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I can’t speak to the operation since I am only to the point of being able to run mine in and out of the garage – although I am pleased with a system that stops as well going in reverse as it does forward!
In terms of longevity, my 845 apparently had 55000 miles when it was retired and left to sit after WWII. When I dissassembled the power brake unit the soft woven clutch material appeared to have no wear, was in good shape and I just put it back in. There was a spot of very minor surface rust in one area of one of the pressure plates that I easily removed with very fine sandpaper to match the original surface finish. I think the key to longevity was maintaining transmission oil in the system that keeps the liner wet and lubricated. I imagine the most likely problem is leakage of the seals around the brake output shaft that would drain the transmission. The many PASB messages over the years seem to indicate the friction characteristics of the clutch material are very important to how the unit performs including whether it wants to creep at a stop. For this reason I was relieved that mine seemed to be in excellent shape and didn’t need replacement with some other material which inevitably will behave differently to some degree. If the liner is shot of course, one has no choice.
If the pressure plate faces are damaged, I would expect that turning them accurately flat and replicating the original surface finish would be very important. Theoretically speaking, too course a finish would tear up the liner quickly and too smooth might reduce the braking power.
Jim
Since Evaporust also makes a related product specifically marketed for cooling systems called Thermocure ,why not run it? I recently used it to run through my ’35 P-A to clear up the last of the rust that didn’t come out from flushing with a swimming pool pump/filter. I think the active ingredient is the same, perhaps the product is the same also, just different packaging or perhaps concentration.
Jim
I have three cars without a front plate, the only one I had a problem with is a 74 Alfa that is my everyday driver and it is only an issue if I park at a meter on the street where a meter maid can give a ticket so I avoid street parking. I figure the ticket is less than the cost of manufacturing a front plate bracket where there never was one. I do keep the front plate in the car in case.
Jim
Paul, did you have a chance to take pictures of your 845 original fuel line routing?
Thanks, Jim
Oivind, thanks for flipping the picture!
Is there anything new to report on the new top material after Hershey? Is it now available?
Jim
The car is in Minnesota.
The chart with the Studebaker engine.
Yes, it is a simple formula that doesn’t say anything about how a 250 cu in engine would produce 160 hp, although engines were doing that in the 1960’s via higher compression, better breathing, overhead valves, etc.
In this case my note at the bottom caused more confusion.I have dyno data for a 1935 Studebaker 250 cu inch engine which had eight cylinders of 3 1/6″ bore and 4 1/4″ stroke, that is 31.3 cu in/cylinder, 250 cu in for all eight. The Pierce 429 cu in 12 had twelve cylinders of 3 3/8 bore x 4″ stroke, 35.8 cu in/cylinder, x 12 = 429 total cu in. The 462 was bored out to 3 1/2″ with the same 4″ stroke to get 462 total cu inches.
Engines of similar era – downdraft carburetion, 5 to 6 compression ratio’s, etc would have similar power vs speed characteristics, so I simply scaled the 110 peak hp of the Studebaker engine to match the 160 hp claimed by P-A (a factor of 1.46). The friction and breathing of an engine is basically a function of piston speed, which is rpm x stroke, with the V-12’s having a slightly shorter stroke than the Studebaker, so I also scaled the RPM slightly to get the peak hp levels of the V-12’s to occur at 3400 RPM per the ratings stated in the Pierce spec sheets. The resulting torque was calculated and plotted at each hp/rpm combination.
It would be interesting to actually have dyno data on a Pierce engine, but I don’t, so I think this is a reasonable approximation.
I have added the Studebaker to the same chart for comparison.
Jim
Here is the chart with less confusing labels.
Jim
My labeling on the chart is probably misleading. The labels for “160 HP” and “175 HP” were just meant to convey the version of the engine, not that they were producing that HP anywhere except at the peak of the hp curve.
Jim
Just for fun I generated an approximation of what I think a power and torque diagram would look like for the Pierce V-12’s by scaling dynamometer data I have from a 1935 engine of similar bore and stroke to the P-A V-12.
Jim
Peter,
Torque in ft-lbs = HP(33000 ft-lbs/min-bhp)/(2 x pi * RPM).
Our torque estimates come out the same if you assume 160 hp @ 2300 RPM, but peak hp is stated at 3400 rpm. Power is basically torque x RPM, but max torque drops off as the RPM goes up due to increased engine friction and poorer breathing. At wide open throttle the engine producing 160 hp at 3400 rpm would be producing less than 120 hp at 2300 rpm.
