Deck height and head thickness are critical dimensions and IIRC Gary aka icanfixall has those available so PM him or wait for his response here.
Hope this helps.
Hope this helps.
86 f250 6.9 rebuild/refresh advice and questions
- Thread starter stealth13777
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stealth13777
Full Access Member
It does! I will try to keep those numbers on here for the next guy doing this job, in case he's as clueless as I am haha. icanfixall has been very helpful throughout this process (thanks!).
On top of those dimensions, is there possibly a simple factory service manual limit for cutting the heads/ deck to zero them? I have found numbers such as .008 for other engines like the 6.0. I don't believe this engine has been apart before, although of course it is hard to tell. I will still check deck height as I reassemble. One other thing I saw was that during a proper head job, they will bring everything in spec (and they are). This to me means that just the head resurfacing should not affect valve to piston clearance, which is the critical issue, correct? Would hate to build up a nice engine, just to start it and ruin it.
oregon96psd
Full Access Member
Resurfacing the head absolutely effects the valve to piston clearance.
If valves are correctly set to depth required it won't affect piston to valve clearance what so ever.
What will affect it is if they DO not check valve face depth...and do not adjust that depth.
Also decking block will affect piston to valve clearance as well. This needs to be figured into any machining process, which in turn means maybe having pistons decked if they protrude to far above deck of block...
These tolerances stack up and stack up very quickly....in a bad way.
Once things start going sideways you also need to consider valve stem height, installed valve spring heights and pressure, along with pushrod length all of which affect valve train geometry.
Just saying...
stealth13777
Full Access Member
Based on my talks with them, the heads have been done correctly in every way. This is backed up by references I had before using this shop and is the reason I am using them. Had not thought about the pushrods, but will do whatever extra measurements I need to and shave the pistons if I have to. As nothing was in horrible shape, I don't anticipate problems, but as you saw cutting that stuff has made me nervous. Relaxed a little now as my knowledge slowly improves on the subject, and I appreciate all the help. The engine did overheat, however briefly, and good mating surfaces on an engine that puts high stress on the head gasket isnt a bad thing I guess.
I know for a fact spring height and pressure have been checked, and a full 'valve job' has been done, which at a reputable shop should mean everything else as well. But I will be sure to ask about all that you mentioned above. Cannot be too careful; it's why I prefer to do my own work, even on projects like this where I'm obviously behind the learning curve. Hoping icanfixall will chime in with the deck height and head thickness numbers so I can check those out when I get everything back. Not that there's a rush with my injury.
EDIT: to quote from a PM for anyone looking for this information
"These are the factory dimensions.The heads are 4.795 to 4.805 thick measured from the valve cover machined rail to the bottom of the head. Now the block is a much tuffer measurement to get. From the top of the deck to the middle of the crank is 11.137 to 11.141. Now the valves must be set depressed into the heads. The intake is set to a depth of 0.042 to 0.054 deep and the exhaust is set 0.051 to 0.063. The pistons are set to perturb out of the cylinders as much as 0.031. You can cut them down about 15 thousands if needed to make this dimension. Another setting is the precups. They can sit above or below the head deck by 2 1/ thousands and no more than that. Some of these dimensions are easy to get and some are nearly impossible."
Gary was extremely helpful talking me through what I needed to measure and what I need to do now that the shop decked my block 12 thousandths. I will be checking the piston protrusion before bringing the engine home, and then doing the rest of the work myself. Thought about letting the shop assemble, but having a hard time trusting them now. Thanks to everyone who chimed in, and as always there's no such thing as too much info! Will continue to update as I work through this, and I'm sure will have more questions.
*extra edit: riot warrior said the same thing in his last post; may need to deck the pistons. reread and saw it, must have missed it before. will be measuring!
I know for a fact spring height and pressure have been checked, and a full 'valve job' has been done, which at a reputable shop should mean everything else as well. But I will be sure to ask about all that you mentioned above. Cannot be too careful; it's why I prefer to do my own work, even on projects like this where I'm obviously behind the learning curve. Hoping icanfixall will chime in with the deck height and head thickness numbers so I can check those out when I get everything back. Not that there's a rush with my injury.
