MRM331

A couple of updates on mine regarding issues spoken of in this thread:

I just sold off my original suspension which meant a chance to revisit the build excel sheet for the car. As of right now, not including wear items (tires, brake pads, track-only wheels, oil, filters, windshield wipers, etc.) I have just under $20K in the car as of this point. That includes the original purchase price of the car with hardtop ($5000). I had the car dyno'ed on the same mustang dyno I had it on before the MS2 install and it gave me a little more torque but the HP was exactly the same-270 to the rear wheels. With how amazing different the car feels with the MS2 I really expected better. I could pull my timing up a little under 4500 to gain a little but I really think it's time for me to dump the GT40 heads for something that can flow a little better. I really like the P-38's that Jacko keeps talking about. I'm probably going to go that route or a set of AFR 185's. The difference is about $600.

On another note, my father just purchased Jacko's Monster. We're in the process of deciding if we're going to do a "tub swap" with my dad's current stock 1990 or sell that one off and have the V8's tub cleaned up. We drove it and mine back from DC to PA (190 miles each way) and he was able to get almost twice the mpg's I got. My wideband died so I have HEGO correction turned off but still got around 19 mpg's. He had to of been in the 25+ range at least.

-Jason

mgb-v8

Jason, I know that your Dad bought a great car and as I stated to the both of you, they are still people around that believe in straight shooting and honesty when selling something to another hard working individual; I hope that your Dad enjoys and have tons of fun with the car.

As far as your car's modifications, I would definitely go with the P-38 heads and a custom grind camshaft from Jon Kasse. I would also look into an operating system that handles sequential injection; that way you can tune each individual cylinder; most modern performance cars have it for a reason.

I already miss my Miata but as you can tell I have a very promising MGB-V8 that hopefully when finished would help me with the better sitting position while traveling long distances.

Jacko

Meierznutz

If I might chime in here.... I took my LS-1 swap for a little road test a couple months after it was first fired. We went from Connecticut to Ohio and then participated in a little road rally called "The Fireball Run Adventurally". It was an 8 day 14 city 2500 mile road rally to bring attention to the plight of missing children in America. Over the course of the run I did freeway, spirited back road, city, and some performance driving. Nadine averaged 23 MPG for the entire trip!
I am not sure if it would have helped or killed mileage but I just found out that one of the little things I overlooked was the fact that I hadn't adjusted the Miatas gas pedal stop point so the entire time we were only using 2/3 to 3/4 the available travel. DOH!
Even with this goof up I managed to get a clocked 0-60 in 4.80 sec/280.3 feet and a quarter mile of 13.4@109 with luggage/fuel/2 adults in the car!
Qvox- if you want to build a v-8 Miata there is no SANE reason to do it. There is no way to justify the build. I tried to convince my wife of why had to be done and she plainly looked me in the eye and called me a liar....then said "Do it, you're gonna anyway" ....Love that girl!
BTW, Nadine runs a stock '99 LS-1, 02 T-56, 3.73 Cobra 8.8 and 205/50-15's all in a Boss Frog wrapper.

Old Chuck

It seems to this newby that most of the GM power seems to get better MPG. If this assessment is correct, maybe it is because many of the Fords are pushed farther from stock then the GM or it could the be the gear or then I could be completely wrong. Trying to decide what car I want and learning all I can, I understand your concerns however, given the fun factor and that life is short, I personally, would put MPG way down on my list but it is your build and you have your own priorities. It is an interesting topic and I learn a lot from the posts here that I will use when ready to purchase a car. There are some great guys here and have more knowledge then I could ever hope to possess but maybe I can learn from posts such as this..

Meierznutz

Chuck, lets not forget that the GM swaps are being done with engines and fuel injections computers that are at least 10 years newer than most of the Ford stuff. That ten years brought a lot of power to the computers and processors in the ECU's of our fuel injection systems allowing for better fuel/timing maps. Hell, there is even a company out there using GM processors to run the Hemi engine! If it would fit in my engine bay I would have a Hemi 6.2 in my car now!
There have been a lot of improvements in the GM ECU's too.... just the difference between speed of the 98 and 99 is noticeable, and the aftermarket now has stand alone stuff so you don't need the stock harness at all.

