Hi Jimbro, need your advice please.
To cut a long story short, My 89 GF (13k miles from new)has blown the head gasket 3 times in the last 2 years. The first 2 times I had the head skimmed but it happened again which pointed towards a damaged block. Upon removing and stripping down the engine it was confirmed that the block was slightly damaged at the point where the gasket kept blowing and I have had the block skimmed. There is also slight water damage to the 2 bores where the leak occurred so I am having it re bored to install first oversize pistons (from 86.4/standard to 86.8/.4 oversize). I have been trying to source oversize pistons and I was steered towards Vicks Auto in the States who sell them for $199 inc the rings. They are described as 'Highest quality cast pistons available/Specs-OE [not sure who makes them though]). I spoke to a friend tonight who is ferrari trained and has his own specialist workshop and he informed me that I should not even consider cast pistons but should fit forged instead, especially as I am also having the head gas flowed..it's also fitted with a 4-1 CSC exhaust, Lumenition, K&N etc..He said that cast pistons would eventually break up if the car was driven hard over a period of time. My questions to you are 1/ I presume that original spec engines have cast pistons. Is that correct? 2/ As a non expert I don't know whose advice to take. The forged pistons will cost about 4 times as much, which isn't a problem, but is it neccesary?. I obviously want to have the job done properly to avoid having to strip the engine ever again! Incidentally, apparently the problem was originally caused by a jet being blocked by debris (the idle jet?) which caused the engine to run lean and hot-the first time it blew was after a 3hour 90mph run from Calais to Paris-by the time I got to Paris there was virtually no water left in the cooling system but it failed to register on the temp gauge until I stopped at a toll and the temp needle shot up into the red.
Your advice on this and which direction I should take would be much appreciated..Thanks

Welcome along and what a lovely looking car.

Sounds like you've been having a bit of a time of it and my knowledge is extremely limited. The only vehicles I've ever had forged pistons in are extreme boosted turbo's, drag bikes and my Uno Rally car.

This is subjective but I personally wouldn't use forged pistons in a road car. They are inherently stronger but take longer to warm up and expand properly to fill the cylinder. Under normal road use this isn't likely to happen and the piston can slap a bit causing more block damage. You'll notice more piston wobble when fitting forged pistons compared to cast ones. Cast for the road forged for the track.

From the sounds of things you have all the bases covered with the block skimming and so on. Personally I'd get the bottom half of the engine built and taken somewhere to get the crank balanced.

I always put a few hundred miles on an engine after a rebuild and check things like head bolt torque and such to ensure all is well before giving the car a push.

Good luck she sounds like she's going to be a beast when everything comes together.

Thanks for the insight LK. That's kind of what I wanted to hear as the easier option would be to buy cast rather than have custom forged, obviously. I had considered getting the bottom end balanced and will discuss this with the mechanic. Would make sense now that the engine is in bits.

Anybody else out there have an opinion?

Thanks once again LK.

I agree, as I understand forged pistons are overkill for a NA road car. Best of luck getting the car back together.

I'd be surprised if the problem was caused by a blocked jet, if it was a pilot jet the car wouldn't tick over properly and if it was a blocked main it wouldn't run properly at larger throttle settings, you would notice.
I agree with Liquid Knight, you need to re-torque the head bolts after a few hundred miles, I failed to do this on my Panda and had to redo the gasket after a while when it failed again.

Its a bit of a faff with an x1/9 as the cam housing needs to come off... unless you have the super rare special fiat tools... :-(

Thanks for your input guys. I have now bought some oversize pistons..I'll update this post once the car is back together and running and let you know how it went! I'll be sure to have the head bolts re torqued after a few hundred miles..