EDIT: to quote from a PM for anyone looking for this information
"These are the factory dimensions.The heads are 4.795 to 4.805 thick measured from the valve cover machined rail to the bottom of the head. Now the block is a much tuffer measurement to get. From the top of the deck to the middle of the crank is 11.137 to 11.141. Now the valves must be set depressed into the heads. The intake is set to a depth of 0.042 to 0.054 deep and the exhaust is set 0.051 to 0.063. The pistons are set to perturb out of the cylinders as much as 0.031. You can cut them down about 15 thousands if needed to make this dimension. Another setting is the precups. They can sit above or below the head deck by 2 1/ thousands and no more than that. Some of these dimensions are easy to get and some are nearly impossible."
Gary was extremely helpful talking me through what I needed to measure and what I need to do now that the shop decked my block 12 thousandths. I will be checking the piston protrusion before bringing the engine home, and then doing the rest of the work myself. Thought about letting the shop assemble, but having a hard time trusting them now. Thanks to everyone who chimed in, and as always there's no such thing as too much info! Will continue to update as I work through this, and I'm sure will have more questions.
*extra edit: riot warrior said the same thing in his last post; may need to deck the pistons. reread and saw it, must have missed it before. will be measuring!
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stealth13777
Full Access Member
Alright, machine shop has everything finished and mocked up the block. Piston protrusion measured .035, with some very slight variation between pistons. This is close enough to make me ask the question: is three (up to maybe five) thousandths enough to warrant spending more money to have the pistons shaved, or should I buy the thickest head gasket out there (fel pro right?) and call it a day?
Shop says if they built it they would warranty it without shaving pistons. But they aren't building it.
Also curious the difference between factory and aftermarket gasket thickness.
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Shop says if they built it they would warranty it without shaving pistons. But they aren't building it.
Also curious the difference between factory and aftermarket gasket thickness.
Sent from my iPhone using Tapatalk
Knuckledragger
blowing chunks and grabbing porcelain
Sorry I didn't see this until now. Have you taken the pistons off of the rods? If not, you might do yourself a favor and have the piston wristpin bushings replaced. That may well be the difference in your deck height variation. When I rebulit my engine a few years ago, I was surprised to see how much slop was in the bushings.
Another thing that counts is the ring grooves. After a lot of miles, they can get loose, so a good looking round and clean piston could still be junk if the ring lands are out of spec.
Don't mean to rain on your parade but as long as you have it apart, there are still things you can do to improve its durability for the future that don't cost a lot but make a difference.
And no, three to five thousandths is not worth machining. But if you are concerned about the extra protrusion, turn the pistons on a sheet of 200-400 grit wet or dry sandpaper on a flat surface and rub it off yourself. 3 to 5 thousandths will come off pretty easily.
Another thing that counts is the ring grooves. After a lot of miles, they can get loose, so a good looking round and clean piston could still be junk if the ring lands are out of spec.
Don't mean to rain on your parade but as long as you have it apart, there are still things you can do to improve its durability for the future that don't cost a lot but make a difference.
And no, three to five thousandths is not worth machining. But if you are concerned about the extra protrusion, turn the pistons on a sheet of 200-400 grit wet or dry sandpaper on a flat surface and rub it off yourself. 3 to 5 thousandths will come off pretty easily.
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stealth13777
Full Access Member
Thanks for the tip. Ring grooves spec'd out ok but will be checking again before putting new rings in. Already being over budget and knowing the engine was in pretty good shape to start with, I'm leaving the wristpin bushings alone. If I keep this thing long enough for that to be a problem, hopefully I'll have a better budget then too!! Thanks for the tips! Hopefully this thread will help others in my shoes as much as it's helped me.
As for the clearance, that's great news.
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As for the clearance, that's great news.
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PwrSmoke
Full Access Member
I went thru this with the heads but not the block in 2009. Head data is below and note minimum head thickness. Mine ended up at around 4.785" but as long as the valve recession is correct, you don't have to worry about hitting the piston with the valves, as several said above. The block is more problematic but Federal Mogul offers destroked pistons (0.010" destroke- in '09 they were part Sealed Power # 2770PN) that will drop the piston protrusion to reasonable levels so you don't end up with a super high CR. I don't know how all gaskets are but my older Fel Pro gaskets (installed in the '90s by yours truly) had a compressed thickness of 0.064" when removed. A new Felpro gasket was 0.074" on the main body and 0.089" on the fire ring before installation. I measured my piston protrusion with new Federal Mogul pistons (not destroked and the block deck was not machined) and it was 0.016" (spec is 0.010-0.031")
I would hesitate running that much protrusion without a full mockup and even cc-ing the combustion chamber to calculate the CR. With 0.035" protrusion, you will have a VERY high CR vs stock and remember that the valve recession spec is calculated on piston protrusion being in the specified range. As was said above, tolerance can stack up very quickly. I don't have gasket specs for the OE but doubt it's hugely different than the aftermarket. My advice, if you opt to shave the piston, take off the max allowable or go with the destroked pistons.
