Explaination of the top end oiling problem
Dodge Racing Products
attn: Dave Dodge
16503 Glenfurness Drive
Huntersville, NC 28078
Tel: (704) 892-7961


Through the many years of working with the Honda V-4 engine, the main problems causing cam and rocker arm failure is the lack of a good oil supply and also the way the valve adjustments are done. Since the beginning Honda has made many upgrades to the materials, hardness, etc., but the problem can still occur at any time.

The stock top-end oiling system is low pressure, low volume and unfiltered. One thing that most people overlook is that the top-end is getting it's oil supply from the low pressure side of the oil pump, and to build the pressure to an acceptable level the oil passes through a nozzle with an .080" hole which equals less than 25% of the ID of the metal hoses it feeds. If the oil is not changed regularly, debris can be passed through to the heads which can cause cam journal grooving. Also, when the engine is at idle the pressure can sometimes drop below 8 psi meaning that sustained idle time can cause wear that progressively gets worse. Next is valve adjustment. Because the stock oil system feeds no substantial volume, tight valves can actually wipe the oil from the lobes and rocker surfaces causing even more wear or cam pitting. This is why Honda increased the clearance spec from .004" to .006". When the engine is at running temp., valve clearance is reduced as much as .003" from part expansion. The entire surface of the cam only gets lubricated at the point on the heel of the cam where you have clearance.

There are even occurrences where an engine and cams will be fine for 30K or more miles then all of the sudden cams fail. This can be caused by the last valve adjustment, or a weakened oil pump. An oil system that is barely good enough to begin with can cause problems as the pump loses it's full pressure from wear.

Now with all that out of the way, the cure would be to install a top-end oil system. Whether it is an adapter style or main galley tap, you will be using a high pressure, high volume source of filtered oil. Yes there are many versions of do-it-yourself mods and other companies that produce kits. I have been making and selling these kits since 1982, and offer 3 main styles including the ones you mention. My kits are the only ones available that actually increase idle oil pressure after installation. Even though you do not race, you benefit from my years of beating on these engines which leads to products that far exceed your needs.

I offer three styles of kits which are all designed to provide the best function and fit, at the lowest possible price.do-it-yourselfer.

The kit I am selling the most of right now is my bolt-on filter adapter style oil mod kit. It is similar to the Holeshot unit, but I have made some important improvements, such as, adding an o-ring around the center bolt for better pressure retention and no chance of un-filtered oil entering the main galley. We also use metered feed lines with angled banjo hose ends to better clear the coolant pipes. This kit sells for $249.00. This kit is considered a bolt-on, but does require radiator removal to access the top-end hose connections.

Option 2 is my original DRP drill and tap style. This kit requires you to drill and tap an 1/8 NPT hole in your engine cases for the main supply. The feed supply hose is size #4, to a special made junction block that splits into 2 size #3 hoses and uses the same angled banjo ends as above. This kit sells for $159.00. This is the least expensive, but the hardest to install and requires some long tooling to complete the job. The exhaust system must also be removed in addition to the carbs for full access.

There is also a style known as the "15-Minute" style oil mod. This option uses the same filter adapter as option 1, but has one line feeding the stock metal lines. I supply a special double banjo bolt and fitting to replace the stock single bolt at the transmission. This kit sells for $199.00. This kit is the easiest to install, but there is one variable to consider, that being the stock metal lines and banjo bolts. One other design flaw we found long ago was that the banjo bolts that secure the stock metal lines to the heads have triangular shanks on them. Depending on how these bolts are torqued, there is a possibility of them blocking the oil passage hole in the oil line where it enters the head. The cure would be to turn these bolts down (which I do) to ensure that there is no blockage. Options 1 and 2 use replacement braided feed hoses with recessed banjos to eliminate the potential problem.

Okay, how confused are you now? I spent some time writing this because my new website will include all this type of info, so I will use it later.