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Sign up for our E-newsletterLS PROJECT, PART 2
BLOCK PREP AND BALANCING
by Mike Mavrigian
all photos by author
We swapped out the OE torque-plus-angle main cap bolts for a set of ARP studs. This will provide added strength and will eliminate wear on the block’s female threads during future servicing.
I recently visited Gressman Powersports where Scott Gressman decked our block, honed the cylinders to size and balanced our crankshaft.
With our LS2 block set up in the RMC CNC machine, the block decks and cylinder bore diameters and registers were checked. The left bank was taller than the right bank and we witnessed a slight twist to the decks (typical production block).
Note: The LS blocks feature 100-percent metric threads in all thread locations. We pitched the OE main cap bolts and installed a set of ARP main studs (P/N 234-5608). Our ARP main cap studs are 10mm in diameter. The block engagement threads feature a 2.0 pitch and the exposed nut ends feature a 1.25 pitch. The side bolts are 8mm x 1.25. After installing the studs finger-tight to the block, the caps were installed and the nuts were tightened to 50 lbs./ft. at the inboard studs and 60 lbs./ft. at the outboard studs. The 8mm cap side bolts (included in the ARP kit) were tightened to 20 lbs./ft. By the way, you’ll need a 10mm 12-point socket for servicing these side bolts. Note: We applied ARP moly lube to all exposed stud threads, nut undersides, and side bolt threads and head undersides. The torque specs we followed are recommended by ARP when its moly lube is used.
The CNC machine measured deck height from front to rear and from inboard-to-outboard on each deck. While the published GM OE deck height spec is 9.240″, the front of the left bank measured 9.2402″/9.2364″ (inboard/outboard, indicating a twist), and the rear of the left bank measured 9.2461″/9.2414″ (indicating a slant from front to rear and twist). The right bank measured 9.2386″/9.2346″ at the front and 9.2453″/9.2409″ at the rear.
The lowest spot on the right deck was 9.2346″ so Gressman cut both decks at a height of 9.234″ (indexed from the crank centerline) to achieve parallel decks that are equidistant (and square) from the crank centerline. The need to deck a new block isn’t unusual, as Gressman noted that, in his experience, the LS blocks are usually out an average of about 0.006″ at the decks.
Considering our 4.000″ stroke, our 6.125″ rods and our piston compression distance of 1.115″, our pistons should stick out of the decks by about 0.006″. In order to achieve a zero deck clearance, we’ll likely use 0.045″-thick Victor MLS cylinder head gaskets to compensate.
Regarding our cylinder bores, the CNC machine indicated that the bores were at 4.000″, so removal of a mere 0.005″ was needed to achieve a 0.005″ skirt clearance for our 4.000″ JE pistons.
ARP head studs (P/N 234-4317) were installed in the decks, finger-tight. With sacrificial head gaskets in place, a pair of BHJ torque plates was installed, with nuts tightened to a final value of 80 lbs./ft., in three equal steps, again using ARP moly lube.
Using his Rottler honing machine, Gressman honed all cylinders to a final diameter of 4.005″ using 500-grit diamond stones, followed by four strokes with silicon carbide plateau brushes.
OEM LS MAIN CAP BOLT TORQUE VALUES
Main cap inner…..15 lbs./ft. (first pass) plus 80 degrees final
Main cap outer…..15 lbs./ft. (first pass) plus 53 degrees final
Main cap side bolts…..18 lbs./ft.
OUR MAIN CAP TORQUE VALUES
(USING ARP STUDS AND SIDE BOLTS)
MAIN CAP INNER STUD NUTS…..50 lbs./ft.
MAIN CAP OUTER STUD NUTS…..60 lbs./ft.
MAIN CAP SIDE BOLTS….. 20 lbs./ft.
MAIN CAP TIGHTENING SEQUENCE
Tighten the inside main stud nuts first, starting at No. 3 cap left. That is then followed by No. 3 right, No. 4 left, No. 4 right, No. 2 left, No. 2 right, No. 5 left, No. 5 right, No. 1 left and No. 1 right.
Next, tighten the outer main stud nuts following the same sequence as above.
Finally, tighten the 8mm side bolts following that same cap sequence (No. 3, No. 4, No. 2, No. 5, No. 1).
HEAD-STUD TIGHTENING
ARP recommends installing the studs finger-tight. Nuts should be tightened with all threads and nut undersides lubed with their moly to a final value of 80 lbs./ft. in three equal steps.
The cylinder head fasteners involve two rows of 11mm fasteners and one inboard row of 8mm fasteners. For purposes of torque-plate installation, we only concerned ourselves with the 11mm studs (the 8mm studs will be added during final assembly).
The head fastener tightening sequence is as follows:
Center inboard, followed by center outboard, followed by second-from-front inboard, fourth-from-front outboard, fourth-from-front inboard, second-from-front outboard, first-from-front outboard, rear outboard, rear inboard and front inboard. During head installation, this is followed by tightening the far-inboard 8mm fasteners starting at the center, followed by fourth-from-front, second-from-front, rear and front.
Remember that the head fasteners should be tightened in three equal steps. For our 11mm stud nuts, we started at 26 lbs./ft, followed by 53 lbs./ft., followed by a final pull to 80 lbs./ft.
