Post
by Bleyseng » Sun May 02, 2010 3:17 am
From HodRod mag:
"Flat Tappet Cam Tech - Righting the Wrongs
Flat tappet cams have been failing at an alarming rate lately. We dig into what causes these failures, how to fix them and how to prevent future failures.
From the February, 2009 issue of Hot Rod
By Marlan Davis
For the last several years, many engine builders and individual hotrodders have experienced a raft of seemingly unexplained flat-tappetcamshaft lobe failures. As one engine builder puts it, "I've failed morecams in the last three years than I have in the last 30." There areseveral theories as to the primary causes of these failures, and withall the usual finger pointing and blame game such unfortunate episodesinevitably generate, the result has been a muddying of the waters that'sleft average hot rodders confused and uncertain as to the best course ofaction. What's the real source of the failures, and more importantly,rather than whining over spilled oil, what can be done to minimize theoccurrence of these failures? Various parties have blamed camshaftmanufacturing quality control, inferior flat-tappet lifters, theaggressiveness of today's modern cam profiles, and engine oilformulation as the primary factors behind the failures. What we know forsure is that the most serious complaints have cropped up within the lastthree years or so, around the time that major changes occurred in boththe flat-tappet manufacturing industry and in the formulation ofpassenger car and light-duty truck motor oils.
The Great Lifter Shortage
New automobile manufacturers basically call the tune when it comes tosupplier capacity and even motor oil composition due to the OEMs' hugeproduction volumes in comparison to aftermarket requirements. Flattappets are not used in today's new cars. All current pushrod enginesuse roller tappets, while overhead-cam motors use either rolling orsliding tappets. From the standpoint of the traditional lifter-supplycompanies, five years ago it looked like there was no future in theflat-tappet lifter business -- the projected volume was insufficient tojustify investing in new tooling and equipment.
As Survival Motorsports'Barry Rabotnick puts it, "Go back five years ago and there were a bunchof U.S. companies making flat-tappet lifters -- Eaton, Delphi [GM],Stanadyne, and Hylift [Johnson]. Within about a three-month window, twoout of the four went out of business. Eaton decided it no longer wantedto be in the flat-tappet business --there was no volume -- and it soldout to Stanadyne, which initially added no capacity and in fact shutEaton's line down. Hylift -- the premiere supplier of Johnson lifters tomajor cam companies as well as aftermarket suppliers such asFederal-Mogul -- went through one of those corporate scandals we'vesadly become all too familiar with before going bankrupt."
This led tothe flat-tappet lifter shortage the industry experienced several yearsago. GM was still in business, but it made lifters primarily for GMproducts, and they were pricey. As a major OEM supplier, Stanadyne hadother fish to fry and initially did not increase its flat-tappetproduction capacity. Cheap, poorly made offshore lifters flooded in totake up the slack. Most of these inferior lifters had questionablemetallurgy, a poor surface finish, and an improper crown radius. Butthey were affordable and available.
Major cam companies, including Compand Crane, maintain that they never sacrificed lifter quality or soldinferior lifters. "We figured we were better off selling nothing thanselling junk," says Crane's Chase Knight. Yet some engine buildersinsist there was a definite durability difference in lifters producedprior to '01 compared to some later production runs. At present, GMcontinues in business with a good lifter, Stanadyne has finally gearedup again (it currently has about 70 percent of the lifter market), andJohnson is back in business. But the off shore stuff still permeates themarket, and many budget hot rodders are tempted to use them even onname-brand cams because the price is so low compared to the qualityU.S.-made parts. Unfortunately, without lifter disassembly, it's nearlyimpossible for the average hot rodder to identify its manufacturer --and, hence, its quality. One exception is genuine GM/ACDelco/Delphitappets.
Around the time of the flat-tappet lifter shortage, motor oil was experiencing its own changes. Engines with flat-tappet cams haveextremely high pressure loading at the contact point between the liftercrown and the cam lobe. According to Mark Ferner, team leader for QuakerState Motor Oil Research and Development, "Even stock passenger cars cansee pressure in excess of 200,000 psi at the point of flat-tappet/camlobe contact." To prevent excess wear, traditional motor oil included agenerous dose of antiwear additives, primarily zinc dialkyldithiophosphate (ZDDP). "The chemistry is such that the additive is acombination of zinc and phosphorous," says Rockett Racing Fuel's TimWusz. "Typically the phosphate amounts are about 75 percent of the zincamounts. For example, if there was 0.100 percent zinc by weight in themotor oil, then the phosphate is about 0.075."
Ferner adds, "The zincreacts with the cam lobe's iron surface. That creates a sacrificialchemical coating strong enough to keep parts separated to reduce thewear." Although great for keeping a flat tappet alive, as an engine agesand develops blow-by, some of the additives flow out the exhaust wherethey can degrade oxygen sensor and catalytic converter performance.Faced with ever more stringent emissions standards and the governmentalmandate for extended emissions-control- system warranties, the OEMs gottogether with the motor oil makers and decided to reduce the amount of ZDDP in street-legal, gasoline-engine motor oils. After all, theyweren't needed with modern roller lifters and overhead-cam followers.The reduction first started in the mid-'80s, and it has been a gradualprocess, but the latest API SM and GF-4 specs have reduced ZDDP contentto such an extent that the new oils may not provide adequate protectionfor older, flat-tappet-equipped vehicles running nonstock, performancecams and valvetrains. And it will only get worse; projected future oilspec revisions will likely reduce ZDDP content even more."
My question is "What oil was used that did the damage to the bearings?"
Geoff
77 Sage Green Westy- CS 2.0L-160,000 miles
70 Ghia vert, black, stock 1600SP,- 139,000 miles,
76 914 2.1L-Nepal Orange- 160,000+ miles
http://bleysengaway.blogspot.com/
