Final result, which I'm happy with is 382! Could have maybe got close to 400 with a leaner AFR at WOT, but decided to keep it reliable.

 

Nice!

 

Seems like there should be more there. What cam and what exhaust? Very nice torque curve though.

 

All stock motor with Comp Cam 231/236 on a 112 .617/.602 lift and Flyin Miata headers. Rest of exhaust was recently done with X pipe, high flow cats, and Spin Tech mufflers. Probably could have gone leaner, but did not want to push it. Anybody want to share their AFRs from 4-6500? I was reading AFR at the front O2 port.

 

I target 13 to 1 or 13.1 to 1 under full throttle. A lot of people will argue that is too lean and 12.8 is a better target. I see the Miata more like a motorcycle when it comes to tuning.It is very light so it doesn't load the engine nearly as much as , say, a Camaro or Mustang or Challanger that weigh close to 1500 lbs. more. The rate of change of rpms is pretty quick in such a light car. For timing it looks like 26 to 28 degrees is about where you end up. For comparison my stock bore LS1 with V8 Roadster long tubes (Kooks) and a .565 lift cam with 332 duration on a 114 seperation made 392 hp and 386 lb/ft. The headers were good for 26 lb/ft over the smaller swap headers that are out there.

 

Sorry for the crappy dyno pic!

 

Seems about right. Those LS2 intakes and shorty headers are pretty restrictive. The type of dyno can make a big difference, as well.

My tuner aims for 12.8 as well. Here's my LS2 dyno. Blue line is with stock LS3 top end similar sized cam (222/230 ~.600 lift 114+4) and FM exhaust. Red line is the same engine with 1-7/8" long tubes, X-pipe, no cats, and 3" Magnaflows. Headers really wake these engines up.

 

I have a set of new LS3 heads milled down .30 for compression and ported for flow with a matching LS3 intake. I was going to sell these off, but after seeing some of the numbers here, I may add those. Not really that hard of a job. I was just unsure about fitment with this cam and having to fly cut pistons. Wanted to avoid that.

What other headers fit this application?

 

Highly recommended. The LS3 intake flows almost as well as a FAST intake for 1/3 the price. Also, take into consideration that the LS2 (243) heads are VERY popular with the LS1/5.3 guys. I think I sold my assembled 243's for $550 when I did mine. For me it was a no-brainer.

All you'd need is a set of offset LS3 intake rockers and rocker stands. The exhaust rockers are the same. Not sure how well the cam you have would work, might have to ask around on that.

I was going to have mine milled/flycut as well but I held off to see what gains the exhaust would make.

I believe V8R's (Kooks) 1-3/4" headers are the only aftermarket LT's available. They may seem a little pricey, but the quality is top notch. You couldn't build them any cheaper yourself, trust me

 

I have a new set of offset rockers and mounts in the box also for the LS3 heads. I have everything for the swap, just needs assembled and installed. As soon as car is done at shop getting tuned, I will do more research with LS experts to learn more about that swap and cam combinations. Engine has new lifters and pushrods. I assume I can reuse those.

I also asked them to lean out the fuel from 12.1 to 12.8 at WOT and get new numbers. I will post when I know the results.

This crap is FUN!

 

12.1 is pretty fat. It will be interesting to see how it goes.

 

12.8 also. Was good for 445whp. (LS3 w/ GM hotcam)

....but 465 w/LTs?!?!?! Dammit. I need dis!

 

Yep, those LT headers sound yummy! Did a lot of reading on older posts about installation, and they sound like the monster 302 header installs where you have to drop the subframe and remove steering shaft. What a PITA! Not ready for that. I would rather do a quick LS3 head and intake swap. I REALLY want that 400! I will know more what 12.8 gave me tomorrow afternoon.

 

LS engines REALLY like to breath. I put in my long tubes after my build and you're right. Major PITA, but... They changed the whole character of the engine. It got really happy. As in "Ah, I can breath". Pricey. Labor intensive. And well worth it. The more head work and cam shaft you run the bigger the benefits.

 

As much of a HP snob as I am...it really does get to the point of ridiculous in these cars. I'll be going back to 100 or less wear tires on the next set. The RS3s are fine for cruising but light up too easily under heavy throttle. Even so, LT's and a D1 Procharger are on my to do list. ..if its worth doing, it's worth overdoing! I'm just trying to wait until emissions isn't an issue anymore.

 

I retract my numbers and add 402 to the table. Leaning to 12.8 did wonders.

The 393 was when the car was pretty hot!

 

Awesome!

 

Really love this car, Keep it up man. Will never complain about more pics of that Fasback, either!

From everything I've read, the LS3/L92 head port is well worth the effort, btw. Its the culmination of another decade of research, and they seem to make great power. Long tubes are in my build as well, and as everyone mentioned, a major pain.

Keep in mind, GoKarts headers are 1-7/8, which are good for another small gain over 1-3/4 on a vette, and you can't buy them for the MX5. V8R's stuff is as good as it gets, currently.

Cheers, and awesome results thus far out of that LS2. I'm betting it flies.

http://www.superchevy.com/how-to/070...ine-l92-heads/

 

Nice job!