I'm picking up my block from the machinist today, and I plan on starting the reassembly this weekend. I'll be doing the oiling tweak that I've heard mention here (pulling the plug by the fuel pump, and running a line to the sending unit on top rear of the block, and installing a t-fitting for the sending unit).
My first question is this: how does this tweak work exactly? I would think that both holes will be pressurized equally, so the oil would fill the line through both holes, and not really recirculate. What am I missing?
My second question is, I'm considering getting a high-volume Melling oil pump to help with some of the oiling issues that I've heard are inherent to the 351C. Will a stock oil pan be okay, or should I go with something a little bigger? Is a high-volume pump even necessary?
This is a daily driver, with hopes of taking it out to the strip MAYBE a couple of times a year, so I can't imagine she'll routinely see high rpms.
Any input is appreciated.
- Keith A.
'73 Convertible - 351C 2V - FMX - daily driver
"Beer is proof that God loves us and wants us to be happy." - Benjamin Franklin
I agree with the oil line. Roughly the same pressure at both ends. One of the reasons I did not do it. Another is that I do not think the C's really have an oiling problem. I think the probles arise from the large amount of c's spinning super high rpm in drag cars and starving the pump on 1g turns in a Pantara. Any block would have an issue under those 2 conditions.
I run a HV pump with hydraulic lifters and restrictors. seems to be doing fine over the first 500 miles.....
You will get a divided response on this one, most likely. The 351 Cleveland gets a bad rap for the oiling system. If you were running high RPMs a lot, I would go ahead with it. The oil line mod is intended to balance the oil distribution better. I am in a similar situation as you as far as the intended use for the motor. The only real high RPM driving I plan on doing is in the passing lane... so I am just going to pay close attention to tolerances & go with a stock pump - though I still may use a different spring pressure than stock (some people report good results using 100# spring). With the Cleveland being out of production for so long, it almost seems shrouded in mystery when compared to a Windsor. Bottom line is do a lot of research... the forum listed by the other poster will provide a goldmine of info on the old Cleveland. I am far from an expert, most of my info comes from the forum. Just as a side note: If the oiling systems in the Cleveland are so bad, why did the crank in my high-milage motor not even need turned?
Mark - the Mach is lookin' good... it's come a long way from the boxes of parts you began with. You probably don't recognize me with the new ID... maybe even not with the old one - Pale_Rider. I had PM'ed you a good while ago with questions about the 351C. Just wanted to congratulate you on the resurrection...
For as long as Mustangs continue to exist, the age old debate on the Cleveland’s oil system will continue with more false and misguided information being re-circulated around than the truth. There have been some old sage Cleveland engineers, mechanics and rebuilders in the past that have tried to clarify this area of misinformation but have literally given up the fight over the years. I still have many of their articles and am just amazed how far from the truth we’ve seemed to come over the years regarding this rather simple matter. We seem to know less now than most rebuilders knew in the 1970’s. So – I will reiterate for them who are now too tired to continue repeating themselves.
First of all, the 351C oil system is not a “defective system” for their original factory manufactured application. It works fine in all the 351C engines that were assembled by Ford and installed in their Mustangs, Cougars, Rancheros, Montegos and Torinos throughout its four years of production. And so long as these engines were assembled just as the factory assembled them with their factory parts and operated in the same realm as they were intended to be operated, everything works just fine. There has never been a factory built or stock rebuilt 351C engine that had ever failed due to a defective oil system or because an oil pump was deficient in volume or pressure. That’s a fact! So what happened? In short - the Cleveland was later modified by engine rebuilders to take advantage of its tremendous horsepower and torque potential which put its operation into an entirely new realm. As such, horsepower and RPM ranges exceeded its originally intended parameters.
It’s kind of like the Mustang itself that was originally designed as a sharp looking sports car that everyone could afford. And it was affordable because it was built on the cheep Falcon chassis and frame with mediocre components (ie: partially framed unibody construction, marginal suspension, outdated but adequate front end, adequate brakes and steering, etc). Great for the low income buyer wanting to look cool in a jazzy bodied sports car, but a horrible platform to build a serious high performance muscle machine on. The Mustang’s initial engineers had no clue that their classic chassis & frame design was going to be turned into a 300+ HP muscle machine in the future! The problem was the car looked so good and had so much public appeal as a performance car that Ford just went ahead and engined and styled it for high performance before its inner guts had time to grow into its muscle. Want to see an entire front end twist before your eyes – build up your 351C to 450 hp, drop it into your all stock 1970 Mustang (put weight in the trunk for traction) and stomp on it. Presto – you now have two cracked shock towers and probably a tweeked unibody frame! Now you can drive down the road like a crippled crab. Do you want to see an engine’s oil system fail – double the horse power and torque from factory, increase your RPMs by 50% and do nothing to update the oil system and go race it! On a Cleveland, this is a guarantee for failure due to a now inadequate oil system design for the realm that you are now operating it in.
