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Comano

3.0 Heads over 2.5 engine

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Hello Terry,

 

I found out that both cylinder heads of my 95 2.5 got "spongy" (dont ask me how or why, but they have huge sections of bubbles in their bodies) and both of them need to be replaced since they started to leak water to the oil, I'm having a hard time locating used ones in good shape in order to be repaired and used in my engine.

 

Before starting a new line of searching, I was wondering if the 3.0 heads would be a replacement without modifications; the idea is to use the 3.0 heads over the 2.5 engine and attaching the 2.5 lower and upper intake manifolds to avoid making modifications.

 

Would this be a valid setup? would they be just a bolt on? the idea is not gain power, the idea is just to get the engine back to work and to work fine again.

 

Thank you and regards.

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The larger combustion chambers on the 3L heads would need to be filled and machined to match the cylinder deck. Otherwise the fire ring on the head gasket won't be able to seal. Plus, the 3L has larger valves. The 3L head also has oil drain that would need to be filled and sealed. The 2.5L block is missing the rear drain.

 

I would just keep looking for 2.5L heads.

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Hello Spridget,

 

Points taken, I'll keep looking.Thank you for the explanation.

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Hello,

 

I am analyzing another path; if my wife doesn't find out.... I can get a good Escape engine not very costly (around 1200 USD), for not making so much changes into the car, I think of using the 2.5 lower and upper intakes instead of the 3.0 ones.

 

Would the exausts and intakes would bolt on witout modification into the 3.0 block? Also, I believe a tune would be good even when I am not planing to use it for performance, right?

 

Thank you for your patience.

Edited by Comano

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The Escape 3L block will not require modification to attach intake and exhaust. You will need to shave a couple small "nubs" off the block to fit the alternator bracket.

I believe the Escape lower intake manifold is slightly taller than the 2.5L and Taurus 3L engines. The upper intake manifold may contact the hood and prevent it from closing. A Taurus LIM would fit and prevent that contact.

If you increase the engine displacement, you need a tune. The stock computer programming is not designed to account for a major change. Even if you don't tune for high performance, you should tune for efficient and reliable performance.

Edit:
I missed the part where you said you would use the 2.5L intakes. They will fit. You may need to use the 2.5L cam covers to reuse the 2.5L ignition coil bracket and maintain the factory PCV system. 2.5L intakes are not the best option for maximum performance, but they will fit and retain the factory appearance.

 

Brain fart... disregard

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I dont know what I was thinking.... the 2.5L intakes will not fit the 3L heads without modifying the heads or using an adapater. Neither are very good ideas. You would be better off making the 3L intakes fit under the hood than adapting the 2.5L intake to the 3L heads. You can swap the Escape lower intake with a Taurus / Sable lower intake for better hood clearance.

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Your correct Spridget, much work needs to be done to either do 3L heads on a 2.5 or 2.5L heads on a 3L. Anyway you look at it, it is not really good to do. That does not mean it hasn't been done, several people have done those just because of the challenge but they also have had mixed results up to and including destruction of the engine.

 

AF

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So if I have a 2.5 non SVT CDW27, and desire to install a replacement (read larger) V6, is there a particular engine that would NOT require changing out the heads, yet still provide the necessary hood clearance?

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Hello,

 

Returning to this, and to start making a checklist just to request an initial quote, in case that good 2.5 heads don't show up.

 

What it is needed:

 

  • Escape engine
    • Shave the nubs
  • Upper and Lower Intakes from Sable Engine ==> if I understood correctly, if I use just the LIM from the Sable I can use the 2.5 UIM, please confirm.
  • ECU Tune
  • 2.5 Fuel rail & injectors? ==> this is a 95 model
  • 2.5 valve covers? ==> The idea is to keep the sock coil pack and the same plug wires

Regards

Edited by Comano

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I know someone selling good 2.5 sVT heads. PM me

 

Hello, thank you for your offer, I already investigated that option; buying them in the US; the heads plus the shipping costs to Mexico would end up to be the same as the cost of the Escape engine I already located.

Edited by Comano

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Hello,

 

Returning to this, and to start making a checklist just to request an initial quote, in case that good 2.5 heads don't show up.

