Lacks Top End

F

FF82

New member
Just installed a rebuilt engine in the 29 model A. It runs great, but seems to lack top end. If I'm cruising at 30 -35 no problem, but then it seems like it runs out of get up and go when the old engine still had plenty. I've checked / set the timing, cleaned out the carb etc...and still the same problem. Any ideas? What is max RPM on these cars?

THanks,
 
FF82 said:
Just installed a rebuilt engine in the 29 model A. It runs great, but seems to lack top end. If I'm cruising at 30 -35 no problem, but then it seems like it runs out of get up and go when the old engine still had plenty. I've checked / set the timing, cleaned out the carb etc...and still the same problem. Any ideas? What is max RPM on these cars?

THanks,
Click to expand...

Well, it would help with a little more information like carburetor etc., but slow (retarded) ignition timing could be a very likely culprit. Also if the points gap is not correct, the coil does not have enough saturation time. Is the polarity on the coil connected correctly?? Also, it could be the GAV on the carburetor is set too lean, --or even the carburetor too small.

Is it possible the exhaust is partially plugged, or the engine is still too tight? Maybe the cam gear was mis-installed? Hearing it would help tremendously but since that is not an option, more information would help us all "armchair diagnose".
 
Are you sure the throttle can open all the way? Perhaps the throttle assembly was damaged on installation? Assuming it was the same carb as before.
 
What parts are different from the old engine--dist,carb,etc?
Has it been run enough to "rock on compression" when it is shut off--until it does it isn't good to explore top speed ---

When I last rebuilt my engine I broke it in on the road,2 days, started at the ocean,kept to 35 in NJ,40 to Harrisburg in PA, 45 to Ohio, that night in Ohio it rocked on compression when I shut it off, started going 50-55, by lunch time I knew that 67 was top speed, drove the rest of the way at 60+ ---stock engine, drivetrain-except for original"B" cam-no overdrive, averaged 23 mpg

You can get a good idea if the cam timing is close through a spark plug hole--coathanger and a flashlight--find the spot where the ex valve closes,the intake opens---they will both be open slightly(overlap),the piston in that cyl should be at tdc ---

What Brent is saying about "hearing" it is true, a retarded cam has a distinct sound along with reduced power, different from retarded timing, and a tight engine can be felt, as can rocking on compression both can be felt and heard.

What cam is being used?
 
When he shut the car off the engine did not come to a dead stop. The cylinder coming up on compression released it by letting the crank rock backwards. This let him know the bearings were broken in.
 
Ok thanks guys I'll take a look this weekend and let you know what I find...i think I'll recheck the timing and gap...never hurts to check it twice :)
 
Brent pretty much said it all. If clockwise backlash was left when the cam screw was tightened, the timing will be retarded. If points gap is too small it will have the same effect. If the manifolds seem to be too hot, this will be a sure sign. Most end up with retarded timing when tring to set the timing by the points, especially if they are trying to run the so called modern points. In many cases the timing will end up so retarded that the engine won't start.
 
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