Godzilla 7.3L Swapped Cobra

[jbmatth]

Well it has been a very long time since I've posted in here but thought I'd share my Godzilla 7.3L swapped Cobra. A little background, I've owned this car since I was 24 for almost 12 years now. It is a B&B that was built in 2001, it had a pretty sad 351w and T-5 trans. Here is a photo to get some attention before a lot of writing:


Through the years I've upgraded the brakes to 11" disks all the way around, QA1 coilovers, tubular control arms, 9" axle with 3.70:1 gears, re-wired the engine and dash area, replaced the dash and seat vinyl, replaced the trans 2 times due to breaking 3rd once and 2nd once.

I tried to breath a little more power in the engine by getting it rebuild 3 years ago and after 2 failed attempts the 3rd time was a charm but still only dyno'd 296 hp at the flywheel. I didn't want to spend too much on the rebuilds so just new bearings, seal, gaskets, and a bigger cam with new lifters. First engine only ran 20 minutes total before realizing the crank bearings were .010" too big. Yep I didn't even use plasti-gauge, shame on me. Took it to a small local shop, it lasted 700 miles when I whipped out a cam lobe and bent and broke a pushrod. The third rebuild was by a well known shop and switched to a roller cam but being cheap I kept the iron heads and just had them ported.

No, 296 hp wasn't going to cut it and the Godzilla had just been announced. I waited for a while until more aftermarket support was available and didn't have to do as much development on my own. Then early last year I found out Mast Motorsports was offering a mildly built Godzilla with controls and wiring for at the time $14k with an estimated 500-550 hp. It had forged rods and pistons, a few cam offerings, CNC heads, and was ready to install. I put my order in with them in early April of '21, and the wait began, and continued, and continued and eventually I got to pick out the CAM and saw some dyno numbers. I was stoked by the results on pump gas no less, what do ya'll think:


I made the trip down and picked it up, they have a very cool facility and I got to see some very cool stuff. Got it home and unloaded where I'd already pulled the old 351w and T-5, it was ready for the new engine and TKX full kit I'd picked up from Silversport Trans:


Here is a comparison of the T-5 to the TKX:


I got started test fitting the new engine and building engine mounts:


More to come,
JB

[jbmatth]

I built the headers from 304ss to mate up to the existing side pipes but needed new flanges on them, all 2" mandrel bends tig welded by me, my first set of headers and it took WAY longer than I expected but I can live with the results:


After exhaust I started on the fuel system, I'm running all -8 AN from a new tank mounted pump to and from the tank:


I put the crankshaft centerline back in the same place as the 351w but with the Godzilla pan being so much deeper it just wasn't going to work, 417 Motorsports built a pan 2-1/8" shallower but required a remote oil filter, after MANY iterations this is what I was forced to live with:


This is when I set the car on the ground and discovered I now only had 3.5" of ground clearance under the pan whereas I'd had around 5" before:


Knowing this wasn't going to work I knew the only intake option available short enough was a DCE intake, in the process of ordering that I discovered the throttle body wasn't a factory Godzilla TB at 80mm, but was an LSA TB at 87mm and a different mounting bolt hole spacing, I talked to MAST and they informed me I'd also need an LS MAP sensor both of which would mean sending the parts to DCE to have a one off intake made for my needs. I pulled my old one off and had a look at the head porting, so pretty:


More to come,
JB

[jbmatth]

I should have shown this before, but look at the size difference in the new headers to the old:


Somewhere along the lines I made an alternator bracket to mount a spare Chevy truck alternator I had laying around, I'm on revision 3 of the tensioner now but this will give you the idea of what worked out:


So now the engine will have LS throttle body, MAP, coils, throttle pedal, alternator, and Ford cam, crank, oil pressure, and coolant temp sensors. I'll also have an oil pressure and coolant temp sensor for the gauges in the car. During all of this I also ordered my new wheels and tires, wheels are American Racing VN427's, rears are 305/40-18's on 11" wide rims, fronts are 245's:


Going from 255's in the rear to 305 Nitto 555's should really help out with traction when I more than doubled the power:


Sadly I'm pretty much in a waiting game now the harness and computer still haven't arrived after being told it would be here a few times "in a few days", time will tell. I do have a set of very nice valve covers on order that should arrive next week, something like this but a little more fitting for my car:


I've left a ton of small stuff out, but I'm really excited about where I am now and really looking forward to getting the intake in here in a few weeks as well as the harness at some point. So if you have any questions please feel free to ask, this has been a long time dream to build a fun new engine for the car and never thought I'd spend this much on the entire swap but here I am and really looking forward to driving it this summer.

