Big Block 1995 Miata madness

Entire Alblum Here

My brother and I have seen few V8 swapped miatas, but never a big block. Sure 302's fit great and LSX's are cheap and plentiful but that sounds sane. The car is meant to be an automotive version of a cover band for the 427 AC Cobra. We found a great deal on a miata tub that had all the right equipment (a VIN plate and a title). We're still looking for a good deal on an engine, right now we're leaning towards an 8.1 Vortec. We've got a 460 serving as a stunt double for the BBC right now because the sizes are relatively close. This first picture is with the firewall intact, seeing just how far the engine needed to come back.

Here it is after we clearanced it just a bit.

Now we just need to add in some structure, PVC pipe should handle the torque, right?

But I couldn't get the welder to fuse PVC pipe so we'll have to resort to steel instead.

In reply to psychic_mechanic:

You Are A True Visionary.

This could be fun.

Not so clear on why you started cutting until you had the right engine.

I am guessing that since you are going Vortec, you have given up on keeping this under the hood and accepted the scoop requirment.

What I don't get is why all the firewall work when the LS engines are a known fit with only minor firewall surgery. Correct me if I am wrong, but a Vortec is just a taller LS with an iron block no?

You are going to need a K member. Making your own or buying from the usual suspects?

What is the plan for the rear diff and axles?

In reply to NOHOME:

I was under the impression the Vortec 8100 is an updated BBC, more or less a stroked and metricated 454, has nothing to do with the LSx line beyond the EFI.

NOHOME wrote: Not so clear on why you started cutting until you had the right engine.

Measure twice, cut once is SO played out. Measure once, cut five times!

8100 is an updated BBC, using some ideas GM learned from the LS engines, like intake ports and 8 ignition coils.

To the OP, if you are going BBC, I would go with an older engine. There isn't nearly as much hot rod parts for the 8100 as the older engines.

NOHOME wrote: This could be fun. Not so clear on why you started cutting until you had the right engine.

It was too rainy to do any bodywork outside

I am guessing that since you are going Vortec, you have given up on keeping this under the hood and accepted the scoop requirment. What I don't get is why all the firewall work when the LS engines are a known fit with only minor firewall surgery. Correct me if I am wrong, but a Vortec is just a taller LS with an iron block no?

The insanity gets even more impressive, there's a complete 4.8 sitting like 30 feet or so from the miata.

You are going to need a K member. Making your own or buying from the usual suspects?

They're kind of expensive, I may buy one if I find a good deal, but planning on making one for now.

What is the plan for the rear diff and axles?

We've got an entire 1995 thunderbird thay may donate uprights and hubs along with a dozen or so 8.8 center sections with many different ratios.

81cpcamaro wrote: 8100 is an updated BBC, using some ideas GM learned from the LS engines, like intake ports and 8 ignition coils. To the OP, if you are going BBC, I would go with an older engine. There isn't nearly as much hot rod parts for the 8100 as the older engines.

I'm not a chevy guy so I'm not used to just how cheap the chevy parts are. We found many smoking deals on 454's, but the 496 should have the low end torque we need. There's just something so twisted about having nearly 500 cubic inches under the hood (mostly).

This will be an epic monster of a car.

Psychic, I am slightly concerned about your sanity, and also your ultimate longevity on this planet...

But I am seriously interested in watching the progress on this one!!!

psychic_mechanic wrote: I'm not a chevy guy so I'm not used to just how cheap the chevy parts are. We found many smoking deals on 454's, but the 496 should have the low end torque we need. There's just something so twisted about having nearly 500 cubic inches under the hood (mostly).

Take a 454 + .060 overbore and 4.25 stroker crank = 496 cid. The older engines have more performance cylinder head choices, intakes, cams, etc... 8100 is kinda on its own and what perf parts are available are a good bit higher $$$$$$$.

81cpcamaro wrote:

psychic_mechanic wrote: I'm not a chevy guy so I'm not used to just how cheap the chevy parts are. We found many smoking deals on 454's, but the 496 should have the low end torque we need. There's just something so twisted about having nearly 500 cubic inches under the hood (mostly).

Take a 454 + .060 overbore and 4.25 stroker crank = 496 cid. The older engines have more performance cylinder head choices, intakes, cams, etc... 8100 is kinda on its own and what perf parts are available are a good bit higher $$$$$$$.

This is all true, Leave 8100s for Boat people. An Ity Bity teenie weenie Big Block Will Have all the torque You will need to break Parts and Minds. But we Know you won't Act out. RIGHT!!

