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Old 09-17-2021, 03:05 PM   #1
Jon E
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Default Having trouble getting new Miller-Cragar setup to run

Hello,

This is my first post here, but I have been reading and searching these forums for a while.

I recently purchased a 28 with a Miller-Cragar OHV which is the first early Ford I have ever owned or even worked on, so I am not familiar with these engines at all. It was originally built as a show car by the previous owner and was run very little. I’ve been tinkering with it for a few months since I bought it, but I’m still struggling to get it to run right.

It will start quickly and idles ok, but the off-idle throttle response is very poor. It stumbles and misfires badly as soon as I give it any throttle. On a few occasions, I was able to push through the roughness and it smoothed out and ran great from about 1,700 RPM and up but runs rough below that speed. At the present time, it acts like it's starving for fuel and wants to die as soon as I give it any throttle.

I made a short video of it running and put it on youtube, you can watch it here: https://www.youtube.com/watch?v=eMJEf6NKAmE


The basic specs are:

• Model B with Miller-Cragar OHV
• Two Stromberg 97’s
• Mallory YC Distributor w/ single set of points – unknown springs but advance appears to be working correctly
• 12V system with ballast
• Stock style fuel lines – no fuel pump


My troubleshooting so far has included:

• Replacing the points – gapped at .022
• Replacing the condenser
• Rejetting the carb down to .043 and .041 – currently using original .045’s
• Switching the carb linkage between winter and summer
• Adjusting timing up and down
• Replacing the plugs
• Adjusting valves to .016 (both intake and exhaust)
• Confirmed that I have a hot spark at the plug
• Compression test shows 80-85 PSI on all 4 cylinders (100-110 psi when the other 3 spark plugs are removed)
• Replaced the fuel filter
• Confirmed that the inside of the carb is clean. No buildup, sludge or corrosion inside of the bowls. I did not remove the emulsion tubes, but they appear to be clean.


Can you guys please help me figure out what it is that I am missing?

Is it a fuel problem? Is it ignition? Is the cam timing off?

Any help would be greatly appreciated.
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Old 09-17-2021, 06:50 PM   #2
Dave in MN
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Default Re: Having trouble getting new Miller-Cragar setup to run

Jon E,
Try choking it to various degrees as you try to bring the speed up. Report back.
The air to fuel mixture could be leaning out as you slowly open the carbs.

Good Day!

FYI: I have a Serr Miller HI-Speed head in one of my cars with dual Strombergs and have set up a few Miller-Cragar OHV heads for others.
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Old 09-17-2021, 08:31 PM   #3
joncrane
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Default Re: Having trouble getting new Miller-Cragar setup to run

1. Timing must be advanced much more than an A. Google Timing a Ford B Distributor. You cannot set the timing with the pin.
2. Also be certain you have a B timing cover. The pin location is different from a model A.
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Old 09-17-2021, 10:00 PM   #4
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Default Re: Having trouble getting new Miller-Cragar setup to run

Also give us your location as there might be some one in your area that can help.

Dodge
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Old 09-17-2021, 11:01 PM   #5
todd j
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Default Re: Having trouble getting new Miller-Cragar setup to run

Are you using the stock gas tank? If so it's probably not getting enough fuel to carbs. Strombergs like 2.5 to 3 psi to work properly. I have a Riley 2 Port running on an engine stand with a small fuel tank above the engine and my 2 81's starve at times. I will be running a fuel pump in the car
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Old 09-18-2021, 08:18 AM   #6
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Default Re: Having trouble getting new Miller-Cragar setup to run

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Jon E
I am not familiar with the Strombers but here is what I have learned from my Weber. The carburetor should have some holes in the side of the body that are uncovered when the throttle plate is opened slightly. These allow transsion from idle to the main jet. The flow through these holes is controlled by an idle jet. In my Weber I had to install a larger idle jet to get the proper response at low throttle settings. In my case the idle flow is also controlled by the idle jet so I had to screw the idle mixture in a bit after the larger jet was installed.
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Old 09-18-2021, 11:46 AM   #7
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Default Re: Having trouble getting new Miller-Cragar setup to run

Two carbs is a lot of fuel delivery for a 4-cylinder even if it is a 200 cid or larger oversize. The Winfield model S downdraft carbs or the already mentioned smaller model 81 Holley 92 carbs may be better. A progressive linkage may be in order so as not to flood the engine on acceleration.

Likely any combination can be made to work but will need fine tuning to get the right amount of fuel delivered during acceleration. With two power valves and two accelerator pumps, a lot of fuel will be dumped in. It may work better if only one carb has the acceleration circuit but I'm no expert on a set up like this.

Back in the day, rodders used air pressure pumps and fuel regulators on a lot of these type set ups so they could get more fuel delivered. An electric fuel pump with a regulator might be the way to go.

Make sure it has a good ignition system too. I can't comment when not knowing if it is a point & condenser set up or an electronic set up. Things can go wrong with either if not set up properly or some component is faulty. Vacuum leaks with a more complex manifold could also be a problem.
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Old 09-18-2021, 02:22 PM   #8
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Default Re: Having trouble getting new Miller-Cragar setup to run

I chased some issues on both of my Cragar equipped Model A’s. This might not be a popular fix, but some of my problems disappeared when I replaced the 81’s with Carter-Weber’s, on my coupe; which has been a new car since. Like you, I went though almost all of the things that you did.

