Well, I seem to have found the right guys. Ran across a group of individuals at the track last time I was out that run an auto shop really close to where I work. Drove the Miata over the other day to talk. Turns out, they are trying to start their own monster project, and had lots of questions. They also are passionate about tuning cars. They are the perfect combo. One guy knows the computer settings and engine performance theory and the other knows mustang 302's inside and out. In fact he has his own blown 302 there at the shop which they tuned.
So, took the car in yesterday. With a fresh stock motor, I pulled 212 a year ago. With new AFR heads, 24lbs injectors, calibrated MAF, and 70mm throttle body, pulled 252 without a tune. Shop has Moates quarter horse hooked up to computer changing some parameters. Currently at 269HP and shooting for 280HP. They have cleaned up MAF curve, spark advancement, and air fuel ratios. Still working diligently. I will post final results.

 

Really nice gain! Are you still running the stock 5.0L HO cam?

 

I have an E303 cam.
Ran into a fuel problem later in the day. My pre-detonation came back. Maybe it was not high intake temps after all. When things got hot, they saw a spike in my air/fuel ratio. It went super lean. Watching my fuel pressure guage, they saw it drop significantly. It's either fuel getting hot and vaporizing, or something is causing fuel pump to turn off. We are starting with running a larger guage wire direct from ford ECU to Miata fuel pump in case resistance is increasing and causing an issue. To be continued tomorrow.

 

That's awesome. Just a bunch of "free" horses sitting there waiting to be let out of the corral. Lucky find in that shop.

 

Is the gas tank becoming pressurized as the car warns up?

 

Adding a larger wire to the fuel pump did not work. Just finished changing the fuel pressure regulator and the vacuum line to it. The old vacuum line was thin, and the thought was it was collapsing under WOT and when warm. This would leave the regulator open and send fuel back to tank and not pressurize the rail. Tank seems to be venting fine. I have an open line under the hood where the old charcoal canister was and you can smell the fuel venting out.

Should know more tomorrow.

 

Still having issues with losing fuel pressure. Thought we had it after a clogged fuel filter. Got some good runs in adjusting timing. At 288hp now. Just put in a new Walbro 255 this afternoon and will see if that helps. Maybe mine was tired and not pumping well when warm? More to come.

 

Looks like the new fuel pump fixed the fuel pressure issue, but unfortunately ruined the entire tune. We have to start over on the process because the new pump gives smoother delivery and changes all my fuel curves. Tuner said it runs much better now and can probably get a little more power. Hope to have it out tommorow.

 

At least the problem has been found. And a few more ponies as bonus. I'm sure it'll run smoother and cooler too.

 

It's amazing how little things change everything! Glad you are making progress with it.

 

Finally done. With good fuel flow, my numbers dropped a bit because it was not running so lean. We went with a good safe tune at 273.8HP and 315.1LBS TQ. Not too shabby for a 2500 Lbs car. With good tune, new tires, and larger brakes, she is ready to get back to the track.

 

Awesome increase with just heads and bolt ons. What Afr heads are you running?

 

That torque curve is a beauty. Over 250 at 2krpm. Can't beat that.

 

AFR 165 heads with stud mounted Comp Cam Pro Magnum 1.6 roller rockers, guide plates, and springs. Bought from a forum member with about 6K miles on them. He was making about 280RWHP, so I am right in that ballpark.

That's probably as best I can go on this motor without forced induction (unless anyone has some ideas LOL). Have not drove it yet, but the HP curve looks nice and smooth all the way to 5K. Should be fun at the track. I have a shake out day scheduled for May 28th, and then a driver training event scheduled for June 13/14 at Houston Motorsport Ranch.

 

347, AFR 205s, higher compression, maybe on the next rebuild, you could squeeze a bit more out of it. But it sounds like a solid, well sorted motor at current. I wouldn't complain, for sure.

 

You're in 'vette hunting territory as is.

 

Looks good! Would a custom cam be in order? And porting the intake?

 

Hey Gunpilot.

