Sonix

iTrader: (1)

So I have an LG4, with flywheel (153 tooth I think), and a starter that has a straight bolt pattern.
I'm building a 350, based on a '78 block I believe. This has only two bolts, and they are staggered. I had a flexplate for this, (useless), and a giant starter. Now the starter for the 305 won't fit due to the bolts not lining up (duh). The 350 starter is too far away from the flywheel, as it's meant for a 168 tooth right?

So what are my choices here? Buy a new starter, or flywheel, or both? I'm really hoping I can buy some sort of starter that has the offset bolt holes, and fits a smaller flywheel? (A flywheel is more $$ then a starter right?)

I searched and it looks like this is a very common problem, with varied solutions.... what's my best (cheapest!) bet? drill and tap? special starter? flywheel?

Thanks!

sofakingdom

iTrader: (1)

No, you cannot buy any starter that will work. It is not possible.

Look at the inner bolt hole, and notice that if the starter shaft were located such that it could mate with the ring gear teeth, that inner bolt would go RIGHT DIRECTLY THROUGH THE MIDDLE of the starter drive.

You have 2 options: either use a 14" flywheel/flex plate, which is impossible without changing the bell housing; or drill the required hole in the block.

I'd suggest getting a machine shop to do it, since it requires extreme accuracy; like, within .005" or less, and within a degree at most of perfectly perpendicular. And once that place on the block is screwed up, there's NO WAY you'll ever get a starter to work right.

I know it's not what you want to hear; but it's the facts. Bummer. Better to face it head-on right now, bite the bullet and just fo what it's going to take, than dink around and spend money trying to work around it and still end up having to do it right, or trash something irrevocably in the process.

Sonix

iTrader: (1)

I'd need a different bellhousing? ouch... didn't think about that...

yea, that's kinda what I thought. I figured I could use my LG4 starter, and bolt it with the outer bolt hole, and line it up by eye, then center punch the block through the inner hole in the starter, then drill that. But I figured it'd have to be more accurate than anything I could do by hand, i'm terrible at that...

well crap, ok, shouldn't be a huge problem. I just have to put my 95% assembled motor in the back of the truck such that it doesn't flop over and break my fan, bend my valve covers etc etc.

Sonix

iTrader: (1)

ok, after a lengthy discussion with my machinist, he agreed that the trans-am has a smaller bellhousing, and I couldn't use the bigger flywheel, also that I can't get a hybrid 350/305 starter. However he said he couldn't machine that without me taking my block apart, removing oil pan and main caps.

So he said I should just use the outer bolt, bolt it down tight, make sure it's lined up, c-clamp it down, use a transfer punch, then drill it carefully. tap it, then drill out the first 3/8" or so for the diamond cut starter bolt. I think the part i'm drilling into isn't a boss, but just a 1/2" plate part hanging off the back of the block, so I may not use a starter bolt if I don't have room for threads and 3/8" of clearance.
Well tonight i'll try my luck.


better yet, I have a milling machine at work, I could make a plate with 2 3/8" holes such that it bolts to the staggered bolt holes, and has a 5/16" hole in the right spot for the other straight hole. Then drill through the thick plate with the 5/16" drill bit, then tap it. That should be very accurate. However measuring to a tapped hole in the block isn't all that accurate;

anyone know the hole spacing for an SBC's starter? staggered and straight pattern?

chesterfield

Sonix, perhaps you can find a used beater block in your area that has both patterns drilled in it from the factory and use it as a template to fabricate your drilling guide. This would give you a chance to make several until you're satisfied with the accuracy. Then resell the block.

Sonix

iTrader: (1)

hmm, yea, but that would take a while...

I could just use calipers and measure the current staggered holes, make a plate with that spacing, make sure it fits this block, then bolt the starter to that plate with the one bolt, drill the 3rd hole, then use it for the the guide on the motor... but that would take longer, I was hoping maybe someone had this dimension more accurately....

Vader

You'll need:

1. A new starter nose or accurate template;
2. A drill bushing for the smaller pilot drill. This will be critical since it will guide everything you do to either save or trash the block;
3. A means to square the drill, which could be the new starter nose and a bushing, or a portable drill press (Portalign) if you have room;
4. Lots of luck.

Sonix

iTrader: (1)

hmm yea, the hole in the starter would be 3/8" or a W or some sort of clearance hole? Then the hole I need to put in the block is 5/16" (tap drill size for 3/8"NC)....

