: 94 STS cracked block



rblud87
12-08-06, 12:49 PM
We started w/ a possible head gasket, found leaking valves instead....cooked the heads...all new bolts and gaskets and helix coils in the block.....torqued to specs... and at the last bolt the block cracked. Has anyone had any luck at welding such a thing? Caddy dealer and autoparts have told us we can't get just a block...only the whole engine.....found a used engine (67000 mi.) but they want $1000. Since we have about $1200 invested in this engine so far.....is welding an option or does anyone know where to find a good block? Thanks for your help. It is not at an oil chamber but rather at a water chamber (?). I've also seen someone suggest JBWeld. Feedback please.

Ranger
12-08-06, 05:08 PM
Tell me you used Timeserts, not Helicoils. If you used Helicoils, redo them with the proper Timesert or Bigsert or go with a new engine. Helicoils will fail in short order, if not immidiately upon torquing.

If it is not a stress point, JB Weld may work but I'd be more inclined to have it Heliarced.

zonie77
12-08-06, 05:41 PM
One advantage of aluminum cyl heads is that they are fairly easy to weld.

Is it the block cracked or a head cracked??????????????

rblud87
12-08-06, 10:11 PM
The heads are fine, the block is crack at the last bolt and it's at a water chamber. Plan to try welding it first. Machine shop is the guy who recommended helixcoils..... what are the timeserts? I read of someone who didn't recommend them. Thanks for all your help.

Ranger
12-08-06, 10:31 PM
Timeserts are the ONLY factory authorized thread repair. http://www.timesert.com

I did a search for Helixcoil and could not find anything. If you used Heli-Coils and are calling them Helixcoils. Remove them if you are going to salvage the engine. They are not strong enough and you do not want to have to do this twice.

zonie77
12-08-06, 11:10 PM
Helicoils are fine for iron blocks, not for aluminum. Use the timeserts.

timesert.com

As Ranger said, it's the ONLY approved repair. Sorry your machinest steered you wrong.

I'd try to get the block welded or get a used engine. Don't swap the parts to another block if you can help it. The bearings must be replaced if you loosen the caps.

Mountie
12-13-06, 02:24 AM
We started w/ a possible head gasket, found leaking valves instead....cooked the heads...all new bolts and gaskets and helix coils in the block.....torqued to specs... and at the last bolt the block cracked. Has anyone had any luck at welding such a thing? Caddy dealer and autoparts have told us we can't get just a block...only the whole engine.....found a used engine (67000 mi.) but they want $1000. Since we have about $1200 invested in this engine so far.....is welding an option or does anyone know where to find a good block? Thanks for your help. It is not at an oil chamber but rather at a water chamber (?). I've also seen someone suggest JBWeld. Feedback please.

I have my old North* sitting at my friend's shop in Oceanside, Ca. It had a spun rod bearing, but everything else was fine. The heads are intact, and if you want it, you can have it. It's a '93. Exact replacement for a '94.

I couldn't locate the photo of the actual 'old' engine, but the 'new' one I got is the same. You will get the heads & block complete. It has 120,000 miles, but it was a very smooth engine ( except for the rod knock noise )

dp102288
12-13-06, 09:47 AM
I just like the pic...cool to see the Northstar naked!

stevebuick23
12-13-06, 07:02 PM
can I have the Northstar for nothing?

Mountie
12-13-06, 09:43 PM
can I have the Northstar for nothing?

Yup.

It has been partially stripped, and it has been covered outdoors, so there may be some "weather" evidence. The injectors are removed.

But as I mentioned, before I removed the engine, I did drive it around, and it was fine. Again, except for the rod knock. The heads & block are fine, the oil pan assy. is still attached. I partially cleaned it when I removed it from the car. I was going to dissassemble it just to learn about it, but I never got around to doing that. I didn't want to keep it, 'cause if I need another major job, I was going to get a factory replacement.

The photo is of the finished job, the original was the same before removal.

I was just asked to remove the engine only last week, so the timing is good.

I don't know where you live, but you can just pay for the shipping, etc.

Contact me by my general e-mail address; mrpete@tfb.com.......

clarkz71
12-14-06, 06:35 AM
found a used engine (67000 mi.) but they want $1000.

That's a good deal for a 67K engine. I might be inclined to cut my losses on the original engine and just get this used one if your sure it's good.

drewsdeville
12-14-06, 07:25 AM
Whats the deal with everyones hatred for the helicoil??? :hmm:

Me and my pops helicoiled a '92 4.9 4 years ago, and no problems arose. It can't be a strength issue because a helicoil's surface area on the block still makes it stronger than the original treads...

Approved or not, I don't see why a helicoil is a problem. Tried and trued by me for 4 years and still going...:bouncy:

clarkz71
12-14-06, 08:29 AM
It has nothing to do with hatred. Heli-coils were designed for and approved for the 4.9 , that's why they worked for you. For the Northstar GM and time-sert designed a specific kit to repair the block and thats the only factory authorized repair method and is the reason they work for that engine.

drewsdeville
12-14-06, 12:24 PM
Yes, but many people seem to make the problem material specific, saying that helicoils don' work well in an aluminum block engine...?

dp102288
12-14-06, 08:47 PM
disregard this post...I got confused.

MonzaRacer
12-18-06, 11:50 PM
drewsdeville, first of all GM would not contract with timesert if helicoils would work.
Straight from a N*/Olds Aurora stress test the time serts held up in abuse testing even under storqued and improperly installed.
similar testing with properly installed helicoils had this design engine "lifting" the heads at an estimated 4000 simulated miles of easy driving.
One due to the manufacturing technique of the block AND metalurgy the time sert works perfectly and has to date in tests never failed due to design.
OLDS used the Aurora (same as N*) stock block in a prototype indy car and decided to turbo it (even though it ran as NA) and they held up to 65 PSI boost with no failure and a helicoiled block failed up on start up and 5 PSI boost "idling" out to the track. Ripped the helicoils completely out of the block and trashed it.
Olds even put out a bulletin that cars complete warranty might be void if Helicoils were used(found out later that they couldnt do that).
But as for me as an engine builder I wouldnt use a helicoil in a deck surface of a block on any engine. I have used them in other less stress full areas but I dont like them in high stress areas. BUT that is just an engine builders choice and I usually build about 25 new race engines and freshen up about twice as many in year and have trashed $5k blocks with decks helicoiled (till I located a beter set up to use larger studs and simply bore out the head bolt holes in the heads and use larger studs, but now I can source neckdoen studs that only use larger threads but centerless ground down to stock diameter (but read this very expensive too) but a set of a SBC run around $800 bucks as we have to give then exact length and hole depth, etc. very time consuming but it works and will save trashing GM CNC bowtie blocks and all of our custom machinework.
I havent tried timeserts in a race block, hmm may try them and see,,,,,.
Lee

clarkz71
12-19-06, 04:58 AM
Great post. My thinking is that the Northstars need time-serts because of the higher compression (10.3:1) because the 4.9's call for heli-coils as well as Mercedes 3.8 and 5.0 aluminum block V8's which have a lower compression ratio. Your point about the turbo aurora's verifies this.

dkozloski
12-19-06, 12:10 PM
I've used Heli-Coils in aerospace applications in aluminum that were very highly stressed but it was not a repair but an original part that was engineered especially for that. The common Heli-Coil repair kits you see are much too short for the long threads in a Northstar block. Use the Timeserts. They were designed for this use and are proven. If you screw that up you can go to BigSerts.