Nasty V6 Miata.

[98AmGT]

Hi guys. I know i'm gonna catch some static on this one, but here goes. My turbocharged 4-miata just isn't up to snuff (no torque). While I love the car for all of its merits. Just doesn't have what the car deserves for power. That said, I also love the 60-degree chevy...always did. I had one in an '84 camaro w/a 3.1 (ol 2.8 snapped 2 cranks) a 4-barrel, wolverine cam, headers, 5-speed, and 3.73 gears.....let me tell you in that light car I ran with stock 5-L mustangs and beat,no killed many a 305 camaros. That was back in '94. I KNOW what these engines are capable of. Now for the juicy part. Does anyone here know if the 3900 block will accept the iron heads? You probably know where i'm going with this. I also know that a custom bellhousing is available for the transition to RWD, i just dont know who offers it. This car even with a 3.4 (if thats my only option) will have forged custom pistons, solid lifter cam, oil mods, forged rods, ported heads, rol.rockers, etc. and around 250horse and real TORQUE in a 2000lb. car. I really can't see swapping a V8 in. Does anyone know specifics on the 3900 short block? Thanks in advance guys.

[IsaacHayes]

Why do you want iron heads on the 3900? Iron heads flow terrible and yes they will bolt to the block, but they won't line up with combustion chambers or coolant ports.... In other words, no.

You can get 250 crank HP easy with a stock 3900 with a cam regrind or swap to gen3 cam with TCE parts. They make a (or are making) a RWD swap for the 3900. 3900 stock is 240hp with variable cam and intake. You can run the non-variable intake 3900 intake, or 3500 intake and then use the TCE stuff to swap the timing cover and get rid of the cam phaser and put in a gen3 normal cam which you can get custom grinds at WOT Tech here. No need for solid lifters. No need for forged rods, or forged pistons. The gen3 rods and crank are good to 450hp or so, and the gen4 (3900) have a forged steel crank.

For 250hp you do NOT need forged stuff. Now if you're gonna turbo, you'll be fine on stock stuff as long as the tune is good and you are running around 12psi tops. Anymore and forged pistons is a good idea, and the 3900 has the same bore as the LS1, so there are cheap options there I hear.

Or you can just do turbo 3.4 RWD block, with the camaro 5spd, and put on 3400 or 3500 heads and intakes and turbo that or NA.

A non-vvt 3500 in a cav (super dave) is pushing 300+ crank hp NA. Just ported, big cam and headers. It's stock compression.

So you have all kinds of options. But don't bother with iron heads...

What are your goals and do you want to turbo? 250+ hp can be done NA or exceeded with boost. And depending on engine it can be done easy NA or with a lot of mods for that power. On a ported 3400 with stock cam and compression with 10psi a member dynod ~358hp is another example.

[98AmGT]

Well, its like this, I plan on spraying it instead. The 3500/3900 heads are a very attractive option. I have made sheetmetal tunnel rams before, but the intake manifold for the V6/60 looks to be too much of a challenge. If edelbrock only made a single quad manifold for the newer heads that would open up so many possibilities. Not just mine but also for the stalker gang and MG midget racers. After drag racing for years with nitrous and hooking the bottle up at the track, rejetting my carb for qualifying rounds has become second nature to me. Maybe i'm just old school and don't have the know-how to set the computer up. The thought of a 3900 with 2-16g turbos makes me melt in lust though. But, in all reality: a 3900 with little mods would put my little roadster deep in the 12's with my 4.30 torsen rear diff and drag radials. No compromises on handling either. The Baltimore city police keep sending their wrecked impala 3900 cars into the local pic-yur-part. These motors can be had for a paltry $150! 10.5:1 compression will support A LOT of cam.

[Joseph Upson]

The iron heads will fit on the 3900 block and when I checked it appeared they would also bolt up properly to the stock iron head manifold although I didn't check physically beyond the appearance. The problem is the 3900 deck surface is larger than the iron head deck surface, Sappy stated some time ago there would also be a quinch area problem among other things. It would be a bad idea even if it would work.

Look at the pictures toward the bottom:

http://www.fiero.nl/forum/Forum2/HTML/080440.html

[geoffinbc]

If you had to make a sheet metal intake to fit 3900 heads to run a carb it would be no harder than doing the same on iron heads. I would use the LIM on the 3900 mill away what you don't need and start welding up some aluminum.

I know a lot of people are still hooked on carbs. I guess they love the head scratching and guess work. But once you "push ok to tune" you will never go back.

