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1987-2006 Jeep 4.0L Inline Six - Inside The Inline

Stroking Jeep's 4.0L Six, Part 1

By: Courtesy Mopar Performance, Jim Allen, Photography by Jim Allen
  • 11. We used 0.030-inch-oversize Sealed Power hypereutectic pistons (PN H802CP), which are a performance piston for 4.0L applications. In addition, the skirts are Teflon-coated to reduce friction. We measured an 18.83cc dish volume (including ring land). People get by with ordinary cast 4.0L pistons quite well also.
    11. We used 0.030-inch-oversize Sealed Power hypereutectic pistons (PN H802CP), which are
  • 12. You are best off with the '91-and-later high-output cylinder head. It flows better than the '87-'90 "low-port" head, though not by a massive amount. We used a '00 H.O. cylinder head (casting No. 0331). These aren't the best H.O. heads from a performance standpoint, because they have smaller exhaust ports. (Reportedly, the best H.O. heads come from '91 to '98, and have the casting numbers of 7120 and 0630.) From the flow bench numbers we've seen, the differences aren't huge. Overall, if budget is a concern, all the heads can be used effectively. A dual-pattern cam with longer exhaust duration really helps the 4.0L exhale.
    12. You are best off with the '91-and-later high-output cylinder head. It flows better tha
  • 13. For a timing chain, we went with the reliable Cloyes double-roller set. They last forever and have the option of making timing changes. The three options (see red arrows) are 4 degrees advanced, "straight up" (zero advance), or 4 degrees retarded. These options can be used to correct timing errors or for a specific tuning purpose. Advancing the timing enhances bottom-end performance at the expense of upper-end performance, and retarding the cam timing does the opposite. Bear in mind that the '00-and-later blocks use a different timing set. The Crane cam we used was set up for the earlier unit so the Cloyes was ordered to fit the earlier setup.
    13. For a timing chain, we went with the reliable Cloyes double-roller set. They last fore
PartCasting
Number
YearNote
Block53005535'87-90Non-HO
Block53008405'91-95HO, early
Block53020569'96-99HO, late, best for pre-2000 Jeeps
Block53010449'99-06HO, metric fittings
Crank3199738'71Drilled for Borg-Warner automatic, bad pick
Crank3214723'72-8012 counterweights, long nose, strong & heavy
Crank3235477'81-864 counterweights, long nose
Crank3727'87-904 counterweights, short nose, best pick
Con Rod154'64-665.875 length, 232ci, weak rod!
Con Rod207'64-796.125 length, 199 & 232ci, weak rod!
Con Rod707'71-815.875 length, best pick short rod
Con Rod352'82-905.875 length, ok
Con Rod53020126'87-066.125, 4.0L rod, best pick long rod
Cyl Head2686'87-90Non-HO, Renix engine
Cyl Head7120'91-95HO, good pick, 55.22-58-22cc
Cyl Head0630'96-99HO, good pick, 55.22-58-22cc
Cyl Head0331'99-06HO, so-so pick, 55.22-58-22cc
Piston-'87-064.0L, 1.60 pin height, 13.5cc dish
Piston2229c-Keith Black, 1.58 pin ht, 11.5cc dish
Piston677CP-Sealed Power, 1.592 pin ht, 17.5cc dish
PistonH802CP-Sealed Power, 1.585 pin ht, 17.5cc dish

Bold text indicates the parts used in the UNO buildup.

To Get Deck Height (DH)
deck height = block height* - rod length - piston pin height - 1/2 stroke

To Get Compression Ratio (CR)
CR = total cylinder volume combustion chamber volume

To Get Combustion Chamber Volume (CCV)
CCV = cyl head volume + head gasket volume + deck clearance volume + piston dish volume

To Get Cylinder Volume (CV), Deck Clearance Volume or Head Gasket Volume
CV = 0.7853942 x bore2 x stroke
Note: For head gasket, used compressed distance.

To Get Quench Height (QH)
QH = deck height + head gasket compressed distance
*Block height = Distance from crankshaft centerline to block deck On a 4.0L= 9.450-9.456-inch

SOURCES
ARP
531 Spectrum Circle
Oxnard
CA  93030
805-278-7223
KB-Silvolite Performance Pistons
www.kb-silvolite.com
Crane Cams
530 Fentress Blvd.
Daytona Beach
FL  32114
3-86/-252-1151
N/A
www.cranecams.com
Mopar Performance
Mopar.com
Custom Design Performance
www.cdpautomachine.com
Quadratec
8-00/-745-2348
quadratec.com
Golen Engine Service
17 Dracut Rd.
Hudson
NH  03051
Sealed Power
Hesco University of Northwestern Ohio
By Courtesy Mopar Performance, Jim Allen
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