Hi guys!
I recently bought my Dad's Fitzjohn bus project. Its 35' 25k lbs powered by a '63 534 Ford driving an Allison MT-40 6 speed automatic. This is the first time I have tinkered with a gas giant, so maybe I'm just expecting too much out of the old beast, but WHAT A POOCH!!! This thing is lucky to make 25mph on a modest grade. It idles well, but when you open the throttle it takes about 5 seconds to reach 3000 rpm standing still with the trans in neutral. Is this normal performance for this motor, or does it have issues?
Also I have noticed that when taking off from a stop you kind of need to feather the throttle to get it moving. If you just stand on the gas it will cough and sputter and somtimes die.
I should say that it has been vacuum and strobe timed, has new points, plugs, wires, coil and condenser, and allegedly has had a valve job I would guess less than 10,000 miles ago, and it has a newer Holley carb. have to check the exact model, but its a big double pumper.
I have read thru most of the old posts regarding 534's and can say that it has big dual exhaust thats not restricted. My first guess is carb/fuel problems, but hopefully one of you guys can give me a starting point.
I thought these things were supposed to be stump pullers! This thing just has NO TORQUE!!! My old MarkVII HO 302 would probably move the bus better!

 

Does it smoke out the tail pipe?? (which maybe a sign of too much gas)

 

Doesnt seem to smoke any more than you would expect for a motor that old. I was actually impressed by how little it smoked, but you can see a small amount coming out both sides at idle. The old bus has over 500,000 miles on it. Not sure how much was put on after '63 when it was re-powered with the current eng/trans setup.

 

Hmm I just came across this old post in a search for something else. Taking ages to rev up in neutral means something is really wrong. Maybe the timing was done on the wrong cylinder? It sounds way off. Maybe the cam is mistimed to the crank?

 

Thanks for the reply. I checked the timing at the cylinder. Its definitely right. I was told that one of the previous owners did a valve job on it. I adjusted the valve lash, and it seemed a tiny bit better, but no "Ahhh,, theres the problem" moment. Is it possible that the cam is off by one tooth and still looks right on number one cylinder?

 

Kind of sounds like you have too big a carburetor on it. People think that since this is such a large engine, it needs a large carburetor. Not true! The 534 doesn't turn very fast. Stock carburetor was less than 600 c.f.m.. You don't need a double-pumper anything!

 

Well if the cam were a tooth or more off this could definately be the problem. To diagnose this without taking off the timing cover might be a tad tricky. You can put a piece of wire or long screwdriver in the spark plug hole and rock the engine back and forth to find the true TDC, then double check the timing marks and remark as necessary.
Then take the valve cover off, and rock the engine to find the middle of the valve overlap of the cylinder. This should also be TDC on older engines with "straight up" cams.

Another simple thing to try would be to rotate the distributor body a few degrees each way and see if there is an improvement in performance. Paint Mark the distributor body to engine first so you can get it back to its original timing location as necessary.

I agree that a too large carburetor will be a poor performer. Are you sure that it is a "double pumper"? Can you get a part number off of it?

 

Okay, I was with you right up to the valve overlap of the cylinder. Is that the top of the compression stroke when both valves are closed? Dad tried vacuum timimg and with a light when he owned it. Timing was my first guess when I drove it also. He says is seems "happiest" where it is now. (cant remember off hand how many degrees bef. TDC that is, but close to the factory mark) I think I'm posting in a couple of places. I found out that Dad thought exactly like that about the carb. Joe,,, Replaced whatever was on there with the big Holley. Cant remember what the part number is, but looked it up on the Holley website and shows to be a 750. I actually talked to one of the techs on the phone and he had a formula for rpm, hp, and flow. Said the 750 will cause hard start, no bottom end torque, and poor fuel econ. -exactly the symptoms I'm seeing...Suggested a 570 Street Avenger, (vacuum secondary manual choke) which I bought new off ebay for $322. Also have a new Holley fuel pump/regulator/psi guage, and misc. pieces parts. Got a week vacation coming up the 5th for the big tear-down and rework. Currently the wimpy little fuel pump is pushing fuel 25' thru 3 filters to get to the back of the bus. I'm wondering if its just running away from its fuel supply?!

