07 grand marquis 4.6 into 04gt ?s

Itsnothin

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Apr 15, 2021
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Like the title states this is the swap I am about to do since my 4.6 has bit the dust and I only have a few questions.

I know the intake doesn't have to be taken off (just the TB/plenum needs to be swapped) but the one that came on this engine is cracked so I'll be using the one I already have, with this in mind do I buy intake gaskets based on the 07 grand marquis or the mustang since thats the intake I'll be using?

As far as seals such as rear main, etc are they all interchangeable on 2v Romeo blocks or will I have to get the seals specifically for the grand marquis and not mustang?

My last question would be about the valve covers, I did a lot of research and I'm assuming since it's a Romeo block I can swap my mustangs valve covers onto the grand marquis 4.6. Is that right?
 
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wmburns

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The long blocks are the SAME. Therefore the motor gaskets are the same. But just for your own piece of mind try this. Look up the part on Rock Auto by make, model, and year. Compare the part numbers pulled up between the two model year combinations. Are they the same?

But you may find that the 07 Grand Marquis does not have an ECT temperature boss on the intake cross over. Some do, Some don't. If yours does not then the intake swap is actually a good thing for you.

Yes you can swap the value covers.

TIP. the Grand Marquis has slightly different wiring harness routing than the Mustang. There are wiring harness stand offs on the outside edge of the valve covers. I found out the hard way that I should have removed and swapped to the no stand off versions used by the Mustang.

Note, the Grand Marquis from that model year will have a CHT and a knock sensor that the Mustang does not use. Either remove the unused sensors or just don't reattach them.
 
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7991LXnSHO

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Now if @wmburns can also tell us the cheap way to make another 40hp on the 07 4.6, that would really be awesome. Dual exhaust and a computer swap for 10 Hp, then gears is a lot of money for the limited benefit.
 

Itsnothin

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Now if @wmburns can also tell us the cheap way to make another 40hp on the 07 4.6, that would really be awesome. Dual exhaust and a computer swap for 10 Hp, then gears is a lot of money for the limited benefit.
Lol I'd pay for that info but I already know the answer to that question, get some giggle juice and even still, that's not cheap lol... The 2v has expensive taste, gotta spend $$ if you want her to put out lol.

My next plan is to drop in a built 2v from mmr (if they're still good, it's been a min since I've checked) my last gt had 3.73s, magnaflow xpipe, magnapacks, cai, and a tune. It felt quicker but I complained more about the gas than anything lol. For the price of all of that I could've just gotten some trickflow heads.
 

Itsnothin

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Apr 15, 2021
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The long blocks are the SAME. Therefore the motor gaskets are the same. But just for your own piece of mind try this. Look up the part on Rock Auto by make, model, and year. Compare the part numbers pulled up between the two model year combinations. Are they the same?

Thanks for your response, I did check the part numbers for the intake gasket and it was different so I just said eff it and bought the seals for the GM

But you may find that the 07 Grand Marquis does not have an ECT temperature boss on the intake cross over. Some do, Some don't. If yours does not then the intake swap is actually a good thing for you.
Can you elaborate a little more on the intake swap? Where do I find the ECT temp boss thing to know for sure and if it does im guessing that I'll need an intake manifold for a GM?
Yes you can swap the value covers.

TIP. the Grand Marquis has slightly different wiring harness routing than the Mustang. There are wiring harness stand offs on the outside edge of the valve covers. I found out the hard way that I should have removed and swapped to the no stand off versions used by the Mustang.

Awesome, so because I'm using the mustang valve covers I don't have to worry about this right?
Note, the Grand Marquis from that model year will have a CHT and a knock sensor that the Mustang does not use. Either remove the unused sensors or just don't reattach them.

Noted
 

wmburns

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Can you elaborate a little more on the intake swap? Where do I find the ECT temp boss thing to know for sure and if it does im guessing that I'll need an intake manifold for a GM?
The GM doesn't use an ECT (engine coolant temperature). It uses a CHT (cylinder head temperature) sensor instead.

The Mustang GT uses an ECT and does not use a CHT.

If you were to purchase an intake manifold for a late model GM you MIGHT find the spot for the boss where the ECT is drilled and tapped is NOT be present.

Since the Mustang does use an ECT then what ever replacement intake is used also needs an ECT.

