Air flow through a stock head

[alex22]

Hello all,

I'm new to jeeps, just bought mine a month ago. Its a 96 XJ sport with a 4 inch lift.

To the point. I work in an automotive machine shop, so I am planing on building a new engine to replace the one with 148k on it. Has anybody here done any flow testing on stock heads? Also, Which casting number/year heads are the best to use?

I am planing on building a 4.6 HO stroker, not sure which kit or if I will put my own together.

~Alex

[sjkimmel99]

Look around Dr. Dino's site here: http://www.jeep4.0performance.4mg.com/index.html
Head flow info in the Tech Spec's link. Also check the Ported Head link.

[j99xj]

'91-99's (castings 7120 or 0630 are the best flowing).

The earliest heads and the surprisingly the latest heads flow worse than the heads in this performance sweet spot.

[5-90]

IN order of preference...

#7120
#0630
#2686 (RENIX. I know - but they don't crack...)
#0331 (OBD-II with COP ignition. Get a "revised" head if possible, the first run of these tends to crack between #3 and #4. Since I don't know how to spot them - yet - they rank below the RENIX head, which I've found reliable.)

[alex22]

WOW. That site has alot of good info in it. :yelclap: It answered just about all of my questions about the 4L.

Is there a minimum bore size I need to use the chevy valves in the jeep head?

[5-90]

WOW. That site has alot of good info in it. :yelclap: It answered just about all of my questions about the 4L.

Is there a minimum bore size I need to use the chevy valves in the jeep head?

Me being me, I'd see if it can't be taken out to 4.000" even (RENIX block - ChryCo blocks won't survive this, and RENIX blocks still need to be checked...)

However, I think there are still some shrouding issues with the 2.02/1.60 valves in the stock 242 bore (3.875",) but I'd have to crunch some numbers to figure out just what sort. But, if you insist upon putting in 2.02/1.60 valves, you should massage the sides of the combustion chamber and probably 'flare out' the top sides of the cylinder bore to help airflow.

And, even the #7120 is borderline to support the larger valves, unless you do some serious porting and flowbench work, methinks. I'm not saying it would be impossible - just difficult, and you may end up seeing very little return for large capital outlay (porting on any head that the shop doesn't do all the time - like AMC sixes - is done by the hour, not by the job. A lot of "on and off" on the flowbench to check work...)

Might one ask what you're trying for? It's easier to give advice on performance buildups once one knows what is being done - and you'll have an easier time knowing when you've gotten where you want to go once you know where that is. First thing I tell anyone wanting to do a performance buildup - sit down with a three clean sheets of paper. 1) Write down your "ideal goal." 2) Write down the "minimum acceptable." 3) Look at those two, and write down a "happy medium." What you end up with will probably be closer to the middle than the other two - but at least you'll now know where you're trying to go...

[streetpirate]

if someone had big valve ported heads for sale, how much would they be worth to you?

[5-90]

if someone had big valve ported heads for sale, how much would they be worth to you?

Look up an archived version of Accurate Power's site - Mike used to do "big valve" heads on your core.

I'd probably rather go for more lift - or, ideally, a rollerised cam/lifter setup (wich allows a more aggressive ramp profile and you can get more dwell time at full opening. Both of these can give more airflow for less work than going to a larger valve.)

What would they be worth to me? I don't know - it would depend highly on how much additional porting and massaging they'd had, and what casting they were based upon.

[alex22]

When you say that the #7120 "is bordreline to support the larger valves" do you mean that the head is thin around the seat and there might not be enough iron to keep the valve from crushing into the water jacket?

The porting and flow bench work is not really a problem for me since I am the one who would be doing the work. The shop has a Superflow SF-600 with the flow com computer and Performance Trends software hooked up to it.

I am mainly concerned about how low the flow on the exhaust is. I would like to put the 1.6 Ex valve. The stock flow numbers on Dino's site say that the exhaust only flows 68% of the intake.

The XJ will be a daily driver and might see some offroad/haulin down dirt road paths once in a while. I want to build it more for low end torque than high RPM HP, within safe power limits of the 5spd and DANA 35. I don't actually need the new engine but since I can do all the work myself and get the parts through work I really don't see why not.

I saw on Dino's site that the 00-06 intake manifold has smaller runers and is better for torque. Will that manifold fit on the 7120 head with a port match or are the bolt holes in diferent spots?

~Alex

[5-90]

When you say that the #7120 "is bordreline to support the larger valves" do you mean that the head is thin around the seat and there might not be enough iron to keep the valve from crushing into the water jacket?

