quote:Originally posted by Coolvet:
So what is the solution George? You show a photo of sleeved lifter bores. Please explain what you have done here, why you did it and what the benefit is?
Thanks, I love learning how experts have solved these issues.
AusFord did a good job of summing it up. The large ports on the side of each tappet bore give rise to cavitation and excessive oil leakage. The cavitation worsens as engine speed increases and eventually reaches a point where it inhibits the flow of oil to the central 3 main bearings. Oil leakage starves the lubrication system for sufficient oil to performs its task. The bushings resolve those problems ... and several others.
The performance of the lubrication system has always been an unavoidable subject when the topic is the 351C. Many show-room new motors could barely reach 50 psi hot oil pressure (when measured with an accurate gauge) yet most of us considered 50 psi hot oil pressure as “marginal” or “dismal”. Ford’s original spec for 351C hot oil pressure was 50 to 70 psi by 2000 rpm. So the prevailing opinion was something needed to be done to bring the hot oil pressure within spec when we were hot-rodding the stock motors. Dyno Don Nicholson was among those who advocated 60 psi hot oil pressure that holds steady until the rev-limit as enough pressure even for Pro-Stock racing. Seventy psi hot oil pressure was considered “excellent”, in fact some would call 70 psi “more than enough“ or “over-kill”. But Ford’s Pro Stock Pinto book also warned us to shut the motor off immediately if the hot oil pressure dropped below 50 psi at high rpm.
With very few modifications the Cleveland becomes a motor that invites the driver to rev it hard. One thing many of us discovered the hard way, the con-rod bearings would show signs of under-lubrication when the motor was run at high rpm, even if the hot oil pressure was 60 psi or more. High oil pressure alone did not reliably guarantee the rod bearings were receiving sufficient lubrication.
I must at least mention that limiting the amount of oil flowing to the valve train is essential when building a high performance 351C. When more oil flows to the valve train than what is needed to lubricate parts and cool the valve springs it is diverted from the main and rod bearings were its really needed. The 351C has always had tappet incompatibility issues as well. The wrong tappets will pass too much oil to the valve train, in some cases the oil pan will be pumped dry at higher rpm because the oil is pumped to the valve train faster than it can drain back.
I was doing a solid lifter motor for a guy about 1976; I went to my local Ford speed & machine shop to pick up some parts, including the high pressure oil pump spring so loved by Jack Roush. The guys at the speed shop told me that the spring (introduced in 1972) had fallen out of favor for solid lifter motors and the new hot tip was tappet bore bushings. Ford had begun selling a very expensive do-it-yourself kit for installing them at home about 1974. That was my first introduction to tappet bore bushings.
Since Ford had ceased printing the OHO Newsletter prior to the 1973 race season the word about the tappet bore bushings never got out to the public at large. In fact the Ford Performance book by Pat Ganahl, (published in 1979) quoted the 1972 Pro Stock Pinto book regarding the lubrication system, a quote which recommended the high pressure oil pump spring for solid lifter motors. Of course, boosting oil pressure with the spring (introduced in 1972 the same year the Pro Stock Pinto Book was published) didn't fix the lubrication system so racers continued looking for a solution. Tappet bore bushings came on the scene during the 1973 race season and became the ultimate solution. Ford began selling the tappet bore bushing installation kit about a year later. Unfortunately by quoting the Pro Stock Pinto book regarding the lubrication system Pat Ganahl's book perpetuated old (erroneous) information and has mislead 351C enthusiasts regarding the lubrication system for decades.
So the four modifications listed below became common for solid lifter motors to prevent rod-bearing under-lubrication, but only common for those who were aware of the tappet bore bushing solution:
(1) The main bearing and rod bearing clearances were increased.
(2) Clevite 77 bearings were installed, which included fully grooved main bearings.
(3) Cam bearing oil passage restrictions were installed
(4) Tappet bore bushings were installed using a self-piloting do-it-yourself kit sold under the table by Ford or via Ford’s contractors and various Ford engine shops.
Even though Ford’s bushing kit was very expensive it was considered an essential modification for solid tappet motors to prevent rod bearing damage. And although my opinion is different today, 40 years ago we didn’t feel the bushings were essential for hydraulic tappet street motors. There were three schools of thought regarding modifying the 351C lubrication system for hydraulic tappet street motors:
(1) One school of thought preferred no modifications at all. The guys who advocated this insisted the lubrication system and bearing clearances were good “as-is” up to 6000 rpm. Checking oil pressure with an accurate gauge however revealed that 351C’s could not achieve 60 psi hot oil pressure off the show room floor, most couldn't achieve 50 psi hot oil pressure. And the factory spec for the bearing clearances was very tight. So even though some guys insisted the short block was good "as-is" the rod bearings told a different story. When we pulled piston & rod assemblies we always found signs of rod bearing “harm”.
