HO head on Renix

[bzdel2441]

Plan to build an "all go" MJ....

I am think about upgrading to an HO head (91-95 ODBI), ported and polished of course and along with a header and 99+ intake. Can anyone think of somehing holding me back from doing this? I have been told that everything will bolt straight on, and my only problem will be with teh throttle body sensors.

Any ideas?

Thanks
Chris

 

[5-90]

That's pretty much the lot - but it is possible to make an adapter to put the RENIX TB on teh HO manifold.

If you can source it, go with the 99+XJ/WJ manifold and head (head casting #0331) since it has cleaner ports and better intake runners.

I'm actually trying to get my hands on all four 242 heads so I can saw them up, take port castings, and otherwise tear them to bits and check them out for my book. Know anyone that has some arped or cracked heads withing driving range of San Jose?

5-90

 

[bzdel2441]

I thought the 91-95 head was better becasue of emissions regulations getting tighter jeep had to change the flow of the heads in teh later years. I haev no problem going with a new head only if it wont cause me any problems durning the install. And I think adapting the Renix TB to the HO is just a plain stupid idea. I have a 93mm bored out TB ready to install once I am all done with the conversion.

Chris

 

[5-90]

I'll have to dig up my notes, but I think there were some differences in TB sensors and bolt-ons (like the IAT and TPS) after the RENIX era, and thay may or may not cause electronic issues for you.

Part of emissions control, tho, is increasing efficiency (not economy - two different issues!) Efficiency is increased simply by making everything work better, and improving airflow through the cylinder head and manifolds does just that (assuming everything else works) and allows more power with the same or slightly less "harmful" emissions.

So, you'll have no trouble with the 0331 head ("late" OBD-II) for your application - it would be like putting the LT1 top end on a 60's SBC - you aren't changing the engine, but putting more efficient parts on to make it work better. If it weren't for the CA Air Police, I'd probably do the swap myself (but I've got tne 88 with EGR, and there is no provision for EGR on 1991-up 242...)

5-90

 

[bzdel2441]

I'll have to dig up my notes, but I think there were some differences in TB sensors and bolt-ons (like the IAT and TPS) after the RENIX era, and thay may or may not cause electronic issues for you.

Part of emissions control, tho, is increasing efficiency (not economy - two different issues!) Efficiency is increased simply by making everything work better, and improving airflow through the cylinder head and manifolds does just that (assuming everything else works) and allows more power with the same or slightly less "harmful" emissions.

So, you'll have no trouble with the 0331 head ("late" OBD-II) for your application - it would be like putting the LT1 top end on a 60's SBC - you aren't changing the engine, but putting more efficient parts on to make it work better. If it weren't for the CA Air Police, I'd probably do the swap myself (but I've got tne 88 with EGR, and there is no provision for EGR on 1991-up 242...)

5-90

Yes I have a write up here on how to convert the TB sensors from the renix to the HO ( http://www.rockmodified.com/2003/april/TB/tb_perf.htm ) so I will for sure be doing that so I can swap over the HO TB along with the manifold. I am not sure what you mean by putting an LT1 top end on is there a write up somwhere on that or do you have any more info on that one? See then the EGR was another concern for me with removing the EGR how much more "polutants" will be comming out? I mean now when I got the truck tested it has so many holes in my exhaust only probably half the exhaust was comming out the tail pipe, thus giving me really really really low numbers. But with a completly new exhaust along with the EGR deleted from the system how will this react? I know emission will be higher to..

