Air flow through a stock head

[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: