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No Power in 17 Roadster??


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Hi All,

 

I've appreciated the help and ideas I've received her before, so I'm back to get your thoughts on a mystery I'm having.  My newly acquired 1917 Roadster has no power.  This might get long, but I'll strive to give you every detail I can think of.  I have a few other 4cyl Dodges and am accustomed to their power output as a point of reference.  This car will start and idle just fine, and even sounds good at sustained high rpm in neutral, however when I make the upshift from 2nd to 3rd, it just falls flat.  There is absolutely no power for acceleration in 3rd.  It starts popping/backfiring through the carb when it's under any kind of load.  The problem seems to get worse when it's hot.  I have a very very slight incline to my driveway and when I first back it out of the garage, it will pull back up the driveway on the poor side of decent in second, but after I'm out test driving for 10 min or so, it lacks power to pull even this slight incline in second when I return home without racing the engine and slipping the clutch way more than appropriate and it will even start popping through the carb, so it definitely seems like it's an "under load" power issue.  I've noticed that my first upshift from 2nd to 3rd when I start out with a cold engine doesn't have near the power I'd expect, but it doesn't pop through the carb and I'm slowly able limp it up to about 20-25 which seems to be all she's got, and it takes about 3 blocks to baby it to get there.  It's not until I drive a couple more blocks to the next stop sign (when it's warmed up a bit more perhaps?) and that's when the popping accompanies the lack of power.  The car will pop through the carb so much that half the time it stalls out, but always restarts fairly easily.  It's like it really doesn't do well when you ask the engine to do anything that even minimally puts it under load.

 

I've read through the book.  I set the timing.  I thought perhaps I messed up and it was too advanced, but experimentation while driving only leads to less power when i retard it on the lever, as you'd expect.  I've replaced the coil and condenser with modern ones, and have a brand new set of C18 spark plugs.  The points look beautiful and are right at .020.  On to the gas side... I initially figured it may be too lean, and no adjustment of the choke stop screw would make a difference, so I removed the carb that came with the car and replaced it with one I took completely apart, cleaned, installed new gaskets, set the metering pin 1/16 off of lifting the air valve.  The swapped-out carb made no difference in performance, so doesn't seem to be a carb issue.  As I am experiencing the lack of power and carb popping, I've even tried pulling the choke out different levels to see if richer would help, with no improvement.  I've put new gaskets in the vacuum tank and cleaned the inside of the inner and outer tanks and all appears to be fine, including the flapper on the bottom of the inner tank.  I've checked the valve clearances when hot and all are well over the .003/.004 listed in the book.  While I'd like to tighten these up a bit, it seems that popping through the carb would be related to an intake valve clearance being too tight, which these don't appear to be, so I'm leaving valve adjustment as a matter of "performance tuning" until after I have this issue figured out.  It seems that I'm on the safe side with them too wide as far as the issues I'm experiencing.  I've tested compression both hot and cold, throttle wide open, all plugs removed and hitting the starter for 5 seconds or so.  Compression on 1-3 is 60psi and on 4 is maybe 61-62, which is basically equal across all but I'm including that detail as I'm reaching the end of my ideas here!!

 

I'm not claiming to be any expert here, so if you think I've done something wrong or should go back and take a second look at something I've already done, I'm open to any help/ideas.  The one thing I have yet to do is take the head off, but I'm not sure what I might find wrong in there when the compression checks out good, maybe even on the high side, as I think the book mentions closer to 50?

 

The car had been restored previously, but had sat for at least 5-8 years prior to my purchasing it.  The previous owner used it almost exclusively as a parade car once per year.  He would use the electric winch in his trailer, load the car, trailer to the parade, unload it, and drive the parade route and then winch/load the car back in the trailer and drive home.  As such, I'm guessing he wouldn't have much reason to be in a situation out of first or second where he was asking the engine to put out power, so he likely wouldn't have realized these issues even if they had been going on for quite some time.

 

I'm eagerly awaiting any discussion, or ideas you might have as I'd love to get this car to a point where I can use it and I've grown quite frustrated as nothing I've seemed to do has made one bit of difference.  It's so lacking in power that it's completely unusable in it's current condition and I hope to change that!  Thanks in advance!  - Travis

Edited by dbtravis
spelling correction (see edit history)
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Hi Travis,

Is your car fitted with a distributor or a magneto?

 

I have never heard of a “C18” plug nor can I find any reference to this plug.

However it is not unheard of to have a faulty “new” plug.

 

The nearest plug on the market suitable for our early Dodges (in my opinion) is the champion W89D, (not easy to find, I buy mine from the UK) it is the closest to original in electrode length to allow combustion in the chamber rather than up in the head. It is also the closest to the original AC brand 76S in heat range. Both points are important.

 

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I would suggest checking the electrical firing of each cylinder when hot to see if it is one or more cylinders.

 

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Thanks Tony.  A valve sticking in the guide had crossed my mind, but I kind of pushed it aside when I found I had good compression when it's hot and it will rev just fine in neutral - this issue is only when under load (upshift from 2nd to 3rd, power to climb even the smallest incline in 2nd, etc)  But... since it only occurs when it's hot, I wonder if you could be on to something and maybe the extra pressure in the motor when its under load makes it more apparent and not something that I'd notice if it's just in neutral.  Since the previous owner used it just in parades at low speeds, there could be quite a bit of carbon in there that never had much chance to burn off.  Looks like a valve job is in my near future.  It may be a few days, but I'll post back on my findings and possibly even a few photos, if I can figure out how to upload them!

