1987-2006 Jeep 4.0L Inline Six - Inside The Inline
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. | 
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. | 
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. |
Strokin' Gear | Part | Casting
Number | Year | Note | | Block | 53005535 | '87-90 | Non-HO | | Block | 53008405 | '91-95 | HO, early | | Block | 53020569 | '96-99 | HO, late, best for pre-2000 Jeeps | | Block | 53010449 | '99-06 | HO, metric fittings | | Crank | 3199738 | '71 | Drilled for Borg-Warner automatic, bad pick | | Crank | 3214723 | '72-80 | 12 counterweights, long nose, strong & heavy | | Crank | 3235477 | '81-86 | 4 counterweights, long nose | | Crank | 3727 | '87-90 | 4 counterweights, short nose, best pick | | Con Rod | 154 | '64-66 | 5.875 length, 232ci, weak rod! | | Con Rod | 207 | '64-79 | 6.125 length, 199 & 232ci, weak rod! | | Con Rod | 707 | '71-81 | 5.875 length, best pick short rod | | Con Rod | 352 | '82-90 | 5.875 length, ok | | Con Rod | 53020126 | '87-06 | 6.125, 4.0L rod, best pick long rod | | Cyl Head | 2686 | '87-90 | Non-HO, Renix engine | | Cyl Head | 7120 | '91-95 | HO, good pick, 55.22-58-22cc | | Cyl Head | 0630 | '96-99 | HO, good pick, 55.22-58-22cc | | Cyl Head | 0331 | '99-06 | HO, so-so pick, 55.22-58-22cc | | Piston | - | '87-06 | 4.0L, 1.60 pin height, 13.5cc dish | | Piston | 2229c | - | Keith Black, 1.58 pin ht, 11.5cc dish | | Piston | 677CP | - | Sealed Power, 1.592 pin ht, 17.5cc dish | | Piston | H802CP | - | Sealed Power, 1.585 pin ht, 17.5cc dish |
Bold text indicates the parts used in the UNO buildup. Stroker Math 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
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