Just like Mustang enthusiast have since reinforced their frames, shock towers, brakes, steering and suspension components for their supped up MuscleStangs, the wise high performance Cleveland rebuilders have made engine modifications to make allowances for higher HP and RPM ranges. And when properly done, their oil systems run just fine. Would you install stock u-joints on a driveline that’s going to double the torque delivered to it? Still, with all this being said, it’s a fair statement to say that the Cleveland’s factory oil system was not designed for high performance capability. Other engine’s oil systems might be directly adaptable for high performance, but the Cleveland’s was not. But wait – I thought it was designed as a high performance engine? Yes it was, but its oil system was not. Everything else in the Cleveland was aimed at high performance, but the pressure to save on production costs compromised that one critical area. The bean counters got their way with casting & drilling a less expensive oil gallery layout and the rest of the world of Cleveland performance enthusiasts have had to pay for it ever since. Even still, up to 5500 or even 6000 rpms and 300 HP or less, it’s perfectly adequate. But if you rev up a Cleveland up to 7-8 grand, especially if it’s a built up Cleveland using today’s available parts and inadequate “Cleveland Specific” assembly knowledge, bad things are going to happen.
First of all, the gallery system design prioritizes the lifter bore channels (with the exception of crank bearing No. 1). The first place the flow is directed to is the right (passenger) side lifter gallery where this gallery intersects each lifter bore by almost quarter of its bore diameter. It’s got an immense exposed area for its oil feed. Fine for 5500 rpms using factory lifters. Keep in mind this is repeated 16 times - once for each lifter bore. If you have much lifter bore wear at all, that’s a lot of leakage potential, especially when it’s at the priority lubrication site. Ford actually had “351C Specific” lifters with specially sized oil holes to control the oil flow up the push rods to the upper assembly. Now think for a moment: Suppose you rebuilt a Cleveland and stuck aftermarket lifters (having larger oil orifices in them – which the parts guys know nothing about) in old worn lifter bores and used aftermarket pushrods that also had your typical large (relatively speaking) oil holes and then ran this engine up to 7500 rpms. What do you think happens? Here’s what does: 1st – the oil pressure builds and it squeezes out towards wherever the resistance is least. If the lifter bores are fairly worn, a bit squeezes out of each (that’s 16 small leaks). If you didn’t buy “Cleveland Specific” lifters (not even available any more) or pushrods with restriction oil orifices, then each lifter’s larger than “Cleveland Specific” oil hole size now allows lots of oil to shoot up to the top end. Remember there is an unlimited source of oil supply to each lifer from its huge oil gallery exposed area. That’s again times 16. Now that’s a lot of oil going up to the top end with potentially a lot leaking around the lifters as well. With the oil pump reving up to 7500 RPMs, that’s more flow than was ever initially accounted for, especially without the factory limiting lifter holes. Fluids don’t compress, so the faster the pump turns, the more oil it moves. This can be so much flow that the small (factory) oil drain holes in the stock heads often can’t drain it as fast as its coming up all 16 supply tubes. It’s even possible for the entire right side (that’s the oil flow’s first delivery side) valve cover chamber to completely fill with oil and then shoot up through the PVC valve and into the intake manifold. Don’t need to tell you what that does. That’s why you may see some older high performance 351C with oil leaking all around the valve covers, especially the right.
