Re:
"0331 had the smallest exhaust ports to speed the heat up process for emission reasons......
0630 and 7120 are the best flowing performance heads...with the 7120 being a little better.........leave the 0630 alone..."

Thanks! - One less priority to spend...

 

Yes, it was an 0630. Guess I typed the wrong number, a couple times. Somewhere between my driveway and the keyboard I switched the numbers around.

 

The OEM 0331 head may have been replaced because the PO got his "0331 Club Card" punched for him.

The 0331 heads (1999-2001) tended to crack atop the casting, between the #3 and #4 cylinders, right under the oil filler cap (coincidence.) This resulted in coolant in the oil, and oil that resembled a chocolate milkshake. Oops.

As mentioned, the exhaust ports were reduced in size (for emissions reasons) from the 7120 to the 0630, and again from the 0630 to the 0331. The intake ports were effectively left alone.

The coil rail can be hung from homemade brackets that would attach to the valve cover screws, and that would retain the weight of the coil rail and get much of it off of the spark plug boots and terminals - which makes life simpler. It is correct that the 0331 head is the only OEM cylinder head to have the D&T bosses for coil rail mounting.

The simplest swap is to use a 2002-2007 0331 cylinder head (they revised the casting by 2002, and it wasn't prone to cracking anymore) and it will be a straight swap. If you swap to an 0630 or a 7120 (especially the 7120!) you may need an adapter plate to cover the parts of the exhaust ports that are not covered by the exhaust primary inlets. If you don't have the OEM header with the two precats, you can also use an aftermarket header - the primaries on them are sized for the largest ports they will see - in this case, the 7120 ports.

The 0630 can benefit from a little port cleanup (just smooth the surfaces, do not remove enough materials to change the shape or significantly change the size of the port without a flowbench for testing!) to encourage laminar airflow. Since the MPFI system uses a "dry" manifold, laminar airflow results in VE improvements without fuel puddling or separation.

 

Are you sure it was 2002? I heard 2003.
The precats are not part of the header. Also, after market headers for 00-01 work with the precats and should work with the earlier heads.

 

Wow. I appreciate the information very much. I think I may have a couple questions later...

 

Thank You. Who makes a good aftermarket head?

 

Head or header?

 

Header? I don't know.

Head? Patriot Performance and HESCO sell an aftermarket aluminum head that is supposed to work on any 1975-1990 258ci and 1907-2007 242ci,using later style manifolds. It's spendy. It's aluminum. I don't have any hard performance data on it, but it seems to have gotten going using discussions among several of us on the old "Strokers" e-group ca. early 2002.

 

Cylinder head...

Wondering if the current set-up is going to cause me any problems if I don't modify it right away?

Also would like a good performing set-up where I don't loose anything in terms of performance, and a mechanic would be able to figure it out without instructions.

Really appreciate the help, all.

Thanks!

Al.

 

AFAIK, there is only the one aftermarket cylinder head - it's the one sold by Patriot and HESCO. It's fairly recent - as I said, it got tossed around (design phase, most of it) in FEB2002, I dropped the information off with Russ Flagle at ICH in mid-2002, and the head itself came out in (I think) 2005.

However, its track record seems to be pretty good so far.

 

Patriot stooped selling the aluminum head about 3 years ago. Hesco is now the sole distributor of Aluminum heads. Patriot does offer a cnc chamber iron head for $800 (pricing was about a year ago). Besides the Hesco Aluminum head, the Patriot CNC head and the Alabama cylinder head there aren't any other after market heads I know of. There is no problem with the 0630 head. And unless you are running a boosted application there is no reason to mess with the expensive Hesco head.

 

Thank you guys,

It really helps to know this information. I was plenty confused before.

Al.

 

Thanks, I didn't know that Patriot had stopped selling the Al head for the AMC six...