First 89 Renix Stroker, have some questions

[NickInTimeFilms]

First time post but I've been reading for a year or two now. I've got a stock 89 Renix engine with 180k miles and she's been puffing blue clouds so it's time for a rebuild. I'm running 35" tires, 4.56 gearing, and AW4 Auto Trans but I'd like some more power. My rig is 40% street and 60% trails (Mud and Rocks) so I'm looking for some nice torque and the ability to pass people if I need too but I don't need a racecar. I'm aiming for 87 Octane and keeping things simple as long as I'm not losing too much power from it.

I just ripped the motor out and haven't ordered anything yet but here's my plan so far. It's a mild 4.6L from the sounds of it.

Clegg Engines 4.6L Stage II Stroker kit:
4.2L 3.895" Scat Crank
4.0L 6.125" Rods Reconditioned
Icon 4032 Forged IC668 Pistons .030" over w/ 27.5cc
Cast Piston Rings #E667 Scat
Kings Connecting Rod and Main Bearing Set
Stock Renix Cam: Dur 270 deg / .424" Lift / LSA 112 deg
Stock 2686 Renix Head
Mopar/Victor 0.043" head gasket
Zero Deck Clearance
24lb/hr Injectors
Stock Renix Intake/Exhaust
SCR: 9.1 / DCR: 6.72 / .043" Quench
I set the deck clearance to Zero on the forum calculator, so hopefully I'm not missing something important with how it calculates things.

Cheromanche's posts have helped me quite a lot and I've got some good tips for running 87 from him. My goals are to keep the quench at .050" or less, my DCR under 7.5:1, and feather any sharp edges in the combustion chamber. My DCR is still pretty low with this set-up so I should be safe but I'd like to push closer to 7.5 DCR.

Clegg Kit Upgrades
There are a few upgrades available from Clegg and I'm wonder if they are necessary or not for my build.
- Upgrade to Perfect Circle Moly Piston Rings +$30.00
- Upgrade to Clevite Bearings +$60.00
- Upgrade to Scat Forged Rods +$195.00

I'm going to assume that there is no reason I need Forged Rods but let me know the goods and bads about the rings and bearings.

Deck Questions
From my understanding quench is pretty important for keep the charge where you want it and it helps to cool things down a bit which helps with pre-ignition. I should be aiming for a zero deck and a high performance .043" head gasket then right? How much can I mill before I run into issues with pushrod length? Anything else I need to take into account when zero decking a block? I've heard a lot about Bulltear Pistons and If I'm understanding correctly they can do any kind of custom piston and I wouldn't even have to worry about decking except for checking flatness then right?

Cam Questions
I noticed the Renix cam is set with -8 degrees of retard from the factor which is keeping the DCR quite low. Can I set that to zero or even advanced to make the engine run better or is that not quite how things work? I'd like my power around the 1,000 to 4,000 RPM range so wouldn't the new IVC angle of 67 help bring the torque down lower or is this too much?

If I set the timing to zero then my DCR jumps to 7.19 and If I go .060" over bore instead then it raises to 7.29. That a lot closer to my max limit of 7.5 so I would think I've got a decent set-up, correct me if I'm missing something here. Is the jump from 4.6L to 4.7L really worth much or any harm in doing so?

Also, if you really think I should go with an aftermarket cam for some reason then let me know. If a new cam is a must, I want a smooth idle and preferably more of a fuel economy grind. Wide lobs seem like the smart choice. Clegg has what looks to be a decent cam in their Stage 1 kit for my needs.

Head Questions
Right now my plans are to use my stock Renix 2686 head. I wasn't planning on a port and polish so hopefully I'm not loosing too much on that. I hear that helps with higher end breathing but I'm rarely up that high for long. How much am I losing out If I don't get a 7120 head? Is it really worth the swap?

Intake / Exhaust Questions
If I were to do the 7120 Head swap, I'd probably want the 99+ Intake to fully take advantage of the better flow then right? Would that combination be noticeable enough to make the swap worth it? I figure worst comes to worst I can always swap a head and intake later if I need the flow.

If I stick to my original plan and keep the stock intake and exhaust, is that going to choke my engine too much? Should I at the very least bore my throttle body and if so how much? Is the stock 2-1/8" Exhaust going to be too restrictive? Are high flow cats/mufflers worth anything?

Other Special Doodads
Am I going to need an adjustable FPR or MAP sensor or is that for some kind of fine tuning? ARP Rod bolts and other hardware things? I just bought an MT2500 Scanner so I can see what the ECM see directly and see if anything doesn't jump out at me. Anything else I may need to look into?

I know almost every square inch of my Jeep, but I'm lacking in the performance regions so any good threads and tips would be greatly appreciated. I feel like I'm at least on the right track so far. I'm gonna call Clegg up soon and see what kind of input they may have for me and I'll post my findings here. Thanks for the read!