So - what do you think is happening to the oil level in the pan at this point? Yep, it’s getting really low, especially in a stock 5 quart volume oil pan. It might even be sucking out faster than it is returning at real high RPMs. Keep in mind that oil pressure is also probably running low not just due to the 16 lifter bore leaks, but even more so since the oil is finding very little resistance (like more leaks) through the upper valve train (unlike the original factory assembly parts). So you’re now running at reduced pressure (32 leaks in all) with less flow to the crank (it’s mostly going to the top end) and a decreasing pan oil level. Now say you are racing this on a track and you’re cornering at a few G’s. What’s the oil doing in the pan now? Yep, what little is in there is all pushed over to one side. Sssssuuck….cavitate…no flow! …zero oil pressure!…crank bearing seize! …BANG Pieces of Cleveland everywhere - all in a split second! That lesson was first learned back in the ‘70’s . Did you know that little bit of very old history? Do you understand it? Think an oil bypass line would have made any difference? It’s primarily a leakage problem, not a supply issue - that is until you’ve pumped your pan dry. But it all started from internal leaks which were aggravated at high RPM because of an oil gallery design that didn’t prioritize the crank bearings and required special lifters to keep from over oiling the top end. The problem was then aggravated by oil drain holes that couldn’t keep up with the high oil flow to the top end at high RPMs. A higher flow oil pump would only aggravate the situation! In this racing scenario where you experience sustained lateral G’s, a high capacity baffled oil pan (7 qt or better) would have helped.
As previously stated, the oil system dilemma stems from a oil gallery design that prioritized the right lifter gallery (with the exception of crank bearing No. 1) and then supplies the cam, crank and left lifter gallery all as a second priority. Now if the next successive path of least resistance is through the left side lifter gallery (for the very same “leak” reasons as the right), then that’s where the pressure will direct most of the remaining flow, even though the distance is shorter to crank bearings 2-5. Anyone understanding basic hydraulics realizes that a fluid will flow to wherever the resistance is least, which is wherever the pressure is bleeding off the quickest - which means where the leaks are. You can’t redirect flow if there is a pressure differential fighting this new direction. Attempting to redirect oil flow to the back side of the right lifter bore gallery accomplishes absolutely nothing! One must fix the leaks before anything else you do is going to matter! This is basic fluid dynamics.
There’s another faulty aspect to the by-pass line theory: The rear top oil port on the Cleveland where the oil pressure sender is normally attached (where a by-pass line is theoretically transferring pressure to) is at the end of the right side lifter gallery, not the left side. This is the gallery that is directly fed from the main pump port exiting the filter. This lifter gallery has a ½ inch I.D. and is a straight 19 inch shot directly over to the rear of the engine where this ¼ inch port for the pressure sender screws in. That means the rear port itself is half the size as the main lifter gallery itself and yet a hose to it is supposedly going to “supplement” it?? But even more than this is the fact that this long multiple curved by-pass line itself is going to be much longer and is typically only ¼ inch in diameter, most having fittings that have 1/8 inch holes at each end. This entire path is literally dozens of times more restrictive that the block’s straight shot to the back having twice its diameter. It is insanely ludicrous to think that this by-pass line can possibly supplement anything! Now if this line were to connect to a port that is directly feeding the left side lifter gallery, one could possibly argue stating that it supplies more than the port junction does at the top side of main bearing No. 5. But that isn’t the case! It is impossible for a by-pass line to supplement any flow or pressure beyond what the lifter gallery itself provides to this location unless one were to first stick a marble into the right lifter gallery to totally restrict it. Enough said!
But there is one really good, very common sense solution to all this. Simply put: Fix the leaks! All these mentioned internal leaks and excessive oil transfer starts it journey from the cavernous lifter bore cutouts. So ….why not simply bush these lifter bores thereby eliminating those huge cavernous bore gallery areas from where the oil flow problem first begins. If you do this and drill a sized oil orifice in each bushing for your particular lifter and valve train design, the oil flow passing through will meet the demands of the lifter without allowing an excess to bleed through to the top side. Just the inserting of new bore bushing alone will help eliminate the leak potentials around all the lifters (which adds up with 16 lifters). And presto – you’re done for all but some of the more extreme high performance applications. For those who want everything out of a Cleveland where you’re topping 8500 RPMs or better, you might at this point need to install flow limiters in the cam bearing gallery ports to redirect more pressure to the crank bearings, but that’s overkill for street applications. In ultra-high performance Clevelands, you might even need to go to a high performance oil pump as well. Novice rebuilders installing high volume oil pumps into street use Clevelands who haven’t bushed the lifter bores and are using aftermarket Non-Cleveland specific lifters are only making the problem worse! And those installing the oil bypass line are ignoring the basic laws of hydraulics and sanity! Re-direction doesn’t override the fact that oil still flows to the path least resistance regardless of how many ways there are of getting there. Additionally, if that line leaks or ever breaks and shoots oil all throughout your hot engine bay, better have about 20 fire extinguishers on hand or it’s bye-bye Mustang! If you still must ignore hydraulic laws and common sense, at least install metal brake line, not hose!
