Mach 1 Engine Swap

[99Venom]

So I've done some poking around and it seems popular opinion is that a 2003 mach 1 engine harness will not work in a 99 Cobra. I have a complete mach 1 engine with harness ready for transplant, but I still have my 99 harness. The only visual differences I noticed was the sensor on the mach 1 pcv (which the 99 doesn't have) and the male pins on the main pcm plug were different. However, it looks like the female end of the plug has holes to accept all possible male pins. I just got the motor today so that was all I noticed at quick glance. I'd like to use the mach 1 harness if possible because it's all plugged in and routed. If don't use it than I have to pull the lower intake to unplug the knock sensors.

So what's the verdict, can I use the mach 1 harness? If not, can I simply keep my 99 harness and plug it in?

 

[99Cobra_vert]

Keep your '99 harness and remove the mystery.

 

[99Venom]

Are the lower intake gaskets reusable?

 

[MrBrain]

Are the lower intake gaskets reusable?

I reused mine but that doesn't quite answer the question. The gaskets are good gaskets like on the rest of the motor with proper sealings that looks a bit like a o-ring.

Now when I'm rebuilding I bought new just to be sure, it's such a money pit that the price of the gaskets doesn't matter...

 

[99Venom]

Ok, I'll take the mach 1 harness off and use my original harness, I know that will work and it's easy because the mach motor is out of the car right now.

 

[IUP99snake]

There are a few other differences besides wiring that may or may not be of concern:

Did that motor come out of an automatic car or a manual car? If it was originally paired with an automatic, it'll have a 6-bolt crank instead of the usual 8 bolt crank that's standard with most other 4V motors. If you want to keep a cobra clutch, you'll need to get a 6 bolt, 11" flywheel and install a pilot bearing. Don't worry about it if it came with a manual.

Although your existing manifolds or headers will physically bolt up to the newer heads, they have a different shaped exhaust port. I don't know if the earlier manifolds and headers are port matched or not. I just bought a set of 03 Cobra manifolds for $20 bucks and called it done. You're in luck if your take out motor came with manifolds.

Homer

 

[CJK440]

Make sure there isn't a connector on the lead that goes to the knock sensors. My 97 cobra had a small sub harness that allowed the main harness to be removed without removing the manifold to unplug from the sensors.

 

[99Venom]

There are a few other differences besides wiring that may or may not be of concern:

Did that motor come out of an automatic car or a manual car? If it was originally paired with an automatic, it'll have a 6-bolt crank instead of the usual 8 bolt crank that's standard with most other 4V motors. If you want to keep a cobra clutch, you'll need to get a 6 bolt, 11" flywheel and install a pilot bearing. Don't worry about it if it came with a manual.

Although your existing manifolds or headers will physically bolt up to the newer heads, they have a different shaped exhaust port. I don't know if the earlier manifolds and headers are port matched or not. I just bought a set of 03 Cobra manifolds for $20 bucks and called it done. You're in luck if your take out motor came with manifolds.

Homer

I was on the lookout for that so I got the engine from a manual Mach 1. As far as headers I got JBA shorty headers and already bolted them up (the motor did come with the stock manifolds). The drivers side outlet flange looks off by about 2-3 inches from the stocker, so I hope I can muscle the midpipe to connect to it.

Make sure there isn't a connector on the lead that goes to the knock sensors. My 97 cobra had a small sub harness that allowed the main harness to be removed without removing the manifold to unplug from the sensors.

Good point, I will check that when I get to it. Thanks!

 

[99Venom]

Ok, after a detailed comparison of the 99 cobra harness compared to the 03 mach 1 harness, here is what I've found. It might be good detail for people looking to do this swap.

1) cobra has a coolant level sensor in the bottom of the overflow tank, mach 1 does not. This sensor sets the coolant idiot light on right? If it does than I stopped caring about this sensor long ago.

2) cam position sensor is mounted differently with a slightly different connector, but terminals and wire colors look the same. Doesn't matter because the cobra connector snapped into the mach 1 sensor with no issue.

3) mach 1 has heated pcv, cobra does not. Shouldn't matter since my pcm doesn't think there is a heated pcv in this car.

4) mach 1 master plug that goes to the pcm has (1) more male pin than the 99 (for the pcv maybe?). I don't think it should cause any issue.

*) from what I can tell the fuel injectors are the same, can anyone confirm this?

Everything else matches perfectly. I dug around and it looks like I'd have to remove the lower intake to unplug the knock sensors and swap the cobra harness in. After looking over the wiring I should be fine with the mach 1 harness so I'll leave it on and drop the motor in tomorrow. If there is a problem the harness it can easily be swapped with the motor installed.

 

[99Venom]

I've had a hell of time getting the mach 1 engine to mate with my T45. I can get it the input shaft through the clutch but that last push into the pilot bearing has been giving me headaches. Just to make sure something stupid isn't going on here, can someone please verify that the T45 and 3650 have the exact same input shaft??? I know they have the same splines.

 

[Michaelslilgray]

it sounds like the input shaft is hanging on the pilot... if its only missing by half an inch or so, try putting some lubricant on it and slowly walking it down from side to side... either by hand or by bolt. Be extremely careful not to damage anything with the bolt walking technique... and most wont advise doing so.

 

[RX1Cobra]

Pretty sure the Mach harness is different at the mass air too. Mach had integrated iat and the cobra has a separate one.

 

[99Venom]

it sounds like the input shaft is hanging on the pilot... if its only missing by half an inch or so, try putting some lubricant on it and slowly walking it down from side to side... either by hand or by bolt. Be extremely careful not to damage anything with the bolt walking technique... and most wont advise doing so.

I finally got it by having a buddy lift the tranny while I whacked the output shaft with a rubber mallet, it went in slowly but it finally seated all the way. Damn, the past 2 times I've done this I never such a hard time with the pilot bearing.

Pretty sure the Mach harness is different at the mass air too. Mach had integrated iat and the cobra has a separate one.

The mach motor only came with the throttle body, so I still have my IAT sensor, MAF and intake with my stock 99 harness.

 

[na svt]

early exh manifolds will work on 03/04 heads.

 

[99Venom]

UPDATE: Swap is done! I ended up using my complete 99 harness to be safe. I didn't want to route that whole harness and go to start it up only to realize the mach 1 harness wouldn't work. But I still think it would.

After buttoning up a coolant leak everything seems to be running great, I even drove it 45 miles to work this morning with no issues.

Very easy swap to do. I'm still breaking in the clutch but even being gentle with it, the midrange torque of the 03 heads is definitely noticeable over my 99 C heads. I didn't swap my cobra cams yet, that will come later.

 

[na svt]

the midrange torque of the 03 heads is definitely noticeable over my 99 C heads. I didn't swap my cobra cams yet, that will come later.

The additional mid range power is due to the Mach cams, not the heads.

 

[99Venom]

The additional mid range power is due to the Mach cams, not the heads.

That's kinda what I meant, the mach 1 cams in the mach 1 heads is the way I kept it.