Don St Peter Posted March 31, 2011 Report Posted March 31, 2011 My stock P-9 only gets 10 Mi/gal tops. It has never done better than that since I've been driving it over 4 years now. My carb was overhauled by good shop about 2 yeard ago---no improvement. Float seems set right. Car runs good. I'm thinking I should get about 16/17 MPH. What do some in the know think might be the problem. Thanks Don Quote
aero3113 Posted March 31, 2011 Report Posted March 31, 2011 Could your brakes be dragging? Also check e-brake. When is the last time you checked the timing,points and plugs? Quote
greg g Posted March 31, 2011 Report Posted March 31, 2011 Is the vacuum path to the step up valve open, and is the mechanism moving freely up and down? how is your compression and where is your timing? Points gapped correctly. How do your plugs look??? Quote
Don St Peter Posted March 31, 2011 Author Report Posted March 31, 2011 In fact brakes were dragging a little and adjusted that out. Noted very little MPH improvement. Timing is just below TDC ( as indicated by timing mark ). Points, condenser and dist. cap are good; however the plugs are new but show small amnt. of oil on all of them when i check regularily but very little carbon buildup. I have to slightly tap the accellerator petal to get good idle down. I just cant seem to work that out. I'm thinking it's probably the friction in the linkage. I have not had compression checked but think at least 1 cyl. is down a little. I'm not sure how to do a precise compression test. What milage do you thinK I should get around town? I put a George Acshe OD in it a couple of years age' but have not had it out on long trip to determine MPG. Thanks Quote
aero3113 Posted March 31, 2011 Report Posted March 31, 2011 Does your car have a heat riser? Is it stuck in the open position? Quote
greg g Posted March 31, 2011 Report Posted March 31, 2011 I get 17/19+. A few years back member Bob Van Buskirk has his OD equiped 54 wagon yielding about 11 o 12 on the highway with the OD egaged. He fixed his step up valve and started getting 16/17. Advance your timig to about 5 degrees BTDC. check for interferece withthe highidle cam on the carb to make sure you can attain a proper idle. http://www.aa1car.com/library/compression.htm Quote
Don Coatney Posted March 31, 2011 Report Posted March 31, 2011 (edited) I get 17/19+. A few years back member Bob Van Buskirk has his OD equiped 54 wagon yielding about 11 o 12 on the highway with the OD egaged. He fixed his step up valve and started getting 16/17. Advance your timig to about 5 degrees BTDC.check for interferece withthe highidle cam on the carb to make sure you can attain a proper idle. http://www.aa1car.com/library/compression.htm I thought VanBuskirk also had an issue with his timing chain being off one tooth or something to that effect. Edited March 31, 2011 by Don Coatney Quote
Plymouthy Adams Posted March 31, 2011 Report Posted March 31, 2011 in addition to the already mentioned items, have you verified the vacuum advance on the distributor for operation and ability to pull to the full advancwe designed into the unit? of course things like short runs where the engine never get to operating temps is a mileage killer, driving habits and tire pressure..ensure the car is in an excellent state of tune and get to temp...run a good course and check the mileage for a good base line...if you have not been on the raod lately and so called blown the cabon out..you are not getting the best indication of MPG Quote
Young Ed Posted March 31, 2011 Report Posted March 31, 2011 My p15 without OD and a 3.73 rear gets high teens regularly if I keep 55. Pushing it to 60-65 seems to really drop it down. Quote
greg g Posted March 31, 2011 Report Posted March 31, 2011 Don, Bob did wrestle with cam timing also, but in the end he also had the gasket under the cab misalligned, which blocked the vacuum to the step up. Once he fixed that his mpg went back to normal. One other little deal, where is your accelerator pump linkage set? Quote
Don Coatney Posted March 31, 2011 Report Posted March 31, 2011 Don,One other little deal, where is your accelerator pump linkage set? Short stroke (summer setting) both Carburetors. I have made no changes in 5 years. Quote
bearheart Posted March 31, 2011 Report Posted March 31, 2011 Oh boy, I hate making myself sound really dumb, but here goes: Whats a step up valve? Quote
greg g Posted March 31, 2011 Report Posted March 31, 2011 Internal carburetor circuit that takes over for the accelerator pump after it gives its initial shot. It is a gaduated needle that gets pulled out of a jet by a spring proportianal to the vacuum drop in the intake manifold. When you let off the gas or arrive at cuising speed, the higher intake manifold pulls it closed against the spring. If the vacuum signal is blocked it stays open at all time providing an over rich mixture at all times. Quote
