So I know places like supersix motorsports offer 4.2L or 4.3L stroker kits with forged internals, but I'm looking into a more economical stroker kit with OEM quality parts. I know the forged parts are a good idea if you plan to go forced induction but they really won't do much for power on a simple stroker kit alone. If you look at the supersix rotating assembly it sells for $1950 and their forged internals sell for $1600 alone. So obviously the majority of the cost is in the forged internals. I've been doing as much research as I can on what parts are needed to do a simple OEM quality part (quality aftermarket parts are ok) stroker kit but I'm still unsure on a few things. So I know I need a 4.2L crankshaft with the 3.74" stroke from a 1997-2008 truck/minivan 4.2L V6. I also know the connecting rods for the 3.8L and 4.2L engines are identical. There seems to be some confusion on whether the pistons between the two engines are the same. IT LOOKS LIKE THEY ARE DIFFERENT AND THE 4.2L ENGINE PISTONS SHOULD BE USED BUT I AM UNSURE ABOUT THIS? Also, I've heard both that the 3.8L flywheel along with 3.8L harmonic balancer/damper and 4.2L flywheel along with the 4.2L harmonic balancer/damper should be used, I THINK I WANT THE 4.2L FLYWHEEL/HARMONIC DAMPER BUT AM UNSURE? And lastly, I know both engines have the same connecting rod bearings, BUT I DON'T KNOW IF I NEED CRANKSHAFT MAIN BEARINGS FOR THE 3.8L OR 4.2L ENGINE? This is actually the thing I'm most confused about, I have no idea which crankshaft main bearings to use? Any help would be much appreciated, and I don't want to sound like an ass but please only respond if you know for sure or are pretty sure of your answer, any guessing won't help and only complicate things more.
Non forged internal 4.2L/4.3L stroker kit help
The_Red_Stig
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So I know places like supersix motorsports offer 4.2L or 4.3L stroker kits with forged internals, but I'm looking into a more economical stroker kit with OEM quality parts. I know the forged parts are a good idea if you plan to go forced induction but they really won't do much for power on a simple stroker kit alone. If you look at the supersix rotating assembly it sells for $1950 and their forged internals sell for $1600 alone. So obviously the majority of the cost is in the forged internals. I've been doing as much research as I can on what parts are needed to do a simple OEM quality part (quality aftermarket parts are ok) stroker kit but I'm still unsure on a few things. So I know I need a 4.2L crankshaft with the 3.74" stroke from a 1997-2008 truck/minivan 4.2L V6. I also know the connecting rods for the 3.8L and 4.2L engines are identical. There seems to be some confusion on whether the pistons between the two engines are the same. IT LOOKS LIKE THEY ARE DIFFERENT AND THE 4.2L ENGINE PISTONS SHOULD BE USED BUT I AM UNSURE ABOUT THIS? Also, I've heard both that the 3.8L flywheel along with 3.8L harmonic balancer/damper and 4.2L flywheel along with the 4.2L harmonic balancer/damper should be used, I THINK I WANT THE 4.2L FLYWHEEL/HARMONIC DAMPER BUT AM UNSURE? And lastly, I know both engines have the same connecting rod bearings, BUT I DON'T KNOW IF I NEED CRANKSHAFT MAIN BEARINGS FOR THE 3.8L OR 4.2L ENGINE? This is actually the thing I'm most confused about, I have no idea which crankshaft main bearings to use? Any help would be much appreciated, and I don't want to sound like an ass but please only respond if you know for sure or are pretty sure of your answer, any guessing won't help and only complicate things more.
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1,214 Posts
If you just want to go OEM. Then just find you a nice used 4.2L engine to drop in. Cause it sounds like your trying to only swap specific parts into your 3.8L. I wouldn't really recommend that since there is a lot of work involved which will still leave you with a weaker setup. Why, because when I did my 4.2 conversion I noticed that the 4.2 block (which is basically the same as the 3.8 block) has a bigger and stronger/reenforced grapel on the wider and heavier 4.2 Crankshaft.
Also the many other differences are (some you already mentioned)
- The oil pan is the same boltup and size, but has a bigger volume to hold oil below the crankshaft level. Since the bigger crank reaches down more.
- the piston connecting rods are the same, but the piston head itself on the 4.2 is shorter. Also the piston dish is deeper to keep the compression almost the same as the 3.8. So no you cannot technically use the same Pistons.