(2) A second school of thought preferred following the advice given by Jack Roush in a 1976 story published in Hot Rod magazine. Jack Roush recommended a standard volume oil pump, the Moroso high pressure oil pump relief spring and the Moroso cam bearing restriction kit used in conjunction with 0.0020" to 0.0025" main bearing clearance and 0.0025" to 0.0030" rod bearing clearance. The motor’s cold start oil pressure ran about 120 psi with the high pressure oil pump relief spring installed, enough to burst an oil filter canister if the driver inadvertently blipped the throttle when the oil was cold, as many guys found out the hard way. A Motorcraft high pressure oil filter # FL-1HP was needed if the high pressure spring was installed.
(3) The final school of thought preferred a high volume oil pump to deliver more oil to the rod bearings which had the clearances increased to 0.0025" to 0.0030" (in conjunction with main bearing clearances increased to 0.0020" to 0.0025"). But installation of a high volume oil pump alone without taking any measures to control where the extra oil was flowing would also supply more oil to the camshaft bearings and the valve train. So to control the oil flowing to the camshaft bearings the small restrictions from the Moroso cam bearing restriction kit were installed, and push rods having restrictions in the tips or thick wall 5/16” OD push rods with 0.072” passages through the middle were installed to control the oil flowing to the valve train. In this way the extra oil supplied by the high volume oil pump was routed as best as possible to the rod bearings where the clearances had been increased. This was the lubrication scheme Ron Miller liked to use (Ron Miller's shop was one of my hang-outs in the 1980s).
Engine RPM is only part of the equation regarding the need for tappet bushings however; the lift rate of the camshaft lobes is another part of the equation because it affects the speed of the tappets. In turn, the speed of the tappets is going to affect the severity of cavitation at any given rpm. A modern 351C street cam can easily lift the valves 0.570” to 0.600" off their seats (or more!) in a relatively short duration, therefore those tappets are moving a lot faster than hydraulic camshaft tappets did 40 years ago. Modern cam grinding equipment allows cams to be ground which lift the tappets very fast, even in modern street cams. So although we all once believed the bushings were strictly a high rpm solid lifter motor modification that is no longer the case.
In light of the diagnosis of cavitation and oil leakage being the root problems with the 351C lubrication system, the installation of tappet bore bushings is given heightened credibility as the logical way to prepare the lubrication system of any 351C performance motor, street or otherwise. I am of this opinion for three reasons (1) because it is the only measure that isolates the tappets and tappet bores from the oil passages thus eliminating cavitation in the main oil passages, (2) it is the only measure that prevents oil being bled away from the lubrication system, and (3) because the reasonably priced do-it-yourself tappet bore bushing installation kit available from Wydendorf Machine (selling for approximately $400 USD) makes it affordable and within the budgets of a large range of engine projects. Denny’s kit is a better kit than the kit once sold by Ford, and the price is substantially more affordable.
The alternative is to:
(1) Live with the fact that there is some degree of cavitation occurring within the lubrication system
(2) Live with the fact that there are 16 leaks equivalent to one 7/32” hole bleeding oil away from the parts of the motor that require lubrication.
(3) Take steps to insure the motor is operating at the pressure specified by Ford (50 to 70 psi hot oil pressure by 2000 rpm)
(4) Hope the oil pressure doesn’t sag in the upper rpm range due to cavitation or oil leakage
(5) Limit the maximum engine speed to whatever rpm the owner thinks is safe
(6) Hope cavitation is not too severe below that rpm.
(7) Limit the amount of oil flowing to the valve train via the push rods.
Limiting a 351C equipped with 4V heads to a “safe” engine speed, such as 6000 rpm, is incongruous; as is living with a cavitating lubrication system when it is so easy to fix while you have the engine apart. Tappet bore bushings having 0.060” orifices combined with 5/16” restrictors in the passages supplying oil to all 5 camshaft bearings (also having 0.060” orifices) provide the following benefits:
(1) They eliminate cavitation in the main oil passages
(2) They eliminate oil being bled away from the lubrication system via the tappet bores or the camshaft bearings
(3) They alter the lubrication system to function as a main-priority system
(4) They eliminate tappet compatibility issues
(5) They limit the amount of oil flowing to the valve train
(6) Hot oil pressure is no longer an issue because the lubrication system operates at generally higher hot oil pressure when the bushings and restrictors are installed; yet the bushings and restrictors also make the lubrication system capable of functioning very well with lower pressure
(7) The main and rod bearings will be properly lubricated at any conceivable engine speed
(8) They repair excessive tappet bore wear on high mileage blocks
(9) They prevent the loss of motor lubrication if a tappet pops out of its bore.
In all sincerity, if a person installs the tappet bore bushings in their motor they shall not regret it after they observe how well the lubrication system performs once they get the engine running again. In fact most people who have installed them say they'll never build another Cleveland without them. Of course, you need a good gauge to observe that. You can look upon bushing installation as fixing the lubrication system or as hot-rodding the lubrication system, whichever perspective makes you feel better about installing them; either way the bushings are a big improvement. In my opinion it’s the best thing you can do for the lubrication system. If you’re only going to make one modification to the lubrication system, that’s the one to make. It’s far more beneficial than things like high volume oil pumps. The price is right using Denny's kit.
-G