Confirming 4.7 Setup

[604rail_king]

ive spent the last week or two reading up on this forum along with Dino's page... Very detailed and helpful!

as most members who haven't actually started their build yet, i want to get a confirmation on my setup before buying parts or more importantly machining. the only parts i have acquired is a running donor 91 engine for my 95 XJ.

in my planning, i believe that ive come up with an ideal poor man's 4.7 stroker. my goal is a simple stock-like setup that's very reliable, pumps out nice low-mid range tq, hopefully runs 87 or 89, and keep the cost low. i drive mainly on the street and mild wheeling, so i don't want anything extreme.


Parts List:
4.2 crank and rods
KB Silv-o-lite 2229c .060 cast pistons (11.5 dish)
zero deck clearance
stock 96+ cam
stock 91-95 intake, 60mm ported stock tb
felpro 9076 .043 head gasket
Stock 7021 head
ford 24# injectors
2.5" exhaust, possible removed cat


using the Static/Dynamic Compression Ratio Calculator, ive come up with the following ratios:

4.66L (aka 4.7L)
SCR = 10.91
DCR = 9.0:1
Quench = .043

from what ive read so far, the DCR and quench are in ideal ranges, and should be be able to run 87 or 89 oct without pinging.(?) also what ive seen in threads so far, im a fan of sticking with the stock cam - ideally the 96+ to get the most tq. i live in Vancouver, Canada where we can see -15C to +35C weather at times.

i plan on building an adjustable map controller soon and trying it out on my 4.0 first. ill be strapping my xj on a mustang dyno with a wideband to ensure the AFR's are in line. should be interesting to see the before/after results!

thanks in advance

any suggestions or comments?

[Cheromaniac]

4.66L (aka 4.7L)
SCR = 10.91
DCR = 9.0:1
Quench = .043

from what ive read so far, the DCR and quench are in ideal ranges, and should be be able to run 87 or 89 oct without pinging.(?)

With that SCR and DCR, you're likely to be heading towards ping city even with premium fuel. If you really want a 4.7L "poor man's" stroker here's what I suggest:

4.7L (4657cc) "poor man's" stroker

Jeep 4.2L 3.895" stroke crank
Jeep 4.0L 6.125" rods
Keith-Black UEM-IC944-060 pistons
9.4:1 CR
Stock '96-'98 camshaft
Ported 7120 HO 1.91"/1.50" cylinder head
Mopar/Victor 0.043" head gasket
0.070" quench height
Ford 24lb/hr injectors with MAP adjuster
Stock 39psi FPR and stock computer

[604rail_king]

is the SCR too high?

4.7 displacement is not my most important target.. running 87 or 89 and keeping costs down are. ill be assembling the motor myself to help aid in this. my thoughts are if this is a budget motor, its essentially a throw away if it ever blows up... so why not just bore it to the max displacement since im already boring the the cylinders.

im also not fully convinced forged pistons are ideal for long life motors, but my experience with them has been with high boost applications (30psi DSMs EVOs, Skylines). which is why i chose the cast pistons. however my jeep is my weekend toy and i doubt id ever put 100k miles on it.

again to keep costs down, im trying to eliminate as much machine shop work as possible - meaning no re-doming pistons, ect.

just trying to find a good combo of off-the-shelf parts to use... guess its back to the drawing board.

[604rail_king]

With that SCR and DCR, you're likely to be heading towards ping city even with premium fuel. If you really want a 4.7L "poor man's" stroker here's what I suggest:

4.7L (4657cc) "poor man's" stroker

Jeep 4.2L 3.895" stroke crank
Jeep 4.0L 6.125" rods
Keith-Black UEM-IC944-060 pistons
9.4:1 CR
Stock '96-'98 camshaft
Ported 7120 HO 1.91"/1.50" cylinder head
Mopar/Victor 0.043" head gasket
0.070" quench height
Ford 24lb/hr injectors with MAP adjuster
Stock 39psi FPR and stock computer

also is porting the head necessary in this combo? im inclined to leaving it totally stock as ive never ported ahead before and its not in the budget.

[Cheromaniac]

is the SCR too high? An SCR of 10.9 is definitely too high if you want to run 87 or 89 octane

im also not fully convinced forged pistons are ideal for long life motors. Hesco use Diamond forged pistons in their engines, and the IC944 pistons I'm suggesting for yours only require a piston-to-bore clearance of 0.0035" so there are no longevity issues.

again to keep costs down, im trying to eliminate as much machine shop work as possible - meaning no re-doming pistons, ect. just trying to find a good combo of off-the-shelf parts to use... guess its back to the drawing board. Not really. I've just handed a nice combo to you on a plate.

also is porting the head necessary in this combo? No you can leave it stock but you'll end up with about 20hp less than with a ported head.

[604rail_king]

thanks for the input on the head. ive talked it over with a jeep friend who can help port the head as we will be building the same stroker combo

4.7L (4657cc) "poor man's" stroker

Jeep 4.2L 3.895" stroke crank
Jeep 4.0L 6.125" rods
Keith-Black UEM-IC944-060 pistons
9.4:1 CR
Stock '96-'98 camshaft
Ported 7120 HO 1.91"/1.50" cylinder head
Mopar/Victor 0.043" head gasket
0.070" quench height
Ford 24lb/hr injectors with MAP adjuster
Stock 39psi FPR and stock computer

after some further research and an email to KB , ive decided the IC944 are the easiest route due to 4032 material. as i mentioned before i was weary about forged pistons due to the usage life cycle but that was with other piston material in hi boost applications. there is NO PLANS for boost with this motor... just want as much turn key reliability as possible

i will be picking up a 4wt 54mm nose 258 crank this week. any thoughts on this over using the 12wt 64mm nose other than rotating weight?

the only part(s) i havent sourced are the 96+ cam

[Cheromaniac]

i will be picking up a 4wt 54mm nose 258 crank this week.

Good choice. Do the journals need to be reground or have they been done already?

[604rail_king]

i have yet to remove the crank from the 258 long block i plan to pick up on friday hopefully. will have to see what my machinist will say

ive been told the engine is from the late 80s, so that would make it the short nose. i do have access to a 12wt crank but its still in a running motor (or apparently running)

[604rail_king]

well ... spent the last day n a half stripping both a donor 4.0 long block & a 4.2 long block. neither motors were on engine stands and my trailer is an oil mess of leftover scrap metal !!!

crank confirmed - 4.2 is #3727 (4wt 54mm nose). looks to be good condition! in fact the entire long block looked good ... the frost plugs looked like they had been replaced possibly. only one bearing looked like is had seen some minor abused but no scoring.

the crank will still go to my machine shop once i get around to ordering my pistons and other parts from summit.

4.2 rods ill likely post up for sale if anyone is in need of a set

[604rail_king]

purchased my pistons today! went with the IC944 .030 which will net a 4.6L stroker.

from playing with the calculator ALOT and taking in considering all the factors, the .030 made the most sense. i could have got the .040 but i was unsure if i would have to get the crank offset ground like the .060's (according to the stroker recipe page) so i just kept it simple. doubt the minimal displacement difference would be noticed.

overall this should yield a SCR of 9.6-9.7, DCR of 7.9-8.0, and .043 quench

the crank is at the machinist and said it was untouched. there was some light markings so they are taking .010 off

[Cheromaniac]

purchased my pistons today! went with the IC944 .030 which will net a 4.6L stroker.

from playing with the calculator ALOT and taking in considering all the factors, the .030 made the most sense.

the crank is at the machinist and said it was untouched. there was some light markings so they are taking .010 off

Sounds like you're on your way with the stroker build now. Should be fun making it all come together.