Psychic, here's another idea for you that I've been tossing around (albeit for a much bigger, heavier car): since there's not much in the way of support for the 8100, how about a single turbo Vortec 454?

That would be the last gen of the big block, and according to Wikipedia anyway, they even made an HD version with a forged crank, rods, and pistons. I would think that one of those bad boys with a slightly thicker head gasket and a big turbo pushing low boost would be pretty powerful and long lasting (unlike the 8100 when pushed hard from my understanding.)

Other fun references: Car Craft ran a budget BB series with a lump from Demon engines in CA and they were able to put down some serious numbers somewhat cheaply. Also, on BangShift, they featured an 80s cutlass wagon with an 8100 and a Doug Nash 5 speed that was done on the cheap.

Best of luck with whichever direction you go with. We'll be anxiously awaiting any updates!

In reply to Jambo:

Car Craft Also Put A Single turbo On that Same Demon 454 and made Stupid for the money Power. Stick with Gen IV BBC stuff for Huge Aftermarket support.

454 stuff is really cheap but we just like the 8.1 for some reason. we found one that the owner wants to sell for a decent price so my brother and i should be able to go pick it up this weekend. Im just looking at a for the 8.1l with some headers and maybe a cam to make some where around 425hp.

we are still looking for a trans for it hopefully find a M21 or a super T10 think the 8.1 will make enough torque that a 4spd will be just fine i have a set of 2.76 or 3.08 that will be just fine in the 8.8.

If your going to go nuts go all the way and put a quickchange in the rear at least then blowing up cheap spider gears is the only thing you will do.

JacktheRiffer wrote: This will be an epic monster of a car.

or MB diesel miata part 2. bouncing around the forum like herpes owner to owner never actually getting done. hope this one sees better fate.

wearymicrobe wrote: If your going to go nuts go all the way and put a quickchange in the rear at least then blowing up cheap spider gears is the only thing you will do.

And a 4 speed dogbox.

Kenny_McCormic wrote:

wearymicrobe wrote: If your going to go nuts go all the way and put a quickchange in the rear at least then blowing up cheap spider gears is the only thing you will do.

And a 4 speed dogbox.

Looking at the pictures and where you have the structure hacking the entire tunnel and footbox out and replacing with some sheetmetal. I have a cobra and that footbox looks even smaller then what I have at this point. Trust me it will be un-driveable without the extra space or you will have to offset the steering wheel and seats which make for some interesting issue.

454 is cheap, you can turn a 454 into a 496 or a 502.

460 is not as cheap but you can bore and stroke a 460 into a 559 with off-the shelf components and a factory block.

Or, you can just buy a lighter Caddy 500 and have all the torques, stock, with room for more (but it's expensive)

Buick 455 is super light, reasonable to build and is a killer street motor (510 lb/ft in 1970). This would be the one I picked if I had a choice of all four.

Trans_Maro wrote: 454 is cheap, you can turn a 454 into a 496 or a 502. 460 is not as cheap but you can bore and stroke a 460 into a 559 with off-the shelf components and a factory block. Or, you can just buy a lighter Caddy 500 and have all the torques, stock, with room for more (but it's expensive) Buick 455 is super light, reasonable to build and is a killer street motor (510 lb/ft in 1970). This would be the one I picked if I had a choice of all four.

Here is said engine in an MGB. They left the firewall in place.

In reply to wearymicrobe:

we do have a 455 Buick and a collection of other old engines but we wanted a fairly new engine.

Boombeartree wrote: In reply to wearymicrobe: we do have a 455 Buick and a collection of other old engines but we wanted a fairly new engine.

I am all on board for a new engine. I am done doing old engines in new cars trust me.

I have no idea how you are going to get tires under this beast. I can overpower RA1's in a 295 width in my cobra with 300 rwhp. Are you going to be able to get the power to the ground in any sort of fashion with that much weight on the front nose.

In reply to Boombeartree:

It's only 30lbs heavier than a SBC. Put aluminum heads on it and it's the same weight.

Think about the chassis you're putting it in. BBC's are heavy.

A "modern" big block isn't exactly an advanced design. There's not a whole lot to be gained over a 1960s engine.

In reply to wearymicrobe:

I have a worked on building cars with big block mopars, fords, pontaics, and even olds engines but never a big block chevy that's one reason for the 8.1 and also the 8.1 we are getting is really cheap and runs so it was hard not to use it. but yea the 8.1 is pretty heavy will be doing lots of weight reduction to keep the car under the 2500 lb goal.