The porting and flow bench work is not really a problem for me since I am the one who would be doing the work. The shop has a Superflow SF-600 with the flow com computer and Performance Trends software hooked up to it.

I am mainly concerned about how low the flow on the exhaust is. I would like to put the 1.6 Ex valve. The stock flow numbers on Dino's site say that the exhaust only flows 68% of the intake.

The XJ will be a daily driver and might see some offroad/haulin down dirt road paths once in a while. I want to build it more for low end torque than high RPM HP, within safe power limits of the 5spd and DANA 35. I don't actually need the new engine but since I can do all the work myself and get the parts through work I really don't see why not.

I saw on Dino's site that the 00-06 intake manifold has smaller runers and is better for torque. Will that manifold fit on the 7120 head with a port match or are the bolt holes in diferent spots?

~Alex

Later manifolds should all swap (1991-up,) but a quick way to tell is to check the gaskets. If you can lay them all one on the other and see through the screw holes, you're good (I don't think the ports moved past 1991, but the exhaust ports were reduced slightly in 1999/2000 to improve catalyst light-off.)

If you have access to a number of heads, I'd like to see raw flow data for lift in .100" increments, including .100" (I've got some flow data, but it's different heads, different operators, and different benches. So, some error has to be assumed...) I'm also trying to collect heads for analysis - if you get any warped/cracked heads in for the AMC six, I'd like to hear about it. If your PT software also supports cam measurement and you get access to OEM AMC six cams, I'd appreciate data on those as well (since definitive data on OEM and MPP cams is difficult to find, and I'd like to flesh out both sections of my book...)

By "borderline," I'm more meaning that the head just isn't designed to flow that much air. I'd really want to put seats in anyhow (I don't think you'll hit the water jacket, but I'd rather "hit and fill" than guess...) but it would take an awful lot of massaging to make the big valve work useful - especially at low RPM (which would benefit more from an aggressive cam than valve opening anyhow.)

So, you're not trying to build a stump puller - that should help (although you should make sure that your Dana 35 isn't the "C-clip" version...) And, since you've got a 1996, you've got the AX-15 5-speed, which will support some mild engine improvements. At least it's not the damned Peugeot... If you go too far, you're going to want a better box - the NV3550 comes to mind - but you shouldn't have too much trouble with the AX-15 (provided you keep it on a steady diet of GL-3.)

I think you'll find that most production heads in the last 15 years or so don't have the exhaust flow that they really should - mainly, to reduce catalyst light-off times (keeping the ports small helps the hot gasses get there faster, which gets the catalyst up to its operating temperature faster. Not entirely sure I like that solution, tho - it increases pumping losses and parasitic drag, reducing specific power output and specific fuel consumption...)

The only "real" manifold change that I can think of happened 1990/1991, when the ChryCo OBD-II system was added, the #7120 head was introduced, and the intake ports were raised about 5/8" to improve intake airflow (by reducing the angle that the flow had to go through to get into the chamber.)

If you want to discuss this at length, we may have to go backchannel - but this has a lot to do with why I've written the Power Manual (information on my website and at groups.yahoo.com/group/JeepPower - it's a "support group" for the book.) There's a link in my sig.

[alex22]

I think I do have the C-clip style, is there a quick way to tell without taking it apart?

I have only seen a handful of 4L heads in the almost two years I've worked at the shop so I don't have alot of information about them. We do not have the Performance trends program for the cam information, only the flowbench program.

The shop is no stranger to extensive porting research. I have spent days on a cylinder head going from the flowbench to the porting bench, discusions with the boss and other porting guys, and back to the flow bench. Epoxy, weld in port stuffers changing seating angles from 45 to 30 and vice versa. A few months ago I put about a week of porting, clearancing and Chamber resizing into a set of Gurney Westlake heads.

You mentioned a backchannel, I'm new to this forum so I am not sure what exactly that is.

~Alex

[5-90]

I think I do have the C-clip style, is there a quick way to tell without taking it apart?

I have only seen a handful of 4L heads in the almost two years I've worked at the shop so I don't have alot of information about them. We do not have the Performance trends program for the cam information, only the flowbench program.

The shop is no stranger to extensive porting research. I have spent days on a cylinder head going from the flowbench to the porting bench, discusions with the boss and other porting guys, and back to the flow bench. Epoxy, weld in port stuffers changing seating angles from 45 to 30 and vice versa. A few months ago I put about a week of porting, clearancing and Chamber resizing into a set of Gurney Westlake heads.

