Oversize Bore Head Gasket

Micha D.

Low Mileage
Hi all!

First of all, I am very new here, but I came across your forums on my search for the solution of my little problem.

Short introduction, I have two old Fiat Panda's, one from 1984, one from 1985. I bought the 1985 one as my first car when I was 17, already 8 years ago. Last year I started with the engine overhaul, namely increasing the cilinder size to accommodate 67,8mm pistons.

My current issue is that the head gasket doesn't fit anymore. I could have one made to spec, but I would rather have a of the shelf solution, so I can later buy another one if needed. A Abarth A112 head gasket does not fit as the first and fourth cilinder are offset slightly compared to the Panda engine.

I came across quite a few 'tuners' topics on these forums, so I was wondering if anyone has a possible solution for me?

See attached some pictures of my Panda (for fun), and some pictures for the sizes of the engine.

I hope someone can help me!

S36A1.jpg
 

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short answer is, you won't find one.

When you fit the larger panda 4x4 965 (67.2 mm bore) pistons into a 903 (65mm bore) block, you should offset the bores of the end cylinders, basically I give my engine guy a 903 head gasket and a 965 head gasket so he can properly bore the block... sounds like you haven't done this...

best option if you want off the shelf parts (head gaskets) is to get another block and start again... or sleeve 1 and 4 and rebore them with the needed offset, probably not what you want to hear.

SteveC
 
Haha, for sure not what I wanted to hear, no. I think then my best guess is to have a head gasket made.

EDIT: Additional question. If you bore the cilinders offset, does that not conflict with your crankshaft and the positioning of the pistons? Maybe very stupid question to ask, but I simply don't know.

EDIT2: Thanks for you answer by the way Steve!
 
you may run into issues wit the cylinder spacing between 1/2 and 3/4 being too small to;

a) get sufficient width to the fire ring of the gasket or/and
b) have a themal issue with the minimal amount of material you have betwen the cylinders, i.e the cylinders wont stay round

offset boring was how Fiat approached the problem, and I always say that they wouldn't have done this for no reason

SteveC
 
That is definitely true, and it is a concern I have myself. I was hoping to partially prevent this by installing an oil cooler. The company I had the work done had no concern about the thermal issues though.

I just wish I would have had this information sooner, so I could have approached the project differently.
 
3.3mm bore spacing is tight... down almost 1/3 from the 4.5mm you would have if you offset bored... or you could view 4.5 as almost 50% increase over the 3.3 you have...

I would think thermal issues and bore roundness is going to be an issue myself.

SteveC
 
EDIT: Additional question. If you bore the cilinders offset, does that not conflict with your crankshaft and the positioning of the pistons? Maybe very stupid question to ask, but I simply don't know.
no offsetting the bores on the end cylinders is how Fiat made the 965cc, it uses the same fixed gudgeon pin pistons as the 903, It does mean the gudgeon pin will sit a little offset but thats obviously not an issue as it was the factory solution.

the 1050 has a different piston with a full floating gudgeon pin and a totally different conrod.

SteveC
 
I think then my best guess is to have a head gasket made.
Given what you already have to work with, I think that's how I'd approach it at this point. Much more cost effective solution, and I'd consider having it made in a multilayer steel (MLS) design. That will last forever and reduce the likelihood of needing more made in the future.

I wish we had Pandas here. :)
 
Thanks Jeff! I am still very much in doubt whether to go through the trouble again of having another engine block made with the correct bore. It seems the better option for the long run, but financially it will be another burden :rolleyes:.

I don't know where here is for you, but in The Netherlands they are quickly disappearing and getting more expensive. Whereas you could buy a decent Panda from the mid 90's for 500 euro a few years back, now it will easily cost you three times that, if not four times.
 
I don't know where here is for you, but in The Netherlands they are quickly disappearing and getting more expensive. Whereas you could buy a decent Panda from the mid 90's for 500 euro a few years back, now it will easily cost you three times that, if not four times.
I'm in the USA. I know what you mean about the prices for some older cars. It seems there were lots of various models available for little money just a few years ago, but lately things have become much higher. Even for junk cars. Here there are a lot of what we call "baby boomers", people born around the second world war in a campaign to increase the US population (I guess as a future military force). It created a huge surge in the number of people within a certain age range. And as that surge in population reach various stages in life, we see a big result. Now they are all retired and seeking to relive their youth with classic cars. That seems to have affected the prices.
 
So to have a quick update. I have decided to have another block made with normal, non-oversized pistons. I don't want to go through all the trouble and issues again, also I now realize some things have not been thought out well enough. One of which is whether the original head can be used when using an offset boring, mainly with regards to the positioning of the original indents and valves. But also the increased compression, how big will it be and what are the exact results of that, or should the head be altered to counter the increased compression. I just do not have enough experience with these types of adjustments to make a good judgement on the topic, so that will maybe be for later!

Thanks for all your help guys, I will be reading and following all you are doing to your cars and engines :).
 
So to have a quick update. I have decided to have another block made with normal, non-oversized pistons. I don't want to go through all the trouble and issues again, also I now realize some things have not been thought out well enough. One of which is whether the original head can be used when using an offset boring, mainly with regards to the positioning of the original indents and valves. But also the increased compression, how big will it be and what are the exact results of that, or should the head be altered to counter the increased compression. I just do not have enough experience with these types of adjustments to make a good judgement on the topic, so that will maybe be for later!

Thanks for all your help guys, I will be reading and following all you are doing to your cars and engines :).
I think that is a smart move. It can be easy to start climbing down that rabbit hole. Sometimes it is much wiser to recognize the reality of your situation and take a step back. Even if that means losing a little to start over. Better to lose a little now than a LOT later. Just wish I could learn to do all this myself. :rolleyes:
 
They say 'sorry' is the hardest word to say, but sometimes it is 'I was wrong' 😂. Such a shame these mistakes are so costly.
 
You certainly wouldn't be the first person to not offset the bore on 1/4 and try to use the Panda 4X4 pistons, and I very much doubt you'll be the last...

My opinion would be now that the bore is too big and not offset, rather than scrap the block how about sleeving it back to 65mm? (standard size)

Standard size pistons are plentiful and much cheaper than oversizes... I know the bore sleeves wont be cheap, but being able to go standard pistons gives you a lot a life in that block, and sleeves can be had in better grade of material than the standard blocks cast iron

Then if you find another block, get it done with an offset bore so you can use the 67.8 pistons you already have to build a 995cc engine.

Modifying the head is simple, just put a couple of head dowels in and place a 1050/965 head gasket over the head face, carefully scribe a line around the inside of the fire ring, that shows you the limit of were to remove material from the combustion chamber edge. No need to go the the expense of finding a 1050 or 965 cylinder head, a regular 100GL head can be made to work just fine.

There are also valves from the later FIRE engine that are larger head size but will fit the seats, you have a slightly different stem length to deal with, but nothing too difficult to sort out... 995cc overbore with minimal chamber mods yields close to 10:1 static.

SteveC
 
I do have another block lying around, so I will get that done with standard pistons to start with. That at least gives me the opportunity to continue finishing the Panda. I think I will keep the pistons and look for another blok to bore offset in the future. I also have a spare head, so that would be a perfect victim to butcher into a off-set-bore-head (if you know what I mean). Thanks (again) for the great tips. I didn't know how to adapt de head, but now that you describe it is seems perfectly logical.
 
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