IDRIVEAG8GT

So I was sitting at Taco Bell's drive-thru today, my truck was idling just fine and it was about 80* outside, water temp 180, all was good. I placed my order and then dropped it in drive, and it decided to drop a cylinder. Dead. So I went home let it cool off, and checked the compression. It went as follows:

1. 135
2. 138
3. 135
4. 130
5. 138
6. 137
7. 142
8. 134

Decided to go ahead and drop a fresh set of TR6's gapped at .030 in as well.

Fired it and I heard a rattling noise, the likes I have which I have never heard before.

It had no miss, until it got warm then the dead miss came back, but the noise quieted some.

It has had a slight lifter noise ever since I built the motor but nothing out of the ordinary to me.. They are LS7 lifters. And also since 200 miles ago, my warm oil pressure at idle has dropped from 37 to 30psi.

I've never turned the motor past 6700. Cam specs are: 232/244, .575/.595, 116+2, 6* overlap. Patriot .650 Gold springs

You guys have any suggestions?

-Robbie.

KRAZY K 2000 TA

iTrader: (5)

have you checked your rocker arms? or pushrods?

White Shadow

Did it sound like it was coming from the bottom end of the motor or the top end?

IDRIVEAG8GT

Headed out there to pull the valve covers right now.

IDRIVEAG8GT

Honestly it sounded like top end, but I wanted to do a Compression test just to make sure.

S10xGN

iTrader: (11)

Can't help you with the dropped cylinder issue, but I am curious as to why all your numbers are soooo low. They are fairly tight as a group, but you're giving up a lot of power because of the low numbers. I'm guessing your static compression ratio is 8.0:1 or lower. Each "point" of static compression ratio is worth 4%. Although, as-is that thing ought to be able to run on kerosene or lamp oil...

DietCoke

iTrader: (18)

Sounds like a spring broke

IDRIVEAG8GT

Ok well the motor is built at 10.5:1 CR, and the reason the numbers are so low is because I did the test one spark plug at a time, anotherwords all spark plugs were in and tight except for the one I was working on. Sorry I failed to mention that or else the group would be around 165.

IDRIVEAG8GT

Checked all the springs and none were broke. I fear for the worst on cylinder number 4, because when rolling the motor over there was a definite squealing noise coming from it every time the exhaust valve opened. I honestly think one of the lifters failed What freaked me out even more is the fact that at the same time I had the valve squealing a noise a little puff of steam would come from somewhere I could not identify. I think that is what the rattling noise was, but it was more pronounced at a slow rpm with the valve cover off.

chriswtx

iTrader: (5)

Man, you've got the worst luck with motors...

IDRIVEAG8GT

Well it was fun while it lasted I'm just gonna go smash my head into a wall a few dozen times and then I'll be all better.

The good news is that the up and down motion for the lift on the intake and exhaust is nice and smooth despite the noise so I'm praying like hell it didn't hurt the cam.

IDRIVEAG8GT

Just an update, I pulled the head off the suspect side of the engine, and pulled the lifters out. The lifter rollers themselves look very good, but I'm not really sure about the internal parts of them though. I have them and the buckets out right now if you guys would like pics or anything.

I spent a great deal of time cleaning and inspecting the head combustion chambers, intake ports, and exhaust ports for anything out of the ordinary, and found nothing.

I also extensively cleaned the tops of the pistons and did a visual and physical examination of the top of the pistons for cracks, dents, or anything else. Being forged pistons they came out shining just like brand new after I finished with them. Nada there.

I put each piston down to BDC and mic'd the holes and checked for scratches. Each had no variance whatsoever and there was no sign of broken ring land scratches, premature ring wear, etc. Each hole was clean as a whistle.

CNC-Motorsports built me a beautiful short block that's for sure.

I assumed it was lifters causing the problem miss and we went ahead and got a set of Lunati Link Bar Hi-RPM hydraulic roller lifters from SDPC. Expensive, MF's, but I see why they get all the money for them.

(Thanks SDPC for finally getting everything worked out. My dad and I are very appreciative.)

I already set the cleaned head back on that side and am going to head back out there in twenty minutes or so to torque the studs down on that side with the new Lunati's installed.

I'll then start on the other side and let you all know how it looks.

Let me know if you guys think there is more I should check.

-Robbie.

IDRIVEAG8GT

This may sound like nothing, but something that I did not mention to anyone yet, is that when starting the engine cold, it takes approximately anywhere from 15 to 30 seconds to build oil pressure. When it builds it, it's 50 pounds, but on a few occasions it'd take so long that the "Stop Engine Low Oil Pressure" readout would go across the display and then it would build oil pressure and the readout would go away.

Main and rod bearings most likely don't do that, and I know that if there was a plug out of the block, it wouldn't build oil pressure like that. After the truck builds oil pressure it's good for the rest of the day, like jump in, fire up, and instant oil pressure. So would a bad lifter being pumped down due to spring pressure cause something like that?

Just a thought.

Fb0dy0nly

iTrader: (10)

Im not qualified enough to tell you what your issue is but I DEF do not like that it takes that long to build pressure, something aint right even if its just the electronics acting goofy but then it should happen more than just at cold start up...hmm.
I was gunna say switch the lifters around and see if anything happens then but since you've got new ones, no point now.
hopefully you will figure it out and good thing it happened at idle and not WOT and the block is okay. Good luck dude.

litle88

iTrader: (20)

Did you soak the lifters for a looong time? What preload did you use on those lifters ? Did you see if the oil pan sensor is ok? How about the oil sensor on the back of the block? Did you damage it when removing intake manifold?

Just my .02

Jimbo1367

I'd recheck the oilpump pickup o-ring. Get a BRPhotrpds girdle

IDRIVEAG8GT

K got it all back together with the new lifters. No more missing! I'm starting to lean towards an electrical problem for the oil pressure. Even though it takes the gauge forever to build oil pressure when cold, on a cold fire with the valve covers off, oil positively spews all over the place from the pushrod holes instantly, and there is never a lifter rattle like of what happens with no oil pressure. The oil is super clean. Etc.

Thanks for the suggestion because no I HAVE NOT checked the sensor in the pan. What all does it do?

IDRIVEAG8GT

? A BRPhotrods what?