Options for freshining up a 1500

[bpimm]

2 years ago our 1980 was in storage for the winter in My Aunts Garage when we noticed most of it's engine fluids on the floor, I think it's engine oil and tranny juice as well, it always leaked a bit but this was a puddle about 4 feet around. The engine is carbed and the carb is s^*t, I have been planning to swap it to FI and decided now was as good time to get it on the road again. I bought a derelict car from Mike M he had picked up some time ago, he discovered it had a decent running engine in it so my plan was to swap the engine in the 80 then rebuild it's engine and swap back. After I came to my senses I decided to check out the engine from the "Bottomfeeder" X as Mike had named it, I pulled the pan and checked the bearings and they looked almost new, so I scoped the bores and they had a nice crosshatch showing almost like it had been re-ringed. If I remember the story Mike told me, there is a chance they did a quicky rebuild on the engine but never finished the car to get it on the road. While I was scoping the bores it looked like the crosshatch stopped short of the head, something didn't look right so I thought I'd pop the head off and see. After building a head removal tool it became apparent that this head had never been off the engine and the car had 120K miles on the clock. After getting the pistons out the bores looked pretty good except for the top 1/2-3/4" which had a fair amount of carbon buildup. So I guess it wasn't re-ringed after all. Is it possible that an engine with 120K would still show clean crosshatching on the cylinder walls?

So here is where things are now I have it torn down and mostly cleaned up, I would like to reuse the pistons and replace bearings and rings and have an engine that will last. So now the questions start...

I found the specs in the factory manual from the wiki page, thanks to whoever put that together for us. Nominal bore size is 3.4015" Max is 3.4035", after measuring the bores all of them are above the 3.4035" mark by a bit my measurement range is 3.4036" to 3.4049" with 1 outlier at 3.4054. the pistons measured 1 & 2 were 3.401" 3 was 3.399" and 4 was 3.400". I'll attach the actual cylinder measurements to this post. I ran a dingleball hone in the cylinders to clean them up before measuring.

Is this block to worn to run stock pistons? What is the max piston to bore clearance that can work for a street motor?

My Mic checks good at the 3" standard but I don't know how accurate it is at 3.4" so there could be some error there, I have a set of gauge blocks coming so I can check it at 3.4 so I know what the error is there.

It' been about 30 years since I built an engine so any advise is always welcome.
to read the notes, the dial bore indicator was set to 3.4015 and the numbers recorded on the list have the 2 leading 0's left off so they are really .00nn so just add them to the last 2 numbers of the set value. 3.4015 +30 would equal 3.4045, hope that makes sense.

 

[Dr.Jeff]

Brian, It's been ages since I've done a complete engine rebuild as well. So I'm in pretty much in the same boat. With German engines (I'm more familiar with them), it is considered o.k. to rering and install new bearings without necessarily having to remachine everything. They are very robust and forgiving engines; hone the cyls as you have done, file the new rings to the proper gaps to fit the cyls, thoroughly clean the ring grooves on the pistons (and everything else), and reassemble with new seals and gaskets. As to the cylinder bores and new rings, you can also get oversized rings for the stock pistons rather than replace the pistons.

There will be opinions about this. I recall back when I was a youngster and first learning about such matters, it was normal practice for repair facilities to "overhaul" engines this way. A complete "rebuild" with all new machine work was reserved only for engines that had suffered actual damage...not just normal wear. I even knew guys that would just throw in new rings without even honing the cylinders and get another hundred thousand miles from it.

But there are those who believe all of this is improper; that you should ALWAYS completely remachine everything regardless. Every engine must be blueprinted and assembled in a mil spec clean room to exacting tolerances. So I guess we'll hear opinions both ways. To me a big part of such decisions is your budget and goals. Is this a daily driver that you will depend upon to get the kids to school on time? Or a occasional weekend play car that won't matter if it develops issues later? Do you never want to touch the engine again? Or actually enjoy working on it and won't mind if you have to again? Can you afford to throw unlimited funds at it? Or is it a hobby car on a limited budget?

Not sure I addressed all of your questions. But hope these comments shed a little stimulus for thought.