You mentioned a backchannel, I'm new to this forum so I am not sure what exactly that is.

~Alex

C-clip axles can be readily identified by looking at the side gears in the differential - you'll see a "C" shaped washer in there if you have them (if you don't, you have "retainer" axles where the shaft is held in by a retainer plate.) The C-clips are usually a bit weaker than a retainer plate, and you can lose the shaft if a C falls out - a retainer plate will hold it in place, since it holds against the outer bearing - which is itself pressed onto the shaft. You'll still need to remove the cover (you could look for the retainer plate under the brake drum, but it's a pain and usually too dirty to tell...)

"Backchannel" means an alternative communication channel. Here on the boards, we're a bit limited - there's a maximum post length (I'm not sure what it is,) there's an inability to use attachments inline, and they'd be limited in size anyhow. "Backchannel," on a board like this, usually refers to direct email - which has a much higher length/content limit, supports attachments and larger files, and what-have-you. So, if you hear someone ask you to "take it backchannel," get an email address if you want to do so. Make sense? Telephones can also be considered backchannel comms - but I hate phones, and need to keep my line clear anyhow.

So, if you'd like to dig into this any further than we already are, you can ping (another technical word...) me at dragonland2001 AT yahoo DOT com, and we can really dig into this. Engine theory is something I've long enjoyed, and I've had to do a lot of research lately to update my first book while writing my second... It keeps me busy!

[alex22]

Thanks for clearing that up for me.

Tomorow I will talk to my boss about the chevy valves in the head and see what he thinks. Time & money vs flow & power. I will send you an email sometime tomorow.


~Alex

[5-90]

Thanks for clearing that up for me.

Tomorow I will talk to my boss about the chevy valves in the head and see what he thinks. Time & money vs flow & power. I will send you an email sometime tomorow.


~Alex

Cool. I'll be around - I try to respond to all email within about 24 hours, so I may need you to be patient...

[Bouncy]

I have to go back to my notes.

The short list. I used a 7120 head. Put in 2.00" LS1 or LT1 valves...can't remember. I put in 1.5? or 1.6 exhaust. The 2.02 were too big and shrouded too much. 2.0 was the biggest for effcient use.

I ported the hell out of my first head. Doing everything possible to cut down the short side. Its THIN there. I found out the hard way.

All you can do is port match, smooth out the walls, smooth the short side but not completely reshape it. Polish the chamber and deshroud the valve walls.

Keep in mind the bigger valves going in with have a larger seat...thus it will create a shroud as the valve seat is cut. So you need to open it up a bit to eliminate the shroud.

I wish I would have gotten flow numbers to compare. All and all...I am using a 1999 intake. I also ported it to smooth down the injector bosses and removed casting flash from the runners.

On the low rpm side, its a little laggy but once you hit the throttle, it really rips along. I am still having trouble with running mega rich with my 24lbs injectors though. So it wont run too long before dying.

[Flash]

Cool. I'll be around - I try to respond to all email within about 24 hours, so I may need you to be patient...


Don't shut this conversation completely down............Inquiring mind want to know too;)


Flash.

[5-90]

Don't shut this conversation completely down............Inquiring mind want to know too;)


Flash.

Oh, I know - it's just that going backchannel can open up comms. I may ask about adding people to get messages via email and summarising later - I don't mind, if other participating parties don't mind either...

[alex22]

Its not always nesescary to cut down on the short side. some head designs actually benifit form epoxy on the short side. What often helps is widenig the short side radius and a nice polish.

While boosting the flow is very important you should also think about the fuel/air mix. A slightly rougher floor before the short side may decreace the flow by a few numbers at high lift, but it will produce turbulince on the floor which will prevent the gas from settling. I know this comes into play on carbourated engines, i am not sure how big of an effect it will have on a fuel injected engine.

~Alex

[5-90]

Its not always nesescary to cut down on the short side. some head designs actually benifit form epoxy on the short side. What often helps is widenig the short side radius and a nice polish.

While boosting the flow is very important you should also think about the fuel/air mix. A slightly rougher floor before the short side may decreace the flow by a few numbers at high lift, but it will produce turbulince on the floor which will prevent the gas from settling. I know this comes into play on carbourated engines, i am not sure how big of an effect it will have on a fuel injected engine.

~Alex

With a carburetted engine or an engine with throttle body injection, that's true. However, using port fuel injection frees up intake design - usually because the fuel injector sprays directly into the intake port (and also usually right on the back of the intake valve.)

