Drill a hole in your engine block???

[Flyman 27]

I had the problem with an intermittent no-start condition. After a few days of trouble shooting I figured out that it was the starter itself. So I was well on my way to my first plenum pull and did quite a bit of searching online to see what I could find.

I found a GM Service Bulletin #92-307-6 (09/21/1992) that describes the starter fail and what the GM recommendations are to the Dealers. Obviously they recommend replacing the starter with the corroded Solenoid and say that the problem was caused by insufficient drainage in the "Vee" area of the block (where the starter resides). My drain was plugged solid.

The Bulletin recommends cleaning out the valley drain and also recommends drilling a 3/8" diameter hole in the valley at the rear of the block to add additional/necessary drainage.
It took me awhile to adjust to the idea of drilling a hole in my lt5 engine block, it seemed kinda gutsy.
BUT, I had no luck in cleaning out the OEM drain, no matter what I tried, carb cleaner, brake cleaner, degreaser, etc. Nothing would loosen the clog and it was hard as a rock, I couldn't poke anything through it no matter how I tried. I was able to drill out the clog up to the 90 degree turn, but that was it.

So, I drilled the hole to the dimensions in the SB and it worked great without hitting anything unintended. So the service bulletin was correct and it did work.

If you suffer a starter fail, maybe you should consider the same?

You can do your own search online for "GM Service Bulletin #92-307-6" it is fairly easy to find. So you can verify it yourself.

[We Gone]

I just don't get it wet, I know my 91 has a tube at the rear that exits over the bell housing. I would think a piece of copper wire hooked to a drill would clean it out.

[BigIke]

Great thread! Thanks flyman

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[tpr60]

Use an old inner speedo cable on a drill to clean out the tube. Every oil change blow compress air up the tube from under the car to keep it cleared out.

[Flyman 27]

I guess my main point here is that back in '92, GM said that the single 5/16" drain is insufficient for the job. They recommended cleaning out the 5/16" drain AND adding the 3/8" drain hole to help the drainage problem.
Iv'e read a lot about the starter problems here but have not read about adding the drainage hole, even tho it was recommended to Dealers by GM way back in '92.
Just sayin, if you have to do the job, maybe you should follow GM's recommendations on how to fix the known problem.

Dan

[RussMcB]

I guess my main point here is that back in '92, GM said that the single 5/16" drain is insufficient for the job. They recommended cleaning out the 5/16" drain AND adding the 3/8" drain hole to help the drainage problem.
Iv'e read a lot about the starter problems here but have not read about adding the drainage hole, even tho it was recommended to Dealers by GM way back in '92.
Just sayin, if you have to do the job, maybe you should follow GM's recommendations on how to fix the known problem.

DanIt sounds like a worthwhile mod, to do while you're in there, even if the original hole is clear. Thanks for sharing (of course, I'll never remember this until right after the next time I put the plenum back on). :-x

[Paul Workman]

NOT to steal the thread, but while you have your drill out, drilling and plugging the rear differential - i.e., adding a drain hole - is also a VERY worthwhile project....Just sayin!:thumbsup: See Marc's(?) web site for specific details.

[Hib Halverson]

Paul is right, while you got your drill out, put a drain plug in your drive axle. When I had my '95, I used Marc's instructions to do that to mine. Made my life a lot easier when it came to axle lube changes, which I did every 3-years.

As for the block drain, my 95's engine had the big drain. Apparently, that was a change GM made after it discovered problems with debris plugging the smaller hole.

[jss06c6]

Guys,

My top end is out for porting.. just wanted to know, where is the 3/8" hole to be drilled? My drain tube is clear on my '91, but I'm game for improvement!

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[Flyman 27]

I can't post you a link here so,

You can do your own search online for "GM Service Bulletin #92-307-6" it is fairly easy to find. Verify it yourself.

[jss06c6]

I can't post you a link here so,

You can do your own search online for "GM Service Bulletin #92-307-6" it is fairly easy to find. Verify it yourself.
Thanks!

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[Bob Eyres]

Here's a thought. What about drilling out the drain hole as indicated, then pressing in a metal tube from the drain hole exit to below the engine.

Hook up a Shop-Vac to the tube to create positive ventilation under the plenum when you're washing the engine, to avoid drowning your starter.

:dontknow: eh?

[rkreigh]

great idea! then you could also blow it out if it gets clogged


even keeping the hood down and the engine dry, the LSV was one filthy puppy after 104k miles

[rkreigh]

gee I never noticed this before but the hole in the back of the block does have a drain hose on my 95


that would also be prone to clogging up based on the gunk accumulated under the plenum

[dcarroll95]

Had the car for about 3 months, first time I took the plenum off, got some coolant on top of the engine, so naturally I hosed it off when I put it all back together. Next week starter wouldn't even click when the engine was hot from a 10 minute drive.

Replaced starter with an ebay NOS and DRILLED THE HOLE as per the service bulletin. Cleaned out the original hole as well and cleaned out any gunk or tiny leaf bits that could plug the holes. Tested the ability to drain water out with just the original hole and with the additional 3/8" hole using a hose. Drains much faster (3-4x faster) with both channels. Wish someone who owned the car over the past 29 years had done it for me.

Get a new 3/8" Titanium drill bit and it will cut through the block like it's made of butter. I created a 45 degree guide out of cardboard cut 6" x 6" to help align the drill. I was off by a little bit, but it still worked great. Took off the plenum and the fuel line between the two fuel rails. Don't need to remove the fuel rails or the injector housings.