Bottom line. You need to match the ELECTRICAL requirements of the original car. The car's computer is expecting to see the sensors it was born with. The PCM doesn't know (and shouldn't care) that the long block from an 07 GM has been used. Which if all of the electrical wiring and sensors are in place will be true.

I have been asked in other threads about the late model GM and the ECT. The question is "why not just drill and tap the cross over for the an ECT sensor". The problem here is that the extra metal that forms the BOSS has been removed from the casting. Therefore if you were to attempt this, it's likely that there isn't enough metal to support drilling and tapping.

Don't over think this. If you compare side by side the two intake manifolds it will be obvious which manifold has an ECT sensor and which does not.

OBTW, I have done this swap. The motor currently in my 2000 GT originally came from a 2003 Grand Marquis. Since I have over 100K miles on the swapped motor, by an measure the job has to be considered a "success". In fact I have put so many miles on the swapped motor I have had to replace the timing set.
 
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Itsnothin

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Apr 15, 2021
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The GM doesn't use an ECT (engine coolant temperature). It uses a CHT (cylinder head temperature) sensor instead.

The Mustang GT uses an ECT and does not use a CHT.

If you were to purchase an intake manifold for a late model GM you MIGHT find the spot for the boss where the ECT is drilled and tapped is NOT be present.

Since the Mustang does use an ECT then what ever replacement intake is used also needs an ECT.

Bottom line. You need to match the ELECTRICAL requirements of the original car. The car's computer is expecting to see the sensors it was born with. The PCM doesn't know (and shouldn't care) that the long block from an 07 GM has been used. Which if all of the electrical wiring and sensors are in place will be true.

I have been asked in other threads about the late model GM and the ECT. The question is "why not just drill and tap the cross over for the an ECT sensor". The problem here is that the extra metal that forms the BOSS has been removed from the casting. Therefore if you were to attempt this, it's likely that there isn't enough metal to support drilling and tapping.

Don't over think this. If you compare side by side the two intake manifolds it will be obvious which manifold has an ECT sensor and which does not.

OBTW, I have done this swap. The motor currently in my 2000 GT originally came from a 2003 Grand Marquis. Since I have over 100K miles on the swapped motor, by an measure the job has to be considered a "success". In fact I have put so many miles on the swapped motor I have had to replace the timing set.
Thank you so much your input was invaluable, and I totally understand what you mean now, I'm using my original intake from the mustang and after reading your previous message I went to the shop to compare what was on the GM engine and the intakes look exactly the same. Everything was swapped over to the GM block and I literally couldn't tell the difference in how it looked compared to the engine we just took out.

Just have to finish sorting out the connections on the harness and you were definitely right when you said the mustang standoffs are better lol. My engine had flexfuel so the rails and injectors were swapped to the new block as well and I was lucky to not have to swap the oil pan because it cleared the kmember so now it's mounted in the bay and we'll be mounting the trans and she should be good to go.

20210501_151622_HDR.jpg


(I know my girl looks rough, we've seen better days lol)

I bought the GM engine with 110k on it, I couldn't pass it up at only $400 from lkq and I'm sure I can get another 75k easy lol (maybe more, I don't drive it hard) and despite the mileage the engine was extremely clean when we popped the valve covers off. (Not that I had any reservations about that, I've purchased engines from them before and never had any issues) I'm just mad I didn't take a pic
 

Itsnothin

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Apr 15, 2021
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New Orleans, La.
The GM doesn't use an ECT (engine coolant temperature). It uses a CHT (cylinder head temperature) sensor instead.

The Mustang GT uses an ECT and does not use a CHT.

If you were to purchase an intake manifold for a late model GM you MIGHT find the spot for the boss where the ECT is drilled and tapped is NOT be present.

Since the Mustang does use an ECT then what ever replacement intake is used also needs an ECT.

Bottom line. You need to match the ELECTRICAL requirements of the original car. The car's computer is expecting to see the sensors it was born with. The PCM doesn't know (and shouldn't care) that the long block from an 07 GM has been used. Which if all of the electrical wiring and sensors are in place will be true.

I have been asked in other threads about the late model GM and the ECT. The question is "why not just drill and tap the cross over for the an ECT sensor". The problem here is that the extra metal that forms the BOSS has been removed from the casting. Therefore if you were to attempt this, it's likely that there isn't enough metal to support drilling and tapping.

Don't over think this. If you compare side by side the two intake manifolds it will be obvious which manifold has an ECT sensor and which does not.