greg g Posted March 31, 2011 Report Posted March 31, 2011 It's and internal fuel enrichening circuit that reacts to a vacuum signal provided from the intake maifold. It functions to take over after the accelarator has given its initial butst of extra fuel. Basically a tapered needle that gets pulled up out of a jet by a spring. When you stop acelerating or reach cuising speed, the vacuum pulls down against the spring seating the needle, and returning fuel flow to just the main jet. If the vacuum path is blocked, the spring keeps the jet open povidig an over rich mixture at all throttle positions. Quote
TodFitch Posted March 31, 2011 Report Posted March 31, 2011 It's and internal fuel enriching circuit that reacts to a vacuum signal provided from the intake manifold. It functions to take over after the accelerator has given its initial butst of extra fuel. Basically a tapered needle that gets pulled up out of a jet by a spring.When you stop accelerating or reach cruising speed, the vacuum pulls down against the spring seating the needle, and returning fuel flow to just the main jet. If the vacuum path is blocked, the spring keeps the jet open providing an over rich mixture at all throttle positions. I don't remember how that is put together on those "new cars" from the late 1930s and 1940s, but on the first generation downdraft B&B fitted to the early cars like mine, the actuation of that enriching circuit is via a brass piston in a pot metal cylinder inside the carburetor. Between wear and years of pot metal aging, that piston no longer worked in my carburetor. The problem manifest itself as a starvation issue when transitioning from the idle circuit to the main jet circuit. Thought it was the accelerator pump at first but it turns out the pump was working. Too much clearance between the piston and cylinder, which was dealt with by grinding a groove in the piston and fitting an O-ring. Two take aways: Just because it is hooked up correctly does not mean it is working, so it might be worth putting a vacuum pump on it and watching the operation. Second take away is that in the case of my car, the mileage was not affected. I drive my 1933 pretty hard and it has the original 4.375 rear end and 190 cu.in. engine. It also has the aerodynamics of a barn door. With all that against it, I've been getting between 14 and 18 MPG depending on speed, load, etc. The 1940 should have the 201 with higher compression (i.e. better volumetric efficiency) and a 4.11 rear end. It is also a bit more rounded body shape. I'd expect mid to high teens for MPG if you drive it like I do and maybe into the low 20s if you are gentle or put an overdrive on it. Quote
Cpt.Fred Posted April 1, 2011 Report Posted April 1, 2011 which part exactly is the "idle orifice tube" in #39? the right screw-in part of the step up assemby? i already posted this in another thread yesterday, but here it goes again: take the carb off the engine and lift the lid of the float chamber. put a vaccuum pump on the small hole in the carb's foot, like this: if everything works fine, you'll see this part move up and down: i did that last year and seriously raised my MPG on the old 201... Quote
Joe Flanagan Posted April 1, 2011 Report Posted April 1, 2011 Ingenious. I'm tempted to take my carburetor off and do that just for the fun of it. Quote
Young Ed Posted April 1, 2011 Report Posted April 1, 2011 Joe you mean you don't have a box full of spares to experiment with? Quote
Joe Flanagan Posted April 1, 2011 Report Posted April 1, 2011 Spare carburetors, no. I have spares of lots of other stuff, though. I have to figure out what I'm going to do with it all when my project is done. Quote
Jim Yergin Posted April 1, 2011 Report Posted April 1, 2011 . . . when my project is done. Joe, If you are like many of us, that will probably never happen. I know it hasn't for me after 22+ years. I think it is more correct to say, "when I am done with my project." Jim Yergin Quote
Joe Flanagan Posted April 2, 2011 Report Posted April 2, 2011 I'll take your word for it. Maybe the objective is to never be done. Quote
Greenbomb Posted April 3, 2011 Report Posted April 3, 2011 You can be done without the project being done. I do that all the time!! Quote
Joe Flanagan Posted April 3, 2011 Report Posted April 3, 2011 I do that, too. But my wife isn't crazy about it. Quote
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