Ford 6.9L Head Data
Good Casting Numbers: 1805855C1, 1809215C91 (’84-86)
Bad Casting Numbers: 1805296C1, 1809199C1 (mostly ’83, prone to cracks)
Minimum Head Thickness: 4.795-in. (4.805-4.795-in)
Seat Angle: 30 deg. int., 37.5 deg. ex.
Valve Margin: .0112-in. int., 0.053- in. ex.
Recession: 0.042-0.054-in int., 0.046-0.058-in ex.
Valve Spring Free Length: 2.050-2.075-in.
Valve Spring Installed Height: 1.80-in.
Open Test Pressure: 200-lbs @ 1.397-in.
Closed Test Pressure: 72-80-lbs. @ 1.798-in.
Valve Guide Clearance: 0.013-0.0055-in. int. & ex.
[/B]
I would hesitate running that much protrusion without a full mockup and even cc-ing the combustion chamber to calculate the CR. With 0.035" protrusion, you will have a VERY high CR vs stock and remember that the valve recession spec is calculated on piston protrusion being in the specified range. As was said above, tolerance can stack up very quickly. I don't have gasket specs for the OE but doubt it's hugely different than the aftermarket. My advice, if you opt to shave the piston, take off the max allowable or go with the destroked pistons.
Ford 6.9L Head Data
Good Casting Numbers: 1805855C1, 1809215C91 (’84-86)
Bad Casting Numbers: 1805296C1, 1809199C1 (mostly ’83, prone to cracks)
Minimum Head Thickness: 4.795-in. (4.805-4.795-in)
Seat Angle: 30 deg. int., 37.5 deg. ex.
Valve Margin: .0112-in. int., 0.053- in. ex.
Recession: 0.042-0.054-in int., 0.046-0.058-in ex.
Valve Spring Free Length: 2.050-2.075-in.
Valve Spring Installed Height: 1.80-in.
Open Test Pressure: 200-lbs @ 1.397-in.
Closed Test Pressure: 72-80-lbs. @ 1.798-in.
Valve Guide Clearance: 0.013-0.0055-in. int. & ex.
[/B]
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stealth13777
Full Access Member
Awesome numbers! Thanks! Hmmm, compression ratio. Still trying to reuse pistons and rods as they spec'd out fine. But I do have a turbo, albeit just the banks kit that might hit 10psi, and I do plan to stud the motor.
Still undecided on shaving the pistons then. Been told .015 is as much as I should take off, so conservatively if I did it I would go .010. Trying to decide if it's worth it, or if I will be fine as is.
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Still undecided on shaving the pistons then. Been told .015 is as much as I should take off, so conservatively if I did it I would go .010. Trying to decide if it's worth it, or if I will be fine as is.
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PwrSmoke
Full Access Member
I have a Banks (1st Gen installed in 1987) too and studded the engine during the overhaul. The boost really adds strongly to the list of good reasons to do something with the pistons to make sure the CR isn't too high. Add more air to a cylinder thane compress it even more than normal... that can result in a very big bang! Head studs will be even more worth it. I guess the risk revolves around how you plan to use the truck. Work it hard and the high combustion pressures might be a durability issue long or medium term. If you opt to throw her together as is, you can be our guinea pig ( : < ) After the engine breaks in, it would be interesting to see a compression test. All I can say is to make sure you spin her over before full assembly to make sure nothing hits! IIRC, there is only about 0.010" between the piston crown and the head with piston protrusion within limits
FYI, I was nervous enough with mine that I bolted the head on with shims to simulate the compressed head gasket and checked clearance with clay. I also cc'ed one combustion chamber after I had a head on. For the life of me, though, I can't find the paper with the numbers and where I worked out the static compression. All I can remember is that it was OK. If I find it, I'll post it. I've rebuilt hundreds of engines and only been more nervous than with mine a couple of times back when I wrenched for a living (a particular customer's Porsche flat six and Jag V12 that really shoulda gone into the scrap pile). Both the customer's engines worked out fine and so did mine.