Note: While ARP naturally used metric sizing for all block engagement locations, it did customers a favor by making its head studs with inch threads at the top (nut end). The head studs, while 11mm x 2.0 for block engagement, feature 7/16″ x 20 threads at the nut ends. This makes it simple for users to easily locate replacement nuts (if nuts are lost, etc.), since 7/16″ hardened nuts are commonly used in many head stud kits (ARP and others). They did the same with the small far-inboard head studs, which feature the needed 8mm x 1.25 thread for block engagement, but feature 5/16″ x 24 upper threads and nuts.
OUR FINAL DISPLACEMENT
Our bore diameters are 4.005″ and our stroke is 4.000″. This gives us a total displacement of 403.13 CID.
(BORE X BORE X STROKE X 0.7854 X NO. OF CYLS)
4.005 X 4.005 X 4.000 X 0.7854 X 8 = 403.13 CID
OUR PISTONS
For this build, we chose JE’S new FSR (forged side relief) pistons (P/N 243016). These are sized for a bore diameter of 4.005″.
These pistons are flat-top 15-degree slugs, designed for use with our 4.000″ stroke and our 6.125″ connecting rods. The valve pocket volume is 5 cc. Compression height is 1.115″ and piston weight is 402 grams. JE included rings, including 1.5mm top, 1.5mm second and 3mm oil rings (with spacer rails). The full-float wrist pins are P/N 927-2250-15-51C. The pin locks are P/N 927-073-MW. The oil ring support rails are P/N RA4000-183.
Due to the need for clearance between the rear-mounted crank timing reluctor wheel and No. 8 piston, all pistons feature a “box” style, with a narrow pin boss area. This is a common requirement for LS engines that feature a crankshaft reluctor wheel. The potential interference occurs at No. 8 piston only, but naturally all eight slugs need to feature the same design from a balance standpoint.
BEARING CHECKS
Our main bores measured at 2.750″ (spec is 2.751″).
Our installed main bearing (MAHLE Clevite MS2199HK) I.D. measured 2.5605″.
Our crank main journals measured 2.559″, which would provide only 0.0015″ oil clearance.
We have two potential fixes: either switch to 1X main bearings (which would provide an additional 0.001″ clearance for a final 0.0025″ oil clearance), or to align-hone the block’s main bore by an additional 0.001″.
Due to the timeframe, we won’t be showing the final short block assembly in this issue, but we’ll have this sorted out before the next issue.
As far as rod-bearing clearance is concerned, with our MAHLE Clevite rod bearings CB663HNK installed in our Lunati H-beam rods (and with rod bolts tightened to a rod bolt stretch of 0.0053″), our installed bearing I.D.-measured 2.1025″.
The rod pins measured 2.100″, which gives us a rod bearing oil clearance of 0.0025″.
Note: The ARP rod bolts that were supplied with the Lunati rods are ARP 8740 bolts, featuring a 7/16″ diameter and a shank length of 6.100″.
Per Lunati’s specs, these bolts are to be tightened to a stretch value of 0.0052″-0.0056″ (or to a torque value of 80-85 lbs./ft. with 30W oil).
ROD-TO-BLOCK CLEARANCE
Since our stroke increased from the OE stroke of 3.622″ to 4.000″, it was obvious that we needed to check for rod clearance.
With one rod (with bearings) and piston test-installed (in each bore, one at a time), we carefully rotated the crank and found that the bottom of each cylinder required clearancing to allow the rod outer bolt heads to clear the bottom of the bores. Using a mini 3/8″ belt sander, I’ll grind a relief pocket in line with the bolt head at about 0.420″ wide x about 0.220″ deep.
CAMSHAFT SPECIFICATIONS
Crane hydraulic roller P/N 144HR00162. Grind no. HR-256-367-2S-14. This steel stick features a valve lift (with 1.7:1 rocker ratio) of 0.624″ intake and 0.624″ exhaust, with an advertised duration of 313.0 degrees intake and 321.0 degrees exhaust (at 0.004″ tappet lift). At 0.050″ tappet lift, duration is 256.0 degrees intake and 264.0 degrees exhaust. Horsepower range is 3600 to 7100 rpm, with valve float specified at 7200 rpm (when matched with 137 lbs. closed/354 lbs. open springs). Refer to the cam card for full details.
POWER GUESS?
Our anticipated horsepower (OK, we’re taking a semi-educated guess) with a carbureted setup and a pair of Trick Flow CNC ported cylinder heads will likely be in the 600 HP range. If we make anything near that number, you have to admit that’s not bad for a naturally-aspirated all-motor smallblock streetable deal that essentially involves a bolt-together approach.
STILL TO COME
In upcoming issues we’ll tackle the cylinder heads, pushrods, rocker arms, intake manifold/fuel system, water pump, valve covers, ignition system and oil pan.
The next article installment will feature final short block assembly and a detailed look at our cylinder heads.
Tags: ARP, BALANCING, BEARINGS, BLOCK DECKS, BLOCK MACHINING, BOBWEIGHTS, BORE & STROKE, CAMSHAFT SPECIFICATIONS, CNC, COMPRESSION RATIO, CYLINDER HEAD CLAMPING SEQUENCE, CYLINDER HONING, FINAL DISPLACEMENT, GRESSMAN POWERSPORTS, J&E, LIFTER BORES, LS, LS2, MAHLE CLEVITE, MAIN BORE, MAIN CAP TIGHTENING SEQUENCE, MAIN CAP TORQUE VALUES, PISTONS, RMC, ROD CLEARANCE
