ERE-383 #78

ERE 383 #78

4-bolt main short block for an LT4 Corvette with GM LT4 heads and valve train.

We are off the a quick start.
Eagle Forged rotating assembly with
Mahle -16cc D-dish pistons.

I begin by grinding for clearance at the cam tunnel area.  This is the area I hope will give clearance going by past experience.  The type of I-beam connecting rod that I'm using will always need additional clearance in this area..  An H-beam will not require additional grinding.

I decided to put the rear main cap oil galley plug in at this time.  I can always punch it out and install a new one if I end up having to do more work on the block such as grinding and cleaning.

The main bearings are the King MB577XP and the oil hole does not line up with the block.  I decided to clearance the bearing instead of grinding the block.

Main cap bearing clearance process begins.  Here we have the main thrust cap, (#5) at 0.0034"

And the rest:  All using standard size bearings top and bottom.  .0021 to .0034"

Main thrust by feeler is .004"

Main thrust after crank installed, (crank end-play) = .007"

#1 Rod bearing clearance at .0026" (standard size King bearings CR807XPN).  All the rest were from .0026 to .0028"

Time to see if the rods will clear the block.

Right off the bat #1 rod shoulder bumps the inboard cylinder bottom...(marked in yellow).

Here is a close up.  I will need to remove the crank/rods and grind in that area.  On purpose I did not install the cam bearings for just this situation.  After all the block grinding is complete then I will install the cam bearings.

It turns out that all other rods clear.  It was only #1 that does not.  That's not all too bad.  Next on the to-do list is to disassemble and grind/clean and reassemble.

More clearance grinding at the bottom of #1 bore.

After a thorough cleaning of the block the camshaft bearings are installed.

Here is a reference photo of the cam numbers. This is a mild street cam grind #62801-62702-112, 215/227/112, .546"/.565" with 1.6 rockers.

Camshaft installed.  Oil galley plugs installed.  These have weep holes for oil cooling of the timing set.

Ring gap:  Top ring at .018", 2nd ring at .014", (Street/Strip all natural) per Mahle suggestion.

The ring gap is also checked with ring in the bore.

Timing set on.  This is so that I can check each piston/rod combo one at a time for clearance with the camshaft.

One final look at the rod/piston.

All installed and no interference with cam or block.

Rod side clearance is .020" to .022"  Rod bolts at 70ft-lb

Crank sprocket installed at "O" (zero).

Intake centerline is dialing up at 106*.  The cam card spec is 108*.

Trying the +4 sprocket setting gives 102* ICL

Trying the -4 sprocket setting gives 110* ICL.  I decided to put it back to zero and go with 106* ICL.

The heads are mostly bone stock genuine GM LT4.  The owner did a valve lap and new springs and seals.  The non adjustable rocker studs are shown in the photo.  The pushrod length will need to be established.  In a nutshell the pushrod has to allow for 1 turn past zero lifter pre-load.

Turns out I have an adjustable pushrod and I set the pushrod length that gave a tight rocker nut at 1 turn past zero pre-load.  That ended up being 7.310", (Stock is 7.200" and so I'll order a set of 7.300" pushrods).

I also want to check the valve spring height with various keepers/locks.  This shows 1.748" with the locks in the Lunati spring kit.

In the vice a 1.748 compressed spring gives 170psi.  I like it.

Back to the bottom end.  I have a re-supply of Milodon windage studs and have them installed.

The stock windage tray is massaged up and away from the rods.

Melling M155 oil pump.

Now with the oil pump pickup.

Now the Corvette oil pan.  Surprisingly it did not need to be massaged for rod clearance.

FelPro 1074 head gaskets.  .039" - .003" = .036" piston to head clearance.

Heads on with ARP head bolts at 70ft-lb

Back to the valve spring and making sure they are mostly all the same spring height.  Since there were no shims installed, (just spring locators), I want to make sure all of the springs are similar in height.  Some valves are showing less tip than the others indicating the spring would be installed higher, (1.760").  I checked all that were "off" and installed Crane locks which brought all of the springs in the range of 7.740" give or take .005"

Here is a visual of the shorter valve tip.

The one on the left is the 1.740" spring and the one on the right is 1.760"

Swapping valve locks.

Back to the pushrods.  Turns out the 7.300" pushrod was too long.  Thankfully I had a set of 7.250" by TREND.

All rockers are from 3/4 to 1 turn after zero pre-load.  The preload is not adjustable.  The 7.250" pushrod allows for the 1 turn after zero pre-load (tight rocker nut bottomed out on the rocker stud).

 Ellwein Engines 2017