Classic/Antique Car Repair: SPEED / TRANSMISSION, spark plug wire, horspower

Question
Dick Hi

I dont think its in the mounts, the cars engine was rebuilt and the
engine was recently installed.  Its for the 38 Bantam, the problem
is the amount of pep that the car has,  its very slugish in first gear.
In reverse its very peppy, and Idles fine. I have no other wat to describe it.



thanks

Ken
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Followup To
Question -
Dick hi

I have a general queston regarding the speed of
a car.  The car Im working on runs great and goes really fast in reverse.It I dles good also. But when I place it in first gear, it looses power and dont have the horspower as in reverse.  Do you know what will cause this and do you have a solution-

thanks

Ken


Answer -
Knowing what kind of car we're talking about would be a big help.   Normally, there is no effect on the engine from whatever gear is selected. However, there are some cars whose motor mounts are weak, and shifting to a forward gear makes the engine rock over in the chassis to the point where a spark plug wire or some flexlible hose can get shorted or pinched.   Chrysler 440s are famous for this, for instance - the #4 spark plug can hit the frame during acceleration, thus you lose one cylinder.

If you give me enough information, I might be able to help.

Define what you mean by loss of horsepower, too.  For instance, if the engine revs up to a higher RPM, but doesn't move the car as well, you have a transmission problem in drive that you don't have in reverse - probably a slipping internal clutch or the low band, depending what transmission is in your car.

OK< now you've got some homework.  Let me know what you think about all this and I'll try to help more.

Dick

Answer
The engine doesn't know what direction the car is moving - it rotates clockwise either way.  The reversing is done inside the transmission.  But the driveshaft reverses when you back up, thus the engine moves to the right during acceleration in reverse, while it moves toward the left during acceleration in a forward gear.  If the motor mounts are weak, this motion is exaggerated greatly.  Rebuilding the engine does not include replacing the motor mounts.

So your impression of less power has to be caused by the different forces on the engine. Are you absolutely sure that the accelerator linkage is not affected by the direction?  Try letting the engine idle in neutral, then reach inside the hood and grab the top of the engine and push it side to side.  See if that affects the accelerator linkage.  Perhaps the linkage is hitting something when the engine rocks to the left, and that is keeping the throttle from opening all the way.

Are you sure you are getting first gear?  Perhaps the shift linkage is out of adjustment, and you are trying to take off in 3rd instead of first.  That would cause the feeling you have.  Of course you can sort this out by noting how fast the car is moving for a given engine RPM.  If it is moving much faster in "first" than it is in reverse, I think that would be something to investigate.

Other than that, you have a problem that is going to take someone with some experience with these cars to investigate.  If you haven't already, join the Austin/Bantam club and get someone else to help you dope this one out.

Let me know what you find out?

Dick.