Broken Timing Gear Bolt in Cam? Need a new Cam? Recommendations for a lifted DD?

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boy&hisdogs

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I messed up. I was changing my timing chain and gears, and when I went to torque the bolts broke one of them of. I thought I was being gentle, going around doing just a little at a time, but still snapped the head off one of them. The others were stretched/deformed and look like they would be about to break. I tried to use an extractor kit, didn't work. The extractor just kept stripping out. I tried to weld a nut on the end of the broken bolt and apparently some of the weld got away from me and I ended up partially welding the broken bolt to the cam. I ground it down as much as I feel comfortable with and it's still fused. I don't know what else to do besides replace the cam at this point.

Any recommendations for a replacement cam? The truck is a 1998 K1500, 5.7/4l60e, 6" lift, 4.88 gears, 14bsf rear end, 37" tires. It's daily driven mostly on the highway and higher-speed country roads. The good and bad news is that I live in California, but I'll be moving to a no-smog state in about six months, but I'm also due for smog right now so whatever I get will have to pass on the stock tune. Typical cruising RPMs are 2000-2500.


It seems that my options are:
1) Junkyard stock cam, do the bare minimum just to get it back on the road for now and maybe upgrade later
2) New stock-spec cam
3) Mild aftermarket cam and risk opening up that Pandora's box on a truck that's already been running bad and fighting me every step of the way for months

But I'm open to other suggestions, be it about a new cam or if you have an idea to get the bolt out.
 

tayto

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if you don't have the means or money to get a tune, i wouldn't bother with an aftermarket cam. i would personally pull your cam and take it somewhere to get the bolt removed. it sounds like you already made it worse, but this is still probably your cheapest option. drilling is the LAST thing i would do especially insitu. i'm assuming you used the bolts to draw the timing gear onto the cam? next time tap it on with a deadblow or a block of wood and hammer. then I run the bolts in by hand and put the chain on and hammer on the crank gear.
 

L31MaxExpress

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GM 94666492, just over $100 and it is a GM steel roller cam, ever so slightly larger than the L31 cam and shorter duration than a LT1 cam and fits with stock vortec springs. It runs extremely well even in a TBI on the stock tuning. I am just finishing a L31 build with this camshaft and have used it in the past on a couple of other EFI small blocks. The cam is a Vortec 350 marine cam, meant to idle slow and smooth, have good torque and make about 300 hp with stock iron vortec heads. BluePrint and GM are getting 383s through smog requirements on the stock Vortec tuning, your PCM will care less about this tiny little bump in camshaft.
 
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L31MaxExpress

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if you don't have the means or money to get a tune, i wouldn't bother with an aftermarket cam. i would personally pull your cam and take it somewhere to get the bolt removed. it sounds like you already made it worse, but this is still probably your cheapest option. drilling is the LAST thing i would do especially insitu. i'm assuming you used the bolts to draw the timing gear onto the cam? next time tap it on with a deadblow or a block of wood and hammer. then I run the bolts in by hand and put the chain on and hammer on the crank gear.
The tune has to be STOCK in California. They check for that.

You do your chain exactly backwards from me. I install the crank gear first, socket over the crank and a rubber dead blow to ease the crank gear on. Then I line up the cam with the upper sprocket, then the chain and upper sprocket. Run the bolts finger tight. The cam sprocket should mate to the cam with almost no tension on the bolts. Sounds like he may have used too much torque. The cam bolts only get like 20 ft/lbs of torque. I can easily get that with a 1/4" ratchet head in my hand. I use my short 3/8" drive torque wrench for the cam bolts, set at 20 ft/lbs and in all honesty I seldom torque those because I have built so many and do sometimes see the bolts break trying to torque to a value, I use blue loctite on the bolts. I heat the bolts up with a propane torch before I remove them. I also take the torx head bolts out of the cam retainer plate and use a standard bolt the right length. Those torx bolts are dumb.
 
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tayto

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we just talked about that cam, and yet i forgot about it... definitely a cheap option. i didn't know they checked the tune in California i thought it was just a sniff test like what we had up here in vancouver for 20 years (now shutdown).
 

boy&hisdogs

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Could I use a threaded insert like you wou
The tune has to be STOCK in California. They check for that.

