Bent Cooling Fin Repair +

[Seadog]

Back working on my Dream engine. I have one bent cooling fin. I'd really rather not break it, so I thought I'd ask how it should be bent back. Should it be heated, or should I just push it back into place cold?

Also, does anyone have any experience soda blasting an assembled engine? Good idea/not so good idea? My engine is absolutely cruddy - any other alternatives?

[G-Man]

Seadog

I have had some success with heat. If the part is already cracked it will break whether hot or cold. Direct the heat at where you need the part to bend and keep gently trying as you heat it. Just lever gently against the root of an adjacent fin. You will feel whe it starts to 'go'. Don't overheat the part, just geep it gentle.

You may want to lag the rest of the engine with fleece or fire bricks.

http://www.cupalloys.co.uk/brazing-anci ... /index.asp

G

[pemdoc65]

I second G-Man's method. I also use some thin hardwood wedges between the adjacent fins that I pry against. This seems to give a more solid base to lever against, and it distributes the force over several sets of fins below.

[Seadog]

Thanks to you both. I'm going to check for cracks before I do anything. Better to live with the bent fin than a broken one.

[hondadreamca77]

I have not soda blasted but did use very fine grade sand to sand blast an assembled engine. I spent tons of time sealing up ports, seals, etc. 3x each before performing the job.

Directional control skill and a good nozzle tip are non negotiables.

I know some would debate this and not sure I would do it again but it worked. No problems with engine after several oil changes still going strong four years later. And no, it's not gonna break now.

Extreme meticulous preparation and stong nerves are key here.

Hope that helps.

[Seadog]

Thanks for the information. In the end, I've just cleaned the engine up as best I can with carb cleaner for the grease and wire brushes for the corrosion. At this point, it needs a good wash, which I think will brighten it up a bit more. I'll do that as soon as it's warm enough outside to use a garden hose. I did manage to straighten out the bent fin.

I have not soda blasted but did use very fine grade sand to sand blast an assembled engine. I spent tons of time sealing up ports, seals, etc. 3x each before performing the job.

Directional control skill and a good nozzle tip are non negotiables.

I know some would debate this and not sure I would do it again but it worked. No problems with engine after several oil changes still going strong four years later. And no, it's not gonna break now.

Extreme meticulous preparation and stong nerves are key here.

Hope that helps.

[jkv357]

I've seen companies repair bent aluminum auto wheels, and they always use heat. Usually a significant amount.

It will almost surely crack if done cold.

I like the idea of using the wedge for even and controllable pressure. I would support the fins below so as not to move them at the same time.

You might want to research the optimum temp, and have a IR temp gun handy. Know that the temp of the fins will not read properly though - it will read lower than it actually is because of the silver surface. Most temp guns will only read the proper temp on a flat black surface.