Poor power on hill climb

Merc Cruzer

Merc Cruzer

Well-known member
255 (60 over) engine in 53 Merc: New engine 1200 miles ago....compression all good and equal...great power on flat roads (5,280 ft) with mild elevation changes....my trip each time coming home involves a 3,000 foot incline in a 10 mile streach .... when it gets to about mile 9 (the steepest part of the trip - elevation 8,700 ft) I have almost no power and car down to 35 mph...clear the top of the hill and all is good again at elevation 8,300 ft....poor gas mileage....temp is OK (190 to 200)....plugs show a good burn....tappet noise on start up but goes away shortly....I am thinking valve adjustment (loose).....any other suggestions?
 
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Suspect that unless you have a means to manually lean the fuel mixture at altitude (as piston engine planes do ) you are just going to have to live with it.
 
Unless the tappets are WAY loose they are probably making things better rather than worse.

As already mentioned the mixture usually needs to be adjusted slightly at altitude. I say "slightly", because the carb is self-regulating up to a point. A big factor to power reduction at altitude is the loss of air pressure. That is, the height of the air column above the carb is much different than at sea level. No amount of mixture adjustment can replace the lost weight of the column.

I suggest increasing the CR(compression ratio) being certain the timing is at maximum value and down shifting to keep the revs in the 2000 RPM range(if you have a stock cam). I said maximum value for timing because the poor air slows the combustion process. Of course, the timing must meet the general requirements for operation in other areas.
 
Is the dist advance working properly??, there was a big difference in power with the Merc engine I had in a 46 truck climbing "hills" between before and after setting on a dist machine, and fixing some small leaks in the carb-dist pipe.---it turned I think I can,I think I can to catch me if you can.
 
I am thinking your manifold vacuum is almost zero at the loaded point on the hill. A loadamatic distributor would have no advance at that point Just switching to a mechanical advance distributor would change the entire engine performance...
I would loan ya one to try if ya want???
 
Cam ,cam gear,Carb jets ,Distributor , but first I would mark the distributer and advance it a little ,and try again ,
 
BUBBAS IGNITION said:
I am thinking your manifold vacuum is almost zero at the loaded point on the hill. A loadamatic distributor would have no advance at that point Just switching to a mechanical advance distributor would change the entire engine performance...
I would loan ya one to try if ya want???
Click to expand...
I was under the impression that the loadamatic took the vacuum from the carb. venturi and not the manifold ( could be wrong ) please enlighten me/us.
 
This does have the famous Merc-O-Matic Trans....
 

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Merc Cruzer said:
This does have the famous Merc-O-Matic Trans....
Click to expand...

looking at your pictures, your distributor position looks to be retarded a bunch. set it about 1/4" btdc. that will be about 4-6* btdc (before the bump on the pulley) not after. the timing pointer will be to the right of the bump when you are facing the firewall.
check with a timing light.
Hope it works for you.
 
jdl said:
looking at your pictures, your distributor position looks to be retarded a bunch. set it about 1/4" btdc. that will be about 4-6* btdc (before the bump on the pulley) not after. the timing pointer will be to the right of the bump when you are facing the firewall.
check with a timing light.
Hope it works for you.
Click to expand...
Timing could be right on, just the rotor position off location by one tooth. ( number 1 should be at the 6 o'clock position )
 
51-Merc-CT...let me know what you think as to the 6:00 for #1
 

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Merc Cruzer said:
51-Merc-CT...let me know what you think as to the 6:00 for #1
Click to expand...
At this point if your timing is correct there is no need to rotate the distributor.
But if you choose to, rotate rotor one tooth ccw. This will put the clamp near the center of the clamp pad (where it should be) and then re-time.
 

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51-Merc-CT...thanks, I can do that....I was going to add a couple of degrees to the advance to see if that improves things today ayway.
 

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At full throttle the stocker is supposed to advance from the venturi pressure drop rather than the nearly zero manifold drop. This is VERY often too weak to function properly and I think it is very likely you have too little advance when you go to full throttle. A good Loadamatic will operate quite well at part throttle and cruise but wadvance will be somewhere between weak and completely dead at full blast.
(by the way...Ford called for jets one step leaner for cars operated at 10,000 feet and up, so you are right at the change point. I'll have to look it up but I thing they went down by 2 numbers, maybe if there's a jet splitting that difference...?)
 
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Bruce:

You are correct as to the jets...the sea level ones are 56's and I am running 54's. Tried 55's but too rich.
 
The Holley Load-A-Matic will just get you by OK under normal conditions. Under extremes, it falls flat. The thinner air going through the venturi won't react as well up at those altitudes. I think the high altitude carbs also changed the power valve but I'm not sure if they made a small one or not. I'd make certain you don't have a leak in the advance diaphragm.

I can remember struggling to get up mountain passes when I was a kid. The old 51 Merc was set up for the Kansas flats and didn't like climbing any hills. We always had to lock it out of overdrive too.
 
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