mrsleeve91's DOHC build thread

[Indy]

You installed new main caps, yeah? Did you have those align-bored to the block?

[Series8217]

Man that really sucks!

One thing I noticed when building my motor is the mains changed shape dramatically depending on bolt torque. You MUST use the same final torque as you used when line boring it, or they come out of round.
Is it possible that your main bolt caps shifted during installation? I know the stock ones are a very tight fit in the block so that they line up.

[Series8217]

Oh another thing.. the same exact thing (badly scored mains, rod knock, rod bearing damage) happened on my motor when I first "refreshed" it because I did not replace the intermediate shaft bearings. Apparently the front bearing has an extremely high rate of failure; all the ones I've seen had the top layer delaminating from the copper. This completely came apart on mine and sent debris through the motor.

Another cause of this, which is what happened on Blue Shift's motor, is he blocked off the throttle body coolant bypass... this caused massive temperature fluctuations and the block warped to the point that he was seeing metal flakes in the oil from the excessive bearing wear. As soon as he replaced the coolant bypass line, the cooling problem went away, and the metal did too.

[Aaron]

That's too bad, I'm sorry to hear it.

So will you need new rods, or just the bearings? What about the crank, is it ok? Hopefully nothing too expensive got messed up, and all you have to do is change bearings!

[The Dark Side of Will]

Primed?

[p8ntman442]

with the extent of this build I cant imagine he didnt use moly lube and prime the pump. But, failure on all bearing surfaces indicates a lack of oil pressure. Bad pump?

[Aaron]

Primed?

The DOHC engine is a difficult one to prime, it can't be done conventionally. I haven't primed any of them. This includes the one I rebuilt, and 3 crate motors now (Including my turbo one). None received a conventional break in period either. All 4 are still going strong, no hints of damage. Not like it's worth much, but I also had a GM Tech tell me not to worry about priming the pumps.

On one of my crate motors, I was feeling skeptical, so I unplugged the injectors, and cranked it over in pulses until I got full oil pressure. It made me feel better. Beyond that, I don't think it did much. I added oil to my motor through the oil fill, got it running, let the cams break in for a few minutes, and hit the rev limiter through a few gears.

[Series8217]

Judging from my experiences and retard's, I doubt it was caused by any issues with oil priming.

All I have ever done is pull all the spark plugs out (so there's no compression) and turn it over until I have pressure. As long as the pump is working though, it should be fine after the first start.

I have had one case where the oil in the filter was preventing the pump from drawing oil up.. not sure what was going on. I took the filter off, emptied it, put it back on, and all was fine.

[The Dark Side of Will]

One thing I noticed when building my motor is the mains changed shape dramatically depending on bolt torque. You MUST use the same final torque as you used when line boring it, or they come out of round.

The shop that has my Northstar block does the Enfantis bros 2JZ-GTE's. He said that they were wiping a set of main bearings every race weekend. He dug into it and picked their brains and finally found out that they were zinging the engine mount brackets on with an impact gun and pulling the #4 & 5 mains out of round. He had them torque the brackets the exact same way he did when align honing the mains and the problem went away. Now a set of mains lasts 5-6 race weekends, which is about what you'd expect when running a production block at 5 times its production output.

Little things can matter a hell of a lot when you're dealing with a .001 gap between concentric circles.

[fieromadman]

Sucks to hear! Figure out the cause for sure! I was really thrilled to hear about this thing running problem free till now!

[Atilla the Fun]

Sure wish that cat jumping was a full video rather than just a snapshot.

[mrsleeve91]

So anyone want/ need a set of MLS head gaskets? Ordering some this week, $300 shipped.

Cause the mains were so bad Im just going to tear it all down and check everything..

[The Dark Side of Will]

What supplier are you using for those gaskets?

[mrsleeve91]

Gaskets to go. I was skeptical when I ordered them but the looked good and worked great.

[coinage]

Ever finish this?

[mrsleeve91]

Not completely, Its back together, several hundred in machine work and gaskets. Just waiting for a thermostat housing.

[fieromadman]

I think I speak for everyone when I say, KEEP US UPDATED!

[Atilla the Fun]

Car craft did a pretty good DIY pressure luber. The LSx is hard to prime, so they built their own. Then you just use your air compressor to pressurize the top of the bucket, with oil in the bottom, the hose from the bottom to the oil pressure port. Simple, cheap and helpful.

[Aaron]

Or you just take out the spark plugs and turn it over with the starter like you do every other GM motor.

[Atilla the Fun]

better than 99% of the time, that's fine for most newly-assembled engines. It works about 50% of the time with salvaged engines. But with proper priming, salvaged engines live about 90% of the time. That alone is reason enough to invest $20.