear applications like cam lobes. The combination works really well. The moly gives the needed extreme pressure protection while the STP provides a very strong film strength. >I know it's not always scientific to tailor your behavior based on some >one else's experiences. You usually don't have access to all the factors >that led to the destructive event; which makes it easy to draw incorrect >conclusions. With regard to STP, what I saw convinced me to steer clear >of the stuff. A minor point of interest. I saw several top fuel mechanics this weekend using pure STP as the assembly lube. ... Mmmm damn, memory is failing me. I dictated notes to my pocket dictaphone but it's in my wife's car. I'll cite some specific names as soon as I retrieve it. >Most cam manufacturers specify moly-disulfide and some even recommend the >use of GM's Engine Oil Supplement (as Ron mentioned). I've always had very >good results with this approach. I've had 100% good luck with my mix in the 20 years I've been using it. This includes engines that were delivered directly to customers, a result of which was I had no control over the breakin. I have no doubt that today's commercial breakin lubes are as good. When I concocted my mix, moly was very new and not generally available and "cam lubes" of the day sucked bilge water. The reason I continue to use and recommend it, aside from the fact that it works, is Moly 77 is fairly cheap if bought from an industrial wholesaler (no automotive markup) and a 1 lb can will last a lifetime. A related lube I use for ball and roller bearings (mostly a motorcycle issue) is Moly 77 in vaseline. The vaseline is thick enough to stick around to get the engine running and then dissolves in the oil without residue like grease would leave. John From: pumaracing@aol.com (PumaRacing) Newsgroups: rec.crafts.metalworking Subject: Re: Help with cam lobe destruction Date: 31 May 1999 16:24:57 GMT For some reason I can't see the original post to this thread. However, the theory and practice behind cam follower design and break in procedures is as follows. Pushrod engine type followers have a radius of about 1 metre ground on the running face. They are also offset from the centreline of the cam lobe by between 1 and 2 mm. The cam lobe is ground at an angle of around 3 thou per inch to ensure initial contact towards the side of the follower. The combination of angle, radius and offset ensures that the follower rotates to even up wear over the entire running surface. If a follower stops rotating it wears out in very short order. The break in procedure is not just to "match" the follower to the cam lobe as is commonly thought. It is also to work harden the surfaces for which cast iron is an excellent material. The high point loadings rapidly compress the surface skin of the lobe and follower and create a hardened skin which then resists wear. All cam systems wear at a given rate during their service life and the rate of wear depends on lubrication, material hardeness, regularity of surface finish and other factors. The aim is to reach a rate of wear at which the freshly exposed metal work hardens quick enough to resist further wear. If the follower stops rotating or the lubrication boundary fails then wear takes place faster than hardening takes place leading to catastrophic failure. Modern overhead cam engines running on bucket followers use hardened steel as the bucket material and these are ground flat not radiused although there is still an offset to ensure rotation. Break in procedure is to coat the running surfaces with molybdenum disulphide lube and then run at 1500 to 2000 rpm for 15 to 20 minutes. Low speeds create high point loadings and high speeds create rapid wear rates. Intermediate engine speeds allow work hardening to take place without excessive point stress on the parts. 99% of cam failures are due to inadequate break in procedures. Dave Baker at Puma Race Engines (London - England) - specialist cylinder head work, flow development and engine blueprinting. 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