Is that in the factory service manuals? I have the 6 volume ford service manuals, and should just sit and read some every so often, but so far only check then before any repair I make. Those were the first things I bought off ebay when truck was new to me

 

No, it's a general Tune-Up section from 1950, it's got some interesting observations. I like reading old technical pubs. They didn't waste too many words. I've skimmed over stuff as far back as the 1920s and it's exactly the same principles that apply, it's pretty remarkable, they had this stuff pegged a long time ago, it's all computerized now, but the basic faults are pretty much the same.

 

Another possibility for the low compression numbers, what condition is the gauge in? I have used an old one I had sitting around a while and it gave low numbers, but the were still consistent and even across the engine. Since you say it runs well, even when pulling a load, I wouldn't worry too much. My first thought when reading your thread is go back through your carb and clean it really good and check all the specs. Use a Vacuum gauge aswell like Tedster9 showed. Good luck!

 

Gauge is a brand new one from harbor freight. Today was its first use. I know its probably not gonna blow up tomorrow, but this definitely changes the game

 

What's spark plug # are those NGK? Wonder how hot they are. WR5? Should be in the middle, higher numbers are colder, in the NGK lineup.

Ya know,If it runs reasonably well, doesn't burn oil, plugs don't foul... Manifold vacuum is good....? Work on the ignition timing, make sure distributor is functioning right including both mechanical and the vacuum advance ... make sure carb innards is clean, float level good, choke pull off adjusted, idle mix, and good hot spark.

Good point about (maybe) trying a known good compression gauge. Not much to 'em, still...

 

Y e s plugs are wr5 gapped at .044 for the pertronics. Choke is set per service manual, allowing a 1/8 drill bit to squeeze past w h e n closed. Oh, and one spark plug keeps opening its gap. I had them ar .45 but one keeps opening to .50 but it still firing clean. As far as timing. I have some kind of problem with that. . Haven't tried in close to 8 month, but I remember when first checking it, it read like 35 past tdc. There is paint lines at 6 and 10 but moving it to those lines ran very poor. Dont know how to change advance, and there has never been a vac line to vac retard side of pot. If the timing skipped a tooth wouldn't cause the low comp due to valves opening on compression stroke? Timing is at 16 past center now, and has been for the past year

 

Worn timing set causes late valve timing, that will tend to cause lower cranking or running compression. Chain stretch. One way to tell is to rotate the engine backwards a couple times around to take up the slack and line up TDC, keeping an eye on the distributor rotor, and rotate the engine forward slowly and evenly. It's easier with the plugs removed.

Note the exact point where the rotor just starts to move, and stop. See how many degrees on the damper are indicated. Ideally it would be none, but I've heard of 10° or more with high mileage. Just a few degrees can make a difference. A related issue is the factory in some years installed camshafts with retarded valve timing for emission purposes. A worn timing set just makes this even worse.

Valve or camshaft timing is completely different than ignition timing. Advancing the ignition timing is a way to try and compensate for a stretched timing chain or late valve timing. But it doesn't really work that way. Manifold vacuum should meet the factory specification of 18" to 21" at sea level at the factory base timing, e.g. 6° or 8°, say, if it doesn't, then chain stretch and/or incorrect camshaft phasing may be the likely culprit.

Late valve timing definitely causes sluggish response and hard starting. It changes the cranking compression. When it comes to ignition timing, it's important to make sure TDC on the balancer really is TDC, a piston stop tool is used most often for this. A long 18 mm bolt works for this. The idea is to rotate the engine by hand in both directions till it stops against the #1 piston, and mark the balancer at both points. Exactly halfway between is the true TDC. Both the mechanical weights and springs, breaker plate, and the vacuum advance on the distributor needs to work smoothly and properly up and down the RPM range, and provide sufficient advance or retard at any given RPM or engine load.

 

@Horsethief Any updates?

 

Well I did what you recommended, and the tick went away. Also oil pressure was always at the bottom of gauge, but over the past 3 days it is floating around the middle, and the engine sounds like it's running submerged in a bath of oil. Very smooth, and "wet" for lack of a better description. The exhaust tone is bubbly, liquid , and quieter, but compression in cylinders went up only 2-5 lbs per cylinder. It starts up without pumping gas pedal all day, and that first start in the morning only takes a few pumps, and one try. Still have to feather the throttle for 15 seconds on that first start until it holds idle, but mabey I am just asking too much on these old trucks. Just want that no pump instant start at all times, and feel it is achievable

 

Sounds good ... keep testing and checking stuff out, definitely a learning curve to this stuff.

 

I'm curious, was timing chain slop checked? Valve timing does make a difference in cranking compression. That would be one more data point to look at.

 

It was not. I had plans to open it up when I was replacing water pump, but forgot about it until I finished cleaning up my tools and mess. When I do go in there though , I am just gonna have a set ready to replace so I dont have to go back in later. That is definitely on my list, as I have had a car bust the timing chain, and kill a whole motor with only 50,000 miles on it. ....
Come to think of it, I dont even need to open timing cover to check that do i?

 

You mention getting 15" of engine vacuum in the high country, but, at what ignition timing? Late valve timing usually means it's necessary to increase the distributor timing in excess of factory spec to get any kind of good manifold idle vacuum. For actual diagnostics though, set ignition timing to factory specs of say 6 deg. Late valve timing events can be caused by stretched or worn timing chain, and '73 was right in there about the time Ford severely detuned their motors. One of the ways they did that was retarding camshaft timing.

Seepost #38. 'Retarded camshaft + worn timing chain on top of it cripples both performance and any nod towards fuel efficiency such as it was, especially any grunt on the low end. It's a little trickier to to remedy because buying a new timing set and installing "straight up", is no bueno - it likely already has several degrees camshaft timing retard built in.

Valve timing is completely different than ignition timing. Don't really need a degree wheel as such (although it's best) but knowing at least what side of valve overlap the camshaft centerline falls on is VERY useful. Advanced the camshaft in my slick 4° and the powerband is much better, I did this because replacing the timing set, it's the same amount of work to do it right as do it wrong. The slop from stretch had delayed valve timing by maybe 8 to 10 deg. It now pulls 21" vacuum at 12° base timing, a big improvement and cranking compression improved 5 to 10 psi. They all read 150 now.

If it turns out you've a lot of slop in the chain set now, and decide to replace it, make sure to buy a timing set for an earlier motor. Late valve timing is never a good thing for a stock or street driven motor, especially a truck, and even especially bad at any kind of altitude. Not saying this is your problem but it's something to check. Advancing the camshaft will compensate for chain stretch too, they really crippled that era of engine direct from the factory.

 

Gott it. I will do some investigation today. I know that when I first set timing it was at 6, but ran like crap. I noticed as I got up to around 15-30 or ran alot better, and smoother. Went all the way to 30+, a bit past the factory Mark's into the blank space , and it seemed to run the same as when it was at 6 . Just past 30 is where it started to cough at idle speed so backed it up slowly until it ran best to my ear. That point was I think 20 or 22, but to me I t r u n s I d e n t I c a l. B e t w e e n. 15-22 so I left it at 16, and it's been there driven daily for the past year and a half. Those numbers never seemed right with me, but it ran so good , and still does, that I left good enough alone. Low end power is sluggish as you said. Throttle response is instant, and at 15-20 mph I can tap the throttle and it takes off like crazy, but from a stand it's like a chugging locomotive. Especially steep hills. Seems like it should have more power for that. Hmm. Any excuse to hang out in the shop all day with the turntable spinning records is good with me