[jeepxj3]

Scat forged rods end up being less than $100 more than the cost of reconditioning 4.0L rods.
Scat rod bolts are good, ARP bolts on stock rods are a good idea. So Scat rods end up being cheaper than 4.0L rods + reconditioning + ARP bolts. Both are good to 500hp.
0 deck is good. If Icon pistons- mill block and need shorter pushrods, if Bulltear pistons- just clean up deck and stock pushrods. Pushrod length needs to be checked regardless.
Stock cam good with stock valve springs, aftermarket cam will need different valve springs for the additional lift.
Head and Intake swap is good idea, either way, Will need at least bored 62mm TB.
2.5" exhaust and new high flow cat and muffler are definitely worth it.
Roller rockers are good, 1.7:1 works well with stock cam and springs. Non-adjustable will fit under valve cover. Adjustable need 1/4" spacer.
At least new head bolts or better are ARP head bolts. Studs- you can't remove head when engine is installed in vehicle.

[Cheromaniac]

Sounds like you're planning something close to this:

4.6L Modified "poor man's" stroker

Jeep 4.2L 3.895" stroke crank
Jeep 4.0L 6.125" rods
Custom forged +0.020" bore pistons, compression height 1.380", dish volume 26cc
9.25:1 CR
Stock 4.0 camshaft
DIY ported HO 1.91"/1.50" cylinder head
Mopar/Victor 0.043" head gasket
0.043" quench height
Ford 24lb/hr injectors for '87-'95 engines
249hp @ 4900rpm, 303lbft @ 3500rpm ('87-'95 camshaft)

Apart from the quench, the specs are the same as my engine's (I used 258 rods & 677P pistons) and I'm running an '01 XJ intake manifold, 65mm modified Mustang TB, homebrew CAI, Borla header, 2.5" exhaust, Ford Racing 24lb injectors, MAP adjuster set at 5.30v, stock FPR, stock PCM.

I suggest you also go for a 7120 head, '99+ intake, 62mm TB, header, and 2.5" exhaust. A 4.6L stroker needs to breathe and the stock Renix hardware won't cut it, though the stock cam is fine (I'm running 1.6 ratio roller rockers, stock valve springs).

[NickInTimeFilms]

Alright, thanks for the input guys. Glad to see I at least got the engine specs pretty spot on. I'll see If I can't score a 7120 Head and 99+ intake and accessories. As for the exhaust headers, can anyone recommend a decent one that won't break the bank? It wasn't a topic I've researched much but I'll start looking and reading up and report back if anything catches my eye.

[NickInTimeFilms]

Update. Scored a 6130 Head with the temp sender from a 96XJ. Got a 99+ Intake and TB. Got an Ebay Header and 2.5" Muffler/Cat. My Engine guy ordered parts based off my list but the place he ordered from suggested Icon 944 21cc Pistons to boost the Compression just a bit and go with an Erson RV12H Cam 280/288 deg, .448/.458 Lift, LCA 122 to help it breathe better. I said sure and he got around to putting it together yesterday.

Deck height with the pistons is .034", is that going to be an issue?
Even with a .043" Head gasket my Quench is still .077" which is above the .050" mark.

With the Erson Cam, the Static Compression comes to 9.09:1 and Dynamic 6.89:1. Even with the high quench I should still be safe on pump gas right?

He's already got the rotating assembly, cam, and timing set in so it would be a bit of a setback to tear it all down to mill the block. I forgot to ask him to check deck before he put it all together so I'm kind of stuck. Do you see any major issues with this or should I just leave it be? I guess I just have to hope for the best since the numbers are still safe.

Pictures of what he sent:

[jeepxj3]

Give him a $100 bill for the labor and have him pull it apart and deck the block. Now is the time to do it before it is really too late.

[NickInTimeFilms]

Alright Gentlemen, Good news and Bad news. Bad news is the engine was most of the way together so decking the block did not happen, I'll have to live with .034" down in the hole. My DCR is low enough that I'm not worried about it.

Good news is I got the engine in, went to start and she'd crank but no start. Diagnostic pointed to no spark and a shot CPS, no ohms across terminals. Swapped in old one and she fired up. Broke the cam in for 20 minutes, then drove it 20 miles with lots of medium throttle and long decel to seat the rings. Things are looking good. No more shaking as the parts have worn together and have 130 miles on her now. Runs fine on pump gas with 0 ping reported from my mt2500. Power isn't breakneck off the line, but when you get into it, she moves nicely. Brings the Jeep back to life.



Other Bad news and questions:

Took it through NJ Inspection and failed. Moderately High Hydrocarbons and Very High Carbon Monoxide.