[98AmGT]

I sorta had a good mind to make an open plenum intake rather than using long runners. Hell, a buddy of mine suggested what you said.... but do so w/ an electronic Hilborn-like approach. verrry cool,ehh ! Kudos I've heard of a mega-squirt?!? .....is that a stand-alone fuel management?

[geoffinbc]

Yea megasquirt is a stand alone engine management system you can use on pretty much anything if you supply it with the sensor values it needs. Hilborn's would be sick!



That is a mechanical setup, but you can get electronic stuff now.

[BMC]

I don't know if anyone has said this but there are a few miatas out there with the GM 60 degree V6. There are also several Hundred MGB V6 cars out there Mine and Scott's are posted in the garage section of this website.

Here is mine: http://60degreev6.com/forum/garage_v..._vehicle&id=11

I like the idea your going for but most people don't want there car to be down for 1-2 years so your better in most cases to choose an engine that you like and build off that. USe an iron head 3.4L or if you want to spend a little more for custom components and an aftermarket ECU, go for the early 3500 with the long stroke (its a 3.4L with a longer stroke) or blow by all that and go for the 3500/3900 big bore engines and you'll end up needing more components for RWD conversion but you'll end up with something very quick.

This sire is the Source for the 6-60 but when it comes to RWD conversions, it gets a little more difficult to gather intel on some items. For the generic RWD conversion, do a google search for MGB for generic info on MG sites and search for conversions and do a search on MG V6 which will give you a number of sites that have more specifics on RWD conversions. Also, look through the store on this site and others that may have conversion components so you can get an idea of what needs be done such as headers, starter locations, flywheels and so on.

-BMC.

[98AmGT]

I must say that you guys have been a great help so far at mapping out this swap. Thank You ! I will be spending the next couple of months combing through the electronics end of the deal. Theres a lot of options here. Hell, more than I ever thought at first. So far, it seems to me that for all practicality purposes, I should scrounge up a core 3.4 rwd short block and then rebuild it using 3400 pistons. Then top it all off with the 3500 non-vvt upper-end. Also get the computer and wiring harness for the 3500 as well. (I believe the OBDII) I may end up turbocharging that in the future.

[evilmiata]

I can't help you with building a hybrid motor but I might be able to give you pointers on making things fit in your engine bay or stand alone ECU. Here's my Haltech 3.4l.

[98AmGT]

Hey Bud, I LIKE that combo you have. Have you driven it yet since getting it all together?

[98AmGT]

Hey Bud, I LIKE that combo you have. Have you driven it yet since getting it all together? Oh, by the way Happy New Year!

[evilmiata]

No, I haven't driven it yet. I've experienced a ton of setbacks and have had to make a ton of changes. I'm modifying the headers I built and anticipate getting this thing on the road soon.

[BMC]

Evil Miata,

Aren't you the one I sent the Haltech program to that you couldn't get to work? That was a long time ago!!! The MGB that I put together with that is now in someone else's hands. My MGB with the stock PCM is running fine. Not picking on you but respectfully, why not just use the Stock PCM? The power difference was in my opinion minimal but it did gain power. The point is, you could have many thousands of miles on that car of yours by now. I don't recall how many MGB 3.4L L32 cars are running around out there with a completely stock unhacked OBD 1.5 PCM, but enough to put to shame all those who said they were worthless or had to be tuned before use. My car gets between 23-31 MPG depending on the way its driven. Official log book records show 25-27 mpg, no stumbles or weak spots in the acceleration and a generally fun car. On the track, the throttle is plenty of fun, that said, the brakes are pulling but I have HUGE brakes for it next year. I think the brakes on the MGB will rival my S10 brake setup. More brakes than brains? (and tires)

Anyways, thats my rant about using the stock PCM. Every time we get a specialty project like the 3500 in here right now, it means more time down to begin with. In the end, the 3500 is going to be well worth it but if I was going to use a 3.4L in a Miata or another B, you should get it on the road first, then worry about building a wiring harness and ECU for it's upgrade later. You'll be very pleased with the iron head power. If you go for the alloy head, I suspect that the 3.4L PCM has enough maps to run within reason, probably not 100% on, but most guys who do their own tuning usually have a glitch somewhere in the program- its just natural.

-BMC.

[evilmiata]

I don't have a stock computer and my motor has already run with the Haltech. It turns out that I had several other problems besides the computer. For example, did you know that the E6K can't control more than 4 low-impedence fuel injectors? Neither did Haltech. For now, I'm redesigning one of the exhaust manifolds for better clearance around the oil filter. At this point, I'm happy to make even a little bit of progress every other weekend.