- The main bearings are the same. But if you were to choose one, go with the 4.2 version. (Which might end up being the same part number, but still ask for the 4.2 kind).
- You can bolt which ever Flywheel/Harmonic Balancer from a 4.2 or a 3.8 you wish. It will boltup, BUT it has to be a BALANCED flywheel since all the 4.2 are already INTERNALLY BALANCED and some 3.8s arent (making them externally balanced).
- The camshaft on the 4.2 has larger lobes than the 3.8 for a bigger valve lift.
- The heads are the same
- The lower intakes are the same, but the upper intake may vary by which setup you choose.
So to save up on money, time, confusion, ext. Just get a good used 4.2 engine that already has everything you need on it, which would also be cheaper than getting every part separately.
Also the many other differences are (some you already mentioned)
- The oil pan is the same boltup and size, but has a bigger volume to hold oil below the crankshaft level. Since the bigger crank reaches down more.
- the piston connecting rods are the same, but the piston head itself on the 4.2 is shorter. Also the piston dish is deeper to keep the compression almost the same as the 3.8. So no you cannot technically use the same Pistons.
- The main bearings are the same. But if you were to choose one, go with the 4.2 version. (Which might end up being the same part number, but still ask for the 4.2 kind).
- You can bolt which ever Flywheel/Harmonic Balancer from a 4.2 or a 3.8 you wish. It will boltup, BUT it has to be a BALANCED flywheel since all the 4.2 are already INTERNALLY BALANCED and some 3.8s arent (making them externally balanced).
- The camshaft on the 4.2 has larger lobes than the 3.8 for a bigger valve lift.
- The heads are the same
- The lower intakes are the same, but the upper intake may vary by which setup you choose.
So to save up on money, time, confusion, ext. Just get a good used 4.2 engine that already has everything you need on it, which would also be cheaper than getting every part separately.
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222 Posts
Thanks for the reply izzy, your info helps a lot. It's good to know that either flywheel and harmonic balancer combo works. But as far as the flywheel being internally balanced, I thought all new rotating assemblies had to be balanced anyway before being installed (the crankshaft, rods, pistons, flywheel and harmonic balancer), or is that just an option? Also, I did some more research and found out that your right, the 3.8L and 4.2L main bearings are the same. Since the 4.2L crank extends further into the oil pan, do I also need to swap oil pans? That's interesting about the 4.2L cam, I didn't know that. I've looked into getting a Comp cams camshaft along with valve springs and lifters. That would cost about $655. I've made an excel spreadsheet and priced out how much everything would cost. If I got a new oil pump, timing chain tensioner, and engine gasket kit at the same time all the parts would cost $1,208.34 shipped to my house, ($954.37 if I could reuse my connecting rods). That's not including costs to have the rotating assembly balanced or the PCM tuned. I haven't looked into how much a complete 4.2L engine swap would be, but I assumed that would be a lot more expensive and possibly difficult. If I were to go that route, I would also need the 4.2L PCM wouldn't I? And would it bolt right up to the T-5 tranny?
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9,165 Posts
As izzy, said, it is easier to just drop a 4.2 in. You have to swap a couple things over but it is cheaper than building a motor. Consider doing a fresh motor you will need to pay for some machine work as well.
You need to run the 3.8 oil pan and oil pickup tube.
---------- Post added at 09:14 AM ---------- Previous post was at 07:52 AM ----------
How To 4.2 V6 Swap
You need to run the 3.8 oil pan and oil pickup tube.
---------- Post added at 09:14 AM ---------- Previous post was at 07:52 AM ----------
How To 4.2 V6 Swap
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1,214 Posts
Some 3.8 engines were externally balanced, meaning the flywheel and harmonic balancer have counter weight to balnce the crankshaft. No not all engines came out balanced, that was a inconvenient truth for me to learn to when swapping over to a 4.2L. Thats why its best to get a used engine with all the external components needed already compatible with the engine.
The oil pan is the same size as the 3.8, it just has an extra area that is added to it that was cut out of the 3.8 oil pan. Its hard to explain so just google an image of the two to better understand what Im talking about. But I would recommend going for the 4.2 oil pan to have better oil level. But also like SlowSix says, use the 3.8 oil pan and pickup tube. Im actually running with the 3.8 oil pan aswell.
You cant use the F150 4.2 pcm (Im not sure about the Van) because they dont use CCRMs so the computers are not compatible to be used on a mustang setup. You will need to tune your current pcm.
Yes it will bolt up with a T5.
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