JB

[patrickt]

Excellent. Spectacular post.

[eschaider]

Very nice work!

Did you weigh the engine as you intended to dress it out for your car?
.
.

[jbmatth]

Originally Posted by patrickt

Excellent. Spectacular post.

Thank you sir, it has been fun playing with errr working on this thing again.

Originally Posted by eschaider

Very nice work!

Did you weigh the engine as you intended to dress it out for your car?
.
.

I sure did, the 351w from clutch to intake with all accessories was 559 lbs, the Godzilla dressed the same way was 618.8 lbs, both with no fluids other than residuals after draining. The new intake will likely weigh more than the old so say 70 lbs total for the engine side. The TKX is 40 lbs more than the T-5 so a total of 110 lbs more there. I don't think with the boost in power it'll be a big deal though.

JB

[Tom Wells]

From my 1981 Mercury Zephyr wagon with the 557:



If the 7.3 had been available 12 or so years ago, I may have chosen it over the 385-series.

Good work on the Cobra! And if you could provide a short example of its sound, that would be delightful!

Tom

[jbmatth]

Originally Posted by Tom Wells

From my 1981 Mercury Zephyr wagon with the 557:



If the 7.3 had been available 12 or so years ago, I may have chosen it over the 385-series.

Good work on the Cobra! And if you could provide a short example of its sound, that would be delightful!

Tom

Tom,
Very fitting plate, I picked mine up about 11 years ago and still holds true to this day, but could be much worse.

I was over the moon when they came out with the 7.3, I couldn't see spending the money for a built FE or SBF when I'd be deep into it and only marginally more power than the LS stuff I've worked with. I also couldn't bring myself to putting an LS in it as it just didn't seem right. The Mod motors or Coyote would have been nice but I seriously doubt they would have fit.

The best clip I can get is on Mast's IG page, they still haven't given me the harness so I haven't even heard it run in person:
Mast dyno test

Here it is when they displayed it at Holley's Ford Intergalactic Fest:
Mast Display Video

JB

[Tom Wells]

JB,

Pure music! It will be interesting to hear it once it's in the Cobra. The new headers and sidepipes will probably give it a little more bass which should be a fine enhancement.

You are doing an enviable project.

Tom

[jbmatth]

Originally Posted by Tom Wells

JB,

Pure music! It will be interesting to hear it once it's in the Cobra. The new headers and sidepipes will probably give it a little more bass which should be a fine enhancement.

You are doing an enviable project.

Tom

Thank you sir, I'm sure looking forward to hearing it rumble to life, I might just shed a tear not gonna lie. I believe the side pipes will give it a very good sound, I mean the 351w even sounded mean with under 300 hp.

I hope to see more of these swapped in Cobra's, there are only 2 others I'm aware of and those were done by professional builders. I'm just a guy in an old barn with no insulation, but I do have a lift and a lot of toys...tools so that helps.

JB

[eschaider]

Originally Posted by jbmatth

Thank you sir, it has been fun playing with errr working on this thing again.



I sure did, the 351w from clutch to intake with all accessories was 559 lbs, the Godzilla dressed the same way was 618.8 lbs, both with no fluids other than residuals after draining. The new intake will likely weigh more than the old so say 70 lbs total for the engine side. The TKX is 40 lbs more than the T-5 so a total of 110 lbs more there. I don't think with the boost in power it'll be a big deal though.

JB

That's waaaaay impressive JB.

When you think about it, today we can produce boatloads of power compared to the cars back in the day and it is delivered in a well mannered, reliable engine package. Your car will be very enjoyable to drive and reliable to boot.

Killer job and great pick in your engine selection..

[Grubby]

The dyno power curves are WOW. That car should be fun when you push the pedal down and I would expect drivability to be nearly the same as the 300hp Windsor.

I am curious to see your follow-on post when you drive it.