Did I see your car sitting outside of a Firestone on Clear Lake City Blvd a couple of months ago? I also live in Clear Lake and my best buddy owns a local shop called Leading Edge Tuning. They also have a dyno. You need to come check out the shop. My Monster Miata project is there while we build it. We have a VERY knowledgeable 302 guy. I am using the SCT switch chip with my car. The owner of LET is a tuning wizard!!

look up Leading Edge Tuning and you will see his rep speaks for itself. I PMed you my number so we can get together.

 

Yep. 2 Brothers Automotive. They just finished my 302 tune and are now helping with my LS tune.

 

I have a couple; free and fairly priced for value received!

Those AFR 165 heads are awesome for a practical, powerful yet tractable street machine. However, with a HP peak at 5000 rpm, you are not nearly taking advantage of all they have to offer. They flow enough air to easily spin that motor to 6000 rpm with an otherwise very streetable combo. Actually, you are ending your rev range right where the AFR's resoundingly pull away from lesser heads when matched up to other, well-balanced components.

I see you have a Cobra style intake. The upper flows plenty of air to feed the AFR 165's, but the lower does not. The stock Cobra lower flows about 205 cfm compared to nearly 250 cfm for the heads. If the lower hasn't been ported, I would highly recommend it. You can get the intake flow up to a close match for those heads for a reasonable cost.

I'd highly recommend Tom Moss (TMoss); he's done a jillion of these and does great work at a fair price. He did an Explorer lower for me, which is virtually identical to your Cobra lower. Beautiful work, and he has you make a paper template of your head's intake ports so he can also port match the manifold to your heads. Sweet.

Considering the rest of your combo, the ported lower should gain you AT LEAST a 15% increase in your overall system airflow. (I'm assuming your MAF is larger than your 70mm throttle body). The good news is, you stay with the longer runner manifold which has excellent street characteristics; i.e., great low and mid-range torque. It won't post quite the peak HP number one of the several 6000 rpm EFI street manifolds will, but it will out-pull them everywhere below about 4500 rpm, which is where you drive it 90% of the time. Great street manifold when ported to match those great heads.

The E303 cam is also a little shy of optimizing your heads' potential. The designer of the AFR 165 heads specifically recommends a 224/224 duration roller cam on 302 cubic inch EFI motors. You don't need a dual pattern cam with the AFR heads as they have fantastic exhaust flow. 110 degrees lobe separation is probably close to theoretical optimum for average power under the curve, but the EEC-IV computer will hate that. Go with 112 degrees lobe separation and make tuning (and living with it daily) easy. You have good valve train components, so more lift makes sense to match the heads capability; something approaching .530" - .550" should do. Just check and verify your spring pressures, and of course, piston to valve clearance. Run between two and four degrees of cam advance, as PTV clearance allows.

You should give up very little in everyday tractability with this combo, but it should pull hard to 5500 - 5700 rpm before the long runners shut down the fun. At that point I'd be surprised if you weren't knocking on 300 WHP's door. This motor, properly assembled and with good valve train components, is quite durable at this rpm. The only other upgrade I'd suggest is making sure you have a good harmonic balancer (not a 25 year old stock one).

There's not a thing wrong with the combo you have now; it's just that the AFR heads give you the potential for substantially more if you want it.

 

Good info here and very encouraging for the direction I'm headed..thanks for posting.
My 92 combo is very similar to the OP combo....AFR165, x303 cam with 224/224 dur., 542/542 lift on a 112 LSA. Stock ported E7 intake with 70mm throttle body, 80mm mas air and 24# inj. With high flow cats. I just purchased a tubular gt40 intake to replace the ported stocker and will be having TMOSS port the lower. He's done work for me in the past and is awesome.

I just Dyno'd my existing combo Saturday and my initial pull was 252rwhp, 330rwtq.
After fuel pressure and timing adjustments, the final was 270.8 rwhp and 325rwtq

I'm expecting that the GT40 tubular upper, coupled with the TMOSS ported lower will put me over 300. Time will tell....I'll post up in a month or so once it's swapped and re-Dyno'd..