 

[MikeHynes]

Did you perform a leakdown test before you opened the engine up? That would really help to figure out how to proceed.
As you know the engine will run with the pistons that are currently installed. If you re-ring them, and get the gaps right, the engine will still run, and it should run better - for awhile. Maybe for a long while? But, because the piston skirt to cylinder wall clearance will be larger, and perhaps out of spec, the pistons will rock in the bore a bit more than when new. Also the used pistons will have some wear of the ringlands, meaning the rings will "flutter" just a bit more than they would in a new piston. The piston rock and ring flutter will decrease the ability of the rings to seal things up - just a bit. But it will still run, and may not smoke as much as it did before the re-ring. But, the rings will wear out sooner in the used pistons than they would in new ones. Given a 120K life of the rings that are in there now it's not unreasonable to think that the new rings in the old pistons will give acceptable service for, what, 50K more miles? Maybe more, maybe less?
So, it all comes down to what do you want out of the engine? To perform like new, or to just perform well enough? To last another 120K miles, or just another 20K miles? Do you have a budget, or do you want to spend as little as possible?
What about just leaving the rings that are in there now in there? Sure the engine will probably use a bit of oil, maybe a lot?
I think that you'll get the biggest bang for the buck by concentrating on the cylinder head first. Get that right first, then anything you do to the shortblock will be just that much better.

 

[bpimm]

Dr.Jeff, you're absolutely right this could be a can of worms discussion. The car is a summer fun car only not a daily driver so If I get 50K out of it that will get me 10 years.
I will be shaving the head to get rid of the decompression ring as well as adding the most cam I can with the stock FI so it will have a bit more power than stock but still not enough to get away from your average mini van. This is the better half's car and I need to make it run good so I can Part out the Miata to help fund the one I want to build. The budget is flexible as low as possible but machine work can be done if needed, I'd rather spend the play budget on the play car but I also have to keep Rae happy.

 

[bpimm]

Mike, I did do a leakdown test and it was OK, not great but not bad either. I don't remember the numbers, they're written down somewhere....

I'm not expecting new performance out of a freshen up, I haven't measured the ring to land clearance yet so that may tell me more about the piston condition.

After posting this last night and staring at the cylinder measurements I was having trouble forming a picture with 9 measurements per hole so I did a bunch of averaging to form a better picture in my head of what the wear is and cyl's 1-3 are .001 over and 4 is right at the max spec, taper is .0005 on cyl 1 and .0002 on the other 3, The pistons measured 1-2 3.401 3 3.399 and 4 3.400 giving me clearance numbers of 1-2 .0036 3 .0057 and 4 .0038. I think the only one that worries me is #3 at .0057, that might slap a little when cold. If I could find another 3.401 piston that cylinder would be right with the others, I have 2 other blocks... What are the thoughts on swapping a different piston in that hole?

I'm going to at least do rings and bearings, I haven't checked the crank yet I might just send it out to be cleaned up and then decide on bearings, I can't feel any grooving on the crank journals but they have some discoloration, but that may be from sitting for years without moving I need to get some plastigauge and check it before I make that decision.

The head is going to get milled and a cam added, I'd even consider some port cleanup if I could find a pictorial of what needs to be done.

Some day I would like to do an all out build on one of these engines, this is just not the time, I have other projects in line first.

 

[Dr.Jeff]

What are the thoughts on swapping a different piston in that hole?

Or how about shifting the existing pistons around to other cylinders to get a decent combination of sizes/clearances? I did not look at your numbers close enough to see what could be done with that.

If any of your other used pistons are in good condition, it shouldn't a real problem using them - given you will be installing new rings. Make sure the pins fit the rods well (possible difference in wear rate). However you might also be exposing some new variables by doing this; depending on the condition of the other pistons and their exact dimensions (eg. crown heights, pin location, skirt length, weight, valve clearance notches, etc.) - I'm not completely sure how consistent Fiat pistons are?

I need to get some plastigauge and check it before I make that decision.

Exactly what I was thinking. I tend to view rings as the primary "wear" item, much more so than bearings. Just consider the fact these engines don't even have cam bearings (that still rests uneasy with me). But if the oil pressure was good, the journals are clean, and plastigauge shows acceptable wear, then the bearings might not even need to be replaced. However if it has 120K then it would be a good idea to replace them. Having the journals polished might put them into a greater tolerance range (same as added wear). Depends on how clean they look.

So, it all comes down to what do you want out of the engine?

I think that you'll get the biggest bang for the buck by concentrating on the cylinder head first.

