No low end power

[Blackhawk2940]

Hey everyone. Although I have been researching this site for some time now, and it's been very helpful, I now need some help. If anyone has some insight for me, or can direct me to a thread that already covers this, it would be much appreciated.
52' M37 that I took over the restore on. Everything is stock so far. Alright, so as it sits, it will start and idle just fine, drive out in 1st gear, still really no issues, but when I shift into 2nd, 3rd, and (if I'm going down a grade) 4th, on the lower half of the throttle, it seems like it's missing and I get a choking/popping almost as if it's running out of gas. But if I baby it, it get it through the lower half of the throttle, it will run better in the upper half of the throttle. On a slight decline, I managed to get it into the upper half in 4th gear, and the most I got out of it was 30-34 mph.
Clean fuel going into carb, rebuilt carb twice, it has the mechanical fuel pump, I have the timing set correctly (4btdc), points are correct (.020), new points and condenser, new plugs, cap is good, no cracks (I have already tried swapping it and the coil with new ones, no change).
So if anyone could point me in the right direction, I'll stop getting so mad at the thing.

Thanks

Ben
SSG Wagner

 

[elkhtr]

Have you done a compression test.
When I got my m151 it would start and idle fine.
first and second were good, after that it was a gutless wonder.
compression tested it, and two dead cylinders.
Two broken lifters later, runs like a top now.

 

[NDT]

I would call the experts at Vintage Power Wagons and make sure you have the right jets in the carb. Sounds like it is running lean. Have you tried a partial choke application?

 

[ranger.41]

Blackhawk 2490,
Do a compression test. . It should have 105 lbs or higher in each cylinder. Put a vacuum gauge on it at the intake manifold On the vacuum gauge it should be steady at 19 to 21 in of vacuum. The needle should be steady. Check your plugs they should be clean or white on the cone. Grey too lean black too rich. If all checks out did you move the govenor setting? or is it set at all?

 

[Blackhawk2940]

I'll do a compression test again in the morning, along with a vacuum test and report back. The last I checked, I had around 90 on each cylinder. And I have done nothing with the governor, not even sure where it is.

 

[SturmTyger380]

That sounds exactly like what mine was doing. I did the compression test dry and then with oil. Only one cylinder was close to the right compression. So I am heading to a tear down and decisions on which way to rebuild.

 

[Blackhawk2940]

Alright, so here we are. Did a vacuum test and compression check this morning and it pulled 16 psi at the manifold and
90psi black carbon on plug but white on cone.
91 psi black/white
90 psi black only
90 psi black/wet
82 psi black/white
90 psi black/white

I do have a crappy compression gauge, and #3 might have been wet from cranking while I was doing check. All plugs have white/orange spark.

And judging by the take-out parts I got from the guy who started the restoration, I do know he rebuilt the motor. Unfortunately he passed away, so I can't ask him what he all did to it.

 

[ranger.41]

Blackhawk 2940,
Those compression numbers are low. It may have been rebuilt, but you are going to have to disassemble to see what is going on.
The govenor is on the side if the carb.

 

[SturmTyger380]

If it was rebuilt but the rings did not seat, then you may get away with lightly honeing the cylinders and new rings.

 

[rosco]

That's a simple engine. It should run with what you have done. When I was a kid, an Old Timer told me, "you missed it".... the problem. Did you do the compression test with all the plugs our? Did you put a squirt of oil in & re-test it? Difference? The only other possibility is that its timed "one tooth off". You can check that by watching the valves & rotating it to TDC on #1. As I remember, that engine can be assembled with the wrong head gasket. I also remember that as a young man, I was sure that I could do an "in-frame" easier then doing as the book said, and pulling it. I proved myself wrong.

 

[Blackhawk2940]

I did compression test with plugs in and no oil. Correct head gasket and correct timing. The guys at Vintage Power Wagons said compression will be low after a rebuild until rings properly seat. The previous owner was a engineer for Bell Helicopters, and jjudging by his work, notes and attention to detail thus far, I'm almost certain he did the rebuild correctly. Like I said, idle and high rpm it seems ok, but it's low rpm that it chokes. I may just order a new carb on the 1st in case there is a passage I just couldn't get totally clean.

 

[Blackhawk2940]

Well the guys at VPW believe I have a vacuum leak seeing how it's only pulling 16 psi. So, I tried the carb cleaner around the carb and intake to look for leaks, no joy, everything is tight. Is there anywhere else that I can look to for a vacuum leak? Also, the mechanical fuel pump does leak some oil, would that cause a vacuum leak?

 

[Roller]

Crankcase ventilation valve stuck open? Plug manifold where valve connects and see if vacuum increases.

Frank

 

[Blackhawk2940]

I put in some oil in each cylinder for a few hours, no difference.
I plugged crankcase vent, no change. At 3btdc I got the best vacuum so far at 17 psi. I'm becoming more puzzled every day.

 

[Blackhawk2940]

I also notice that every time I pull the plugs, the middle 2 are always wet, is that common? I checked them for spark, and they are producing good spark like the rest of them, but those two are always wet, and the other 4 are dry with white tips.

 

[Blackhawk2940]

I'm an idiot. I'm a man, I'll admit it. I'm not sure if the fellow before me had them labeled wrong, or what, but I should have checked before I did anything else. Either way, I want to thank you fine men for your advice and help along the way. #3 & #4 wires were backwards.

 

[ranger.41]

Blackhawk2940,
Are you up and running? Over 35mph?

 

[68t]

Well that great, you got it going. A blackhawk person can do anything. drop a pm about aviation. Clear right and left

 

[Blackhawk2940]

Yup, up and running, I've even gotten 45 mph out of her, but thats faster than it should be driven. Either way, now I'm just trying to figure out why she doesn't want to start immediately after driving it for a few miles. I drive it to the store, then gotta wait 15 min or so before she will want to start again.

 

[TGP (IL)]

Carb flooding or possible mild vapor lock issue ( gas boiling in fuel line or bowl)
Make sure you have a heat shield on the fuel pump, route pump to carb fuel line
As far away as possible from the manifold(make new line).
Manifold heat in "summer" position.

Also Carb float level setting on these B&B carbs is critical.

Tom