So, fuel "puddling" isn't as much of a concern - since the manifold is "dry" (no fuel.) Therefore, you can work more toward laminar airflow, and pay less mind to controlled turbulence to keep the fuel droplets in suspension.

[alex22]

I was able to flow test a stock, untouched #0331 head off a 2002 with approx 7000 miles on the stock valve job. The head did vacume test good and had no leakage when it was mounted to the flowbench; a Superflow SF600 linked to a laptop using Performance Trends "Port Flow Analyzer." The bench's calibration was verified last month with the calibration plate provided by Superflow.

Dino,
I checked my numbers with the numbers for the #0331 on your site and there is a large variance. Not trying to slam you with my results, I would like to find out why there is a diference in our results. Do you have any information on the head used in the test for your site or what flowbench was used?

http://i68.photobucket.com/albums/i25/shaq787/Stock0331jeep40LCFMreportfinalsm.jpg

http://i68.photobucket.com/albums/i25/shaq787/Stock0331Jeep40LCFMgraphsm.jpg

*** The graph is just a connect the dots, the straight portions do not acuratly represent the flow.


5.9, Did you get the email?

~Alex

[5-90]

Alex -
Yes, I did - I've just been Overtaken By Events for the last couple of days. Interesting, the idea of coming up with viable CNC porting programmes for the AMC six heads... I can see where you're not finished yet, but it's still better than any site I've done (but I'm a minimalist anyhow.)

Also, note that there is often quite a wide variation between flowbenches - and climate can also play a role. If Dino is using flow numbers generated locally, he's using the climate of Araby - while you're not (Connecticut, yes? BIG difference.) That's why I'd like to get flow numbers for all five of the heads in question - on the same flowbench, and preferably with the same tech - as an "apples and apples" comparison. The five heads are:
#2685 (AMC258, late, "wide deck." Will also bolt up to AMC242)
#2686 (AMC242, 1987-1990, also called "RENIX.")
#7120 (AMC242, 1991-1995, OBD-I head with mods by ChryCo)
#0630 (AMC242, 1996-1999/2000, early OBD-II head)
#0331 (AMC242, 2000/2001-2007, late OBD-II with Coil On Plug ignition)

Having them done on the same bench would probably be sufficient, but I tend to be thorough. That's part of the reason I've been trying to collect heads - I can section the #1 cylinder for mechanical profiling, flow the #2 cylinder at school using their flowbench - one after the other, all on the same day! - and then do some port castings and porting experiments with the rest of the cylinders, and compare results with head castings and port modifications. Take "before and after" port castings using metrology rubber so the beginning and final port shapes can be compared (and, if I can get port castings of the aluminum head that Hesco and Patriot are putting out, that would be a very interesting comparison...)

However, I would like baseline figures on unported, unmodified heads to add to the Archives, and to use for baseline dyno sims. So, if you've got a notebook, would you please keep results as you find them?

[alex22]

Which flowbench do you use at shool? The Flow Comm on the flowbench has a build in barometre to correct for that but there is not a correction for air density. I don't think I will be flowing each casting number since I plan on using a #7120 head for my build. I am leaning towards using the LS series valves but I havent checked stem length or install height yet. The head actually flows very good stock. For comparison, a set of Fuelie heads for a SB Chevy will flow about 220 with oversized valves.

I forgot to mention that the I6 head will not fit in the CNC machine, kina a bumer. I looked on patriots website and I didnt see their I6 head.

[5-90]

Which flowbench do you use at shool? The Flow Comm on the flowbench has a build in barometre to correct for that but there is not a correction for air density. I don't think I will be flowing each casting number since I plan on using a #7120 head for my build. I am leaning towards using the LS series valves but I havent checked stem length or install height yet. The head actually flows very good stock. For comparison, a set of Fuelie heads for a SB Chevy will flow about 220 with oversized valves.

I forgot to mention that the I6 head will not fit in the CNC machine, kina a bumer. I looked on patriots website and I didnt see their I6 head.

I don't recall what they've got at school offhand.

Bugger that the inline head won't fit - what is the bed length, about 20"? You probably need 30" or so to fit an inline six head...

There's no need to hurry - as I'd said, just note what results you get from your 0331 head and your 7120 head - you'll probably get a 2686 and 0630 head in eventually, and you can add them to your notebook then. (Then, add them to mine!)

