This page is an overview of my V8 conversion project.  I have had a turbocharger of some form on my miata for about 10 years; while it has been a blast to drive, the V8 bug has bitten hard and so now I'm entering a new phase for my miata.  The engine going in will be the result of influences from my friends on miata.net and other Ford forums, friends in the miata community, friends at work, local machine shops/garages/speed shops, and basic research from reading up on 302 Windsor based blocks.  My basic goal is to achieve at least 325hp to the ground (about 375 at the crank) while equipping the car for decent street manners yet reliable enough to withstand occasional track time.  Oh... and it's gotta have that classic V8 sound.

11/26/07 - Well, 2nd gear in the miata tranny failed so it's time to start the tear down and sell off parts to help fund the V8 project.  It has "begun".  I am betting it will be at least a year before completion.

12/5/07 - I purchased a block that hasn't been modified and have dropped it off at Kennedy Performance to be cleaned, checked for cracks, square decked, bored/honed 30 over, align honed, swap oil galley plugs for threaded plugs.

12/14/07 - Block machining work is done for now.  Next step will likely be the rotating assembly (pistons, rods, crank, flywheel, harmonic balancer).  These need to be balanced then installed.  Clearance issues with these parts is a concert so it's the next step in case additional machining needs to be done.

12/16/07 - I've been asked a few times why I'm planning on going with a carburetor instead of electronic fuel injection.  Well, here's why I've decided on going this route:

• Cheaper, fewer parts, simpler
• Possibly more power
• Air filter/intake fits better into the Simpson cowl hood I already have (which allows for a nice path to cooler inlet air) and looks kinda cool under the hood
• Just to be a little different
• and I've just got this itch of wanting to do a carb'd setup that I can't seem to shake.

Here are some pics of a friend's V8 miata.  It's a carbureted 347 stroker.  Lots of things to look at and learn.

I may look back and think it's a crazy idea, but for now it seems that a well running, streetable, carb'd engine is possible.  Although it is older technology, I should have the benefits of a refined design by using the most recent offerings from Holley (or maybe Edelbrock).

12/18/07 - I purchased a 94-95 Mustang timing chain cover and am searching for the 94-95 engine accessory brackets (alternator/tensioner pulley/smog pump deletion pulley bracket and power steering/idler pulley/air conditioning compressor bracket).  Also needed: 94-95 water pump, 94-95 WP pulley, and 94-95 crankshaft pulley.  I think there is also a crankshaft pulley spacer that is unique, as well as the harmonic balancer.

2/01/08 - I now have the 94-95 Mustang GT accessory brackets with new idler pulleys, used tensioner, new water pump, new WP pulley, used alternator, used bell housing and alignment plate.  I also went ahead and ordered the modified oil pan from Monster Miata so that clearances can be verified with the rod cap bolts/nuts.   Pistons, rods, crank, rings, flywheel and harmonic damper will be ordered soon.

2/03/08 - The miata engine and transmission, along with the turbo and other parts have been removed and are up for sale.

2/08/08 - The oil pan from Monster Miata came in.  Looks nice!  Here it is sitting on my spare block.

2/11/08 - I picked up a '93 Thunderbird diff today.  It's just an open diff, no LSD but I'll plan on adding that when it gets torn down.  This one had a little leak and is a bit nasty.  Time for the wire brush.

2/29/08 - I brought my block home from the machine shop today to give it a coat of paint.  I used POR-15 Paint-Over-Rust as a primer and POR-15 Engine Enamel as a top coat (painted on as the primer was just about dry).  Here is a shot of it back at the machine shop after a few days of curing.  The color I chose is Ford Medium Blue which is a bit darker than the Ford Corporate Blue I painted on my spare block.

3/04/08 - The crankshaft, rods and pistons have arrived.  I decided on a 331 cid stroker setup instead of a stock stroked 302 (or 306).  I could have gone as far as a 347 stroker but decided to go with the 331 to try to avoid some concerns I have with the reliability of a 347.  Perhaps I'm a little paranoid, but the 331 seemed like a good compromise with increasing displacement (power), bringing the usable power/torque curve a little lower in the rpm range (which means I don't have to rev it as high, which is good for reliability), and less side loading of the pistons against the cylinder walls.  I wanted to go with an internal balance setup and so I had to spurge for a forged Eagle crankshaft since the cast ones by Scat and Eagle are not internal balanced.  The forged crank is overkill for my power objectives, but that's ok.  I went with Eagle forged I-beam rods.  They will be strong enough for my objectives and are lighter than H-beams.  I went with Mahle forged aluminum pistons.  The pistons I bought weigh about 408 grams which is about 10% less than a similar spec'd SRP piston.  The low rotating mass of the piston and rod should promote better engine longevity and hopefully smoothness.  The pistons also have a coating to help with piston slap, which for a 331 shouldn't be as pronounced as if I had chosen to go with a 347 stroker.