Gas Reading Standard
Idle:
HC ppm - 250 220
CO% 8.30 1.20
CO2% 9.9
O2% 0.0

High Idle:
HC ppm - 251 220
CO% 9.64 1.20
CO2% 9.0
O2% 0.0

Since this test, I found one of my vacuum fittings was leaking from the Renix to HO swap, so that has been plugged and Idle has now dropped from 1,100 RPMs to 600 RPMs. It seems to stumble slightly at low idle, and you have to give it some gas at cold startup and slowly bring the throttle back down or it will die. After driving for a minute it will idle fine. I took some readings with my scanner before and after I plugged the vac leak on the warm engine:

Before:
Idle: 1,080-1,130 RPMs
Injector (ms): 6.2
Exhaust: Rich
ST Fuel: 128
Lt Fuel: 102
Manifold Vac: 18inHg
Spark Adv: 17-21
Knock: 0

After:
Idle: 590-710 RPMs
Injector (ms): 5-6
Exhaust: Rich/Lean
ST Fuel: 28-49
Lt Fuel: 102
Manifold Vac: 14-15inHg
Spark Adv: 15
Knock: 0

After a drive around the block it normalized a bit and everything was the same except it went back to St Trim: 128, Exhaust: Rich and I noticed it was in Open Loop.

Drove it to work today to put some miles on it, I deliver pizza. Throughout the day I was getting a slight headache and was feeling tired so I think the Carbon Monoxide was getting to me. From the sounds of it, she is getting too much fuel. I'm running 24lbs Mustang 0 280 155 715 Injectors on a 91-95 Fuel Rail with stock FPR and the HO throttle body was grinded a little to 59mm at the gasket end.

I'll have to pay attention to the loop status tomorrow but what would you guys recommend I look into first? I'm going to double check all the vacuum lines for leaks, check the intake and exhaust for leaks before the new o2 sensor, and maybe swap in my old injectors to see if less fuel will help it out. Should I be looking into messing with MAP output, AFPR, or a Wide Band O2 Setup? Also any idea on the troublesome start up issues? It won't run unless you give it some gas and let it settle down. Thanks for the help. Can post videos if you like as well.

[Cheromaniac]

At this stage I suggest you disconnect the battery for a few minutes to reset the ECU and start again. The ECU will need to go through an adaptive learning procedure so expect some low idle issues until the ECU has adapted.
I suspect that your O2 sensor may either be defective or there's a short in the wiring from the O2 sensor. You might want to tap into the signal wire from the O2 sensor and check the voltage output to find out if the reading is appropriate for a rich condition.

[NickInTimeFilms]

Is it ok to check voltage from my scanner or is it better to probe the connector instead? It is a brand new Bosch 12009 Oxygen sensor but it's one of the weirdest I've ever seen. It's got an all metal body, unlike all the others I've seen with a metal cage and a white material on the inside. Maybe I'll look into a different brand, I've had luck with NTK so maybe i'll throw one of them in. I'll mess with it some and see if I can't figure this rich condition out. For $160 bucks, the AEM 30-4110 Wideband o2 kit doesn't seem like a bad idea. May or may not get it.

[SilverXJ]

I don't trust Bosch O2 sensors, too many problems with them. I prefer NTK and never had a problem with them.

[NickInTimeFilms]

Alright, I'm convinced my Injectors are too big. Reset the ECU (Thanks) and it fired up just fine. Checked the scanner. Open loop till O2 warmed up, Closed loop and ST Fuel went down from 128 in increments to 0, then went to open loop again. Too much fuel for the ecu to handle. Gonna swap in my old injectors and get an NTK O2 just in case. Thanks for the help guys.

[NickInTimeFilms]

Reset ECU and swapped in old injectors. Things are looking good on the economy side, engine is a little rough but that's to be expected until it relearns. Dropped one of the old injectors and it's leaking at the body so that sucks. Scanner went into closed loop and it reads 106-120 for ST Fuel which is good. Injector pulse width is at 8.3 - 9.0ms so a little higher than the new injectors but that's expected. So it looks like some 0 280 155 712 19.4# 4 hole injectors will be ordered. NTK O2 on the way for good measure.

I noticed Muad'Dib had the same issue with his Renix Stroker. He tried 26# and 24# and both were way too much. 19# seemed to do him well, so maybe we're on to something here.

I'll keep you posted.

[Cheromaniac]

I noticed Muad'Dib had the same issue with his Renix Stroker. He tried 26# and 24# and both were way too much. 19# seemed to do him well, so maybe we're on to something here.

Yeah, the only conclusion I can draw is that there's a wide variance in the way the PCMs are programmed from the factory.
Mine needs 24lb injectors plus a bit of enrichment with the MAP adjuster, while yours runs fine with 19lb injectors. It's head scratching time.

[NickInTimeFilms]

I noticed he has a 1990 Renix and I have an 89. I believe in 88 - 89 the ECU received some tuning that gained 5 extra horsepower. I wonder if that has something to do with the smaller injector requirement. Food for thought.

[Cheromaniac]

The change was from '87 to '88:

'87..... XJ: 173hp at 4500rpm, 220lbft @ 2500rpm
'88-'90 XJ: 177hp at 4500rpm, 224lbft at 2400rpm
'91-'95 XJ: 190hp at 4750rpm, 225lbft at 3950rpm
'96-'99 XJ: 190hp at 4600rpm, 225lbft at 3000rpm
'00-'01 XJ: 193hp at 4600rpm, 231lbft at 3000rpm