FYI, I was nervous enough with mine that I bolted the head on with shims to simulate the compressed head gasket and checked clearance with clay. I also cc'ed one combustion chamber after I had a head on. For the life of me, though, I can't find the paper with the numbers and where I worked out the static compression. All I can remember is that it was OK. If I find it, I'll post it. I've rebuilt hundreds of engines and only been more nervous than with mine a couple of times back when I wrenched for a living (a particular customer's Porsche flat six and Jag V12 that really shoulda gone into the scrap pile). Both the customer's engines worked out fine and so did mine.
stealth13777
Full Access Member
1st rebuild, and as expected costs are stacking up quickly. Didn't expect these clearance worries. Guess the gas rebuilds I've seen were easier (plus the guy doing it knew his stuff). I am also working with limited time. But a bad rebuild is worse than higher cost and longer time to end up with nothing...
All feedback is appreciated as I try to decide what I should do. Like you said, I'm 'hesitating' on just picking it up, shaving a couple thousandths myself as mentioned above, and measuring it all when I reassemble. Guess I could figure out the clay stuff too. And I'm capable of figuring out the static compression, but don't really want to haha. If you find the papers from your work that would be awesome.
All feedback is appreciated as I try to decide what I should do. Like you said, I'm 'hesitating' on just picking it up, shaving a couple thousandths myself as mentioned above, and measuring it all when I reassemble. Guess I could figure out the clay stuff too. And I'm capable of figuring out the static compression, but don't really want to haha. If you find the papers from your work that would be awesome.
PwrSmoke
Full Access Member
There are online calculators to help you with CR calculations. Google is your friend.
I'll leave you with one more word of caution and then I'll stop being an old woman. If time and money are a factor, think how they are going to be impacted if things go wrong.
I'll leave you with one more word of caution and then I'll stop being an old woman. If time and money are a factor, think how they are going to be impacted if things go wrong.
stealth13777
Full Access Member
^^I could figure out the compression np if I sat down and tried. Just studying a lot for work as it is and so that's not my idea of fun haha.
Right there with you, and I am not cutting corners simply watching costs (as they jump higher and higher). Machine shop is finally done. Work has been busy for me so other than cleaning the gallons of grease out of the engine bay I haven't done much. Pistons were shaved .010 to bring everything back in spec; the comments about how high the compression would be, even if the valves and piston didn't touch, sold me. Thanks for the input.
New thought is whether or not to do the lifters too. At this point I'll probably just go ahead and replace them. It's only money right? (now where to find said money... hmm, lol)
Local NAPA has been helpful, as I decided to use them for the internal engine parts. Engine remain kit was one of the lowest prices I've found with all high quality Fed Mog stuff in it and FelPro gaskets. Alas, piston rings were on backorder with no 'expected by' date (are lots of people rebuilding these right now?!?). When I said I would still like to deal with Napa, they said they would figure stuff out, and came back offering to piece together all the parts that would have been in the kit with Hastings rings instead, and adding the valley pan, for about the same price. Really only telling the story as a shout out to excellent service.
That's my update. Between work and obligations I don't even have weekends to work on this right now, but will resume assembly as soon as I can. Need it done before the end of the year.
Thanks again to all who have contributed, your support has been invaluable. Looking forward to the day I can post a (hopefully successful) finished product.
stealth13777
Full Access Member
Upon inspection, lifters will be replaced. Camshaft is fine I'm just going to lightly polish it. Lifters might have ruined it in a little more time.
In the interest of making this thread more, well, interesting, here are pics of the progress so far. Some of these were promised months ago to show the bearing wear, but I never got to doing it. What I see (but I don't really know) is normal but noticeable wear. I have lots more photos but most of them are more to help me in case I forget where certain things go, so no need to bore yall. Anyway here ya go, for anyone interested in the process and/or the wear on this particular engine.
Parts!!! pistons had not yet been cleaned when I took this; they have been now!
Pistons/ rod bearings
the worst ones:
Main bearings (some not pictured are still sitting in the block for now)
Honed. Not visually perfect but functional, I think.
In the interest of making this thread more, well, interesting, here are pics of the progress so far. Some of these were promised months ago to show the bearing wear, but I never got to doing it. What I see (but I don't really know) is normal but noticeable wear. I have lots more photos but most of them are more to help me in case I forget where certain things go, so no need to bore yall. Anyway here ya go, for anyone interested in the process and/or the wear on this particular engine.
Parts!!! pistons had not yet been cleaned when I took this; they have been now!
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Pistons/ rod bearings
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the worst ones:
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Main bearings (some not pictured are still sitting in the block for now)
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Honed. Not visually perfect but functional, I think.
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