I fully agree with Mike's comments. That was what I tried to say in my earlier post. A refresh (including the valves) will improve the engine and get more life out of it. How much additional life you need depends on your long term goals. I think you pretty much answered that, "If I get 50K out of it that will get me 10 years". [That would get me 50 years on mine ]


In general I get your delima. For a occasional use weekend play car that I did not want to sink a lot of money into, it would not bother me to just do a refresh. But at the same time if this is for your wife you don't want to leave her stranded.
I have 3 engines in the same situation (one isn't a Fiat). All three ran, had decent compression, decent leak down tests, decent oil pressure, and could likely be kept as is (aside from the bad head on one). But they are already out of their chassis (for other reasons) so I'm taking a closer look inside them and will refresh as needed.

 

[bpimm]

If I swapped 3 and 4 my clearances would be 1&2 .0036 3 .0047 and 4 .0048

I should have said the head is going to get a 3 angle valve job as well as what I listed, agreed that the head is the place to get the best improvements.

 

[Dr.Jeff]

Is there a spec for the wear tolerance between pistons and cyls? Sorry but all of the numbers get a little mixed up for me without going back to a table or summary. If 1 and 2 are the best, what happens when you switch them with 3 and 4?

 

[bpimm]

Are standard overbore pistons still available anywhere? only thing I've found so far is the Wiesco's from Midwest for 780 for a set, kinda takes it out of the refresh category.

 

[MikeHynes]

If the leakdown test was pretty good I would ask if you paid attention to the places the air leaked out of. If you got a lot of hissing out of the oil fill cap when you did the test, then you will want to address the ring seal. If you got the hissing out of the carb, or exhaust, the head is the weak link.
In any event, with a pretty good leakdown test I wouldn't be overly concerned about the bottom end. In fact if the bearings aren't scored, and look good I would check to see if the bearings still held tension in their caps. If they do, I would Platsiguage a few. If they do hold tension, and look to be in spec, or close to it, I would reuse the bearings. If they don't hold tension, I would consider replacing them. Face it, they are "bedded into the journals" now. Same with the pistons, I might reuse them as is. Depending on what you find when you look at the ring gaps, and how the rings fit in the lands, I might even re-use the rings. The ring gaps will probably tell the tale.
Chances are that new valve seals will have a bigger affect on oil use than new rings.
I would avoid mixing and matching pistons. I don't think you have enough wear to worry about it.
And remember, friction is something to be avoided in an engine. That's why most racing engines are built with loose tolerances. Yes, loose tolerances lower engine life, and can cause increased oil usage, but if you're not trying to build a long life engine, and don't mind checking the oil levels often, then a "seasoned" engine can be a good engine. My advice would be to measure everything and let the measurements be your guide.
Fiats often get a lot of criticism for being cheap, but it's not warranted in my experience. Properly maintained these engines will last a long long time.

 

[bpimm]

The end gap on the rings was .025, .010 over spec. I didn't really like where the conversation went earlier either, I'm now looking at boring it and replacing the pistons if I can find replacement pistons.

 

[Dr.Jeff]

I would check to see if the bearings still held tension in their caps

Mike, I'm not clear what you mean by this. Are you referring to the bearing staying in the cap when the cap is removed?
But I agree with your assessment overall.

I didn't really like where the conversation went earlier either, I'm now looking at boring it and replacing the pistons if I can find replacement pistons.

Brian, what didn't you like?
I saw stock type, first-over pistons listed, but don't recall where at the moment. Seems they weren't as much as you noted earlier but they weren't exactly cheap. If I remember where it was I'll let you know.

 

[MikeHynes]

Mike, I'm not clear what you mean by this. Are you referring to the bearing staying in the cap when the cap is removed?
But I agree with your assessment overall.

Dr Jeff,
Bearings, rods and mains, are designed to have a bit of "spring" in them. It's designed into the steel backing of the bearings. That's what keeps them from just falling out when you turn them upside down once they are installed. That "spring" helps to prevent them from spinning. Lots of use/abuse will "beat" the spring out of them, making it easier to spin them. Most wear/damage to bearings can be seen, sometimes the wear/damage is felt, like when the "spring" goes away. If you don't have to "roll" the bearings in, if they just fall out, then it's time to replace them no matter how good they look. You'll be glad you did.