3/14/08 - The rotating assembly was sent over to SR Racing for a balancing job.  They only needed to do work on the crank as the rods and pistons were already in spec.  To achieve balance, SR did a combination of drilling and turning on a lathe to get the crank balanced.  The crank was then installed and so far so good.  I also ordered a new oil pump.  I went with a Melling Select as they are supposed to be a bit more substantial than the regular Mellings.  The pump drive shaft that came with it was pretty wimpy.  Being that this is a weak spot/critical spot for small block Fords, I replaced it with an ARP shaft.  Visually, it's clearly stronger (thicker).  I also had to order a bolt dress up kit.  All ARP stainless steel hardware is going in this engine (from looking outside of the engine).  We found a stud on the center main cap (the stud that holds the end of the pick up tube) was a little too long.  We'll cut that later once we start putting in the rest of the parts.

3/28/08 A few things to update... The camshaft has been ordered from FlowTechInduction.  I'm looking for a power band of 2300-6500rpm.  The oil pump was tested and the bypass valve was set at only 45psi.  Kennedy Performance was smart enough to check that now and is adjusting it to have a 60psi threshold instead.  A ProGear Camdex timing set has been ordered and received.  Very nice looking set.  The timing cover, alternator/tensioner bracket, and PS pump brackets have been powder coated silver.  The smog pump has been deleted with an idler pulley.  All pulleys are in the middle of being converted to aluminum ones for cosmetic reasons.  I'll probably have them all clear anodized to make them last.  Overall, the short block should be done pretty soon.  I'm guessing about 4 weeks from now.

4/11/08 The camshaft has arrived!  It's now been installed and degree'd by Chad at Kennedy Performance.  Due to the line honing, the Progear timing chain (stock length) is a little loose so a slightly shorter one (0.005") will be swapped out.  I want to start out with as little slack as possible; it will eventually stretch some so I want to minimize problems now w/ a tighter chain.

4/12/08 I went ahead and did a little clean up work on the differential I got.  The main housing got a cleaning and repaint of POR-15 Chassis Black.  I took the diff cover to my local powder coater for a coating of the same silver on my timing cover and engine accessory parts.  I still need to swap out the internal open diff for a TrueTrac but I just had to clean it up now.

4/24/08 The short block is complete.  Kennedy Performace did a great job.  Lots of attention to detail.  Even the oil pump bolts are wire-locked in case something were to come loose.  We ran into a small problem with the oil pan and the ARP rod cap bolts.  Martin at Monster Miata updated his oil pan to now have enough clearance for the ARP bolts, however the pan we received had a slight bend under the #1 rod cap and was causing some interference.  It was in a weld joint with a wall going 90 degrees down from it so forming the metal down with a hammer wasn't successful.  A careful grind of the pan was done and now there is about 0.0060" clearance between the rod bolt and pan.  The new timing chain set with the 0.005" shorter link is installed as well as the remaining rods and pistons.  The oil pan went on as well as the timing cover and water pump.  Gotta love those shiny stainless steel ARP bolts.
6/11/08 There's not a lot to report right now.  The engine build is awaiting the heads which will probably be ordered next month.  During this time, I've be doing a lot more research with respect to the valve train, carburetor and tranny. The valve train clearly needs to be up to the task that my camshaft will require.  Valve springs must deliver enough seat and open pressure to eliminate float and bounce, so I'm using an optional upgraded spring set AFR offers delivering 155lb on the seat and about 400lb at full lift.  Will use titanium retainers to minimize mass in the valvetrain.  Thick walled pushrods; not sure yet which ones.  Link-type Crane hydraulic lifters to withstand the high forces associated with the high ramp rates of the cam.  7/16" rocker studs to handle the higher forces. Looking for a carb that is about 650cfm, probably vacuum secondaries and an electric choke to achieve great overall power performance while keeping it streetable year 'round.  Expecting to look for a good tuner carb, but may consider an off the shelf unit from Holley.  Considering BIGS Performance , Competition Fuel Systems, or Pro-Systems.
7/1/08 While waiting to buy/save some parts for my engine, I started going through my engine bay some.  Since I'm going carbureted, several wires and connectors associated with the original EFI system are not needed so I've begun trimming the un-needed wires from the harnesses (or removed certain harnesses entirely).  I still have not gone through the battery/alternator/starter/ground wires but will probably save that for once the engine is in and I've settled on where to find a good path for those items.  I'm also considering removing most items in the engine bay for a paint job.  Not sure yet.
7/18/08 My good friend Nigel has decided to convert his V8 miata back to a 1.6L 4 cylinder  for various reasons, but a catastrophic engine failure of his 302 initiated the decision.  As a result, he and I have decided to exchange some parts.  It's a win-win situation where I get some kit parts that he no longer needs, and he gets some stock parts I no longer need.  So, off I go removing some more parts.  The K-frame is a key part that will be exchanged and I've pulled it along with various other suspension parts.  That engine bay is looking bigger!
8/30/08 I disassembled the rear subframe assembly, and cleaned it up a bit.  I got a little carried away and ended up having most pieces powder coated.  Most of the rear has been reassembled and installed.  Also, my AFR 185 heads showed up, as well as the RPM Air-Gap intake manifold and hydraulic lifters.  The intake is going to be port matched to the heads (along with the gaskets), then off to be powder coated to match some other engine parts.
8/31/08 Today I started on cutting out the "corners" in the engine bay needed for clearance.  I need to weld in some metal pieces and start on the passenger side as well.  I also started clearing out some lines and such on the firewall to clean things up and likely a repaint.  The flash in the pictures make it look worse than it is, but I'm getting closer to the point where a quick repaint would be easy.