 

[Mike@Accurate]

'91-'95 heads have the temp sensor hole in the back. '96-'98/'99 heads have no hole , but you can drill & tap it (1/8 pipe) '99-on heads have wimpy exhaust ports, 2 accessory patterns (TJ/WJ & XJ) and coil-on-plug bosses. Steer clear of these. '91-'95 HO manifolds have adjustable PS pump for belt tension. '96-on have a rigidly mounted pump. It is easier to mount an early HO manifold, or get the whole accessory system/bracketry from the donor (if late/rigid pump). '99-on manifolds do look better from a design standpoint. No HO manifolds have provisions for EGR. '91-'95 HO's have a return line fuel rail, you will need one of these to do an HO manifold swap. The 2 line rail will fit later, (single line/OBDII), HO manifolds though. Ports look pretty much the same for '91-'98/'99 heads. If you are looking at a '99 donor, some are coil on plug and some are not. I think, most of the time, EGR sucks, you should be better off without it. MIKE

 

[5-90]

Yes I have a write up here on how to convert the TB sensors from the renix to the HO ( http://www.rockmodified.com/2003/april/TB/tb_perf.htm ) so I will for sure be doing that so I can swap over the HO TB along with the manifold. I am not sure what you mean by putting an LT1 top end on is there a write up somwhere on that or do you have any more info on that one? See then the EGR was another concern for me with removing the EGR how much more "polutants" will be comming out? I mean now when I got the truck tested it has so many holes in my exhaust only probably half the exhaust was comming out the tail pipe, thus giving me really really really low numbers. But with a completly new exhaust along with the EGR deleted from the system how will this react? I know emission will be higher to..

Sorry - the LT1 bit was referring to Small Block Chevvy engines, and has nothing to do with our 242s. It were just for illustration...

The deletion of the EGR was enabled by changed to cam timing (I believe it was advanced slightly, reducing dynamic compression and therefore chamber temperatures) so that's not terribly significant unless you are under the jurisdiction of the Air Police.

Results? You'll probably see emissions go up to OEM/Factory levels (which were still agreeably low) with a possible mild increase in NOx and lower CO and HC levels.

The problem is, if you're here in CA, you'll get failed on visual if you delete the EGR setup - even if the engine runs cleaner! Dumb, ain't it...

5-90

 

[bzdel2441]

'91-'95 heads have the temp sensor hole in the back. '96-'98/'99 heads have no hole , but you can drill & tap it (1/8 pipe) '99-on heads have wimpy exhaust ports, 2 accessory patterns (TJ/WJ & XJ) and coil-on-plug bosses. Steer clear of these. '91-'95 HO manifolds have adjustable PS pump for belt tension. '96-on have a rigidly mounted pump. It is easier to mount an early HO manifold, or get the whole accessory system/bracketry from the donor (if late/rigid pump). '99-on manifolds do look better from a design standpoint. No HO manifolds have provisions for EGR. '91-'95 HO's have a return line fuel rail, you will need one of these to do an HO manifold swap. The 2 line rail will fit later, (single line/OBDII), HO manifolds though. Ports look pretty much the same for '91-'98/'99 heads. If you are looking at a '99 donor, some are coil on plug and some are not. I think, most of the time, EGR sucks, you should be better off without it. MIKE

So what exactly will be needed to be done if I do this with a 91-95 head? And I am not understanding what the 2 line fule rail is, do I need to run another line then? Or are you tring to say I will need to run the fuel rail that comes with the intake manifold? If I get everything that goes from the head up and EVERYTHING that is attached to the intake manifold should i be ok then or will there still be alot of work? I think I will delete the EGR now to.

 

[Mike@Accurate]

'87-'95 4.0's had a return line. '96-on don't. You need a fuel rail with a return line.You can use any manifold (power steering notwithstanding) but HO & Renix fuel rails don't interchange. You will have to mod your Renix fuel lines to attach to HO fuel rail. And have a '91-'95 rail to fit the HO manifold. Everything that attaches to the manifold includes the power steering, and then everything that attaches to that. That is why a '91-'95 manifold is easier, they use an adjustable pump (like your Renix). You may be able to swap the entire belt driven accessory group from a later donor (or maybe just the driver's side) and use a '96-on manifold. Go to the junk yard or used car lot and open some hoods, you'll see what I am talking about. MIKE