 

[beezee]

When I rebuilt my '83 there was still a crosshatch pattern in the cylinder bores, and that engine had 120,000 miles on it. Without a bore mic, I used the ring ridge as an indicator of bore condition and in my case there was almost no discernible ring ridge. I went ahead and bought a new set of piston rings and placed one of the rings at various places in each cylinder bore and measured the ring end gap. The ring end gap was always within factory specs, so I went ahead and put everything back together with then new rings and new rod bearings. The engine has run great ever since and does not burn any oil.

 

[bpimm]

When I rebuilt my '83 there was still a crosshatch pattern in the cylinder bores, and that engine had 120,000 miles on it. Without a bore mic, I used the ring ridge as an indicator of bore condition and in my case there was almost no discernible ring ridge. I went ahead and bought a new set of piston rings and placed one of the rings at various places in each cylinder bore and measured the ring end gap. The ring end gap was always within factory specs, so I went ahead and put everything back together with then new rings and new rod bearings. The engine has run great ever since and does not burn any oil.

That's good to hear, that is the leading option for this engine, at least the bottom end. Thanks for the info.

 

[bpimm]

Mike, I'm not clear what you mean by this. Are you referring to the bearing staying in the cap when the cap is removed?
But I agree with your assessment overall.



Brian, what didn't you like?
I saw stock type, first-over pistons listed, but don't recall where at the moment. Seems they weren't as much as you noted earlier but they weren't exactly cheap. If I remember where it was I'll let you know.

Just when we got to swapping pistons and used pistons from other blocks, Just don't think I want to do down that path. I think the car deserves better. now I'm looking for information on High compression pistons so I don't have to mill the head or euro head so stock height pistons could be used. This snowball seems to be getting bigger and picking up speed LOL...

 

[Dr.Jeff]

keeps them from just falling out when you turn them upside down

Thanks Mike, that is what I assumed you were saying but wasn't sure I read it correctly. And I completely agree with you.

 

[MikeHynes]

Just when we got to swapping pistons and used pistons from other blocks, Just don't think I want to do down that path. I think the car deserves better. now I'm looking for information on High compression pistons so I don't have to mill the head or euro head so stock height pistons could be used. This snowball seems to be getting bigger and picking up speed LOL...

It's not difficult to get 11:1 compression by just milling the block/head, but then you have the cam timing issue to deal with...and by the time you spend to mill the head and block, and buy the adjustable cam gear, you haven't saved much over just buying new HC pistons.
You might run into problems with compression of more than 11:1 on pump gas though.

 

[Dr.Jeff]

This snowball seems to be getting bigger and picking up speed LOL...

Got it on your earlier comment, thanks for explaining.
I'm with you, swapping in used parts from another engine does not feel right. However it would not bother me to reuse the same pistons from this engine; either in their original bores if the amount of wear is reasonable, or trading cylinder positions if that makes them a better fit. Provided the pistons aren't completely shot (as Mike clearly described earlier...measuring various aspects for wear), replacing the rings will get you back in the game. That's where the interface is between the pistons and cylinders. And if you are replacing the bearings as well, then you could swap the rods with the pistons, keeping them pared the way they were (not separating the pins).
That is unless you'd rather snowball into high compression pistons?

I was thinking the same as Mike just said. Machine work is expensive and it will cost as much to mill everything down as buying new pistons (which you were considering anyway). Plus in my opinion milling things to the extremes needed to get a high compression on these engines has potential drawbacks.

Slightly different question altogether. Do you really want your wife's car to be a high compression (HC) engine? A stock engine will be more reliable and easier to live with. When you build a HC engine it opens the door for potential issues. Especially if you don't go the full route of machining everything to make it a complete new engine. And absolutely no offense to you or her, but will she recognize detonation when she happens to get a bad tank of gas, or realize it is running hot with a HC engine on a hot day? Could easily destroy all your work on it. But I don't know her driving habits or interests or automotive knowledge, so maybe she wants more power and knows how to deal with a HC engine? Again, no offense, just thinking of the big picture to try and help with your decisions.

 

[bpimm]

It's not difficult to get 11:1 compression by just milling the block/head, but then you have the cam timing issue to deal with...and by the time you spend to mill the head and block, and buy the adjustable cam gear, you haven't saved much over just buying new HC pistons.
You might run into problems with compression of more than 11:1 on pump gas though.

Yep, that's why I'm thinking 10:1 gives us a little headroom. If I can find a euro head and cam and get 10:1 that should make a nice package and not have a thin head and all the fun that goes with it.