The big problem with the inline head is twofold - first, you've got to make a right angle to get air into the head. Not usually so on v-block engines - they "fudge" a little on the intake surface. Second, they're "side-draft" heads, not "cross-flow" heads - so runner space is limited from the off. (Not to mention that the inline six isn't designed for high-RPM life, so there's no huge need to crank up flow to get VE up at high crankshaft speeds.)

Still, I'd be very interested to hear of your results when you're done! I'll even help you generate a writeup if you'd like, and I would vastly appreciate it if you could take "before" and "after" castings using metrology rubber (I'm sure you have some around somewhere...) so we could get a physical look at what you've done. Just because I say it's difficult, doesn't mean I'm not interested...

[alex22]

I haven't used metrology ruber before but someone in the shop probly has. The bed length on the machine isnt the limiting factor, the A&B axix unit is separate from the bed. The longest head it can do is a small 5 cyl.
http://www.centroidcnc.com/images/cnc_cylinder/tilt_table_800.jpg


~Alex

[5-90]

I haven't used metrology ruber before but someone in the shop probly has. The bed length on the machine isnt the limiting factor, the A&B axix unit is separate from the bed. The longest head it can do is a small 5 cyl.
http://www.centroidcnc.com/images/cnc_cylinder/tilt_table_800.jpg


~Alex

It's fairly common - I've even seen it in speed shops and speed catalogues, so I'm sure it's not too much trouble to find. If you can't find it, let me know - and we can sort something out.

Sorry - I'm still thinking in terms of manual machinery, and not CNC centres. I sometimes forget to make the switch...

[alex22]

I asked my boss about the metrology rubber, he has used it in the past. The only problem is that it costs between $80 to $100 for a kit, which has just enough to do one intake and one exhaust. I will just take very good notes and a few good pictures. By looking and geting a good feel of the port I have a good idea of what has to be done to it.

I have done a dicent amount of manual maching, the shop has a Bridgeport and laithe.

~Alex

[5-90]

I asked my boss about the metrology rubber, he has used it in the past. The only problem is that it costs between $80 to $100 for a kit, which has just enough to do one intake and one exhaust. I will just take very good notes and a few good pictures. By looking and geting a good feel of the port I have a good idea of what has to be done to it.

I have done a dicent amount of manual maching, the shop has a Bridgeport and laithe.

~Alex

Whew! Stuff's gone up since I last had to use it on anything... I may have to look around for something that won't hurt so much - but yes, I'd not mind seeing your notes (once you've developed them.)

[Flash]

Thanks for keeping us (me) in the loop.;)


Flash.

[alex22]

No problem. This thread may cool down for a little while, I havent located a block and head to use yet.

~Alex

[1bolt]

The numbers on Dino's site are at 25" of pressure drop, not 28" also the person who got them (on the Strokers Yahoo list originally maybe on jeepstrokers.com now not sure, but a lot of us are); Said he may have obtained them with an intake manifold on, but I doubt that. They were flowed in like 2002. Crazy enough I asked Dino about those numbers just a couple weeks ago myself after John Young gave me his old flow bench.

Elevation + temp are air density right? and I think most flow bench software simply plugs these numbers in when you are calibrating the bench. Just like Dyno's all numbers are corrected for temp, density and barometric pressure.
I wont pretend to be an expert but that's what I understand anyway.

For what its worth my numbers for the 0331 head using NOSIGMA's flow bench are very close to yours. Also all flow benches will show some variation. But mine are also above the ones on Dino's site for an unmodified 0331 intake at the same valve lifts, the number that matters is pressure drop. I'd have to look at John's flow spreadsheet but CFM numbers at 25" of drop are lower than 28".

One thing I don't want to step out on a limb for (but I can't seem to avoid) is that the 0331 head is not a bad flowing head. Until I get more numbers I wont make any bold statements though. It does have the cracking problem and that's all most Jeepers need to know. But as far as Porting goes... well... let me just say it has a lot of potential due to the smaller better shaped Exhaust valves (and better short turn radius).

For example of flow bench variation: as an experiment the home made flow bench crazy dudes at
http://www.tractorsport.com/cgi-bin/forum/cgi-bin/ikonboard.cgi?;act=SF;f=1
passed around a set of orifice plates (look for "pass it around plates") that got flowed on a bunch of benches, including home made, do it yourself and big dollar Super flow benches, and EVEN the giant multi million dollar Ford flow bench... There were variations but they were all shockingly close. A few CFM give or take across many of them, I didn't see a one that was really far off (like more than 10 CFM either direction)... The reporting was blind, no one saw numbers until the end of the experiment. :read: