Penta D1-30F extra alternator bracket fixation

[Username25]

Would be great to get any input on the best way, if any, to deal with such problem. Engine Penta D1-30F with extra alternator. Schematics here: https://www.volvopentashop.com/epc/e...30/7746500_118

Pardon my French, some idiot at a French shipyard used very short screws without lock washers (no. 5 on above schematics) and without engine paint cleaning to fix alternator bracket. Effective screw was just 5 mm long and depth of the threaded hole is 21 mm.

No surprise this resulted in slackening due to paint and vibration, loosening and a wall cracking of threaded hole at aluminium valve cover (no. 39 https://www.marinepartseurope.com/Pe...s500/24405.jpg). Both bolt threads are stripped at the top; one without crack is stripped less.

My idea is to cut down below the crack to have solid round surface. Install full threaded stud, put nut and, if needed, some washers to level with other threaded hole. Then install bracket with flat washer, lock washer and nut.

For stud placement thinking of using the highest strength red Loctite Threadlocker. It requires heat to be disassembled, so could be not very effective with hot engine. Maybe epoxy, e.g. J-B Weld Original Cold-Weld Steel Reinforced Epoxy (withstands 550F/288C), would be a better solution.

Considering both threads are stripped at the top, maybe I should cut both threaded holes to the same level and have identical setup with studs? Any other ideas?

[model 10]

If you don't want to get it welded up, remove most of the the damaged area and spot face the hole so you have a flat surface to work with. Install a helicoil. It should have had a stud or a helicoil in the first place. Make up a stack of washers for the mount spacing. If memory serves, you need 5 threads min for a tension load, 3 for shear. Maybe go to fine American thread for the helicoil size if you are short on depth.

[DougR]

From the photo it looks like you might be able to install a full length threaded bolt in each boss from the bottom side, having an appropriate length of the bolt extend upward from the casting for attachment of the alternator bracket plus washers and nuts. Basically the same as you contemplated with threaded stud, but perhaps a bit stronger. Certainly stronger than the original installation.

DougR

[Username25]

Originally Posted by Ecos

If you don't want to get it welded up, remove most of the the damaged area and spot face the hole so you have a flat surface to work with. Install a helicoil. It should have had a stud or a helicoil in the first place. Make up a stack of washers for the mount spacing. If memory serves, you need 5 threads min for a tension load, 3 for shear. Maybe go to fine American thread for the helicoil size if you are short on depth.

Thanks. Finding someone experienced with cast aluminium welding could be very problematic here. Considering result with no guarantee whatsoever and possible expenses, I would probably go with a new valve cover (220 EUR excl. VAT https://www.marinepartseurope.com/en...lve-cover.aspx). There is about 15 mm of non damaged thread, probably helicoil is not needed at the moment.

[Username25]

Originally Posted by DougR

From the photo it looks like you might be able to install a full length threaded bolt in each boss from the bottom side, having an appropriate length of the bolt extend upward from the casting for attachment of the alternator bracket plus washers and nuts. Basically the same as you contemplated with threaded stud, but perhaps a bit stronger. Certainly stronger than the original installation.

DougR

Thanks. I was contemplating such idea, but had some doubts about structural strength of such solution. Isn't drilling a hole all the way would not make fundament/bottom of the boss weaker?

[Username25]

Did some measurements. Boss height is 26mm, crack is exactly at 5 mm, thread is 21mm, fundament/bottom additional 5mm.

Cutting top 6mm to get solid base, will result in 15mm of effective thread for stud without any further modifications. Then just 6mm nut could be used. Or should I use additional lock washer?

Next I could drill fundament/bottom all the way and make additional 5mm of thread for stud or install upward bolt. In case placing upward bolt, valve cover will have to be removed. Would I need new gasket if valve cover removed? Another question does upward bolt would be significantly stronger solution? Or this would be just minor improvement and all additional hassle is not worth it.

Question regarding drilling a hole all the way and fundament/bottom weakness is still open.

[DougR]

Inasmuch as the holes are not drilled and tapped all the way thru the casting, it's probably not worth doing this yourself. If it were me I would install studs all the way to the bottom of the existing holes, projecting beyond the top of the casting far enough to install the bracket, substantial washers or a flat plate close fitting to the studs, and lock nuts.

I would not trim the damaged boss for two reasons:
- 2/3 of the boss is intact and will support the alternator bracket
- too difficult to match the height of the good boss with washers, without machine shop work, and you do want both bosses to be the same height to share the load

I would attempt to fill the area of the damaged threads in the casting with a high temp filled epoxy resin to transfer bending load from the stud to the upper edge
of the casting where the threads used to be. I would also go to the lower support bolt of the alternator bracket and make sure that this bolt is long enough to engage sufficient thread in the block to provide adequate support. That bolt will be threaded into the cast iron block or cylinder head instead of aluminum, so there is less chance of stripping threads. Make sure this bolt is long enough to have adequate thread engagement and didn't get damaged in the original failure.

If all this fails, there is always the option of a new valve cover....

As an aside, the valve cover "gasket" is a formed "O" ring type of seal and can be reused.

DougR