OBTW, I have done this swap. The motor currently in my 2000 GT originally came from a 2003 Grand Marquis. Since I have over 100K miles on the swapped motor, by an measure the job has to be considered a "success". In fact I have put so many miles on the swapped motor I have had to replace the timing set.

Hey I have a quick question, I def made a mistake with my swap lol. Along with the engine I replaced the transmission too and going off of various forums I read claimed that 99-04 gt's came with the 4r70w. I did see some people say that the 04s came with the 4r75w but I couldn't find anything definitive and I'm kicking myself for not simply calling up my local Ford and confirming what came in my car, which is the 4r75w.

So with that out of the way I'm sure you can guess what problem I'm having. Speedo isn't reading the proper speed, I have a handheld diablosport that's locked to my old mustang that was totalled and I was unable to unmarry it but that's fine as I only use it for live diagnostics and trouble codes. The tuner also showed that the PCM isn't reading the correct speed as well (which is under 10mph, eventhough I'm doing 30mph, which was verified by one of those roadside "your speed" things. That would explain why the needle isn't moving and the car won't shift on it's own out of first, I can manually shift it to second.

So my question is this, would the solution to my problem be either:

1. Find an ECU (or pcm, don't know the proper term but I know what it is) from a 99-03

2. Pay to get my tuner unlocked and change the value that's needed to correctly read the speed being sent from the transmission.

3. Get another 4r75w. I actually know of a good deal on one but I'm not trying to stomach the cost of buying and swapping another transmission out along with trying to find a buyer for the one I have, buying new seals, fluid, etc lol
 

wmburns

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Do you still have the old transmission?

I suspect that the number of teeth for the OSS sensor is different between the two transmissions.

How to find out? Remove the OSS speed sensor and count the number of teeth seen through the hole.
 

Itsnothin

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Apr 15, 2021
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Do you still have the old transmission?

I suspect that the number of teeth for the OSS sensor is different between the two transmissions.

How to find out? Remove the OSS speed sensor and count the number of teeth seen through the hole.

Unfortunately I do not have the old transmission anymore, I was able to find out exactly which transmission came in my car when I called Ford and gave them my vin number. At this point I think I'm going to just order a pcm from a 03 as it seems to be the easiest way to fix the issue. I was quoted $700 locally to get it tuned which is insane lol.
 

wmburns

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At this point I think I'm going to just order a pcm from a 03 as it seems to be the easiest way to fix the issue.
I would like to discourage you from swapping PCM in the strongest terms. This goes even more when the model year of the PCM is different from the original MY. There are differences between the model years making it difficult to predict the problems.

IF this is a PCM programming issue to "adjust" for the different number of OSS teeth THEN this same reprogramming is available on your existing PCM.

Swapping PCM's is rarely a simple operation. In general swapping a PCM creates more problems than it solves. Only swap PCM's when it's confirmed that the PCM is bad.

It would help things IF you confirmed that this problem is a speedometer calibration problem. If true there will be a math relationship between actual and displayed speed. How to tell? Record the speedometer at various known speeds. Put this into a table. If this is a simple ratio re-programming issue then the ratio between reported and actual speed will be the same.
 

Itsnothin

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Apr 15, 2021
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New Orleans, La.
I would like to discourage you from swapping PCM in the strongest terms. This goes even more when the model year of the PCM is different from the original MY. There are differences between the model years making it difficult to predict the problems.

IF this is a PCM programming issue to "adjust" for the different number of OSS teeth THEN this same reprogramming is available on your existing PCM.

Swapping PCM's is rarely a simple operation. In general swapping a PCM creates more problems than it solves. Only swap PCM's when it's confirmed that the PCM is bad.

It would help things IF you confirmed that this problem is a speedometer calibration problem.
If true there will be a math relationship between actual and displayed speed. How to tell? Record the speedometer at various known speeds. Put this into a table. If this is a simple ratio re-programming issue then the ratio between reported and actual speed will be the same.


This is what I've been testing while I wait for another tuner to get back to me. The needle won't hit 10mph until I'm @ about 40mph. It moves a little bit for lesser speeds but I can't really test for anything higher than that because I can't shift the transmission into 3rd manually but so far it's the only thing that makes sense. The speed reading on my tuner shows 10mph as well when I'm doing 40. Literally a factor of x4 (or 4x less?)

As far as swapping out the pcm I guess that's out as well but I wouldn't think there would be much of a difference between the 03 and 04 (beside the trans lol)
 
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