dustinb

Hello everyone, I've had my 1990 miata since 2001, and in those 8 years, have gone through 2 stock motors, and am currently running a 97 1.8, and custom T25 turbo setup at 12psi. I have all kinds of crap in the car: AEM EMS, front mount, custom downpipe charge pipes, 94 rear end with torsen, etc etc. I'm happy with the car, but for some reason I want to do a big motor swap on it. It could be that I see the motor just vaporizing itself, where as a stock V8 will be putting out more power and torque then I currently make.

So I'm looking at the possibility of just selling all my junk, and going head first into a v8 swap. I primarily use the car for drag racing at local tracks, and just in general for having fun in. It's off the road from September to April (when I'm in university), so there's a bunch of downtime to do this. I worked in a high end performance shop on the island here for 2 years, and did my own motor swaps, plus many others, so skill and tools aren't an issue. The main issue for me will be finding the parts I need, and the cost of them.

My initial inclination is a 5.0 swap will be the cheapest route, and probably the easiest to find the pieces, as 5.0 Mustangs are a dime a dozen here. It seems though that everyone is LSX crazy, but looking around at motor prices and the kits, the price seems much much higher. Is it really that much better? Can anyone give some figures on how much it cost them to do either swap?

Thanks folks

MRM331

I've built 3 Ford conversions to date and will be starting my 4th shortly. That said, my comments tend to be a little Ford heavy. However, I think I may have some advice to offer you.

From what I have seen, the advantage of using a typical LSx engine is that it will get you, in stock form, almost 200 more crank HP than a stock 1991 or so Mustang 5.0. 5.0's made 225 crank hp, LSx's make around 400. A used LSx is also newer, so you may be able to find one that can be simply "dropped in". Most donor 5.0 engines at this point are going to need at least a mild rebuild.

The advantage of using a Ford engine is cost. While a LSx driveline and computer may cost you $6K or so, donor Mustang engines can be literally picked up for $50. A9L computers go for about $120 on eBay and if you need a new one AutoZone will sell you one for $100. T-5 transmissions go for $100 to $500, the 7.5 rear goes for about $100 and driveshafts can be made for under $400. Additionally, the Ford kit, while it does cost $4,000, includes much more (including instructions) than the available LSx kits (from what I have heard).

So, in short, the advantage of the LSx route is immediate horsepower if you're not into "building" an engine. If you are ok with building the engine and the car, take your $50 mustang block, pick up a set of GT-40 parts from an Explorer for $100, a stroker kit for $1000 or so, a cheap E303 cam on eBay for under $100, put it all together CAREFULLY and you've got nearly the same 400 crank horse power of the LSx. Sorry, like I said, I'm a little biased...

Here's a link to my three completed Ford Builds should you want to see what's involved:
http://www.mccullyracingmotors.com/i...les/builds.htm

Good Luck with your decision,
-Jason McCully

dustinb

Thanks Jason, that's exactly what I was looking for.

MRM331

Glad to help

-Jason

turbotim

What's the weight & balance difference between a typical LSx build and a 5.0 build?

EDIT for the OP: Also, you could possibly run the 5.0 ford with the AEM EMS using their CAS/distributor gizmo and some coil packs. This is what I'm considering. Yeah, you could sell the AEM unit and pick up a stock mustang ECU with lots of change leftover, but it's obviously not as powerful and you could get rid of the MAF.

MRM331

Tim, a OEM version of that entire coil-on-plug system can also be sourced from a early 2000's Ford Explorer. 1996 and up had a distributorless system with two coil packs and the last 6 months or so of the 5.0 Explorer actually had coil-on-plug. I hear the two systems are not completely integrated into the Explorer computer but rather run off their own seperate computer which pluged into the Explorer distributor and coil plugs. Keep in mind this information cam via the Mustang Corral, not eaxactly the best source for reliable information.

Coil Packs:


-Jason

turbotim

Ha! Look at that, that's exactly what I was thinking, 4 wasted spark coils. I figured on using 2 sets of 1.8 coil packs which I have lying around anyway but it's cool there's a ford setup packaged ready to go.

MRM331

Tim, if that's the set-up you want then you may want to try to find an Explorer engine as your starting point. The yard near me will sell the entire engine including everything but exhaust headers and starter for $130. As an added bonus you'd get a set of GT-40 heads and a GT-40 intake with your coils basically for free. If you like I'd be willing to help you pull it if you can wait until the school year is over (you would, of course owe me any hoagie of my choice from the local WaWa as payment...)