You do your chain exactly backwards from me. I install the crank gear first, socket over the crank and a rubber dead blow to ease the crank gear on. Then I line up the cam with the upper sprocket, then the chain and upper sprocket. Run the bolts finger tight. The cam sprocket should mate to the cam with almost no tension on the bolts. Sounds like he may have used too much torque. The cam bolts only get like 20 ft/lbs of torque. I can easily get that with a 1/4" ratchet head in my hand. I use my short 3/8" drive torque wrench for the cam bolts, set at 20 ft/lbs and in all honesty I seldom torque those because I have built so many and do sometimes see the bolts break trying to torque to a value, I use blue loctite on the bolts. I heat the bolts up with a propane torch before I remove them. I also take the torx head bolts out of the cam retainer plate and use a standard bolt the right length. Those torx bolts are dumb.

I read somewhere that it was 26# and did it with a 1/2" drive tq wrench. I know it was a dumb move to try and use a big wrench at it's minimum value but I didn't know the bolts were going to be so weak. I broke an upper intake bolt with a 1/4" drive tq wrench on this engine too, either I forgot how to use a torque wrench lately or these bolts have gone soft in the 200k miles that the engine has been running.

And you are right, we are aren't allowed any aftermarket tunes anymore, even if it does actually run better/cleaner than stock! :3811797817_8d685371

When I do it I set the crank gear first, then the cam gear and tap it home with a rubber hammer. I already had the gears and chain in fully and was beginning to reassemble when I broke this bolt and turned an hour's more worth of work into days...


I might get accused of some reckless redneckitude but what about drilling it out and putting in a threaded insert? I've done it before with less important things but never anything in an engine besides a spark plug on a car that was already on borrowed time and ended up getting scrapped later that year anyway.
 

L31MaxExpress

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Could I use a threaded insert like you wou


I read somewhere that it was 26# and did it with a 1/2" drive tq wrench. I know it was a dumb move to try and use a big wrench at it's minimum value but I didn't know the bolts were going to be so weak. I broke an upper intake bolt with a 1/4" drive tq wrench on this engine too, either I forgot how to use a torque wrench lately or these bolts have gone soft in the 200k miles that the engine has been running.

And you are right, we are aren't allowed any aftermarket tunes anymore, even if it does actually run better/cleaner than stock! :3811797817_8d685371

When I do it I set the crank gear first, then the cam gear and tap it home with a rubber hammer. I already had the gears and chain in fully and was beginning to reassemble when I broke this bolt and turned an hour's more worth of work into days...


I might get accused of some reckless redneckitude but what about drilling it out and putting in a threaded insert? I've done it before with less important things but never anything in an engine besides a spark plug on a car that was already on borrowed time and ended up getting scrapped later that year anyway.
What about a reverse drill bit? Drill into it and you might get lucky and spin the bolt out. The cam bolt holes in the camshaft have a bit of chamfer before the threads so that the robot could get the bolts into the cam on the assembly line.
 

boy&hisdogs

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cam bolts are 18-20 ft-lbs. 1/2" torque wrench is a bit over kill imo. its possible they are out of calibration?

Sounds more like I just over-did it using too high a spec on too big a wrench. I don't know how to test them so I can't say. I did order a 3/8 one a few minutes ago so now I have all 3 sizes, 1/4 in-pounds and 3/8 and 1/2 ft-lbs

The manufacturer claims +/- 3% accuracy. I bought Husky because they have a good warranty, like Craftsman used to and Home Depot has a pretty easy returns process. I used to work there and you wouldn't believe the crap we used to let people return.
 

L31MaxExpress

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FWIW, you are not alone. I found 2 broken head bolts and a broken head bolt washer in an engine I built a while back while putting a marine manifold on it. What a freaking nightmare an intake swap ended up becoming. However, I guess I am lucky I discovered it before the head warped, the head gasket went, and I had a far more $$$$ failure on a 383 with low mileage. I torqued to 70 ft/lbs per the instructions and later found out that the washers could potentially act like a bearing causing the bolts to be over torqued resulting in them failing. It would not have been such a PITA had I not decided to do the intake manifold at my mom's house that I am helping her remodel more than 100 miles from my shop. Immediately after I started the project we also became sick with Covid and I was down for more than a week. I elected to remove the heads in chassis which also turned out to be a real bear considering it is in my Express van and everything space wise is limited when it comes to the cylinder heads. Finally being in the country everything takes 2 additional days to make it that extra 100 miles. My shop is 20 minutes drive from Summit in Arlington, TX and I have the Oreilly, the Autozone and the Advance mega hub stores less than 1 mile away all at the same intersection. I also have about 6 junkyards that I could almost throw a rock at there. I of all people absolutely do understand the headache working on these older vehicles can become.

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