I was looking through CraigsList a few days ago, and found a NIB forged 383 rotating assembly (Pistons/Rings,Rods,Crankshaft) for the steal-of-a-lifetime price of $1k. Needless to say, the upgrade bug bit me HARD! So now, the Miata is getting a new engine. The old L33 5.3 put down a best of 380/360 at the wheels, and has been (and continues to be) a really fun car to drive, especially considering that the car weighs 2750lbs.....but I want more out of the car.

The car is my daily-driver, and I've logged 15k on it in the last 9 months... so the goals for the new 383 are (in this order) 100k-reliability,25MPG (or so),excellent driveability,loads of TQ under the curve, and (ideally) 550rwhp. It is possible that this engine might eventually be fed 4-6psi, but I'm not sure at this point.

So far, I have:

-LS1 block (being prepped)
-Callies Compstar 4.0 stroke crankshaft
-Diamond 3.905 pistons w/7cc dish and coated tops and skirts
-Scat 6.125 I-beam rods w/ARP 2000 bolts
-Fast 102
-90mm TB
-ATI damper

So, my current "dilemma" is choosing a set of heads to meet my goals. The 5.3 in the car now has a set of ported 243's on it that are flowing in the area of 290cfm @ .600" (IIRC, I'll have to find the flow sheets)...so those are available as possible choices. Other available options are Mast 215's,PRC 215's, etc...all at a fairly steep price point, but still an option available for this build.

Being that longevity is a MAJOR consideration for this build, I'm a bit concerned about using any heads that have silicon/bronze guides installed, as it seems to be a possible "hi wear" area with higher-lift cams (as I understand it). I have Yella Terra rockers on the 243s, so that's a plus...but I'm also hoping that I won't have to go with a monster-lift cam for this build.

I guess that what this post is leading up to, is that I'm looking to start a discussion as to various possibilities. With attention to the above-listed goals in mind, what might get me to my goals? Obviously, I'm not very fond of the idea of spending $2500.00 on heads...but I will if absolutely required to.

So, what do you all think?

 

I think you have the making to a very reliable and fun setup. One thing to look at like you said is you don’t want to run a monster cam, but since there is going to be more cubic inches, it tends to tame down larger cams and make them much more mild. As far as the heads it’s a coin toss, it all comes down to how much you want to spend. I personally would compare the flow specs of your current heads to any comparable aftermarket heads, but they would have to flow a good amount more to justify me buying them. As far as the valve guides, I have seen some people with aftermarket heads have no problems with guide wear and some have wear much faster than others, I guess it just depends on the cam and valvetrain setup.

 

great power for a 5.3 .maybe look at some trick flow 220 heads,or the tsp prc 225 cast heads for $1700.some AFR 210 would be my choice if I had the money.the AFR heads match up great port wise with a fast intake.

 

Agreed. I guess my main reason for wanting to be as conservative as realistically feasible, is that the thought of changing valve springs every 20k is not something that I relish the thought of.

 

Thanks. Geoff@EPS was a GREAT help when it was time for a cam.

 

Get the 243s checked out(redone) by TEA! They can add backcut lightwieght LS3 valves to help u with valvetrain stablity and help the dyno number your chasing as u spin your motor up. TEA has a few tricks that they do to 243 heads to make them powerful on Ls1's. I can only imagine what they would do on a 383! Try them out and you can save a bunch of bucks on not having to buy a set of new heads, JUST A THOUGHT!

 

I've considered that as well, and might go that route. I probably would have them start with a good set of cores though, rather than have them re-do the ones on the 5.3. $1000.00 seems much more appealing.

 

Yeah the TEA Stage 2 LS6s would get my vote. They can do hand-porting, the LS3 valves turned down, and a 50 degree exhaust port... in the end, I think you can make more power with them than the TFS 215s they are based off of...

 

Right! Ya cant go wrong with mike at tea

 

You can get that exhaust port on any TEA head and the LS3 valves... just throwing that out there.