 

Minibago - Thanks for your input as well, you Australia DB'ers are on it!  I stand corrected on the new spark plug I'm using, the "C" in my mind was because it's a Champion Plug; the correct model is a W18.  Sorry for any confusion.  I have a distributor.  Your idea about checking the electrical firing of each cylinder when hot is a good one.  I have an in-line spark tester that I can connect and drive it with the hood off to see quite well what cylinder is firing at what time.  That would at least give me some idea of which one is firing as the "popping" starts and would be some good knowledge to have prior to taking off the head.  I appreciate the idea!

 

Thanks everyone and I'll keep you posted!

 

- Travis

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I have not seen the W89 plugs, will have to look for them. Before I tore it apart I would try a little Marvel Mystery in the gas to clean out carbon. You could put it in through the primer cup. Or even a little water, that would clean out the carbon on a revved up engine. 

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Don't pretend to know much about 4 cyl Dodges, but over the years have found a partially blocked main jet can show those symptoms. Revs OK on no load but does not get enough fuel under load, so backfires, etc. Just a thought.

John

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It's kind of a variable jet, similar to an SU carb, if you're familiar with those.  The tapered needle changes the flow area depending on how far it sticks into the jet.

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  • 2 weeks later...

My bet is that you have a fuelish problem, and it may run the gauntlet from debris in the gas tank, which limits the fuel supply and taxes the vacuum tank. You may be getting bad gas……these engines will still run with rocks in the carb, but absolutely hate a single drop of water in the fuel system. If the engine starts, idles and runs smoothly under most conditions, I’d leave the serious repairs, such as valve adjustment or removing the head, for such a time the severity of the problem makes it worthwhile. The four cylinder dodge carb uses a gravity fed fuel system, and is normally a fairly good way of feeding the engine. But, remember that you do not have the cushioning effect of a intake manifold…..and, let’s not split hair here…..so that any fuel problem can result in popping through the carb, and more dangerous, back pressure through the vacuum side of the vacuum tank. Check to ensure you have a unrestricted and clean fuel supply from the tank, through the vacuum tank, and down to the carb. Check the valves in your vacuum tank. A quick check is to let the engine idle until the fuel in the lower tank is consumed, and the engine should lope a few times while the valves open to provide vacuum to the inlet side from the tank, and allow the float valve to open and refill the lower tank. Check for vacuum leaks in the lines running to the tank and make sure you don’t have leaks which prevent the tank from working properly. A worn metering valve, or improper setting of the fuel enrichment lever will also affect this….but, if you aren’t getting rough idle, hesitation in acceleration or carburetor flooding, I’d keep that in mind, but put it on the back burner for a later worry. And, lastly, have you considered either not backing up the driveway, or having a contractor come out and reverse its slope…..where you back downhill, rather than up?

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On 7/8/2021 at 5:00 PM, Bullfrog_eng said:

Don't pretend to know much about 4 cyl Dodges, but over the years have found a partially blocked main jet can show those symptoms. Revs OK on no load but does not get enough fuel under load, so backfires, etc. Just a thought.

John

Astute observation there Bullfrog. But, with the carburetors used on the old Dodge Brothers cars, any knowledge you may have previously acquired regarding carburetor technology is best shelved for the minute. Unlike the carburetor we learned about on our Chevy 350’s and Ford 289’s, the old Dodge carbs meter the air flow rather than the fuel flow. I will leave exploration of the methodology used in these little marvels to anyone interested in seeking further knowledge. And, accordingly, I will limit what I say to strongly suggesting that these carburetors will probably function if coated with mud and submerged in water. But, they do have their weakness also, and when they die, they do it suddenly and without mercy. The main parts of the carburetor are the throttle plate, the dash pot, the metering valve, the gear (I call it a “rack”) in which the metering valve is secured, the shaft and lever which raises/lowers the rack and affords a method of adjusting it. The float and needle valve are topics for another post. 
All that said, in the sense of a carb using a Venturi, accelerator pump, and depends on a fuel supply of 7 pounds, the gravity fed carbs, which uses the vacuum afforded by the engine intake, are so much more simple and predictable than a Holly four barrel……and a lot more fun to work with.

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  • 3 weeks later...

Thanks to all who have commented and helped!  I have the head off, and all of the valves out.  There is quite a great deal of carbon which I'll be removing.  I'll do a thorough cleaning of the valves and guides to ensure it all goes back together in a manner which should rule out anything hanging up and causing these issues.  The valves appear to have been replaced at some point, they're all single piece valves (good news) and the seats on all should be ok with a standard valve grind, but I do have a seat cutter if I need to true any up even the slightest amount.  Interesting to note that the exhaust valve on #2 apparently had some issues at one point in the last 100+ years... someone has replaced it with a valve with a larger diameter head, but (it appears) same diameter shaft.  The seat wasn't cut into the block in the best fashion - it's about 3x the standard width, but the mating surface on the oversize valve matches the width of the seat.  All on this valve was free of carbon and while it's not ideal to have a mis-matched one, I don't think it will impact performance in a measurable way if I get it all cleaned up and put it back as-is.  At any rate, my main issue was lacking in power and backfiring out the carb which would be more on the intake valve side, and this one is an exhaust.  After I get it all back together, I'll test it out and then can rule out anything internal as a culprit and focus attention on a second pass on the fuel and electrical sides, since that will be all that's left (even though I've already been through them once).  Unfortunately, I did find a concerning issue with the #1 piston, so I have that one out of the car and will be looking for advice on that, but will start a new thread to keep topics separate, so check for more over on my next post!  Thanks again to all - this is a great community!  - Travis

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