John

[RUFdriver]

Awesomeness post! I will enjoy following your progress. UCC, here in Texas , is also working on a Godzilla build.

[jbmatth]

Originally Posted by eschaider

That's waaaaay impressive JB.

When you think about it, today we can produce boatloads of power compared to the cars back in the day and it is delivered in a well mannered, reliable engine package. Your car will be very enjoyable to drive and reliable to boot.

Killer job and great pick in your engine selection..

eschaider,
Thank you for the compliments, but I'm just working on it one piece at a time and hoping for the best in the end. It is really impressive what we get from the factory right now, the heads on this engine flow 300 cfm at .600" and the CNC port job only nets 340. I've seen the stock engine make over 1,000 with forced induction, which is nothing new for the LS crowd, but great for how few of these are out there. I hope to be able to idle in traffic and not hate the experience, well other than the heat.

Originally Posted by Grubby

The dyno power curves are WOW. That car should be fun when you push the pedal down and I would expect drivability to be nearly the same as the 300hp Windsor.

I am curious to see your follow-on post when you drive it.

John

Grubby, no joke right, 450 lb-ft of torque at 2,500 rpm will be very interesting. Something I should have mentioned is that the engine as dyno'd was limited to around 6,300 RPM due to the intake being too restrictive. There were 3 other cams bigger than the one I chose that would have LOVED more RPM, but I chose a more street friendly cam. It is intake duration 232 exhaust duration 246 intake lift .648 exhaust lift 658 with 112+0 LSA. The roller cam I had in the 351W was actually pretty rowdy and didn't like to idle in gear without bucking like a wild bronco.

Originally Posted by RUFdriver

Awesomeness post! I will enjoy following your progress. UCC, here in Texas , is also working on a Godzilla build.

RUFdriver, I'll keep ya'll informed but don't really have much to report until the last few parts arrive, mainly the harness and controller. I would love to see another of these in person, just to see what others are doing to solve some of the problems I've faced.

JB

[Mark O'Neal]

To quote Doc Brown - "When this thing gets up to 88 mph you're going to see some ****."

[saki302]

I normally don't like live axles in cobras, but in your case, I think you need it for the rear end to live!

What a monster of a motor....

[jbmatth]

Originally Posted by Mark O'Neal

To quote Doc Brown - "When this thing gets up to 88 mph you're going to see some ****."

Mark,
You are certainly right brother, it should be a heck of a ride and hopefully I won't be spinning the tires when I get to 88.

Originally Posted by saki302

I normally don't like live axles in cobras, but in your case, I think you need it for the rear end to live!

What a monster of a motor....

saki302, I'd considered trying to go IRS when I upgraded the old 8.8" to the 9" but just couldn't find a way to do it what was in my skillset at the time. I could probably make it happen now but really don't want to deal with it at this point. I don't track my car and have only tried autocross once, but may give it a shot again if I find one close. I wouldn't mind a little more comfort though even if the car will never be comfortable.

JB

[jbmatth]

My new valve covers arrived yesterday from Swiftek Engineering out of Australia, what do ya'll think:


I'm supremely impressed with them, the fit and finish is top notch, and the customer service is the best I've ever experienced bar none:


The only problem is they were built for the Godzilla coils and the coils supplied by Mast are LS based coils so naturally they don't fit, I thought I'd be able to make it work easy enough, but it'll be a bit more complicated than I'd planned. I tried three different types of LS coils I had on hand and even the best fit is still not going to work/look how I want. The Ford coils use a different connector and 1 less pin than the LS coils. This is "fun"

Keep Moving Forward,
JB

[Mark O'Neal]

Originally Posted by saki302

I normally don't like live axles in cobras, but in your case, I think you need it for the rear end to live!

What a monster of a motor....

I loved mine.

[saki302]

I had a live axle in my old FFR. Biggest difference was in ride quality. The superformance IRS is worlds better.

Raw handling (when the road is smooth), the live axle was fine.

It's not something you'll miss until you have it though.

The live axle I had was a 3 link with panhard bar. With swaybars front and rear and power steering, it handled like a go kart ��

The superformance with IRS is smoother despite my fairly high spring stiffness. The manual rack is much less twitchy on the freeway, though I do miss power when on a track (great workout though).