DIY LTCC or similar system for LT1s

[spfautsch]

Perhaps I should buy a toughbook.

Tech moves so fast and can be so inexpensive I don't see much value in buying an extremely expensive piece that will last "forever" and continuing to use it well past it's point of (designed) obsolescence due the fallacy of sunk cost. I tend to buy something nice (by my extremely low standards) on clearance every 3-5 years and consider it more or less disposable. When my current rig dies (an inspiron 13 3-in-1) I'll move the ssd and memory from my old one to my new one and never miss a beat. But then I don't run windows.

I'm not making much progress here either. I did spend some time working on the coil harness over the weekend. That was before I discovered I have a valve stem and possibly a guide, seat that are trashed. I haven't worked up the courage to pull the head yet and assess the damage fully.

[spfautsch]

I know this is ridiculously off-topic, but no-one else seems to be volunteering to build or test a prototype so you're stuck listening to me whine.

One of the items on my "while i have the engine out" checklist was to evaluate pushrod length and determine if what I had was acceptable. Boy, did I open a can of worms.

While I did come up with a more "correct" length and buy new pushrods, unfortunately I found as I was preparing to put the intake back on that I had already trashed all the guides in my newly LE1'd heads. Long story short, don't under any circumstances follow CompCams guide here or anything that sounds like it. It is completely and utterly incorrect. With only 100 hours on my build I have excessive guide to stem clearance from using "geometry" that was determined erroneously using said guide.

Whatever your take on valvetrain geometry, this puts me at least two weeks if not a month (not to mention a considerable spend) away from turning the key on it again. I'm so incredibly p****d words can't do it justice.

[vilefly]

Well, that sounds horrible enough. The instructions I remember are that the rocker arm should be level @50% lift (90 degree angles at rod and valve). Although the LS engines have a higher cam location, this may not be entirely possible. I still need to obtain 8 LS coils to start my tinkering. Too many old 60s luxury cars have been showing up at my shop, and fraying my nerves trying to find parts for these badly wired fords and one failed '71 chevy truck restoration that I have to redo. We don't typically touch these project cars, but we hit a slow spot, and the boss got desparate, and said yes. Blech.
I hate it when people try to drive something that they will never like how it operates.
"Can you adjust the suspension so that my new truck rides softer?"
"You just bought it. Didn't you test drive it?"
"Um....yes."
".........." (incredulous raised-eyebrow stare) "How about dropping an engine block in back, lady? That'll smooth things out."

[Terminal_Crazy]

I know this is ridiculously off-topic, but no-one else seems to be volunteering to build or test a prototype so you're stuck listening to me whine.

One of the items on my "while i have the engine out" checklist was to evaluate pushrod length and determine if what I had was acceptable. Boy, did I open a can of worms.

While I did come up with a more "correct" length and buy new pushrods, unfortunately I found as I was preparing to put the intake back on that I had already trashed all the guides in my newly LE1'd heads. Long story short, don't under any circumstances follow CompCams guide here or anything that sounds like it. It is completely and utterly incorrect. With only 100 hours on my build I have excessive guide to stem clearance from using "geometry" that was determined erroneously using said guide.

Whatever your take on valvetrain geometry, this puts me at least two weeks if not a month (not to mention a considerable spend) away from turning the key on it again. I'm so incredibly p****d words can't do it justice.

Hiya Scott, I got your email - Thanks

That sucks.
I used the Comp Cams pushrod checker and got the smallest sweep and tried 0.050, 0.100 and 0.150 either side.
Hmm thinking about this is making me nevous now :-)

Cheers
Mitch

[spfautsch]

I still need to obtain 8 LS coils to start my tinkering.

Mine are some new "scratch and dent" coils that I found on big auction site for a very reasonable price. The worst looking one has a small chip in the epoxy around the top.

I used the Comp Cams pushrod checker and got the smallest sweep and tried 0.050, 0.100 and 0.150 either side.
Hmm thinking about this is making me nevous now :-)

With the spring loads we're running stuff is bound to wear faster, but if you follow Comp's "procedure" blindly it's a recipe for disaster. They should really take that page down because it comes up at the top of search results, and it's horribly incomplete.

If you ended up with the smallest sweep you're probably fine - this puts the rocker at roughly a 90 degree angle to the valve stem around mid lift. My original setup with stock length pushrods had a sweep pattern close to the middle of the valve about .105" wide so I gave it no more thought. The 90 degree at mid lift method got the sweep closer to .022" but it's on the outer 1/3 of the tip. There's really no way to adjust it in without throwing out the 90 degree geometry other than having custom trunnions made with offset stud holes.

The only reason I noticed this is because the #6 intake valve was cocking sideways and contacting the seat as the rocker started to open it. It was making a faint "clink" sound as the face of the valve was ringing like a bell.

[kur4o]

I hope you made the measurements with modified solid lifter and soft spring, to reduce to minimum lifter bleeding.
Mark the valve tip with same paint and get the contact mark as much as possible to mid point of the tip.

Of course subpar guide`s material is always a possibility.

[spfautsch]

Oh, don't worry. I've learned more about rocker geometry in the last 5 days than I ever wanted to. Lloyd and I have been discussing the subject extensively. I'm debating hiring a medium to channel the ghost of Smokey Yunick to see what he thinks. I bought a new lifter to use for mock-up and blocked the plunger with a piece of bar stock so the running springs could be used, because the deflection caused by the spring pressure is a factor you want to account for also.

I was running stock PR length last year when this damage was done. The wear pattern wasn't perfectly centered but it looked "close enough". Roughly .100" wide and roughly .030" offset towards the exhaust side of head. Obviously that wasn't "close enough".

I used the 90 degree at mid lift method this time to give absolute minimum sweep, and then last night bought an obscenely expensive set of rocker arms that have the stud holes in the trunnions drilled .050" offset, so the roller tip will contact the valve closer to center.

[kur4o]

The greater the force needed to push the object down, the greater the tilting of the object, if the force is applied off-center.
That way the valve will rub the guide sideways. So the higher the pressure, the more exact center location is needed. If the spring were softer you might even not get a failure.

Since the force will be straight centered only at the mid travel, and there will be offset either way I suggest you recalculate the spring rates and use the spring that can tolerate your RPM band and no higher.