The Ford Barn

FF82 · 04-19-2012, 07:10 AM

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,

BRENT in 10-uh-C · 04-19-2012, 07:27 AM

Quote:

Originally Posted by FF82

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,

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".

1931 flamingo · 04-19-2012, 07:34 AM

Brent's just about got it all covered. Re-ck the timing, point gap. JMO

Paul in CT

V4F · 04-19-2012, 07:50 AM

Ditto

Farrell In Vancouver · 04-19-2012, 08:01 AM

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.

Kurt in NJ · 04-19-2012, 08:10 AM

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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?

29ModelA · 04-19-2012, 08:26 AM

What are you talking about "rock on compression?"

Frank Miller · 04-19-2012, 08:33 AM

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.

juke joint johnny · 04-19-2012, 09:00 AM

Is it a stock cam ? or a B regrind?

What gap have you got on the intake and exhaust valves ?

John

FF82 · 04-19-2012, 10:11 AM

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

Jim Parker Toronto · 04-19-2012, 11:57 AM

Quote:

Originally Posted by Farrell In Vancouver

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.

My vote would be with this answer!

Jim Brierley · 04-20-2012, 10:33 AM

If all else fails, check the cam for proper lift. All reground cams are not the same.

Purdy Swoft · 04-20-2012, 11:52 AM

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.

Mike V. Florida · 04-20-2012, 01:16 PM

The first thing that jumps to mind is timing. Check TDC by checking in the #1 cylinder to see it the pin is really at TDC.

04-19-2012, 07:34 AM	#3
1931 flamingo Senior Member Join Date: May 2010 Location: new britain,ct 06052 Posts: 9,390	Re: Lacks Top End Brent's just about got it all covered. Re-ck the timing, point gap. JMO Paul in CT

04-19-2012, 07:50 AM	#4
V4F Senior Member Join Date: May 2010 Location: ca. Posts: 2,522	Re: Lacks Top End Ditto __________________ V4f

04-19-2012, 08:01 AM	#5
Farrell In Vancouver Senior Member Join Date: May 2010 Location: Pitt Meadows BC Posts: 1,003	Re: Lacks Top End 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.

04-19-2012, 08:10 AM	#6
Kurt in NJ Senior Member Join Date: May 2010 Location: on the Littlefield Posts: 6,159	Re: Lacks Top End Sponsored Links (Register now to hide all advertisements) 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?

04-19-2012, 08:26 AM	#7
29ModelA Senior Member Join Date: Jun 2010 Location: Owosso, MI Posts: 673	Re: Lacks Top End What are you talking about "rock on compression?" __________________ 1929 Model A Barn find. California car, just a few more parts to find. Interior, steering box (rebuild), and I am sure much more!

04-19-2012, 07:10 AM	#1
FF82 Junior Member Join Date: Aug 2010 Posts: 4	Lacks Top End 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,

04-19-2012, 08:33 AM	#8
Frank Miller Senior Member Join Date: May 2010 Location: Auburn, MA Posts: 2,106	Re: Lacks Top End 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. __________________ “The technique of infamy is to start two lies at once and get people arguing heatedly over which is true.” ~ Ezra Pound

04-19-2012, 09:00 AM	#9
juke joint johnny Senior Member Join Date: Feb 2012 Location: London England Posts: 908	Re: Lacks Top End Is it a stock cam ? or a B regrind? What gap have you got on the intake and exhaust valves ? John

04-19-2012, 10:11 AM	#10
FF82 Junior Member Join Date: Aug 2010 Posts: 4	Re: Lacks Top End 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

04-20-2012, 10:33 AM	#12
Jim Brierley Senior Member Join Date: Jun 2010 Location: Temecula, CA Posts: 4,092	Re: Lacks Top End If all else fails, check the cam for proper lift. All reground cams are not the same.

04-20-2012, 11:52 AM	#13
Purdy Swoft Senior Member Join Date: May 2010 Location: Alabama Posts: 8,099	Re: Lacks Top End 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.

04-20-2012, 01:16 PM	#14
Mike V. Florida Senior Member Join Date: May 2010 Location: South Florida Posts: 14,054	Re: Lacks Top End The first thing that jumps to mind is timing. Check TDC by checking in the #1 cylinder to see it the pin is really at TDC. __________________ What's right about America is that although we have a mess of problems, we have great capacity - intellect and resources - to do some thing about them. - Henry Ford II