1970 F engine rebuild

Joined
Aug 20, 2022
Messages
14
Location
Chrsterfield,VA
Well finally got my 1970 Fj back to Va at Iron Pig Off Road. Lance did a leak down test and I think his words went something like this, ‘that was one of the worst I have seen….”

Not a good way to start out the day and the first time that I was able to see the vehicle. Even with the bad news on tHe leak down test, I am excited to get the ball rolling on getting this vehicle back on the road. Being that I really want to keep this vehicle as original as I possibly can, we are planning to pull the engine, take it to a machine shop and see what we need to rebuild it. He was very honest with me and let me know that will be a very tall task to get parts. Being the eternal optimist, I wanted to post on the forum to see if anyone could help me locate parts for an original F engine. Keep smiling……
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Skreddy

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Joined
Feb 3, 2020
Messages
1,785
Location
Stanwood, WA
Well finally got my 1970 Fj back to Va at Iron Pig Off Road. Lance did a leak down test and I think his words went something like this, ‘that was one of the worst I have seen….”

Not a good way to start out the day and the first time that I was able to see the vehicle. Even with the bad news on tHe leak down test, I am excited to get the ball rolling on getting this vehicle back on the road. Being that I really want to keep this vehicle as original as I possibly can, we are planning to pull the engine, take it to a machine shop and see what we need to rebuild it. He was very honest with me and let me know that will be a very tall task to get parts. Being the eternal optimist, I wanted to post on the forum to see if anyone could help me locate parts for an original F engine. Keep smiling……View attachment 3164617
What parts do you need?
 
Joined
Sep 20, 2022
Messages
553
Location
35th parallel north
The valve clearances were checked for wiggle, when closed, on a failed cylinder?

Think about it, you can't get horrible leak-down results without other signs of catastrophe, or long-term wear. Does the PCV valve / hose connected to intake manifold look like La Brea Tar Pits?
 
Joined
Jul 5, 2005
Messages
1,866
Location
Ames, IA
Yeah, what was faulty in the leak down test specifically? Low compression isn't really a big deal in an old F engine if it's consistent.
 
Joined
May 26, 2017
Messages
62
Location
Littleton, Co
Well finally got my 1970 Fj back to Va at Iron Pig Off Road. Lance did a leak down test and I think his words went something like this, ‘that was one of the worst I have seen….”

Not a good way to start out the day and the first time that I was able to see the vehicle. Even with the bad news on tHe leak down test, I am excited to get the ball rolling on getting this vehicle back on the road. Being that I really want to keep this vehicle as original as I possibly can, we are planning to pull the engine, take it to a machine shop and see what we need to rebuild it. He was very honest with me and let me know that will be a very tall task to get parts. Being the eternal optimist, I wanted to post on the forum to see if anyone could help me locate parts for an original F engine. Keep smiling……View attachment 3164617
I might have a line on some +0.020" pistons.
I just did a minimum rebuild on mine.
New rings, bearings and seals.
Intake/exhaust flatness and gasket seals were my biggest challenge.
I'm replacing all the seals and gaskets in the 3 speed and transfer case now.
I have all the PTO parts except for the winch reel and gear.
Any ides?
 
Joined
Sep 20, 2022
Messages
553
Location
35th parallel north
Newby question here? Can't new rings be installed in old pistons? I'd recreate a honing pattern (for better surface oiling) in the cylinder wall, and just call it good? Don't replace parts that aren't broken kind-of-approach on antique or non-resotored vehicles. Unless the bores have enough out-of-center or major out-of-round wear, I'd not want to jump to larger pistons; I'd imagine that most engine rebuilders would call me "loco."
 
Joined
May 26, 2017
Messages
62
Location
Littleton, Co
Newby question here? Can't new rings be installed in old pistons? I'd recreate a honing pattern (for better surface oiling) in the cylinder wall, and just call it good? Don't replace parts that aren't broken kind-of-approach on antique or non-resotored vehicles. Unless the bores have enough out-of-center or major out-of-round wear, I'd not want to jump to larger pistons; I'd imagine that most engine rebuilders would call me "loco."
Yes, new rings can be installed on old pistons, once properly cleaned and inspected.
That is what I did on mine. I had 120 p.s.i. on four cylinders and 90, 100 on the others.
I cleaned, inspected and measure piston grooves per the manual.
I installed the old top ring in the cylinder and got 0.044" end gap.
New top (Std) ring in cylinder was 0.020" end gap.
Factory spec is 0.008" to 0.016".
I reamed the ridge out of each cylinder then honed them.

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middlecalf

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Joined
Jul 20, 2004
Messages
4,731
Location
Sweet, Idaho
Newby question here? Can't new rings be installed in old pistons? I'd recreate a honing pattern (for better surface oiling) in the cylinder wall, and just call it good? Don't replace parts that aren't broken kind-of-approach on antique or non-resotored vehicles. Unless the bores have enough out-of-center or major out-of-round wear, I'd not want to jump to larger pistons; I'd imagine that most engine rebuilders would call me "loco."
I did this, similar to what @BloodyMGT describes above. My replacement STD ring end gaps are a little more than his, but way less than what was there, plus none of the rings are broken now 😂, several were before. The bore diameters were 0.010-0.012 which is right at the limit that one piston ring maker says is the max for just re-ringing. The bores were at most 0.001 unconcentric. No more smoke or oil burning, we‘ll see!
 

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