-Jason

turbotim

Wow, that's a killer deal and a great offer. I would take you up on that offer if I didn't already have access to this find (see attached). 8.200 deck height aluminum SVO block. It's an old PRI display engine that isn't being used anymore. I'd have to source 4 bolt splayed main caps for it but it's a deal of a lifetime and as such I feel obligated to use it. I need to take advantage of having access to insanely expensive valvetrain parts. I figure the miata chassis can't handle crazy torque, so I might as well make the thing "lazy" down low but be able to rev. 8500rpm seems like a good number.

But if I went V8 I wouldn't be able to use my car as a build jig for turbo kits anymore

sn95

GT-40 iron heads were primarily used on 93 Cobras. Very few, if any, GT-40 iron heads went on Explorers. Every 5.0 Explorer I've ever seen has had GT-40P heads on it. GT-40Ps are arguably better than GT-40s, they have a more efficient combustion chamber (with a different spark plug placement) and the P exhaust port outflows the standard 40 head even though if has smaller exhaust valve. Some header mfgs make a specific P header because of the plug placement. Not all shorties and long tubes will work with P heads; at a minimum you may need to use 90 degree plug boots on some cylinders.

The P is the best unported overall iron production SBF head, it even outflows the 69-70 351 Windsor castings. A fully ported early 351W will ouflow a fully ported P though. Professionally ported with big valves (1.9, 1.6), the P tops out at about 225-230 CFM on the intake around .500 lift. Home porters seem to get 190-210 CFM depending on their skills and whether or not they upsize the valves.

The Explorer lower intake is better than the old 5.0 Mustang lower too but the Explorer cam is not as good as stock 5.0L HO cam. Lots of Fox body guys have hit low 13s/high 12's in 5 speed cars just putting a HO cam, 1.7 roller rockers and shorties on a stock Explorer longblock.

If you want 350+ rwhp, don't waste time with the Explorer heads and intake.

MRM331

I beg to differ about the GT-40 heads on Explorers thing...I've pulled four sets off "Clunkerfied" Explorers in just the last 6 months at our local yard. They are out there and they are plentiful (and they eBay for a nice return).

Yes, more Explorers were equipped with the GT-40p heads and they are a superior head to the plain GT-40's. However, they have two unfortunate downfalls that don't always make them as usable to us as the plain GT-40s. First, they have no EGR passages cast into them. If you have to pass a visual emissions test and you want your older ECU to run code-free you have to have an EGR system. It also helps with mpg's, if that matters to you. Secondly, the spark plug angle on the GT-40p's was designed to maximize combustion which greatly helps with emissions. Unfortunately the spark plug angle does not work with many kinds of shorties, including Monster Miata's kit headers. This is an issue that Martin is aware of and working on I believe.

If EGR capability and fitting to a certain type of header were not a problem than the GT-40p's would be preferable.

As far as the Explorer intakes go no, they are not the best thing since sliced bread. They are, however, the best bang-for-the-buck upgrade you can make in the intake department. My last car had a set of GT-40 irons and an Explorer intake, the whole lot of which I picked up for under $70 at the local yard. other than those heads and intake, a 65 mm Explorer throttle, a 72 mm Thunderbird Mass air tube and 4 extra cubic inches the rest of the engine (including cam) was stock '91 Mustang. That car made almost 250 to the rear wheels when a completely stock Mustang engine would have made maybe 180. I don't think that was a bad return on my $70 investment when you consider that a set of aftermarket heads and an intake could have cost me literally $2000 more and only got me another 40 or so horses.

I'm hoping that the same intake and heads on a 331 stroker bottom end with an E303 cam will get me pretty close to that 350 mark, at least over 300 rwhp. We'll see....

-Jason

sn95

My bad, I've only seen the P heads on Explorers.

No Smog test around me anymore for pre OBD-II cars so visual is not important. After having fought past the EGR tubes to change plugs in my brother's SN95 5.0L for years, it was very nice to rip all of that crap out (including the smog pump). Takes a few minutes to shut off the EGR toggle and Thermatractor toggles in the Ford EEC-IV if you are using an EEC
Tuner, the Moates hardware, SCT hardware or Tweecer RT. (Pretty hard to optimize bolt-ons and a cam if you can't redo the fuel and timing curves in the EEC IV)

The current model FMS shorty is "supposedly" redesigned to work with both regular heads and Ps. You can do a search of Corral.net and find what shorties and longtubes people have gotten to work with Ps.


