03 4.6 bore out to 5.0 ?

Essentially I want to know if anyone has done this. A friend of mine suggested I bore my 4.6 out to a 5.0 and get forged internals. I currently have a stock 2003 GT with bolt V2 supercharger with intercooler and 3.73 gears.

Whats your end game for power / use?

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Originally Posted by ZR

Whats your end game for power / use?

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More pleasure then anything, currently the cars pumping about 430 to the wheeles but I’d like to hit the 600 range. The cars a Sunday funday for me.


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Do you want 600hp to hit a time target of some kind or just as a personal benchmark?

To go fully forged internals and do all the machining for a big bore conversion to gain that extra displacement you're talking about several thousand dollars. Plus just doing the big bore alone won't net you 600, you'll have to swap pulleys to a much smaller diameter than current to up the boost, retune, etc. Plus at that point may as well just take that stock T45/3650 and toss it in the dumpster.

There are several sponsor shops in GTA that can build you a motor to handle this boost level and power. But you're probably going to spend 2x what you did to do the basic supercharged kit to get there. Go down the rabbit hole if you want but my advice is a mid 400hp 2V is about as much street fun as a 2v gets. Above that the power to dollar spent ration just doesn't add up and you've spent Cobra/Shelby money to get there.

Coyote swap may be cheaper...

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Originally Posted by stangstevers

Coyote swap may be cheaper...

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Would be a wash to loss power wise, trading low 400 for low 400 hp. Unfortunately the 400 range is about the limit to make in a 2v without spending $ALL.

That's what I mean... depends on long term goals... hard to beat a twin turbo coyote lol

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Originally Posted by Laffs

Do you want 600hp to hit a time target of some kind or just as a personal benchmark?

To go fully forged internals and do all the machining for a big bore conversion to gain that extra displacement you're talking about several thousand dollars. Plus just doing the big bore alone won't net you 600, you'll have to swap pulleys to a much smaller diameter than current to up the boost, retune, etc. Plus at that point may as well just take that stock T45/3650 and toss it in the dumpster.

There are several sponsor shops in GTA that can build you a motor to handle this boost level and power. But you're probably going to spend 2x what you did to do the basic supercharged kit to get there. Go down the rabbit hole if you want but my advice is a mid 400hp 2V is about as much street fun as a 2v gets. Above that the power to dollar spent ration just doesn't add up and you've spent Cobra/Shelby money to get there.

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Your probably right, my car runs mint with low kms. I love my body style I don’t want to switch it up. Maybe down the line I’ll do a complete swap


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Terminator swap would be a much better choice, easy swap and a very capable engine, not to mention looks way cooler than a 2V. And fwiw, I don’t think you can bore a 4.6 to a 5.0 safely, you’d need to get an aftermarket clock with thicker cylinders.

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Originally Posted by Ponyryd

Terminator swap would be a much better choice, easy swap and a very capable engine, not to mention looks way cooler than a 2V. And fwiw, I don’t think you can bore a 4.6 to a 5.0 safely, you’d need to get an aftermarket clock with thicker cylinders.

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The whole engine would need a rebuild with forged internals


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Agreed, be happy as is or re-power for big squeeze.
Realistically, what you got is big jam, yes in spite of what the internet says.

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Originally Posted by ZR

Agreed, be happy as is or re-power for big squeeze.
Realistically, what you got is big jam, yes in spite of what the internet says.

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What do you mean ?


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Originally Posted by Zutz2v

The whole engine would need a rebuild with forged internals


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Yes I’m aware of that. But my point is when you bore out and engine, you’re taking material from the cylinder walls, making them thinner, in order to make the cylinder bigger-the problem is, factory blocks don’t have enough material to spare to safely go from a 4.6 to a 5.0, the walls will be too thin after machining-especially for a boosted/nitrous engine.
Basically, if you want a 5.0, you’ll need an aftermarket block since they have thicker walls to stand up to more abuse and overboring.
To be honest it sounds like you don’t really know what you want or why, but you’re listening to someone else who isn’t the one spending the cash, so it’s very easy for him to say do this or that. Basically if he knows about 4.6 engines he would have told you you’ll need an aftermarket block to safely get a to a 5.0, and really, even when you get to a 5.0, nobody will know for sure that you have a 5.0 except the machinist and engine builder. If you just want forged internals to add boost you’d be better off leaving it a 4.6, and buying forged parts, or you could do as I suggested and buy a terminator 4.6 dohc engine, which is forged from the factory. At least if you get a termi engine it will look way better than your current one when you pop the hood.

