cylinder head casting #s

whats the difference between head casting #0630 and the newer 0331 casting head?

Port design.

The four "basic" 242 castings are 2686 (1987-1990,) 7120 (1991-1995,) 0630 (1996-1998/9,) and 0331 (1999?-2005.)

The increase in power between 1990 and 1991 is largely attributable to the change in design of the intake/exhaust ports between the 2686 head (which is nearly a right-angle into the chamber) and the 7120 (the raised intake ports allowed for a smoother flow into the chamber, reduced pumping losses, and a somewhat higher volumetric efficiency.)

Unfortunately, revisions in design slightly but measureably decreased power output with the 0630 head, and again with the 0331 head.

Depending on what you're trying to do, it's generally understood (although not fully agreed upon,) that the best-breathing top end combination is the 7120 cylinder head with the 99-up WJ intake manifold offering the (arguably) best-flowing intake runners to complement the cylinder head design.

Note that the heads and manifolds are not compatible across the 1990 "line" - without some machine work and modification. Fine here - the later manifolds are better.

If you want to do better than the 7120 head, be ready to call Clifford or HESCO and lay out a bunch of dough for the new aluminum head (and I'd like to know who's casting the thing - it's showed up with several vendors rather quickly, and we beat something like this around 1Q2001 on the "Strokers" board - then I took the info to Mr. Russ Flagle at Indy Cylinder Heads in Indianapolis. I wonder... I don't want royalties or anything - I'd just like to konw if I have another place in Jeep history coming...)

5-90

ahh i see.thank you that summed up my question earlier.i am actualy swapping in an 03 grand cherokee motor and wanted to figure out if the 91-?up xj exhuast manifold will bolt in place of the 2 manifold designed 0331 head that is on that motor.going into an 88 xj.but using the renix ecm set up.i already figured out that i have to drill and tap some unfinished bosses on the block for my brackets to bolt up.

It should. The RENIX ECM will look for an input from the knock sensor - there should be a boss on the lower driver's side (down near the oil pan rail) that went unmachined from 1991-on. This is the boss for the knock sensor, and should provide a "blind" hole into which the sensor tip threads.

There is also some minor D&T work for bracketry (as you've already noticed) and you'll probalby have to do some work for adapting your power steering and suchlike - and I'd appreciate documentation of the work you have to do, since I've not had to do any of this yet, and therefore haven't documented it meself.

The RENIX ECM should have no trouble handlind the fuel injectors. You'll probable have to adapt the HO/OBD-II throttle body sensors to take RENIX sensors, or adapt the RENIX wiring to fit up to the OBD-II sensors (mainly the TPS and IAC,) and I think a little adapting will be needed for the MAP (just find a vacuum port right under or within the throttle body that gives you full vacuum - that's what you need.) Most other sensors (IAT, CTS, MAP, f'r instance) typically follow GM curves - which will make the adaptation all the easier. The RENIX ECM likes GM curves - so that makes adapting sensors easier...

5-90

thats all good i am an ase master tech at a chevy dealer.gm is home for me.and i have already modified the 03 tps by slotting it.and plan on using the 03 iac motor as well.i currently have a spark box for lt1-buick gn that allows me to adjust or retard timing if i want so i do not use the knock sensor as mentioned.also have map adjuster box-home made and am using ls1 26#injectors with map adjuster at 3.10 volts plus as a bonus we have a dynojet dyno at my work that i play with when i want to i also do hypo work on vettes.and you have been very informative on this project of mine.i will document the procedure of events that was needed to make this motor work.......why the 03 grand motor--mine has 195,000 very tired miles on it and i got this motor with 10,000 actual miles on it for $700.with intake and exhuast and t body with all sensors they just remove the outside accesorries like starter and alt a/c etc... and cut the wiring harness at the main bulk connector. others have commented no it will not work but i believe they have not looked into it as i am.it should also have plenty of power with being able to control spark and a/f ratio.

Unless you plan on stroking, you'll probably see symptoms similar to overcarburettion with 26# injectors - see if you can't step down to 21# or so (OEMR RENIX are 19#, and OEMR HO/OBD are, I believe, 21# or 22#.) The inline six just doesn't rev fast enough often enough to want the very large injectors - they're typically only needed when increasing displacement.

Not to disparage your experience (I cut my teeth on Corvettes in the 70's and 80's,) but the dynamics of the inline six are a little different from the V8's you're likely used to, and the targets for performance are vastly different (the inline is meant to produce torque at low RPM - something a Corvette has little use for.) I'm perfectly willing to help where I can - especially since I've been working to "understand" the RENIX system at least as well as its designers, and it might be a bit different from what you're used to - even if it uses the sensors you've seen for more years than either of us would care to admit to...

5-90

true i do have 21.5 # injectors from older vette i ll try those and most of all i am just basically replacing my old motor.some tuning and tweeking is normal for me to do.can't leave anything alone.look for renault sites as to try and figure out the renix system-renault and bendix merge-RENIXstill need to pull old motor still driving the xj.i'll let you know.yes i deffinetly agree in line 6 engines take some time to ramp up.compared to 500 rwhp v-8s :us:

Actually - RENIX = Bendix made under Renault contract. I've got enough RENIX gear to take some apart and run part numbers, and it seems that the RENIX electronics were actually made by Bendix/King (yes, the people that do avionics!) and labelled under terms to the contract that Bendix entered into with Renault - which explains much (like the all-original engine control setup with 245kmiles on it, and no hiccups!)

I agree with you on not being able to leave things alone - that's how my first book got written, how I managed across a full set of RENIX electronics, and how my other books are going to get written.

Speaking of which - if you get a coulple late V6/DIX setups that end up needing replacing, is there any way I might be able to talk you out of some core parts? I've got an idea for installing (OBD-I or OBD-II) GM/DIS from a V6 to a 242, and I need to get my hands on some parts I can afford (read: Free or damn close to it...) to play with and see what can be done. I like the programmability of the GM/DIS setup, and the tunability would be excellent for forced induction and/or exotic fuel tuning... I've really got to figure out how to build a Dyno cell, and get some sort of run stand going...

5-90

ahh yes i thought of that also.if i come across some i will let u know.most parts we replace are under gm warranty and need to be turned in.but cust pay repairs do come in also.i may have a 2000 3.4 v6 coil and module pack i need to look for it.if u need some info on ecm wiring and such i can send u what u want up to 2006