4.6 Build in NC

[nukfyrsq]

First I would like to thank everyone who participates in this forum. I’ve been following various builds for about eight months and have developed my plan from most of yours so there shouldn’t be any big surprises here. Plan to take a week off in April to assemble and install, here’s the list.

99 Wrangler Sport 4.0 stick w/AC, this engine will be kept for a spare – 150k+ miles runs great, K&N cold air, TB spacer, Gibson SS header, Borla SS cat back exhaust

1992 4.0 w/7120 head DIY P&P
677p 17.5 cc stock dish pistons .040” over
258 crank (can’t remember the year, I’ll find out if anyone is interested)
242 rods reused
Comp Cam 68-232-4 kit
Crower cam-saver lifters
Mopar performance .043” head gasket
TB and spacer will receive overbore to 62mm
Have 21lb, 24lb and looking at 27lb injectors
Melling HV oil pump
GMB North America HV water pump
180 deg full flow thermostat
Ford Duel speed electric fan
Aluminum radiator
Will change exhaust to shorter path (Dino style) 3” from header to cat
Getting and crunching numbers to determine what additional machine may be required.

Plan to dyno current set up before the above is completed and installed. Will dyno post build and either reflash an ECU or piggy back an APEX if needed. Will install Glow Shift gauges to monitor; wide range air/fuel, fuel pressure, oil temp and exhaust temp along with stock oil pressure, water temp. and volts.

Interesting note, my 1992 FSM list combustion chamber volumn as 64.45-67.45cc. The default on the compression calculator seems to be 58cc.

[dwg86]

You will need 258 rods to use with the 677 pistons.

[nukfyrsq]

Ooops, slip of the fingers, THANKS! I am using the 258 rods. I typed this up at work and was in a hurry. The goal is to end up with a SCR as close as possible to 9.5:1 with a quench height equal to or better than factory, DCR will be what it'll be. Thanks again.

[nukfyrsq]

Ok turns out the SP 677P pistons are dished @ 14cc not the 17.5cc I read somewhere. Here’s the number from the machine shop. I would like some thoughts before I give go ahead on Monday.
Head trued, removed .012”
Block trued, removed .012”
Combustion Chambers 57cc
Deck height @ TDC .040
Below are the number I ran through the CR calculator, Constants:
Bore - 3.915”
Stroke - 3.895”
Combustion Chamber - 57cc
Head Gasket Thickness - .043”
Gasket Bore – 4”
Comp Cam 68-232-4 Intake duration 250 LSA 113
Deck Height/CR/Quench
TDC to Deck height .040” .030” .020” .010”
Piston dish cc 14 18 20 22
SCR 9.76 9.56 9.56 9.56
DCR 8.23 8.07 8.07 8.06
Q H .083 .073 .063 .053

I’m leaning toward the removal of .030” (.010” deck height) from the block with a 22cc dish on the pistons for a quench height of .053” in the hope of reducing or eliminating pinging. In theory this should allow the use of the Crower .055” shorter push rods for correct lifter pre-load.

[Mgardiner1]

Contact board member Oletshot to see if he has experience dishing the 677 to 22cc's. He'd know better then anybody. If possible, then i'd definitly go for the setup with the lowest quench

[oletshot]

22cc's isn't problem for 677p pistons.

[nukfyrsq]

Thanks Oletshot. Based on what I've read I would like to send these pistons to you. However, by the time I pay my machinist to remove them from the rods, checked deck height on all cylinders, ship them back and forth and pay you I'll do better having them done in house. Any words of wisdom I can pass to my machinist? Interesting, I've read in two different places the Sealed Power 677P has a 17.5cc dish but mine cced 14, why?

[6TIME]

I talked to a Federal Mogul Tech about the piston dish they said that they used to be 17.5cc but all of the new castings have changed to 14cc. I have an older 677 casting that measures out to about 17.5cc's with a .135" deep dish. It looks like all of the newer Sealed Power pistons are .116" deep and 14cc dish.