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Discussion Starter · #1 ·
I've been running Delo 15w40 but for a short time. I have a question though, We all know that their is correlation between zddp and cam life. Does the thickness of an oil having anything to do with protecting the cam(ex 10w30, 15w40, 20w50). Say in warmer climates, will a 20w50 with the right zddp protect a cam with high spring loads better than say a 15w40?
 

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James,of talking flat tappet cam protection one thing that comes to mind for me i sthat thicker 20w-50 oil can take a little longer to pump up on initia startup,likely not a biggie but a fact.

But if you have bearing clearnces on the tight side there will be less oil thrown off the crank then lets say with a lighter 15w-40 and the oil thrown of the crank iis also part of the oiling system for the cam/lifters.

The same goes for oil to the lifters,if the lifter bores clearances are tight there will be less oil escaping there for oiling the cam/lifter interface too and thats where EDM lifters can help when running a wild flat tappet cam with high spring rates.

How much this will effect the proper oiling of a flat tappet cam i cant tell you for sure but uisng a 15w-40 oil is good comprimise if you dont know your clearances. Thats becasue the 15w-40 is thick enough to deal with wider clerances better then lets say a 10w-30 but its also thin enough to deal with tighter clearaces then the 20w-50 can.

The 15w-40 is kinda in the middle of the 10w-30 & 20w-50 oil when it comes to viscosity.

But as far as which oil will protect better when its squeezed on hard inbetween a lifter and cam lobe with high spring rates i beleiev the 20w-50 may win out. But thats at the disadvantage of taking longer to pump up when cold and more importantly less oil thrown off the crank & less oil cmming from the lifter area for oiling in general. So if you now you have wider clearances you should be ok but if you dont know the clearances or if the motor is new with likely tighter clrearances i would op for the 15w-40.

And all this was assuming all else was fairly = as far as zddp goes.

Just my 39cents (LOL!!!)

Scott
 

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Discussion Starter · #3 ·
As always, thanks for replying Scott. My 400 was built in 2001. I remember that the mains were .0015 and the rods where .002. However this was from plastigauge which I don't think is very accurate. However, I don't feel that my oil pressure indicates that tight of clearance. In hot Texas weather, oil pressure will go down to 15 psi at 800 rpm with 15w40 and about 55 psi at 3500 rpm. If I remember correctly, 20w50 in the heat will be around 20 psi at 800 rpm and will jump up to 60 psi around 2500 or less. This is with a 60 lb pump, 274 XE cam and cc995 springs, 330+ open spring pressure. Pontiac 400s have 3 inch bearings. FYI, the car has 4.10 gears and cruise at about 3500rpm on the highway.

I guess Like you said Scott its kinda of a give and take with this motor. It does start easier with the 15w40 and on the upper end of the rpm my speedometer needle is really moving compared to the 20w50. But one thing I notice with the 20w50, my car hits harder in the gears(t400) compared to the 15w40. Is this due to the rings sealing better with the 20w50 and better compression?
 

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The viscosity of the oil will have no direct affect on camshaft protection, nor the ability to make rings seal any better or worse. Camshaft longevity (after initial breakin) is a factor of extreme pressure capabilities of the oil "package". The oil package is defined by the base oil product plus additives.
Oil viscosity may have an indirect affect on camshaft longevity, due to the fact that a lower viscosity oil may circulate quicker in a cold start situation and may be thrown from the rods to the cam more efficiently, as Scott has pointed out.
 

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Discussion Starter · #5 ·
Thanks Bill and Scott again. I'm somewhat ignorant to this stuff. You've shed some light on this for me. So, I probably should stay in the middle of the road and stick with the Delo 15w40.
 
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