AMC V8 Oil System Modifications
Let's start with the basics; the goal is perfection. There is no perfect engine. A perfect engine would run forever, flawlessly. Since we have no perfect engine that will run forever, the next best thing is to improve durability to make it run longer without failure.
Highly educated engineers design engines and that process results in what is called a 'blueprint'. The blueprint is the master design, but in many cases compromises are made in order to manufacture the engine at a more affordable cost, hopefully passing on the lower cost to the consumer without reducing the overall attributes or quality of the master design.
The primary purpose of this article is to describe and explain various modifications which can be performed fairly easily by a mechanically inclined 'do-it-yourself' type person to improve the oil system of the AMC V8 engine, whereas the greater bulk of this information relates to the process of what is called 'blueprinting'.
The larger portion of blueprinting an engine is done with very specialized machine work, measuring tools and carefull assembly. All components are checked and/or corrected to match the design engineer's specified critical dimensions. There are tolerances and preferred dimensions. Preferred dimensions generally take more time to perform but will increase the durability of the engine.
Mr Clifford, who founded 'Clifford Performance 6=8', earned his racing fame by meticulously blueprinting and racing the otherwise bone stock Hudson inline six cylinder engine; no aftermarket add-on 'high performance' parts, he just championed all his competition with unbeatable anvil-like durability and consistency.
The term 'balanced and blueprinted' used to be a 'bragging-right' description of one's engine in their car. Could it be that the process of selecting and buying aftermarket parts has slowly taken over, to overshadow what was once a basic common knowledge component part of building up any engine to have 'high performance' attributes?
Have auto enthusiasts been educated to sort through the details of aftermarket high performance parts selection instead of starting with the basic preliminary details of building a superior engine?
Perfection is the goal. Durability is foundational, to preceed the addition of more power. Adding more power to any engine will place a greater load upon it's components until one finds it's breaking point, even if the load placed upon that engine is merely the weight of one's foot upon the gas pedal, as in racing.
When AMC got back into racing with their all new '66-up AMC V8 engine after the Rambler days, it must be admitted there were more than a few engine failures in their earlier Trans Am and NASCAR attempts. If I remember correctly the Penske and Donahue team solved the former TRACO blamed engine failure problems with a belt driven oil pump drawing oil from a dry sump type pan, TRACO getting somewhat of an ill reputaion for building AMC V8 engines wrong.
AMC did not win Trans Am until Penske/Donahue did the dry sump modifications, and AMC did not do well in NASCAR until Mr Allison got interested in the '74-up aerodynamically designed Matador body style. It was during that period when Mr Allison began to win races with the Matadors that the 'valley line' oil tube modification became known; I did not invent the oil line mod, but I heard of it as being one of Mr Allison's team inventions to make the AMC V8 survive sustained high rpm use.
So when I decided to build a 7500 rpm AMC 360 for my '69 AMX (The '71 issued AMC bible of performance build up techniques named "Performance American Style" stated not to use the factory cast nodular iron rods in an engine to run beyond that rpm), I considered to make a careful study of the AMC V8 engine's oil system to understand where to install the internal oil line since there were no commonly circulated instructions how to do it at that time.
Partly due to my own guilty conscience for having 'blown' other AMC V8 engines in the past and partly due to acculmulating knowledge and experience from my studies of a variety of engine oil systems, 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- oil delivery to the rear of the engine. In my opinion, placing restrictions, such as smaller cam bearing lube holes only creates new restrictions, which is a primary factor in this engine's problem of inadequate lubrication to the rear of the engine. To the best of my knowledge, the restriction on the outlet side of the oil pump due to the undersized factory drilled hole should enlarged and this should be the first modification for a 'performance' AMC V8 engine.
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 then new '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 farthest from the pump receive adequate lubrication..."
Rather AMC's later '66-up 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.
In contrast, the Rambler V8 oil system has the oil pump purposefully mounted directly to the rear main bearing cap, pushing oil first to the cam and main bearings first from rear to front, then dividing into galleries to serve the valvetrain, whereas the rear is the hottest, most stressed out part of the engine. Moreover, hot oil flows easier.
