'04 M6 Z06 with 250k miles on the motor. Daily driven, not used on track.
Motor stalled on me earlier this year. Haven't found the definite cause yet, think it may have been the AC pulley locked up and stalled it. Took pulley off, was able to spin motor by hand. Replaced the compressor and belt, put the car back together and when I drained the oil, I found a broken bolt came out. Dropped the oil pan and found what I'm fairly certain is one of three cam cover bolts. Probably reason I've been getting codes for high pos cam. I had already replaced the cam pos sensor behind the manifold, but still getting same codes.

So, plan to do a cam swap. I'm dropping the whole motor/drivetrain as one unit in both cradles as I have a lift in my garage. I also gotta chase down an oil leak. I replaced the rear main seal last year when I put a new clutch/trans in. The leak may be from there or somewhere on the motor. Plan to rebuild anything/everything on the motor with already having high mileage. Looking at doing a HCI job, maybe new internals as well. I have no numbers goal. Just a fun street car. It already has longtubes, mid pipe, bb bullets, K&N, and stage 5 RPM trans. Rear end is stock, motor is stock.

*This will be my first motor rebuild doing myself*
Cam - Looking at doing a cam motion 227/232 as see it mentioned quite a bit on here and FB groups. Or maybe BTR. Open to other options as well. Also, I'm sure it will be mentioned, but I just replaced the harmonic balancer. So thats one less thing to purchase.
Heads - Should I leave the stock LS6 243s alone, send off to be machined, or upgrade? I'm lost on upgrade options. I can hold my own on most stuff, but I rather not rebuild valve train myself. So if I'm upgrading, I will have a shop do it or just buy new heads that are fully assembled.
Manifold - leave alone or replace? open to options
Fuel - Again, just a fun street car, so don't need very big injectors, whats a good size for 400+ power?
Internals - I will know more once I take heads off. I have no plans to go big or do boost, however, with 250K miles, I feel like the rings would be helpful to replace. So if I'm pulling the pistons out, should I go ahead and upgrade piston/rods while I'm in there?
Unknown - What am I missing? Suggestions

And with it being black friday around the corner, anyone seen/heard of good deals going on with what I'm looking to do?

 

I'm no engine builder myself, but I have re-built several engines over the years, mostly Olds, Pontiac, Buick, plus several SBC. Get it torn down and see what you got. If the bores measure good as far as taper, out of round and wear, I'd just Dingle berry hone the bores with proper 45° crosshatch. Go slow rpm and use rapid in back and forth to get the 45°. Use Hastings plain cast iron rings on the stock pistons, check gap. If the bores are trashed get some decent forged pistons. Measure the crank. Replace the rod and main bearings. If you need/want new rod bolts the big end will need to be re-sized. Heads and cam... You will get plenty of opinions. I went with TSP stage IV low lift cam and scored some low mile 243 heads that I had TSP CNC port. Several forum members were instrumental in directing me to get the heads done to get the best bang for the buck from the new cam. They looked like new when I got them back from TSP.
$800 plus springs if you use your existing valves. I'm not sure if they are letting the 25% Black Friday on CNC services? I'd give them a call. Sales guys there are pretty helpful in my dealings with them.
https://www.texas-speed.com/p-1172-p...-castings.aspx
I think vette4fl was going to use that Cam Motion cam you had your eye on? Should be cool enough in Florida that he's turning wrenches for his cam swap now. He should chime in shortly.
My Tuner said I only needed the stock injectors with my power level (430 rwhp) and that they stayed away from modified and aftermarket injectors due to driveability and reliability issues.
Depending on your hp goals and cam selection the stock intake and TB may be okay. The $$$ FAST 92 intake and LS2 Silver Blade TB really drove up the costs on my project. I'd check with your tuner and get their opinion.
I used Summit parts where able like the standard pressure and volume Oil Pump and LS2 Timing chain they offer. Looking back at it I probably should have went with Summit performance lifters as they are made in the USA by Morel.
I went down several rabbit holes that added considerable expense. Here is a link to what I did:
https://www.corvetteforum.com/forums...-coupe-m6.html

 

Appreciate the info. And thank you for mentioning the oil pump and timing change. Definitely want to replace those as well with the mileage my motor has.

 

ha, wasn't planning to drop THAT kind of money.

 

For that cam, I agree that porting is worth the money. I picked up a set of 243 cores that needed love. A valve job is going to cost about $600+, so it’s an extra $400 for the porting if you get both done by Texas Speed. You’re also going to need new springs, lifters, pushrods, retainers, locks, spring compressor, and pushrod length checker, so factor another $1,000, give or take, into the total cam cost.

I recommend that you give Cam Motion a call and tell them what your goals are, your plan for other components (gears, heads, exhaust, etc.) and discuss what would make a good combination. If they don’t have what you need on the shelf, they can grind you a custom cam.

Good luck👍

 

Thank you for feed back. Definitely planning to do all new valvetrain with or without new heads.

 

Agreed if you're going down that path, take it apart and see what you have. You could likely be fine with honing the cylinders, new bearings, new rings, gaskets, and valvetrain. Reassemble and run it.

Cam, heads, intake other mods will depend on budget and goals.

 

Be careful on the honing. If there is one step of the process that it's a very very good idea to spend a little more it's the block prep. You want the bores to be as close to ideal as possible, and the block to be as clean as clean can be. A good machine shop will have a giant block dishwasher with hot high pressure jets to deep clean the aluminum. Then a hone with exactly the right stones for the ring material you're going to use. Probably add a few hundred dollars to your build, but the wrong dingleball can ruin a block in seconds.

 

What he said…^

I would add that while machining is expensive these days, driving over your crankshaft is a real buzz kill, lol.

The shop can torque plate the block and do a proper hone, install cam bearings, and hand it back to you nice and clean, ready to screw together.

 

Yup, Absolutely. Always a good idea to seek professional advice and start with a clean block on any build. I have a local guy I have used in the past (hot tank and sleeve blocks) and I've also honed with flex-hone/dingle berry to achieve the proper cross hatch. Its all about attention to detail. Good measurements and proper clearance on all engine components are key to longevity as well. Hopefully this engine has been run with synthetic oil its whole life and still has the factory crosshatch in the bore. There could also be damage to the block/bores from that bolt bouncing around.
https://racer.com/2014/07/28/the-per...linder-honing/

 

Getting a good machinist is critical and not that easy. 1 of the 2 I trust around here just retired. A very reputable shop honed a friend's motor and was reassembled by one of his employees on the side (a friend of ours) resuing the stock rotating assembly, pistons and all. The motor ran great seeing HPDE time.

If you disassemble the motor mark all of the rods to identify which cylinder they werre in. It is good practice to know where the parts were in the motor. Lifters, pushrods, rockers etc. If you find something that looks off, you have a better chance to put the picture together of what caused it. Also I don't believe we balanced the motor as the rotating assembly was going back where it was.

OEM machining and cylinder wear with the materials and oils used today has come a long way.

 

I have only used Mobil 1 since I bought it in 2013 with 63k miles and now at 250k. Cant speak for before I owned it.

Thank you for the advice! Will do that when breaking it down.