Agreed, the 40s and 40ps with Explorer lower intake are a great bang for the buck.

You should get over 300rwhp with a 331 stoker; you will also have absolutely incredible low end and midrange torque. My comments on not getting to 350rwp w/Ps and Explorer lower were based on a 302 displacement, not a 331. Here is a good thread which documents numerous Stangbangers getting 300rwhp on P heads:

http://socalhorsepower.com/forum/sho...&threadid=8707

FWIW, the E303 cam is better with P heads than 40 heads due to the higher I/E flow ratio of the P head. The 40 head will work better with a dual pattern cam providing more lift and/or duration to the exhaust while the P head is fine with a single pattern cam like the E303. The TFS Stage 1 cam will work much better with 40 heads than the E303 and is usually available used at very good prices.

MRM331

Thanks for the advice. Martin said last time that I saw him that he "thinks" his headers "may" work with GT-40p's. Since it looks like I could easily unload a set if they don't work to some Mustang guy I may pull a set and see for myself. If they do work with his headers I would much rather use a set of them than the 40's. Maybe the p's advances in combustion chamber design will make up for the EGR when it comes to smog...
Thanks for the food for thought. I'm still going to drop the GT-40's I've had done on when I build but I'm surely going to look into the viability of GT-40p's and Martin's headers and maybe drop a set on later.
-Jason

sn95

Yeah, unfortunately it is hit or miss with P heads and headers. We're putting a set on my brothers SN95 (Pypes shorties, ugggh!) this spring and we won't really know until we get it apart. I'm going to slap the P heads on a spare block on an engine stand and see if I can get the shorties to clear the plugs and plug wires on the stand before I even mess with them in the car.

I think the P head will more than make up for the lack of EGR in terms of mileage. Are using an A9L ECU? Lots left on the table in stock Ford tune and the new Moates Quarterhorse (http://www.moates.net/) has great tuning software (Paul Booth's EEC Editor) and is reasonably priced.

The other easy way to pick up gas mileage in "cruise mode" is to use your wideband to spoof the NB signal to the ECU. You can change the signal parameters for the narrowband signal so that the actual AFR is higher than stoic (e.g., 15.2-15.7) vs the stoic standard of 14.7. This should more than make-up for the lack of EGR.

Mitch

flier129

+1

Whats the weight difference?

chpmnsws6

The world may never know....... too many variables

MRM331

My gut tells me that a "typical" Ford Conversion (with iron heads) MAY be slightly heavier than a "typical" LSx build. However, I've heard of some Ford builds coming in under 2300 pounds and some LSx conversions coming in as heavy as 2700 pounds. I think a good rule of thumb is that any conversion is going to add weight to the car in some area. However, the only real affect of this weight is added stability as the power to weight ratio of even the lowest powered V8 Miata is far higher than that of any stock Miata.

Most V8 conversions seem to come in between 2600 and 2700 pounds after the conversion.

-Jason

chpmnsws6

The block on the ford might way more, but the T56 weighs more then the T5.

Its a wash

waterwellwizard

I have a hard time believing that the difference in weight between a T56 and a T5 is equal (or a wash) to the difference between an aluminum block motor and an iron block motor. How much more can the T56 weigh, over the T5? Maybe so, but I'd have to see that on scales before I could buy into that. One of the reasons that I went with an LS3 motor was the weight factor. Gobs of horsepower (480) and torque (470) was just an added bonus. Just one opinion, Wiz.

chpmnsws6

75 pounds for the T5 and 135 pounds for the T56



If I remember correctly, the iron block 6.0 weighs 70 pounds more then its aluminum 6.0 counterpart.

To make you feel a bit better, the added transmission weight might actually better effect the cars front to rear weight, and defiantly helps its CG

chpmnsws6

Quoted from 427 on LS1tech

mx5.7

To build a nice reliable 5.0 to 400hp would cost about the same as letting gm design it for you. Same thing with a small block chevy.

Meanestmiata

What is CG?

chpmnsws6

Center of Gravity.

rupzuk

On the weight issue...
Why can't a guy use the lighter aluminum LS and a Tremec T600 behind it?
I would think the Tremec would be very close to the weight of a T5.