There are other issues that also make one wonder what was Ford thinking. Why build a powerhouse potential engine that requires high revs to make this power (that’s why the cavernous heads and valves, smaller high rev main bearings and even dual points in some cases), but have a cam grind that doesn’t really support that RPM realm or a meager 605 cfm carb that can’t deliver to even a 7000 rpm appetite? Much of that was modified when the ’71 Boss 351 came out, but still there was so much more potential that never got realized because the Fed’s emission requirements literally killed the Cleveland’s performance potential after that. Sadly, after 1971 the race reputation Cleveland became just a “soccer mom’s wagon engine”, but with the heart of an Indy racer. From 1972 on, the heads were screwed with, the timing was screwed with, the compression sucked and yet these lower compression open chambered heads would still detonat at times. In retrospect, the Cleveland really only had two years to live in. But for those who know how to properly build up a Cleveland, the unleashed potential has always been there, but you also need to modify the oil system along with your other performance enhancements.
So the bottom line here is 90% of the Clevelands out there would be remedied by simply installing a lifter bore bushing kit. Even the extra large oil pan would be overkill. Enlarging the head oil drain holes would be a good idea for any Cleveland and most aftermarket 351C heads already have these enlarged. And that’s the old story retold from when Cleveland builders knew more of the 351C oil system peculiarities than we apparently know today. Many high volume pumps, bypass line kits and gallery restrictors have been sold needlessly over the counter for street Clevelands than never needed these measures. Fix the leaks and your Cleveland will run easily to 7 grand with 400 horses and be happier than a clam. Much more than that, then start using the other measures mentioned, but throw that bypass line in the garbage!
P.S. – and case you’re wondering, no, I don’t sell lifter bushing kits or get any proceeds. It’s just that this modification alone directly remedies the oil situation for anyone building up a high performance street Cleveland using parts available from today’s auto suppliers.
I'm no expert by any means, with that understood. The motor in my 1970 351C 4v has been running good for 20 years. For things that may affect oiling that the engine has are high volume pump, motor sport oil pump drive, MPG windage tray, later style factory baffled pan, and it gets 6 quarts of mobil one. Boss 351s ran 6 quarts with the same pan.
If it were to be done again there wouldn't be a high volume pump, haven't had any issues with it. Just worry about losing a oil pump drive or sucking the pan dry.
The engine has seen 7000+ rpm before (enough to blow the govenor apart in a C6). The engine puts out a estimated 375 hp at the flywheel. It rarely gets ran hard anymore.
70machboy seems to know alot, and wrote a good post. I learned alot from him.
Since therre is no published depiction of the Cleveland's Oil system available anymore (not that I've ever found), I'm including this one I drew up which includes photos of where the various ports and such are located on the actual block.
Cleveland Builders: Copy this out, as you won't find another depiction like this ANYWHERE!
P.S. - If you want the Hi Resolution copy of this (and more pics), email me at: firstname.lastname@example.org
….why not simply bush these lifter bores thereby eliminating those huge cavernous bore gallery areas from where the oil flow problem first begins. If you do this and drill a sized oil orifice in each bushing for your particular lifter and valve train design, the oil flow passing through will meet the demands of the lifter without allowing an excess to bleed through to the top side. Just the inserting of new bore bushing alone will help eliminate the leak potentials around all the lifters (which adds up with 16 lifters). And presto – you’re done for all but some of the more extreme high performance applications.
Verb, I ran a C for many years and treated it with total brutality. I ran an HV pump with Moroso restrictors in the feed for the cam journals, and I ran with .003 on the mains and .0027 on the rods. Loose by current standards, but it was still running fine when sold, after I had it for years.....LSG
I wouldnt worry about it for the street.
this came about back in the 70's with nascar blowng up the C's.
if youre not turning those kinda RPMs all day the oil system is fine
id be more concerned with the stock 2 peice valves than anything else
Exactly. I ran a mild 351C with nitrous with nothing more than a high volume pump and had no issues. I'd also ditch the multi-grove style valves and keeps.
1970 Fastback (to be finished outside as a Boss 302 clone)
393 Windsor AFR 205 heads with 11.5:1 compression
Tremec TKO 5 Speed
Link to my Hub Garage and blog about my car http://www.hubgarage.com/mygarage/maxum96
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