rebuilt motor has no power

[C4engr]

I have just completed installing rebuilt motor with Mitchell ****** in 31 sedan.... I get lots of revs without load.. when driving I can only get 25mph. need suggestions as to where to start looking..

Rog

 

[Rowdy]

Without being there it sounds like a timing issue. Rod

 

[Tom Wesenberg]

I agree with Rod. Sure sounds like the cam or distributor, or both are out of time. What is the compression?

Any chance a rag got left in the intake? I've heard of it happening.

 

[H. L. Chauvin]

Hi C4,

From looking at your engine on this Forum from thousands of miles away, a "rebuilt" motor may always sound good to some; however, a few more details such as:

"Who" rebuilt it?, &.

"When"?, &

Just a few more engine details?

may help further to begin trying to guess what may possibly be a few of your
problem(s).

 

[Chuck Sea/Tac]

I'm thinking timing as well. Check your steering column, make sure the spark and throttle rods are lined up, allowing full advance, and throttle.

 

[BILL WILLIAMSON]

Git yo' Dog to rev it up, while you listen fur a SSSSSST------SSSSST at the KZHAUST pipe. Maybe critters have set up housekeeping in the MUFFELATOR bUSTER t. (Ol' Bill jist sed to try a little bit of choke when it won't git over 25 in case the carbunator (sp?) is way too lean)

 

[Mike V. Florida]

What is your model A experience level? Sounds like timing to me. Where is the timing level set when your drive?

 

[Charlie Stephens]

I agree about timing but are you getting full travel at your carburetor? Have someone push the throttle inside the vehicle while you check to see if the throttle plate lever is hitting the stop.

Charlie Stephens

 

[Mitch//pa]

all good suggestions above i was also thinking what tom mentioned cam timing (gears not lined up ).
make sure you have a strong spark at load with a spark tester.
good fuel
as dad mentioned good flow of air out tail pipe
clutch not slipping
brakes released

 

[gweilbaker]

The limited range of throttle from bent linkage and blocked fuel delivery does what you describe. Do as posted before, check the timing. Once you get it running be sure to re-torque the head and manifold nuts a few times.

 

[MrWzrd]

The nice thing about old cars is the simplicity. They only require a few things to run and few more to run well.

Since it runs..we can assume the basics of fuel, compression and ignition are all present. The question is, "are they right?" (and 25mph says "no". )

Fuel - Should be called air/fuel. I think the assumption that the right ratio is there since it does run but verification of the fuel flow and air flow should be done. Not much to restrict on the intake side but as was pointed out, and exhaust restriction can build back pressure and act as a brake. When my exhaust brake on my diesel malfunctioned and remained closed I could not get the truck over 20 mph. As mentioned above, worth checking to make sure but if the exhaust were restricted you should be hearing hissing at the tailpipe.

Compression - easily checked with a thumb or a gauge. And since you can see the piston through the sparkplug hole you can verify that TDC on the timing gear matches TDC on the piston and verify that the timing gear is installed correctly. Compression can be lost by improper cam timing so it is worth the few minutes to verify that the internal parts are all doing their thing at the right time.

Ignition - I have found that the majority of performance problems, especially on old cars, are found here. Timing seems to be a black art. Assuming that everything above checks out... your problem will be found to be that your timing is set a TDC when fully advanced and after TDC when retarded.

(whoa, bold statement! But you did say you get revs but no speed. I am, dangerously making the assumption that it means revs but no power. No power on a rebuild is usually not mechanical or carb....almost always timing)

2 things to check:
1. position engine so that any cam lobe in the distributor is holding the points full open and verify .018-.020 gap. (I like hot sparks so I always go small for high dwell)
2. With the spark retarded (full up), sparkplugs out, slowly rotate engine to TDC on #1 and verify that the points open at that point.

I'm betting they will open past that point by as much as 10 degrees..and running 10 degrees AFTER TDC will run real smooth but really put a crimp in you power, particularly since full advance will probably only give you zero degrees before TDC.

Hope this helps get you up and running at speed.

 

[Tom Wesenberg]

The cam gear timing was shown in the wrong location somewhere, but I don't recall where I saw it. It was pictured (drawn) with the cam gear mark lining up with the left edge of the keyway, instead of the correct RIGHT edge of the keyway.

When the timing pin drops into the dimple, the distributor rotor should be in this position.

It would be interesting to take a compression check with the cam gear one tooth off, just to see how much difference it makes.

 

[C4engr]

Thanks for all the advise.. It turned out to be the throttle linkage was hitting stop pre-maturely.. Replaced with another I had in the barn. Things work well.

My experience on the A is 40+ years. The engine was rebuilt by Scotty (San Jose) in 1970. Been pickled all these years. Never run until yesterday.


Thanks again.. This certainly is an informative site...

 

[Purdy Swoft]

I think that The reason that so many have trouble with distributor timing is because they are trying to make too many things happen at once. With all of the spark plugs removed, turn the engine over untill the timing pin drops in place. Trying to find the timing dimple with the spark plugs in place is difficult. As it gets near the dimple, compression increases and it will usually go past the dimple when having to fight compression. Forget all the stuff about the spark and the points untill you get the distributor cam tightened in place. The trailing edge of the rotor tip needs to point at the number one contact in the distributor cap as Tom has it pictured above with no clockwise backlash. There will be some backlash (free rotation) in the distributor shaft. When the cam screw is tightened, all of the backlash rotation should be in the counter clockwise direction. In other words when the cam screw is tightened it should look just like Toms picture . When tightened there should be no backwards movement of the rotor tip. all of the backlash must be in the counter clockwise direction or the timing will be retarded. Marco has shown a picture of where the tip of the rotor should point. After the rotor points as pictured with no clockwise backlash move to the next step. Check for full advance and retard of the upper breaker plate in the window of the distributor cap body. If you don't have full movement in both directions an adjustment of the steering column tube will be needed or a different spark control rod if you run the seven tooth steering coiumn. If all is good with advance and retard movement, the next move is to retard the spark lever and check the points. The points should be just ready to open. The recommended points gap is anywhere from .018 to .022 . If the points haven't already been adjusted, set as necessary. Points setting effects the timing, you've got .04 adjustment to get the points where you want them. More gap advances the timing, less gap increases dwell. I run the improved distributor cam with 10 degrees more dwell so i'm not as concerned about less gap at the points. I prefer my timing to be a little advanced so I set my points at .022 .The wider gap allows more time before the points will need to be regapped. With the improved distributoir cam, I get the added dwell and the wider gap advances the timing, I call it best of both worlds. I get crisp throttle response, no starter kickback and I can crank the engine with the hand crank without danger of kickback when the spark lever is fully retarded. Setting the timing isn't a black art. The rotor tip should allways point exactly as Tom and Marco has shown it with no clockwise backlash and NO exceptions. The rest is a matter of breaker plate movement and points adjustment.

 

[Joef21]

I bought Scotty's last engine he rebuilt. He was one of the best. You have a fine engine there. I have not found a stock rebuild to match the one Scotty done.