Old Chuck

That makes sense. There have been great advances in MPG and what we expect. I was surprised what my last 2012 5.0 Mustang with 412 HP got for mileage. I really did not care but it surprised me especially IF you could keep your foot out of it. I forget at times that a 25 year old 5.0 is not the new Coyote 5.0 and too bad the Coyote it will not fit well in a Mazda. It did not sound quite as good as an older pushrod 5.0 but it was much faster for the displacement and got much better mileage while doing it. Thanks for the reminder as I am not a true motorhead and I forget much in my aging mind. I do appreciate however the way folks here show you the way without pushing you down a hole...

charchri4

Part of it is just lower rpms running down the road. The 6 speed in the GM cars is a .5 overdrive and the 5 speed Fords is usually .79. I think most guys get around 22 with the GMs and a little less with the Fords overall. If they were not so fun to drive I have no doubt you could add 3 or 4 to that..

I think we would all agree the only reason for a V8 is...

Old Chuck

Jim, You make it hard not to jump on the first one I see with that video. Any idea what power he has in that Miata?

charchri4

Yeah I hear you! Hang in there from what I have seen in the last couple years there is usually about one a month that comes on the market and about every 3 months one that looks too good to pass up.

Oh yeah I did that video durng lunch yesterday so I know the car quite well! The engine is from a 2002 Camaro SS and it is stock except for the cam and tune. I only did the cam for the muscle car idle but with it I have some pretty accurate numbers on it. Car Craft magazine did an engine dyno test on a the same stock engine with a cam with just a little less lift than I am running and came up with 419 HP and 389 ftlbs of torque on their engine dyno. With my tune and a hair more cam I would guess I would pick up another 25 but it’s hard to know how much the headers hurt us in these cars so I always tell folks 425 hp.

Did you see this one from my blog? Sorry to say it will probably make things worse for ya but it is fun to see the car sick view too...

.boB

If the Cobra is your dream car, then you should go for that. Everything else is just second best compared to your dream car, whatever that dream is.

The financuial reality is that you can buld a pretty nice car for less than the cost of the average SUV. And, you can buy one already built for even less.

That's pretty funny. When compared to a well tuned stock original 427 FE cobra in the right hands, you'de have a tough time matching the performance with almost anything else for <$100K.

The reality of the current Cobra's is that they're all different. There have never been very many original cars on the planet, and now there's even less. Most Cobra's are replicas. That means they all appear to be the same, but appearances are deceiving. You can build them any way you want.

Mine makes about 600 dyno proven Hp. Runs on gasoline, race fuel, or E-85. It performs on the track and the street like you wouldn't believe. It's an absolute rocket. It will cruise through town, on the highway, or along the back roads all day long in relative comfort. And, it's gets 20mpg on pump gas.

And, the look alone will take your breath away (at least, it takes mine away). Not many cars attract attention like a Cobra does.

You can have it all, you just have to build it.

I think this is essentially true. A well balanced high performance car is just a joy to drive almost anywhere. But, there is a limit.

charchri4

Bob check this out and don't miss the link to the origional article.

Jim and Jenna build diary, Miata LS1 Conversion: Is the V8 Miata really a modern day Cobra?

I could not agree more about the appearance but I do love being able to put the top up and not worry about it parked at a bar. It's just an old Miata so who would want to mess with it!

PS photos of said Cobra or it dosn't exist

.boB

I hear ya! No pictures... didn't happen.

Street cruising:




Race Track: (took this one yesterday)



Dyno Sheet from a few months ago:


Engine bay, street trim:


Since that picture was taken, I dumped the distributor for a computer controlled coil pack.

charchri4

Wow that is VERY sweet Bob! Could you post up an introduction over in the intro section? I'd really like to hear your story, have these pix there and what you are thinking about doing with a v8 miata.

.boB

I can do that.

MX52NR

With the LS1, Tremec T56 & Getrag (3.42) diff I'm averaging 18-20mpg around town, and 28-34mpg at highway cruising speeds. 34.2 is the best I've gotten (60mph, with the cruise in 6th gear).

charchri4

^^ WOW!! Congrats on the amazing numbers I am envious!

Old Chuck

Great numbers. You are getting better then a vette on the road. Must be hard with that power much to play with. A tall top gear really helps for the road..