repairing broken fins on 911 cyl heads

[stownsen914]

Obviously it's not ideal to have broken fins on 911cylinder heads, but is it detrimental? Can broken fins be repaired if you don't have the broken pieces (I.e. Shape pieces of aluminum and weld or braze in place of the broken piece)?

Thank you.

Scott

[Dpmulvan]

Better off buying new cylinder

[tharbert]

Post a pic.

I don't think anyone's gonna say "it'll be fine..." You'll have to determine you level of acceptable risk. I've read some threads here that suggested a single broken fin on a cylinder is tolerable depending on location and intended use. But, you are talking about a head where most of the heat is generated.

[cgarr]

I would rather have clean cylinder heads than worry about a broken fin: I get some heads in that are just soaked with oil and dirt and have been running for a lot of their life this way.

[J0hnny]

Originally Posted by stownsen914

Obviously it's not ideal to have broken fins on 911cylinder heads, but is it detrimental? Can broken fins be repaired if you don't have the broken pieces (I.e. Shape pieces of aluminum and weld or braze in place of the broken piece)?

Thank you.

Scott

Post a pic.
The fins are there for cooling mostly, but if there is a crack or chipping where it broke off, it may propagate. If there is no cracking, then you can try to repair it.

How? depends largely on how it was broken, you can "build" the fin with a TIG torch, being careful with the temperature, also, the head would have to be preheated.

If it is accessible, you can try to braze a replacement piece of sheet aluminium, again, preheat the head.

[boosted79]

Like Johnny said. If it is a bottom or top fin and is accessible with a TIG torch no problem. If it is still attached bevel the crack with a burr, preheat and fill in the bevel and finish with file. If it is broken off then make a new fin with a piece of AL. It has to be perfectly clean or it will make a mess. If it isn't accessible building up a fin would be touchy and probably look like crap unless it could be cleaned up with a file. If someone tells you they can do it with a MIG and spool gun for running AL I would find another welder who can do TIG.