Starter mounting on a 350

I am new to the forum, my uncle is giving me his old K20 as long as I am willing to put in the work, time, and money to get it back on the road. I have not started working on the truck yet, but I went to look at it today to see what all needs to be done. It has not been moved under its own power in 20 years. The main issue that I am trying to understand is that the outer hole that the starter mounts to has a crack through it. I am wondering if this is something that is able to be fixed or not?

Could you include a pic for the readers?

I found this picture on another forum that shows the problem that I am having. This makes the starter mount loose to the point that the gears were ground off the last time the truck was started.

I bet someone left the rear bracket off.try tofind a rear bracket. Un bolt the starter look at the nose cone on the starter where the 2 bolts go through some nose cones are flat there, some have 4 high spots 1 on each side of each bolt.look for a starter with flat mounting pads,put the rear bracket on and cross your fingers. I still have a car I did this too before my son was born,he's 22 now, and my fix is still working,and mine was busted out way worse than your pic. The right nose cone was a big part though it gave more clamped surface are since it was flat.Ill try to get you some pics. Also use original style starter bolts they are knurled to fit tighter in the nose cone.

That to me appears the inside starter bolt fell out or was unthreaded at some point prior to the starter being engaged. The starter then torqued hard and levered against the weaker point of the block.
Now, if the crack does not go all the way through to the top of the ear......
Verify the hole for the outside bolt is all the way through and ensure the entire length is threaded. Then chase the threads COMPLETELY and then clean out using compressed air or if unavailable, brake cleaner.
Locate a Grade 8 bolt with enough threads to completely engage the entire length of the threaded portion, then apply a small amount of nickle antisieze, thread in the bolt.

Barring anything else, make friends with a reputable weldor, and have him/her weld that up. Pay the weldor the invoice promptly and with a modest bottle of gut-rot - you need to make good contacts early in your career, and this will go a very long way.

You will need to spend some quality time re-forming the bolt hole and re-threading it correctly. If you have an old starter, disassemble it to leave only the portion required to put the bolts through - use that as a guide to ensure everything is square. Use a smaller drill bit with a small piece of hard tubing that fits snugly in the starter hole (guide.)

Good luck.

Okay I'm home now,more time to write,not the first time I've seen this and fixed it more than once. Most everyone knows a triangle is a very strong structural shape. Your starter mounting was a triangle when new, 2 bolts at the nose and a third at the tail. With a missing bracket now your starter mount is 2 bolts in a flat plan and if the engine kicks back while the starters cranking it pushes back on the starter twisting it and breaks the outer bolt hole. I would bet you money, if I was there to look at it with you that the rear bracket is missing. Everything I said in my first post I have done and it worked. Since you have a k you actually are at an advantage. You are going to have to change the flex plate,imho it's just as easy to pull the engine as it is to pull the transfer case and transmission. Since I have not done this before because I never pulled the engine to change the flex plate. I'd make sure that if I made a stud for that outter hole that I would still be able to r+r the starter if so I'd make a stud,sink it as deep as I could in the block,then braze the broken outer bolt hole getting as much brass into the Crack and into the stud threads as possible. Put it back together with a nose cone like I said and the rear bracket, good as new. You could preheat the area with oxy,acetylene and weld it with high nickel rod but I think you'd have just as good of luck with brass.

First starter I grabbed was a good example not a great example.but you will see the area where the bolt goes through is not flat? This one doesn't have as big of a cut out as some. I went through boxes of starters when I was fixing mine until I found 1 flat all the way across. I ve seen people gusset the factory bracket,probably not a bad idea since you already have 1 weak point. Found a pic of both style nose cones side by side I understand better now why it worked for me,it wasn't the surface area its the bolts are tighter,so they keep the starter located better.

Guys keep in mind the picture he provided is NOT of his truck but an example of what he is seeing. I think that is important because his cracking could be much worse or more surficial.

I agree with @Ricko1966 you need a rear starter bracket, they were put in there from the factory for a reason, but all to often are tossed somewhere along the line when someone was changing the starter and couldn't take the 30 seconds to swap it over.

I think what I'd do would depend on the severity of the crack in YOUR block. If the bolt will go in and tighten down good then I wouldn't think anything more of it.

If it's bad and I wanted to try to save it then. If it'll thread in reasonably decently I'd probably slather the bolt in a nice coating of red locktite and snug it up, not crank it down super tight, but if it'll get firm, the locktite will do the rest.

If a bolt won't tighten down, and / or the crack is deep and long then there is probably little that can be done to save the block, but personally I've never seen one that bad.

OMG Becky look at this 55-57 chevy starter plate.I'd still do it the way I said before. Because I'm cheap.

IIRC, proper GM starter bolts have a knurled design near the end, so they are not just standard bolts that have the right threads. I assume the knurling provides additional support, but I don’t really know. This is the type of bolt I am talking about. https://www.summitracing.com/parts/arp-430-3512/make/chevrolet

You are correct.
I wouldn't bother putting the original starter back. I'd replace it with the smaller, lighter mini-starter. They also have different bolt lengths so if you get one from the boneyard, take the bolts too. They also don't require a bracket at the tail.

I want to replace the starter with a lighter starter, since there is not an easy way to mount the original starter. Would I have to change any other parts of the mounting system?

In post 4 I told u about the 2 different style nose cones post 7 I showed u the difference last pic. Well turns out there are 4 style nose cones,but back to the 2 I showed u the early nose cone has smaller bolt holes locating the starter with a little less slop.Sunce u only have 1 good bolt hole I'd want it to have as little slop as possible.My opinion is that with the tighter fit on the bolt starter cannot flex or move as much so the broken hole won't be as critical. If I got any starter besides the one illustrated I would make sure the bolts fit tight like the picture shows.The looser the bolt,the more chance it has to rock around like a removing a fence post.Now it will be pinned and clamped not just clamped.

Id say what everyone is saying.
Smaller, lighter starter (vortec age mini are great) mount the one bolt the best you can with some locktite, tighten the other 2 the best you can, and hope for the best.

Another option that i didnt see anyone else say, is, you could get an older bell housing off of an old 265 or 283, where the stater mounts to the bell housing, instead of the block.
This would work well, only if you have a manual....

All good things mentioned here. I'll only add that the secondary starter brace was not used in later years, I guess GM had decided the starters were light enough at that point. Early 80's maybe? Not sure.

Also as far as factory starters are concerned, the straight mounting pattern was only used with 153 tooth flywheels, which were generally car applications. The staggered pattern was used with 168 tooth flywheels, in many cars and most trucks. There are aftermarket "mini" starters with dual 'straight' patterns that work with both flywheels.