 

What it is needed:

 

  • Escape engine
    • Shave the nubs
  • Upper and Lower Intakes from Sable Engine ==> if I understood correctly, if I use just the LIM from the Sable I can use the 2.5 UIM, please confirm.
  • ECU Tune
  • 2.5 Fuel rail & injectors? ==> this is a 95 model
  • 2.5 valve covers? ==> The idea is to keep the sock coil pack and the same plug wires
Regards

The year model throws another wrench in the gears. '95 V6s used vacuum to control IMRC. All later models were electronically controlled and operated via a cable. I believe the '95s are also OBD1 which can make tuning difficult. I know it has been done but I don't know all the details.

 

If you choose the Escape engine, keep it complete. Only thing to change would be the LIM from a Taurus/Sable for hood clearance. You can find more info about this swap on the Cougar forums where the Escape swap was more common. Using the Escape engine saves you from the hassle of of the upper engine mount and front cover. You still need to swap exhaust manifolds and alternator. Wiring the fuel injectors may be a problem, or use earlier injectors from a '96-97 Taurus/Sable that will match the engine size and the '95 Contour wiring.

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So if I have a 2.5 non SVT CDW27, and desire to install a replacement (read larger) V6, is there a particular engine that would NOT require changing out the heads, yet still provide the necessary hood clearance?

 

Taurus / Sable engines are the most cost effective. They require modifying the upper engine mount bracket to fit, or removal of a head to fit. The front cover from the contour must be swapped over.

 

The Escape engine tend to cost much more. They do not require modification to the upper mount as it is shared with the CDW27. The front cover is also compatible. The LIM is taller which can prevent hood clearance. Taurus / Sable LIMs are cheap and I often see them on eBay.

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The year model throws another wrench in the gears. '95 V6s used vacuum to control IMRC. All later models were electronically controlled and operated via a cable. I believe the '95s are also OBD1 which can make tuning difficult. I know it has been done but I don't know all the details.

 

If you choose the Escape engine, keep it complete. Only thing to change would be the LIM from a Taurus/Sable for hood clearance. You can find more info about this swap on the Cougar forums where the Escape swap was more common. Using the Escape engine saves you from the hassle of of the upper engine mount and front cover. You still need to swap exhaust manifolds and alternator. Wiring the fuel injectors may be a problem, or use earlier injectors from a '96-97 Taurus/Sable that will match the engine size and the '95 Contour wiring.

 

Hello Spridget,

 

You are right about the OBD1, and about the secondaries, the 2.5 is vacuum operated, so there is no control for it from the ECU; the Escape 3.0 is an oval port with no secondaries, so, no control available for the ECU, this make me think that there shouldn't be a problem since both doesn't have this control, what do you think?

 

About the vacuum lines over the UIM, this is my next observation, does the Taurus/Sable UIM has ports to connect them? or where they will need to be attached?

 

I found pictures from the 2.5 injectors and the 96 Taurus ones, they seem that they have the same port, I hope they use the same polarity.

 

With this, the list would be as:

 

  • Escape engine (Shave the nubs)
  • Upper and Lower Intakes from Sable/Taurus
  • Tarurus 96/97 injectors
  • 2.5 valve covers? ==> needed to check the compatibility at least the rear due the UIM and the coilpack.
  • ECU Tune

Thank you for the tip, I will check the New Cougar forum more, I saw some info there but since my model is a 95, I weren't going to locate specific information there.

 

Until now, no good heads were found and I am starting to think that if I find ones, they won't last for long.

 

My main stopper here for me to start this mid term project (I believe it will take at most 1 year to acomplish) is the tune, this would be the decisive point to go ahead with this... or may be the yunkyard :(

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I agree. Tuning may be the hardest part.

 

96-97 injectors will work, polarity is the same. I used these in a 3L swap I built some years ago and the current owner is still driving the car without any issues.

 

The two vacuum tubes on the top of the 2.5L intake will be eliminated after the swap. You will need to connect the lines to the back / underside of the 3L manifold vacuum ports.

 

You are correct about the valve covers. 2.5L covers will allow for the coil bracket. Additionally, the position of the oil fill on the 3L covers may interfere with the hood.

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