4.6 Rebuild or Coyote Swap?

[autoxbob]

My 99 SVT Cobra has been in the family since my brother bought it new. He passed and willed it to my son. We autocrossed it and used for a daily driver. Son decided he didn't want to keep it, and I now own it. I plan to keep it for my grand kids.

It has little over 150000 miles on it and six seasons of just-for-fun Autocrossing. Still runs and drives ok, but is scruffy and tired.

I'm planning a restore project. The powertrain is the first stage. There are two basic options for the powertrain:

1) Overhaul and rebuild the 4.6, add a blower to get about 500 HP, rebuild clutch and trans. This is assuming the block, heads, etc. still look good after a tear-down.

2) Swap in a Coyote making 500+ HP, new clutch, trans, and all that goes with it.

I'm not up to doing this myself. I have estimates for the 4.6 rebuild at about $20-25K, and about $30-40k for the Coyote swap.

I expect to continue to Autox and drive no more than 2000 miles per year for about another 10 years.

My main worry about the 4.6 is reliability and maintainability. Will it last another 10 years? 20 years? If it breaks and can't be fixed, the lower initial cost is a bad trade.

What would you do?

 

[bird_dog0347]

Wait, $20-25k for a 4.6 rebuild??? What all is included in that?

 

[01yellercobra]

You need to get a couple more estimates on the 4.6 rebuild. That's way above what I've seen in the past.

JMO, but I'd keep the 4.6 for simplicity sake. And if you're planning on auto crossing I'd stay N/A. Bump the compression. Maybe cams and ported intake. Less hassle on the track.

 

[DSG2003Mach1]

There’s so many mod motors I don’t see them going obsolete for a loooong time.

Source a used blower kit and I think your estimate is… quite high.

 

[2003RedfireVert]

Always Coyote swap in my opinion. I’m Coyote swapping if my terminator engine blows up. Coyote is king.

 

[decipha]

4.6 over the coyote, not worth it to swap

6k is more than enough

 

[robvas]

If you're going blower, why not go 600, 700 if you can get E?

 

[DSG2003Mach1]

If you're going blower, why not go 600, 700 if you can get E?

I had a 10:1 aluminator with mild blower cams and a d1 at 15# made 650 on 93.

It’s easy to get carried away, 500 is plenty fun on the street. That’s what my stock motor made at 10# in a p1.

 

[Dirks9901]

4.6. Not worth the hassle going 5.0 for a fun street car. Honestly, 500-600rwhp is a blast.


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[FIREBALL]

Unless you absolutely feel the need to keep the car for sentimental reasons, I would sell it and find a low mileage 03/04 cobra, cheaper and easier than what your plans are for the 99.-- 03 04 have 400+hp and a t56 transmission. There is a good chance that when your grandkids get old enough they will not be too excited about a 99mustang. I was fortunate to have found a very low mileage 01 cobra that I only put 2k a year on, its got enough power for me. If I had been in your circumstance I would have gone for a low mileage 03-04. Selling your car would make a good down payment on a 03/04

 

[PC03GT]

I'd say give it some good thought as to what your brother would want it to be, and build accordingly. Good luck

 

[robvas]

I had a 10:1 aluminator with mild blower cams and a d1 at 15# made 650 on 93.

It’s easy to get carried away, 500 is plenty fun on the street. That’s what my stock motor made at 10# in a p1.

What was thinking is that if you are rebuilding the motor, you could just do a 400rwhp setup and avoid the blower altogether.

 

[DSG2003Mach1]

What was thinking is that if you are rebuilding the motor, you could just do a 400rwhp setup and avoid the blower altogether.

eh, project shake and bake had 4.56s to not feel gutless down low, the intake and cam setup it had to make high 300s was definitely a high rpm runner. Just depends on what ya want I guess. By the time you buy intake, cams, full exhaust etc... its probably a wash price wise. My P1 numbers were through stock manifolds.

 

[96dreamer]

OP be weary of the internet advice. Not everyone's suggestions are realistic or necessarily in line with your expectations.

Are your goals rwhp or crank?

You mention the clutch and trans are getting replaced/rebuilt in either scenario so the cost is moot since they will bolt up to either motor.

You can rebuild the 4.6 pretty frugally if you choose. The block heads and crank are likely all reusable with little to no work required. Throw a set of boss rods and a budget forged piston and the car will make 600 crank hp all day with no issues. For a long reliable life do billet oil pump gears, the modified secondary tensioner, modified primary tensioners, upgraded timing chain pivot and billet tension side chain guides. The rest is your run of the mill rebuild parts. Any used blower kit will get you to 500rwp reliably.

With the coyote route you have to worry about accessories, exhaust, and how you're going to run it/ incorporate factory electronics. You still need to do the oil pump/ gears on them as well. Also unless you plan on boosting the 5.0 as well you are going to come up short on 500 rwhp

I would not for a second doubt the reliability of the 4.6 over the 5.0. Both are great platforms that will last for years with proper maintenance.

 

[01yellercobra]

A local guy Coyote swapped a fox. He did all the control packs and everything. He was close to 30k into it before the Whipple went on. And he did all the work himself.

 

[DSG2003Mach1]

A local guy Coyote swapped a fox. He did all the control packs and everything. He was close to 30k into it before the Whipple went on. And he did all the work himself.

I mean there's gonna be huge variations between a used junkyard motor up a built one but either way, a shop is gonna put it to ya doing the swap.

 

[5.0 Hatch]

Rebuilt forged 4.6 with any blower will give you more than 500rwhp for the least amount of money.

 

[01yellercobra]

I mean there's gonna be huge variations between a used junkyard motor up a built one but either way, a shop is gonna put it to ya doing the swap.

I was just trying to give an idea. I know it's a stock long block, but I don't know which gen it is.

 

[98 svt]

I'm a purist. So when I had this very same option, I went 4.6

However if it was a 94-95, I would have gone with a new 5.0 (coyote)

 

[Badaz01]

I rebuilt my 4.6 in my 01 cobra. Went with a D1 procharger and swapped in a t56 magnum. Also did the mellings billet oil pump. Had a shop do the work which ran me up to 26k for all. But in the end I wound up with a badass 01 cobra. I’m conservative on my tunes putting 525 down with 93/torco and 570 on e85. I stayed 4.6 because the car came with a 4.6 just my .02