There are a number of urban legends in this thread which are bad information. What follows will attempt to correct them.
1) Shell Rotella T has 1100 PPM ZDP. That is more than adequate to lubricate most any flat tappet, OHV valvetrain.
2) That ZDP has been removed from Rotella T is incorrect information. In fact, the idea that all ZDP has been removed from engine oil in general is a laughable myth propagated by the additive makers. It is true that, in some
but not all cases, ZDP content has been reduced, but it has not been eliminated. In other cases, it remains at high levels.
3) As for diesel engine oils, specifically, there are rumors in the hobby that the spec for diesel engine oil is soon to change and that will eliminate or dangerously reduce ZDP. That's another freakin' fairly tale.
While CF-5 has yet to be announced, the ILSAC-Oil Committee has stated that the new spec will retain the CF-4 limit on ZDP.
4) If the application is an OHV, flat-tappet engine with any modifications to the valvetrain which increase pressure at the lifter/lobe interface beyond stock, both Shell Rotella T 10W30 and Chevron Delo 400 LE 10W30 are cost effective choices for engine oil offering long term durability. Shell is the best of the two because it's the one that's available in quarts.
5) The statement above...
I dump in a bottle of Comp Cams break in lube at every oil change.
...is foolish and dangerous advice.:bash
You are far better to use the right oil to begin with.
That said, additives are deeply-rooted in automotive culture and some Vettesters, regardless of the facts, will insist on "fortifying" mass-marketed engine. If that's you, at least pick one with known contents. That way, you can add the correct amount to gain the appropriate phosphorous level.
"Cam Break-In" from COMP Cams was engineered as a break-in supplement and not as an additive for regular use. While not intended as an additive to boost an existing oil's EP lubricity in regular use, it can improve oils with low phos content
provided it's used properly. I analyzed it and found: 1) it's active ingredient is molybdenumdithiophosphate ("MolyDTP") rather than ZDP and 2) its nominal phosphorous content is 8400 PPM. "Cam Break-In" has way too much MolyDTP in it to be used one bottle per oil change. In fact, mixed to that concentration, in long term use, you may damage your engine. If you insist upon trying to fortify a ILSAC GF-4/API SM oil, which typically are at about 700 PPM phos., add 1 1/2-oz of COMP break-in additive per quart of oil to bring a GF-4 to 1100-1200 PPM phos. Once you get beyond 1500-1700 PPM in a street duty cycle, you risk long-term damage to to accelerated "chemical wear" of the cam and lifters.
6) The statement above...
I use the ZDDP additive as well. Buy it right off eBay.
...is just as dangerous.:bash
There are no standards of any kind for "ZDDP additives". You buy off eBay and you know no idea how much ZDP (if any) is in an additive or how other components in the additive will interact with the oil into which it's introduced. It is not wise to use any ZDDP additive. There are plenty of oil choices that have superior extrememe pressure (EP) lubrication. But...if you insist on an additive, see my above comments about using one for which content information is known.
7) The statement above...
an alternative would be the mobil1 15w50
their website says it has 1200ppm zinc for flat tappet engines.
...is correct in that M1 15W50 is an "alternative". Problem is: it's not a good alternative. No Corvette engine...well, other than maybe a few very unusual race engines...needs a 15W50. In most cases, 50wt oils increase engine oil temperature and decrease oil pump reliability/durability. The best choice is a 10W30. If you insist on a "Mobil 1" branded product with high ZDP, the one to use in most cases is "High Mileage" 10W30 which has 1000 PPM ZDP.
8) For pre-86 engines with stock valvetrains which are in fully broken-in and in good condition, you don't need any special oil.
9) The problem comes when you make mods to the engine which increase static or dynamic pressures at the lobe/lifter interface over O.E. levels or you use a cam or lifters which are not manufactured to the same specs as OE. Examples are aftermarket "OE-replacement" cams which are not properly phosphated, aftermarket cams with any profile more aggressive than stock, aftermarket lifters from questionable sources, higher-ratio rocker arms and aftermarket valve springs. Once you and any of those parts, you need to use an oil with 800-1200 PPM ZDP.
10) Suggestions for flat tappet engines in all but the most aggressive, all-out, racing applications:
Good
Shell Rotella T 10W30 (1100PPM phos), Chevron Delo 400LE 10W30 (1100 PPM phos), Mobil 1 "High-Mileage" 10W30 (1000 PPM phos)
Better
Valvoline VR-1 10W30, Joe Gibbs Driven "Hot Rod" 10W30. (both 1200 PPM phos)
Best
Red Line Synthetic Engine Oil 10W30 (ester-based and 1200 PPM phos)