Conversion Kit
-Monster Miata (www.monstermiata.com)
-less springs
-add Thunderbird axles

Block
-Seasoned Ford 302 small block (purchased)
-331 Stroker; approx 10:1 compression
-Bored 0.0030 inches over (done)
-Square Decked & Align Honed (done)
-Eagle forged I-beam rods (purchased)
-Mahle forged pistons (purchased)
-Eagle 4340 forged crank, internal balanced (purchased)
-AstroPerformance 157tooth/0 balance flywheel
-ATI Super Damper harmonic balancer (purchased)

Heads
-AFR 185
-Upgraded valve springs to prevent floating/bouncing
-Titanium retainers to reduce valve train mass
-7/16" studs
-Cometic Multi Layer Steel head gaskets

Rocker Arms
-Scorpion 1.6 roller rockers, stud mount

Intake Manifold
-Edelbrock Performer RPM Air-Gap

Air Filter Assembly
-K&N 7/8" drop base (modified to fit electric choke), (60-1430)
-2" high, 14" dia K&N filter
-K&N Xtreme lid

Cam
-Flow Tech Induction custom grind

Carburetor
-Holley 4150 (0-80783C)
-- 650cfm
--Vacuum Secondaries
or
-Holley Street Avenger (0-80670)
-- 670cfm
--Vacuum Secondaries

Carb will likely end up being sourced from an experienced tuner to modify it for my application.

Transmission
-T5Z/World Class
-(2.95,1.94,1.34,1.00,0.63) gears
-T5/302 bell housing (purchased)
-Block alignment plate (purchased)
*this tranny has a 330ft-lb torque rating and is a direct replacement of the T5.  I'm a little concerned about the torque rating.

OR

-Tremec TKO 600 (p/n TCET4617)
-(2.87,1.89,1.28,1.00,0.82) gears
* this tranny has a 600ft-lb torque rating and a very nice gear ratio arrangement for street and track use for a light weight car such as a miata coupled with a powerful engine that might be herky-jerky under 2000rpm or so (i.e. cruising a bit above 2000rpm would result with this tranny).  May require longer drive shaft (probably not)? May require different bell housing.  Price is about $600 more than a T5Z.

Differential
-Ford 7.5inch (from '89-'94 Thunderbird) (purchased)
-TrueTrac LSD carrier

Ignition
-Mallory Unilite distributor (small dia cap; better air filter base clearance)
-MSD distributor
-MSD 6AL (purchased)

Exhaust
-1 5/8" Shorty headers from conversion kit
-2.25" pipe to X pipe
-2.25" X pipe
-2.25" pipe to cat
-2.25" cats
-Magnaflow or Borla Pro XS mufflers
-3" tips

Engine Accessories
For a 94-95 Mustang GT:
-Timing cover (purchased)
-Water pump (purchased)
-Water pump pulley (purchased)
-Alternator (purchased)
-Alternator bracket (purchased)
-PS pump (purchased)
-PS pump pulley
-Smog pump delete pulley (purchased)
-AC compressor (note, if no AC is used, just go w/o the compressor totally, use a smog pump delete and use a 101 5/8" Gates belt)
-PS/AC compressor bracket (purchased)
-Crankshaft pulley
NOTE:
-Close to block design (allows puller fans)
--All parts from:
---'91-'93 Thunderbird (w/ V8)
---'94-'95 Mustang GT
---'96?-'01? Explorer
-Away from block design (pusher fans only)
--All parts from:
---'86-'93 Mustang GT

Misc parts
-Oil pan (purchased)
-Oil pick up (purchased)
-Melling Select Oil pump (purchased)
-Dip stick/tube (purchased)
-A ton of stuff..