 

I have been building F0RD's for 34 years and agree the above combos are great. I use stock E7TE iron heads ported to tinfoil thickness,(LOL not quite), but my years of doing this and blowing through I know the limits. 1.94 intake, 1.6 undercut exhaust valves with 1.6 roller rockers on intake and 1.7 rollers on exhaust works well. I used a truck lower that is ported and modified and port match to the Iron E7TE heads. I make my own custom short runner upper from a piece of 4" tubing for plenum and 2" for runners,( idea copied from "too high psi", I find the long runner intakes are not required for our light weight roadsters and helps move the power up the RPM band. I like making power to 6250RPM and above but not so good for the EEC IV ECM with its hard coded RPM limit, alas I have a Motorsport RPM Extender, ( old school) and a Moates Quarter Horse, (hand built before Moates was around with a Xilinx IC and old college room mate coding).
I found at the track that generally with this combo I could stay with the AFR 165 outfitted cars when I ran FI, if I switched back to my Single Plane Torquer II intake and 700CFM Carb the fuelie boys had no chance.
Where the Iron heads work better, ( my opinion from 20 years testing at track) is when you start to bottle feed our little F0RDs. I used an NX NO2 plate with 300 HP hit and would leave the AFR 165 boys behind with similar systems. It seems the AFR 165 can only take 225 - 250 HP with out the risk of saturating the intake flow and causing a intake NO2 backfire !! not pretty except for the shredded air filter drifting down like confetti. One of the TOP FUEL racers told me it was because I had a higher port airflow speed because of the smaller head port diameter which in theory allowed me to ram more pressurized NO2 / fuel into the same cylinder.?? Don't really care just know from my testing on track that this worked. I also liked clearing TECH and all the AFR boys pointing and whispering, " what he still runs iron heads?". I ran this combo in a stripped 79 'stang with cage that weighed 1700 lbs dry. Have since sold the car 5 years ago but miss it so much I am building a Miata to take its place.

 

All good points. It's pretty commonly known that all things equal, a cast iron head will outperform an aluminum head....keeps more heat in to aid in combustion. That's no longer anything new or novel. My belief is that most folks opt for the aluminum heads for a few common reasons:
Lighter
Run cooler
Cheaper.....yes, cheaper. Unless you can do your own work, you COULD spend 2x to 3x or even more to get the E7 heads to flow what most of the off the shelf aftermarket heads do.

I once entertained the idea of running factory stock about 10 years ago. When I inquired of the cost to have a competitive set of e7 heads done up, it was around $2000.

I can appreciate the attraction of running faster with what appears to be "less parts". That has been my MO as well for years. I recently had a 90 saleen convertible that I ditched the aluminum heads and trick flow intake in favor of ported E7s and a ported E7 intake. The cam and supercharger remained the same. Only changed the heads and intake. I did this because I thought it would be a way better combo for the heavy convertible. IT WAS!
The car made the exact same RWHP.....BUT it picked up 80, yes 80 peak lb ft of torque and had a much broader power and torque curve (way more area under the curve). It made the car "feel" 1000 lbs lighter. For my miata, I prefer the aluminum heads, and to change the intake to move the torque curve up a little bit (and drag the power curve up with it a little).....but not too much. I intend to use the car as a Multi-purpose vehicle, hence the AC and converters...

 

Five-o-joe
Thanks for reminding me I am OLD, LOL. Yes the internet has made all this common knowledge now. I was 19 when the 87GT cheese grater came out and it still feels like a few years ago. I am DIY to the bone and love using," Cobbled together $h1t", to beat a loud mouth check book racer any day. Its all about the sleeper look for me. Going to be rough to hide the rumble of a V8 in a Miata, but at least I can make it look like a stock 5.0. Some satisfaction there. I enjoy the combined knowledge a great DIY forum, will post dyno results of my carb'd 331, fuelie for the next even thinking turbo, I still have a 69 BOSS 302 yet....HMMMMM!

 

I feel you brother....lol. I was 17 in 87! I remember modding the 5 liter when they were new.....time flys! I'm sure you're aware your 331 properly built will prolly make over 400. And with the turbo...depends on the block. My 363, 76 GTS turbo made 977 to the tires. Now I do sleepers too! Lol