AMC V8 Oil System Modifications

Introduction; While it's oil system is adequate for stock engines, the '66 -up AMC V8 design is a near copy of Buick's '62 V6 design, having an external front mounted oil pump on the lower side of the aluminum timing cover, but with two more cylinders added on to the rear, this arrangement moves the hottest running and most stressed out rear engine bearings even further away from the oil pump which is not exactly ideal for a performance type engine. For engines that are built to run at higher rpm speeds, I have put together this information to help solve the AMC V8's tendancy to 'throw a rod' when run at sustained high rpm. In my experience, the AMC V8 typically throws it's five/six rods first, and this is solved by -increasing- to oil delivery to the rear of the engine. Placing restrictions, such as smaller cam bearing lube holes only creates new restrictions, which is the primary factor in this engine's problem of inadequate lubrication to the rear of the engine; a restriction on the outlet side of the oil pump.

For an AMC engineer's partial explaination of oil system theory (not amateur speculation) read here. Thanks to WPS for posting Greg Taylor's old pages. It may be noted in the discussion about AMC's '56 Rambler V8 that the engineer states "It can be seen that the main bearings are fed prior to any oil being bled off to another location. This ensures that the bearings fartest from the pump receive adequate lubrication..." Rather AMC's later '66 V8 design feeds oil first to the lifter galleries, bleeding off oil feed to the valve train, then to cam, crank and rod bearings secondarily.

Actually, in theory, the AMC V8 oil system is backwards.

However, the AMC V8's oil system nevertheless features a few excellent, even superior design elements; carefully engineered oil squirts from the 'big end' of the rods to lube the underside of the pistons and cylinder walls with factory stock windage/baffle in oil pan, plus carefully shaped valve covers to positively redirect the oil squirts from the push rods back down onto the rocker arm tips atop the valve springs.

As far as I know, only Buick engines at the time featured oil squirts from the rods to positively lube the pistons and cylinder walls at the time, having examined many other make engines myself, and never found them... Oh, early Ford Winsdor had them too...

All AMC engines came factory equipped with umbrella type valve seals.

Both the Rambler V8 and the AMC V8 have 'oversized' oil pump gears, compared to a stock Chevrolet oil pump set which looks to be at least one quarter inch shorter in length (that engine needs a replacement high performance type pump for high rpm use, and to install Cadillac valve seals...)

Step One

The first thing -begging to be modified- is the output hole of the pump gear cavity. AMC engineered a fine aluminum multipurpose timing chain cover/oil pump casting, but the design suffered from a 'fast build' production method where the oil outlet from the gear cavity is a drilled hole, unfortunately smaller than the main oil passageway up to the lifter galleries... the small drilled hole functioning as a restriction, limiting the entire operation of flowing oil through the engine. Upon close examination, the astute observer may see this drilled hole near the roof of the gear cavity, the round hole serving as the opening into a "D" shaped passageway. Ultimately, the modification to the drilled hole would be to file away all of the restriction to have no restriction into the "D" shaped passageway. Simply opening up the size of the drilled hole, at least to the drill size of the main delivery oil passageway into the engine is my recommendation. If one does not have an extra long drill bit this size, a similar job may be affected by just using a big drill bit 'pushed sideways', to enlarge the hole. Though I have never personally experienced a problem with galling of the idle gear location shaft of the oil pump gear set, it would be relatively harmless to drill one small lube hole in the valley between two teeth. Slightly chamfered, this would ensure the non-driveshaft gear would not sieze on it's shaft. It would also be harmless to gasket match the output passageway from the pump to the block, using a rotary file chucked in a drill, helping ot aid flow by reducing any churning effect, even adding a rather insigificant bit of volume to the no leak down side of upcliming main oil passageway before it divides to the two lifter galleries. Always pack the oil pump gear cavity with petroleum jelly after serviciing the unit to ensure self priming upon startup. If one has built up an expensive performance type engine, or even just for newly reconditioned engine, a easy homemade drive shaft cam be fabricated from 3/8" copper tubing, one end hammerd flat, that end inserted into a short length of 3/8" rubber tubing, to insert the homemade tool down into the distributor hole to pre-pressurize the oil system using a hand held drill. If one has no mechanical oil gauge, when the oil light goes out, you'll know most of the otherwise empty oil passageways have oil at about 10 psi -better than a 'dry start'.

I would not recommend to drill a small hole in one of the lifter gallery plugs behind the upper cam gear. This notion perhaps stems from the AMC V8 design being similar to the Buick V6 design, and those engines built up for high performancd showing a need for additional timing cover lubrication. Kenne Bell made a name for himself racing those Buick V6s and the mod he used to make was to cut a tiny groove from the front grooved cam bearing, to help shed a slight bit more oil behind the upper cam chain cog, this then would plausibly create better splash oiling for being slung from the upper cam gear rotating double speed. I would not recommend this mod either for the AMC V8.

Why fix something that ain't broke? -I have never had any trouble from an AMC V8 in the timing cover lubrication areas. Whenever I hear of someone who has, my first two suspicions are that 1) the assembled length of the upper cam gear assembly is incorrect -to allow excessive cam walk, this then would cause misalignment of the distributor drive gear set causing the gears to grind away (more common), or to 'jump time' and damage to cam chain and gear set. The fix being to merely make sure to use the factory bolt and washers on the upper cam gear assembly... and not to forget the factory supplied oil slinger on the lower gear!

Text notes still 'under construction'... feel free to Email me at rkt@fbg.net