From there in a Rambler V8, the pressurized oil then goes up to feed the rear of the central oil gallery which has factory drilled holes down to, and around the cam bearings and on to the main and rod bearings through the drilled passageways in the crank. At the front of the engine, the pressurized central oil gallery then splits into two smaller machined channels in the cam thrust plate, acting as a slight restriction, to feed the lifter galleries next, from front to rear. The Rambler V8 designers then tapped the rear of those lifter galleries through a drilled head bolt for oil supply from rear to front for the rocker shaft, the engineers expaining that by doing so it helps to purge otherwise stale oil from the rear of the lifter galleries, to reduce sludging.
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. The valley baffle/intake gasket helps to direct poured in oil onto the rear main and prevent oil from being scalded by the intake exhaust crossover.
All AMC engines came factory equipped with umbrella type valve stem 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...)
The '66 -up AMC V8 oiling system design is a near copy of Buick's '62 V8/V6 design, having an external front mounted oil pump on the lower side of the aluminum timing cover. This arrangement moves the hottest running and most stressed out rear engine bearings farthest away from the oil pump which is not exactly ideal for a high rpm performance type engine.
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 approximate drill size of the main delivery oil passageway into the engine is my recommendation. If one does not have an extra long rotary file, a similar job may be affected by just using a big drill bit 'pushed sideways', to enlarge the hole as shown in the first drawing below.
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 bigger name for himself racing those Buick V6s and the mod he used to make was to cut a tiny groove in the front cam bearing, to help shed a slight bit more oil behind the upper cam chain cog, this then would plausibly create better splash oiling from being slung from the upper cam gear rotating double speed. I would not recommend this mod for the AMC V8.
Do 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! Double check the cam snout stacked assembly with a small lump of clay when dummying on the timing cover, whereas on the AMC V8, the cam walk button is a machined flat inside the cover... if the stacked height ain't right, you're gonna have some tore up parts right there. The factory AMC cam bolt has cut grooves in the head for lubrication; the head of the bolt functions as 'the cam button'. Don't substitute a different bolt! Just torque the stock bolt, not to stretch it, as centrifigal force holds it tight anyway.
My '71 AMC Technical Service Manual states 'the helical cut for the distributer drive gear works with the pressure from the oil pump to control camshaft endplay by keeping it in contact with the front face of the block' ...therefore if the oil pressure is weak, cam walk/endplay will depend more on the cam snout stacked height.
Another consideration is the angle of the hydraulic or solid lifter ground lobes which provide postive lifter rotation; ground the wrong way, all sixteen of the lobes could work in harmony to produce a slight forward thrust, placing more load upon the cam button area, plausibly even more forward thrust with stronger aftermarket valve springs... but I don't know for certain the direction of the cam lobe angles that provide lifter rotation... yet so this theory of mine still remains as speculation. Please correct me if I'm wrong on this matter.
Text notes still 'under construction'... feel free to Email me at firstname.lastname@example.org
Hopefully common knowledge among AMC enthusiasts, the 'angle type' oil pump cover/oil filter mount is preferred to the older 'corner type' because the oil filter outlet passageway of the angle type has no abrupt corner to hinder flow. (a hydraulic engineer would say this is of no concern, but AMC engineers did make the revision -evidencing the idea of modifying the oil system galleries to have smoother transitions at intersecting passageways.
BOTH TYPES; the angle type and the corner type feature a mismatched output passageway to the oil filter.
The botched corner union can easily be cleaned up with a rotary file 'chucked for full extension' in a hand held drill. Exercise care not to destroy the oil filter threaded connector threads in the aluminum cover/filter mount while poking the rotary file in there to smooth out the corner. Both ends of the steel two way threaded connector may be chamferred to round off the crude square shouldered passageway through it.
The output port from the oil filter back to the cover is missing, in the drawings, from the total lack of concern about it, as there is nothing to be modified there, except to switch to the angle type filter adapter.
Oil pump gear protrusion 'above' oil pump gear cavity with no gasket is .0025" to .0065" factory spec. Oil pump gear side clearance is .004" to .006" factory spec. as noted in the '71 AMC TSM.
Feel free to Email me about any oil system concerns or corrections at email@example.com