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1967 - 1972 F-100 & Larger F-Series Trucks Discuss the Bumpsides Ford Truck

Compression Question

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Old Oct 4, 2021 | 01:08 PM
  #16  
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If the king pins, tie rod ends, drag link etc. check out O.K., there is an adjustment screw on top of the steering gearbox that you can use to remove slack in the gearbox itself. It has a screwdriver slot in it, and there is a lock nut around it.
 
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Old Oct 4, 2021 | 01:57 PM
  #17  
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As long as the steering gear box isn't worn out, that will work I will get to all that later.
Lots easier to work on the little stuff if the motor is out.
 
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Old Oct 4, 2021 | 02:26 PM
  #18  
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Just put the piston at TDC on compression stroke when you do it. If it's not, the engine will rotate and open the valves.

A lot of compression testers have quick connect air fittings on the hose. Does yours? Just hook air up to that. You'll find the leak.

Footnote
To me, That engine looks like it has had a spray paint overhaul. Meaning somebody just pulled it, resealed it and painted it to make it look nice.

But, it's impossible to tell from a picture.
 
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Old Oct 4, 2021 | 02:28 PM
  #19  
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This is my update on the Motor
1, 2, 4, 5 and 6 are all 100psi
Number 3 is 30psi wet or dry and 7 & 8 are as I mentioned before
The truck is not in my shop till after Halloween (I build Animatronics for Halloween)
so I used a small compressor with a 14 gal tank that could not keep up with the air leaking out. Started at 100psi each time,
All 3 cylinders blew air out the carb till it got to the same pressure that the cylinder produced in the compression test
It seemed odd that pressure opened the valve from the combustion chamber side but it stopped blowing by instantly at the test pressure
I had the valve cover off one side so I cleaned up the gasket and just set it back on so I could hear if air was coming up the oil returns
Maybe I may could hear some air but I can't be sure at all with the air coming out the carb. Plus when it was running I didnt see any blow by
With perfect color on every plug, (I know there are compression rings and oil scrap rings) every ring in the motor has miles on it.

I will hate to pull the heads with the motor in the truck but it looks like I may have a chance the heads are the issue
I will be able to see the ridge with the head off so that will help me decide too
Lots of work if I end up putting it back together and there still is a problem

 
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Old Oct 4, 2021 | 02:42 PM
  #20  
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351... I did use my compression tester hose But with the cylinders only holding 30psi no chance it would turn the motor over LOL LOL

Question A Cleveland is a big heavy motor. Did your 71 come with that motor and C4 Transmission? I read that the wishbone front suspension has camber issues if it squats under weight. I am not sure I could find a different motor for my truck that isnt in the same shape.
I was thinking I would trade in my 360 for a 390 since it can develop 100 more HP but if I could find someone that has the parts to build one, they will charge my $300 more if my core is a 360. So far everyone I talked to said the parts shortage would put my delivery 6 months or longer
 
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Old Oct 4, 2021 | 03:47 PM
  #21  
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351C isn't big or heavy. Around 500lbs and noticeably smaller than a FE.

No, it's not stock. No 351c was ever factory installed in a pickup.
 
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Old Oct 4, 2021 | 04:08 PM
  #22  
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You can pull the rockers off of the trouble cylinders and repeat the compressor test to ensure that it is not an issue with the valve train holding the valves open.
 
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Old Oct 4, 2021 | 04:17 PM
  #23  
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Originally Posted by motogotor
You can pull the rockers off of the trouble cylinders and repeat the compressor test to ensure that it is not an issue with the valve train holding the valves open.
That's a good idea, and something I was going to suggest.

If it had been coming out of the exhaust, chances are it would've been a sunken or burned valve. But that USUALLY doesn't happen with intake valves. Not to say it cant....
 
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Old Oct 4, 2021 | 09:38 PM
  #24  
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Originally Posted by bushuna
If the king pins, tie rod ends, drag link etc. check out O.K., there is an adjustment screw on top of the steering gearbox that you can use to remove slack in the gearbox itself. It has a screwdriver slot in it, and there is a lock nut around it.
Don't touch the steering box. It takes a very specific procedure to adjust it. Worn out can't be fixed by adjusting it.
 
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Old Oct 5, 2021 | 09:21 AM
  #25  
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My first test was with a dial indicator to see if the intake valve was opening It would read low compression if it could not suck air in
It was odd... At 100psi when I sent the air into the cylinder, it blew out the carb. as the pressure got down to 30psi, it stopped like a check valve sealed. Without touching the motor or rotating the crank, if I let the pressure build back up, the same thing happened again
I have to wait till after Halloween to move ahead.
When I start to tear it down, I will pull the rockers, exhaust and intake and test it again before I pull the head
After the heads are off I can check for a ridge. If it is too bad, I need to rebuild it anyway
I was shocked that none of the reman shops would do it. They all said they didnt have a block to use but even if I sent in mine, they said no parts were available
There is an engine machine shop I found 30 miles from here. He can bore it and set the cam bearings. I just really didnt want to have to do it all
Maybe by the time I get it out and torn down, that will change
I cant buy any parts till I find out the amount they bore it to and the same with the crank
There has to be parts on a shelf somethere LOL
 
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Old Oct 5, 2021 | 09:38 AM
  #26  
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351... I agree. It has an exhaust manifold leak right near 7&8 but when I saw #3 at 30psi it is on the other side
Funny thing, I drove it home. I didnt play or get on it because of the exhaust leak but it ran ok and it did not pop out the carb

Back in the early 80s, I rebuilt a 351 Cleveland The reason I was thinking it was a big motor was I remember the HUGE intake ports in the heads
Back then, my buddy and I rebuild and built a ton of motors.
I was all about a Mopar Drove a 71 Roadrunner with dual quads on a tunnel ram

I built this Jeep 5 years ago... Ground up


 
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Old Oct 5, 2021 | 09:45 AM
  #27  
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Christmas...
Why wouldnt you touch the steering Gear box.
I have a small amount of play in the steering coupling but I have to adjust the gear box
There is too much slack
I have had luck with other steering boxed in the past.
If it is to worn out to get the play out, I will need a new one anyway
I saw they were just under $500
 
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Old Oct 5, 2021 | 12:04 PM
  #28  
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Yes, don't adjust the steering gearbox because a specific procedure is required. Also, don't adjust your carburetor, ignition points, ignition timing, valve lash, headlight aim, or your rear view mirrors beause specific procedures are required.
 
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Old Oct 5, 2021 | 12:49 PM
  #29  
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I'm not saying you can't. I'm saying you don't just start tightening the screw up.
 
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Old Oct 5, 2021 | 10:55 PM
  #30  
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Yep. Cleveland's are famous for their heads. The 4v intake ports are roughly 2" x 3". Huge. But even the 2v ports are still about twice the size of a Windsor.

I don't know why these guys are saying don't adjust the steering box. I've adjusted at least half a dozen on a variety of ford trucks 60s to early 2000s. Sure it doesn't "fix" anything, but it takes some slop out of the steering wheel.
 
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