 

Hi Fitzjohn,
The overlap of the valves is at the TDC of exhaust stroke as it turns into the intake stroke. So the exhaust valve is just closing while the intake is just opening. This can be seen on the rocker arms as they start to move up and down, you turn the crank back and forth and watch for the point where the two rocker arms are about equally just open.
If your father tried running the engine at different timing settings to get the best, then it probably is about as good as you'll get it.
To check the fuel pump output, disconnect the fuel line at the carburetor and direct it into a clear bottle. Start the engine and let it idle and see how much fuel comes out. If it's a heavy stream then the pump output is fine. If it's only dripping or a barely formed stream, it's insufficient. The manuals usually give a specific rate (like one pint in 20 seconds or somesuch), but I always go by the simple visual inspection.

 

Okay,, now I'm really stumped! First I should say that I finsished replacing pretty much the entire fuel system today and theres definitely a huge difference in how the thing runs, ie: lots more power off the line, smoother idle, turnkey start, all thats good, HOWEVER,,,,, it still has some serious issues that I cant run down. I vacuum timed it, re-checked ignition parts, everything I could think of. When I got it out on the hiway it did pretty good at first, but after about 5 or 6 miles it started coughing and lungeing and barely made 25mph. Pulled into a gas station and put $100 worth of gas in, started it up and exactly the same thing. Went good at first then power dropped off and even backfired a couple of times. I managed to limp it back to the caves, but definitely not roadworthy. I also noticed a strange high pitched whistle coming from the new carb when I first start to open the throttle until the rpms increase some. Anyone want to take a guess what the heck is wrong?! Still hopeing its something simple!!
Mike

 

I should also say that the vacuum gauge indicated that I may have a slight intermitttent valve sticking issue, but only drops a couple of inches momentarily and idles slightly rough for a couple of cycles then smooths out.
Heres a stupid question: Does a 534 have an internal EGR system, or am I just missing it somewhere on the motor?! Holley suggested that backfiring thru the carb may be a sticking EGR valve.
Mike

 

Well I'll take on the powering out issue. I'll guess that the gas tank has a lot of rust in it which clogged up the fuel filter. After sitting a few minutes when refueling, the fuel slowly seeps through the filter and fills up the carburetor fuel bowls. Power is good until this fuel is used up, then the engine starves for fuel.
What kind of fuel filter is used? How big?

 

Hi Bean!
I guess It could still be having clogged filter problems. The gas tank definitely has a lot of rust. I thought I had run enough thru it to stabilize the situation, but maybe not. I put a coarse screen billet filter right out of the tank before the fuel pump, next is a Holley blue 97gph rotor/vane type pump, then about 25' of fuel line to the rear engine compartment. Once it gets there it goes thru the factory cartridge/bowl type filter, then thru the fuel regulator and into a standard cannister type inline filter. Next is the fuel pressure gauge (which I can only read while stopped of course) to verify Im still getting 6lbs of pressure going into the carb. All the filters are fairly large, between 2 1/2 to 3" dai. but historically it can clog a big inline filter in a matter of miles. The symptoms are similar to what I have been dealing with since I got the old beast. Your diagnosis is 100% accurate what I found before I rebuilt everything. Maybe the original problem -the junk fuel tank, is still fouling up everything. It was cleaned out 7 or 8 years ago, but looks pretty bad inside again.. I'm thinking Id rather just have a new one fabricated out of aluminum than continue fighting it. Damn frustrating!!

 

Based upon your rust issue in the tank I'd say you need to pull all the lines and blow them out. Then replace the filters. After that I'd yank the carb as some gunk may have gotten into the orifices in the transfer circuits.

Once everything is clean again, I'd rig up a temporary tank to see if that fixes the problem before dropping coin on a new tank. If you can get the old tank flushed, I think a company like Eastwoods may have a tank sealer to keep rust from coming back.

Good luck!

 

Could be the screen on the fuel pick-up tube in the tank clogging when the pump is drawing fuel and unclogging when you shut it off.