LT5 Assembly Project

[Bob G]

Lee When do you want me to come over & check the sleves
Call me

[LGAFF]

Bores and Pistons got a clean bill of health from Dr. 134.......appears to be LT-5 quirk. Total Seal advised me that they would not be surprised to see it on an unfired motor(30-35%) due to the inperfections in rings until they run a few minutes.

[Paul Workman]

Originally Posted by LGAFF

Bores and Pistons got a clean bill of health from Dr. 134.......appears to be LT-5 quirk. Total Seal advised me that they would not be surprised to see it on an unfired motor(30-35%) due to the inperfections in rings until they run a few minutes.

Interesting. Did the good Dr have anything to say about the valve leakdown difference as a function of head bolt torque?? I'm curious about that. Is it an issue, or is it too within the realm of normal LT5 - as yet unfired?

P.

[LGAFF]

Well most people do not leakdown a new motor, so somewhat new territory, remember this started wtih me looking for valves hanging open due to the lifter height.

The 118ft lbs of torque on the head seems to be a factor.....also Bob brought up that building a 660lb motor on stand might also be making some issues.


I tested the valves/heads off the block, they hold fluid.

Total Seal also told me that 30% leakdown would not be impossible on new rings

Weird stuff

[LGAFF]

http://speedtalk.com/forum/viewtopic...5d979&start=15


Interesting note on head distortion

[mike100]

Once I did file-to-fit rings on a sbc and the leak down was 1% on the unfired longblock. It did use oil for a few hundred miles because the finish was too fine for a fast break in, but the compression rings were good from the get-go.. A healthy 350 with 100k miles might be 7-8%.

I never used any rings more exotic than those plasma moly ones (which require a rough hone). Give me regular moly faced/steel top ring style ring sets any day.

All that said, since two cylinders are clearly valve leak air- I would suspect valve/lifter/stem height the most.

[mike100]

thinking out loud:

How doable would it be to install the starter and maybe lower the assembled longblock onto some wood on the floor and run it in for a few times using a 12v battery to run it in for 10 seconds at a time (spark plugs removed, oil in sump). This would prime the lifters and seat the rings a little bit.

[Paul Workman]

Originally Posted by LGAFF

http://speedtalk.com/forum/viewtopic...5d979&start=15


Interesting note on head distortion

Using a torque plate...WITH the spark plugs installed...OR the end valves might whistle...gets the "Arty Johnson - 'Veddy Intorestink!' " award!



For those of you too young to remember the "Laugh-In" comedy hour...you missed a classic that got pulled for being NON-PC! (I'm still laughing!)


p.

[Paul Workman]

Originally Posted by mike100

thinking out loud:

How doable would it be to install the starter and maybe lower the assembled longblock onto some wood on the floor and run it in for a few times using a 12v battery to run it in for 10 seconds at a time (spark plugs removed, oil in sump). This would prime the lifters and seat the rings a little bit.

I did essentially that, Mike. I lowered the long block into the engine bay to rest on the motor mounts - used a 2x4 under the pan for support, and cranked it in place a bit before testing. (Ooops! Don't forget to disconnect the fuel pump connector (under the fuel door lid...[sigh].)

I figured if it failed, it would only take a few minutes to have it outta there again. And, if it passed (and it did - the second time), I'd just finish the installation.

P.

[tomtom72]

Sorry Lee. I can't resist. I guess this isn't something I can do in my parking space! Drat! I gotta find me a garage to rent for just one winter so I can do all this at one sitting.

Sorry for the rant guys. It is frustrating to have a stock slow ZR-1!


Tom