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Originally Posted by Ponyryd

Yes I’m aware of that. But my point is when you bore out and engine, you’re taking material from the cylinder walls, making them thinner, in order to make the cylinder bigger-the problem is, factory blocks don’t have enough material to spare to safely go from a 4.6 to a 5.0, the walls will be too thin after machining-especially for a boosted/nitrous engine.
Basically, if you want a 5.0, you’ll need an aftermarket block since they have thicker walls to stand up to more abuse and overboring.
To be honest it sounds like you don’t really know what you want or why, but you’re listening to someone else who isn’t the one spending the cash, so it’s very easy for him to say do this or that. Basically if he knows about 4.6 engines he would have told you you’ll need an aftermarket block to safely get a to a 5.0, and really, even when you get to a 5.0, nobody will know for sure that you have a 5.0 except the machinist and engine builder. If you just want forged internals to add boost you’d be better off leaving it a 4.6, and buying forged parts, or you could do as I suggested and buy a terminator 4.6 dohc engine, which is forged from the factory. At least if you get a termi engine it will look way better than your current one when you pop the hood.

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You hit the nail on the head on that one. I didn’t know I could do those things. I have a great setup already I just wanted more power. I’ll wait for the car to age a little more. I don’t even have 100k on it yet.


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Richard, your correct about boring the cylinders. The popular way to increase displacement is stroking the engine. As most of the time your purchasing a forged crank.

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Originally Posted by NickD

Richard, your correct about boring the cylinders. The popular way to increase displacement is stroking the engine. As most of the time your purchasing a forged crank.

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That’s true Nick, but stroking is big money. He’s close to the limit of the stocker with his current power level, I’d guess he’s running right around 10psi, next step without breaking the bank is to do forged internals and turn the boost up. Adding cubes is cool but it costs a ton, and it’s pointless for a toy of this nature imo.

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Originally Posted by Ponyryd

That’s true Nick, but stroking is big money. He’s close to the limit of the stocker with his current power level, I’d guess he’s running right around 10psi, next step without breaking the bank is to do forged internals and turn the boost up. Adding cubes is cool but it costs a ton, and it’s pointless for a toy of this nature imo.

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I’m running 6psi, and I want to turn the boost up a little but I wanted to do it safely.


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Start here.
https://www.seanhylandmotorsport.com/M-6009-B53

Then add money until you cannot retire before you are 90.

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Originally Posted by Zutz2v

I’m running 6psi, and I want to turn the boost up a little but I wanted to do it safely.


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General rule of thumb is 8-10 psi is safe as long as it’s tuned for it, the tune is crucial.

Tune and correct supporting mods. Too many try to make big h/p on a shoestring, seldom if ever works out long term.

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Originally Posted by Ponyryd

Yes I’m aware of that. But my point is when you bore out and engine, you’re taking material from the cylinder walls, making them thinner, in order to make the cylinder bigger-the problem is, factory blocks don’t have enough material to spare to safely go from a 4.6 to a 5.0, the walls will be too thin after machining-especially for a boosted/nitrous engine.
Basically, if you want a 5.0, you’ll need an aftermarket block since they have thicker walls to stand up to more abuse and overboring.
To be honest it sounds like you don’t really know what you want or why, but you’re listening to someone else who isn’t the one spending the cash, so it’s very easy for him to say do this or that. Basically if he knows about 4.6 engines he would have told you you’ll need an aftermarket block to safely get a to a 5.0, and really, even when you get to a 5.0, nobody will know for sure that you have a 5.0 except the machinist and engine builder. If you just want forged internals to add boost you’d be better off leaving it a 4.6, and buying forged parts, or you could do as I suggested and buy a terminator 4.6 dohc engine, which is forged from the factory. At least if you get a termi engine it will look way better than your current one when you pop the hood.

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You make it sound so easy to source a terminator engine lol

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https://www.americanmuscle.com/frpp-...oss-block.html

I remember entertaining the thought. I'm not sure if this is a thicker block that was bored to 5.0L

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^Yes, it’s a Boss block, much stronger.
But just so you guys all know, all things being equal a 5.0 compared to a 4.6 won’t net you any noticeable HP gains. Boss blocks are used because of their strength, to be used with high boost mostly.

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Originally Posted by Harbinger

You make it sound so easy to source a terminator engine lol

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It’s not that hard, best off to buy a complete salvage car and use what you need.

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Originally Posted by Ponyryd

^Yes, it’s a Boss block, much stronger.
But just so you guys all know, all things being equal a 5.0 compared to a 4.6 won’t net you any noticeable HP gains. Boss blocks are used because of their strength, to be used with high boost mostly.



It’s not that hard, best off to buy a complete salvage car and use what you need.

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That is a good point. I still feel like it's hard to find a decent well priced deal out of a salvaged cobra

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Yea, could always put out a want ad on Kijiji, never know man, I had one slip through my hands last year. The deal was too good to be true, my buddy told me about it and I kept asking him to call her, he said it was ours for sure, lady said a price and he agreed, he knew her son or brother or some crap, we just had to wait a few weeks, in the meantime she called a salvage yard and they gave her more.

That sucks big time [emoji35]. She coulda notified what the salvage yard wanted. Oh well !

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If you are looking to swap in a 03/04 Cobra or Coyote engine you can check the Parts Farm Facebook page but it is U.S money.