Like what was mentioned, the Cragar OHV requires a lot more timing from stock.
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Old 09-18-2021, 03:33 PM   #9
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Default Re: Having trouble getting new Miller-Cragar setup to run

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Old 09-18-2021, 06:16 PM   #10
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Default Re: Having trouble getting new Miller-Cragar setup to run

More than likely it sounds like going too lean just off idle, generally need more accel pump shot.
Disconnect one carb throttle linkage and put a spring on disconnected one to hold closed
Then try to drive on a single, if it runs better you need a progressive linkage that leaves the second carb closed until needed.
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Old 09-18-2021, 10:58 PM   #11
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Default Re: Having trouble getting new Miller-Cragar setup to run

Adjust your fuel,regulator up or down and see which helps.
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Old 09-18-2021, 11:21 PM   #12
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Default Re: Having trouble getting new Miller-Cragar setup to run

Did the previous owner have any problems with the car or was it newly put together. After rereading the thread, it sounds like the gravity feed fuel system might not be enough.
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Old 09-19-2021, 08:55 AM   #13
Jon E
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Default Re: Having trouble getting new Miller-Cragar setup to run

Thanks for the responses.

In answer to your questions, I am located in the NW FL South Alabama area.

It was a fresh build for the previous owner and was run very little. Mostly just to drive it in and out of the trailer taking it to shows.

It does NOT have a fuel pump nor a pressure regulator. Yesterday I completely filled the gas tank to the top to give it some additional head pressure and that seemed to help. The weather has cleared some today, so I am going to try to road test it. Maybe it will run better once the engine is warm.

In the garage it seems to rev well at higher rpm, but at lower speeds it wants to pop and misfire. Similar to an engine with a badly worn timing chain or a bad vacuum leak.

I tried applying some choke to the carbs, but it didn't seem to help. I will experiment some more with that today.

I have played with the timing quite a bit with the engine running and it seems to have a fairly narrow window where it wants to run at. If I go much above or below that it does not want to run at all.

I'll report back after a road test today.
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Old 09-19-2021, 09:35 AM   #14
nkaminar
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Default Re: Having trouble getting new Miller-Cragar setup to run

I am going to say again that you probably need to play with the jet sizes. There is a good site on Stromberg 97 carburetors at https://www.stromberg-97.com/.
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Old 09-20-2021, 11:41 AM   #15
Jim Brierley
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Default Re: Having trouble getting new Miller-Cragar setup to run

Stock 97 main jets are .045, power valve is #65, stay with those sizes. Be sure the accelerator pump arms are on the "S" setting. (S=summer) What is said above about fuel pumps is accurate but will only affect operation while driving, gravity will work long enough to get you going from a stop.
Check the fuel level in the carbs.
Those heads need a LOT of spark advance. I ran my early Miller with two 97's and set the initial timing at 25 degrees BTDC at idle, that gave 50* at 2,000 RPM. This may sound totally wrong but I've done dyno work on the new Serr Miller and that's what they need.
Two 97's are fine, I run three 81's in my speedster, and it runs great and still gets good gas mileage.

God luck and have fun!
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Old 09-20-2021, 08:28 PM   #16
gh4ds
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Default Re: Having trouble getting new Miller-Cragar setup to run

My experience with an early Miller was exactly the same as JB's where lots of initial advance was needed to make power. The problem then was getting the engine to start without kick back. Anyone have a solution for that problem using a stock 6V starter and an Optima 6V battery?
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Old 09-21-2021, 07:44 AM   #17
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Default Re: Having trouble getting new Miller-Cragar setup to run

Absolutely needs a fuel pump and regulator, don't waste another minute of your time until that's's done, been there done that! Timing as others have said is also a must get right.
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Old 09-21-2021, 04:20 PM   #18
Dan McEachern
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Default Re: Having trouble getting new Miller-Cragar setup to run

" The problem then was getting the engine to start without kick back. Anyone have a solution for that problem using a stock 6V starter and an Optima 6V battery? "


Start cranking the engine and then turn the ignition on.
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Old 09-22-2021, 11:03 AM   #19
rotorwrench
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Default Re: Having trouble getting new Miller-Cragar setup to run

My experience with the high compression helicopter engines over the years was interesting on what can happen when the spark retard system doesn't function properly. I've replaced more than a few starters with broken housings and bendix parts. It didn't matter if the starter was turning or not. When they want to kick back, they will and with a vengeance.

At one time, at least one magneto had an impulse coupling to retard the spark but the engine had to be started on just that one mag. After it was running then the switch could be turned to both to get it up to normal ignition function for two mags. Impulse couplings were problematic so most manufacturers recommended replacing them with electronic vibrator types. On the large and high compression engines, an electronic vibrator that functions through a different set of points in the magneto to give a shower of sparks through the magneto coil as long as the retard points were open. The vibrator was connected into the starter circuit so that it only operated as long as the starter was turning. Some of the higher compression engines had to have this system on both magnetos or the engine wouldn't start well when cold. Now days most all engines use electronic stater vibrator systems for piston engines other than the occasional diesel type.

A person would need to find some way to retard the spark enough to prevent kick back. If that can't be done then they should always keep a spare starter around just in case.
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Old 09-22-2021, 03:20 PM   #20
nkaminar
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Default Re: Having trouble getting new Miller-Cragar setup to run

Park it on a long hill. I had a friend with an old MBZ 190 Diesel that had close to a million miles n it. Not enough compression to start with the starter. He lived on a hill that was about 1/4 mile long. The car would start about at the end of the hill and he simply did not turn it off during the day until he got back home.
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A is for apple, green as the sky.
Step on the gas, for tomorrow I die.
Forget the brakes, they really don't work.
The clutch always sticks, and starts with a jerk.
My car grows red hair, and flies through the air.
Driving's a blast, a blast from the past.
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