Jim
I think that is a bit strong. The Pierce specs claimed max 160 and 175 bhp occurring at 3400 rpm which I calculate at 247 and 271 ft lbs respectively. The maximum torque would normally occur at a lower RPM than max bhp. Based on test dyno data of a reasonably similar engine of the same era I would expect max torque to peak somewhere in the vicinity of 1800 rpm at about 275 and 305 ft lbs respectively. Many years ago I recall someone found some dyno data of a Pierce and it was published in the PASB, but I think it was an Eight and I haven’t been able to find it again since. I remember it was a bad copy and very hard to read!
Jim
I have no idea why my picture above is upside down!
Jim
Paul, A photo would be great, thanks. Based on your comments I suspect I have the direction of the outlet line on top of the fuel pump wrong, it should be coming outboard towards the hood rather than forward. In retrospect it was pretty dumb wondering why the line took the kick up towards the manifold, it should have been turned 90 degrees.
Greg, getting the fuel line over to run fwd along the hood ventilation doors should be ideal. The air coming out of the radiator should roll across the fuel line on its way out when the doors are open. That air is about 140 to 150 degrees, which is actually cooling when the fuel evaporation problem is generally happening with the fuel being heated in the range of 150 to 180. The exhaust manifold goes way over 600 degrees and is probably heating the fuel pump and line via direct radiation more than convection. The fuel line probably shouldn’t be insulated along that run forward as you are trying to use the 140 degree air to cool the fuel line, whereas insulation will block the cooling effect and absorb more radiation heat from the hot manifold. The insulation will absorb more radiation than the copper line.
I would avoid having the fuel line running back to the firewall. The cooling air coming out the radiator is mainly going to flow aft and down over the engine and manifolds then under the car as well as out the hood ventilation doors leaving a zone of air next to the upper firewall trapped by the hood being heated by the 200+ degree engine surfaces and much hotter exhaust manifold. That air is going to be pretty dead at low speed and idle, and perhaps turbulent but with no definite flow path out at cruising speed, meaning it will be hotter than the air in the forward engine compartment.
Jim
I don’t see if it has silicone in it as a protectant/rejuvenator a la ArmorAll. If it does I would worry about overspray onto paint as it can cause nightmares when repainting – moon eyes even if sanded and prepped to bare metal. Might mask or apply by cloth instead of spray if in doubt.
Jim
Bruce, I measured the oil pressure regulator spring on my ’35 845 Eight as follows:
wire dia – .063
OD .405
ID .275
length – 2.12 uncompressed
20 turns total
10 turns/inch
solid ht approx.26
Calculated spring paramters
k = 31 lbs/in
Mine had a corrosion pit that I worried would fatigue and cause the spring to collapse, so I found a close substitute from Lee Spring. They had a 10 minimum quantity to order and I currently have 8 on hand if you want one (no charge).
That spring is not a perfect dimensional replacement, is slightly longer and I added a .125 thick shim washer to get the the same cracking pressure.
I think a broken oil spring could possibly give you valve clatter since it would bypass a large amount of oil flow from the oil galleries that feed all the bearings and the lifters. The lifters are sensitive to the amount of flow reaching them as they have a tight clearance that is constantly leaking. I chased a tapping lifter that had .001 more clearance than the other 15.
Jim
Tony, the Model A lead looks like a winner. Snyder’s Model A catalog shows several different strips that were used but I this one used on Briggs bodies looks like a good candidate. Snyder’s has instructions and pictures for installing this strip including pictures showing it bent to the tight radius curve.
can anyone say if the original P-A strips look like this cross-section?
Thanks, Jim
I’m a bit slow, just realized that the nail is driven first and the ball is peened in on top of it. So I guess the drill – pun intended- is to drill the holes in the strip, drive the nails and punch them under the surface then pound the lead ball in on top? Do you do a countersink in the hole first?
Thanks, Jim
Thanks Jim and Greg, that explains it but more questions. I should look in the PASB’s I guess, but meanwhile…. Looking at Restoration Supply their catalog lists half round and shallower half ovals in various sizes in brass aluminum and steel. I assume one of these -brass or aluminum – is soft enough to bend to the tight radii in the corners (see picture).
Is the oval pre-drilled and countersunk to put the lead ball in before driving the nail? seems pretty tricky trying to drive a nail through a round ball!
Jim
