Rebuilt B engine has no power dilema

B

Brkile

Junior Member
Please bear with me here. I've been fooling with Model A's for 56 years, have repaired/"rebuilt"/patched/cobbled up many A engines, all ran good to excellent based on their condition. I decided to build a really good engine, for once. I did, and now it seems to me it has little power. I located a Model B engine that came out of a running "club tour" type car that was being made into a hot rod (ouch!!). The babbitt looked like it had been done not long ago, the crank was round. I bored it .060 over, decked, head was surfaced, some new valve seats, a small crack in the deck was pinned, new stainless valves, rebuilt carb from Berts. Bearings set to .001-.0015. It starts easily and runs perfectly quiet, doesn't overheat or smoke. None of the usual ticking, clanking, thudding or pounding that my other engines always had. Timing has been checked many times. No water in the oil or oil in the water. It just seems to have very little power. The car , '30 coupe , won't go over 40 mph (rebuilt speedo). The brakes aren't dragging. It has 80-85 psi compression. It turns freely with the hand crank.
Some thoughts, possible flat cam ?, bad coil? bearings too tight? Or is it just not broken in ?? I have only driven it about 50 miles because it is miserable to drive in this Bay Area traffic as it is.
Anybody have any ideas or thoughts on this ?? HELP !!
 
When you check the timing do you have the correct front cover for your timing gear, the pins are in different locations? Model B distributer, Model B timing cover. Model A distributer, Model A timing cover. Attached is a photo of a Model B timing cover with the timing pin hole at the top of an oval boss. The Model A boss is circular. Note that a few post production Model A covers were made with the oval boss and the pint the bottom but these are seldom encountered.

Charlie Stephens
 

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Does the carb open all the way?

When you pull the spark lever down are you getting full advance?

I am assuming the timing marks were lined up when assembling the engine.

Just some thoughts.
 
Brkile said:
I forgot to say, it has a Model A distributor and timing cover. Thanks for responding.
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I suspect your trouble is in the timing. The B cam has different timing from an A. In their original trim, the two motors required quite different amounts of advance. If you're running a mix of components, things won't be right. I don't think an A distributor even with an A timing cover will run right with a B cam.
Apart from that, you might do well to check the carb (maybe try a known to be good spare), no restrictions in the inlet or exhaust and all the usual tune up things (points gap, plug gap etc etc.)
 
Is the advance mechanism in the distributor working properly?
I would advance the timing a 1/8" by adjusting the rotor and take it for a short drive and see what it feels like. If it helps,starts,easy,doesn't get hot then I would do it again. Also look at the plugs.
 
It sounds to me like your cam timing is off. Are the cam and crank gears properly aligned? You may want to pull the head and check that the valves open and close when they should in relation to the crank. Try all the easier stuff first. But if you still don't have good power check your cam timing.
 
Now is the time to install another carburetor in order to eliminate insufficient fueling as the source of the problem. If that changes nothing then you are looking at a timing problem, either valves or ignition.
 
Wick said:
Is the advance mechanism in the distributor working properly?
I would advance the timing a 1/8" by adjusting the rotor and take it for a short drive and see what it feels like. If it helps,starts,easy,doesn't get hot then I would do it again. Also look at the plugs.
Click to expand...

He says it is an A distributor.
 
I recently bought a Model B engine. I compared the lift of Model A camshafts I have with the B camshaft only to find out my B cam had much less lift! The B camshaft lobes are very sharp and wear down easier than the Model A camshaft.

My advise is to pull the camshaft out and measure it. Fordgarage gives some good info on cam lifts.
 
Wick said:
Is the advance mechanism in the distributor working properly?
I would advance the timing a 1/8" by adjusting the rotor and take it for a short drive and see what it feels like. If it helps,starts,easy,doesn't get hot then I would do it again. Also look at the plugs.
Click to expand...

With an 'A' distributor, no need to mess with the rotor/points cam. Just pull the timing lever down a few more clicks!
 
Agree with 909. You can use the A distributor, but it has to be timed to the B cam, so needs a B timing cover with the B timing pin location. Check that the cam is aligned with the crank while you are changing covers.
 
A timing cover and dist should work well together. All B cams are not the same, most have .302" lobe lift, some .315" and the latest one has .339" lobe lift. I've seen reground cams that have as little as .250" lobe lift. Check the easy things first as mentioned above, then cam timing and lift. Another possibility is a restricted muffler.
 
John Stone said:
Does the carb open all the way?

When you pull the spark lever down are you getting full advance?

I am assuming the timing marks were lined up when assembling the engine.

Just some thoughts.
Click to expand...
I would like to expand a little on John's post as I think he may have the answer. Have someone sit it the car and push the accelerator to the floor. Look under the hood at the carb and be sure the throttle lever is going all the way to the stop (6 o'clock). Don't try and take a short cut by just moving things under the hood, find someone to sit in the car. Also check to see that the throttle is completely open when the lever is against the stop.

Also check the spark level travel with someone in the car operating it.

Another thought, do you have access to a good running carburetor that you could swap?

Be sure to post the final solution.

Charlie Stephens
 

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No power update. Thanks to everyone who chimed in on this situation, there were a lot of good ideas.
I checked/thought about most of the ideas offered. Unfortunately, I didn't find anything obviously wrong so think this is a combination of factors. I eliminated a fuel problem as I ran a weepy old Tillotson carb before the freshly rebuilt Berts Zenith and it ran the same. (I've run many Model A engine with this same old Tilloton and they ran great). The pedal opens the carb all the way. Prior, I replaced the fuel shut off valve, stand up in tank screen, and new fuel line. Its got good fuel flow. I took off the timing gear side cover hoping to find a problem with the cam gear but it looked great. I determined, best I could by looking in the #1 spark plug hole that it was at TDC when the timing pin is in the detent.
I timed it the way I always have for 50 years and even checked it with a Nu-Rex wrench and it ran the same, no power. I finally began advancing the timing slightly so it would still start easily and the engine became more peppy. As it is right now , it is more advanced then I have ever had one set and it still starts easily and runs cool (138 d) after running down the expressway. Another thing I found was that I had the accelerator footrest adjusted high so my foot was comfortable but while driving, it may have prevented the accelerator from being depressed fully. I took it on the expressway and it ran pretty good around 46-47 mph and I couldn't go any faster because of the slow traffic (for once, the slow traffic wasn't me!) .
So at this point, I think this was three factors. 1) tight, fresh engine with little break in miles (maybe 50). 2) accelerator foot rest way too high 3) Timing set too retarded. I would really like to hear any ideas as to why the timing now is set apparently advance but the car performs and runs way better.
Once again, thanks for all the help.
 
Like Jim Brierly said about camshaft lift. Measure what you have with a dial indicator. Make sure your cam gear isn't a 2 piece and dont use a macerated gear. I don't trust regrind camshafts. I sent my short block out to have it inserted, babbett had too much endplay on the crankshaft. And they put a socalled regrind touring cam in it. I measured my old cam lift before it left my hands, the regrind came back over .020" less lift. I took it out and put a Bill Stipe Specialties cam in, all lobes measured no more than .001" difference, that was checking it with a dial caliper, (not exactly precise).

I also time mine with a timing light to find full advance with my spark lever all the way down. Mark your front pulley to the total degrees you want and check it from that. Make sure your distributor has no side play. Check your rotor clearance to the distributor body posts.

My first carburetor was a Tillotson and I never felt it had 40 hp like it should have even with a 6:1 compression head.
 
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