I'll first try and find the right dimensions, then make an alignment plate. I'll email world or other block manufacturers and just ask pretty please for the dimensions. If that doesn't work i'll buy or make a drill bushing...

Sonix

iTrader: (1)

alright I did this up tonight.
Thank you all for the tips! I ended up going Vaders way:

-I bought a 5/16" drill bit, extra long, (like 14" or something huge, helps align it though...)
-a drill bushing, aka a piece of brass tube, 3/8"OD, 5/16"ID, from a hobby shop.
-a 3/8"NC taper tap

I think I got the hole aligned well, and tapped well. I'm very pleased with it.....well that would be the ok news....




bad news: While I was bolting the starter in place to use as a template, I was only using the very outside bolt. Now I remembered when I brought in the block for machining, the machinist noticed I had a chunk of metal missing from that outer bolt hole, he said I may want to use a normal bolt there, a bit longer......
anyway, I just used the short starter bolt, just to hold the starter in place, as i'm tightening it down, I thought it felt a bit easier then the last turn.... So I noticed I cracked the boss for the outer bolt hole.
I'll post a picture here in a minute, but i'm thinking i'm either going to use a longer normal bolt, or drill that hole deeper and tap more threads and use a normal bolt.
Is it ok to use 2 normal bolts, or should I use a starter bolt on my inner hole?

Sonix

iTrader: (1)

so I can't seem to take close up pictures to save my life here, $400 camera my ***....

anyway, here's the directory:
pics

crack1.jpg is a close up of the outer crack, oh, and turns out there's a second crack, that would be crack2.jpg. The other pictures are the fullsized versions.

Think it's ok to just use a normal bolt then on the outside? and then should I use a starter bolt on the inside hole?

Vader

You mean, like this?

Vader

You may need to get out the welder and some nickel filler, preheat the area to about 800-900°, run a 3/8-16 bronze bolt into the hole, add some metal to the starter boss, and shot pein or mechanically stress relieve the area:


----------
I ended up with a couple gassy areas in the weld when I repaired this one, but it's only cosmetic. The clearance portion of the hole is a little tight, too, but it holds the standard starter bolt quite snugly.

Sonix

iTrader: (1)

wow, I thought you just modified my picture, that is similar...

preheat to 800-900F ? What can I use for that? propane or mapp handheld torch? Nickel filler, say in a 5/64" stick welder on 70A? I've got a little fischer price stick welder that has 2 settings, 70A being max, would that work?

aces, thank you muchly!

Vader

That's one of the common maladies on mid-'70s SBC castings. Another problem was with the lifter bore perpendicularity, and core shift/thickness of the valley walls. There were other little problems that popped up here and there, but those are fairly common ones.

Another thing I've heard/experienced is engine mount pad machining. Some are not milled high (deep?) enough and cause problems on installation. That is relatively easy to remedy. Some apparently have mount holes in less than optimal positions. That's not so easy to fix. Reportedly, this is more common on four-bolt truck blocks. Before I went too far with this one, I checked the other problem areas. It seemed to be salvageable. It probably wouldn't be worth it to pay someone else to repair the block, however, since used engines/cores are rather cheap.

Preheating is best done with an oxy/accetylene set and rosebud tip. Repair like this is best done on ears, mounting bosses, and lugs, since welding more in the core of a csting tends to only intruduce stress, and differences in thermal expansion rates can eventually fracture the repair. A boss such as this hanging freely out in space has a lower probability of failing due to thermal stress, since there is nothing to contain the added material.

You may also notice the hand scraping marks on the starter pad. I also blued the are and scraped it flat and true to get the starter mounting perpendicular to the flywheel. They're a lot less noisy when the starter doesn't rock.

70A with a smaller rod like that might do it, but you'll need to keep the casting warm. Good luck finding a bronze bolt. I happend to have soke silicon bronze bolts lying around, but they are not commonly stocked in many places.

Sonix

iTrader: (1)

yea, i'm kinda past the point of being able to check the lifter bores, so I just really hope they're ok.... the engine is 90% assembled.

I've got $2000 into machining on this block, so i'll go through hell and high water before I scrap it...

hmm, no access to an oxy-acetylene welding setup... would mapp gas work, or should I go to the trouble of bringing this to someone with an oxy-acetylene setup?

I just need any bolt that isn't ferric, such that it won't stick to the weld right? I *think* i've seen bronze bolts around somewhere, what about brass or aluminum? mcmastercarr is an option for me too...

what did you use to scrape the block there?