swapping engine

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holicori

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2002
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4.7
There is a local guy selling a 2002 1500 extended cab that had a bad motor in it. I'm hoping I can rebuild his original motor (though it seems to be scattered among mechanic and machine shops). I have a couple questions:

1) I've read that the heads on these 4.7's are "unable" to be worked on the majority of the time.

Is this true or are people just not taking their heads to the right people with the right machines?

2) also, if I can't rebuild this one...which engine years will work without having to rewire a bunch of crap or a new ecu?

3) if it previously had bent valves....is it safe to assume the heads are probably cracked? I thought these were non interference, so jot sure how they got bent.

Thanks for the help.
 
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holicori

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4.7
So are these forums dead or do people really not know?
 

xb1230

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South Shore of Montreal, QC, Canada
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2020
Engine
5.7 HEMI
Not as much folks here know about the 4.7L. It is an unpopular engine, and most prefer the HEMI 5.7L.

That being said, the 4.7L is an interference engine, and the timing assembly is a weak point, so if one of the timing chains broke, it is likely the valves have bent.

The heads on these engine can be machined, but it depends on the condition they are in. If they are cracked, they are not machinable. A good machine shop will get them machined and you should consider having the valve seats replaced with new inserts. Take some time to work on the oil returns as they are one of the weak links, that makes these engine sludge up real badly. Also use the OEM exhaust manifold gasket, as they are thicker than most aftermarket, and these engine are prone to generate exhaust leaks at the manifold(you could also ask your machine shop to plane the exhaust ports to help). Aftermarket head gaskets can be used but make sure to use good quality MLS ones. Invest in a set of new valve lash adjuster.

If you are rebuilding the engine yourself, pay very close attention to the Crank. On first front balancer lobe you will find a stamped series of letters. They dictate the original bearing sizes required for your specific crank. Also be careful when ordering your bearings, if ordering OEM bearing I have heard horror stories of them being delivered with nicks and scratches because of the way they are packaged. Alternately you can have your crank machined to your specs in order to use aftermarket bearing.

Make sure the block is leveled, and that the cylinders are all the same. The 4.7L has very tight tolerances almost race like so a small imbalance can create a slew of issues.

When ordering the timing assembly, make sure to match it with your application as there are 2 distinct set that can fit. they are based on the type of ECM you have, JTEC or NGC. The type of ECM can also help out in getting a used engine for compatibility.
JTEC PCM have 3 plugs, as the NGC have 4 plugs.

Hope this helps.
 
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holicori

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4.7
Awesome info, thanks!

Makes sense that the motor is interference now.

Just curious, why is it that the 4.7 is unpopular? Is it one of those ..."if you're gonna go big, go REAL big" kinda things?

I want the 4.7 because I only tow maybe once a month, once every other month. The 6cylinder is too small for towing, and the 5.7 would kill my mpg. So I think the 4.7 is a nice fit. Would you agree?

I have rebuilt one motor before so I'm not completely new, but by no means "experienced." I did have some bearings that I had to send back though.


Due to tight clearances, do you think it would be better to order new pistons (oversized) and have the machine shop bore the cylinders to size so I know they are right?

The guy is selling it for $1500...so if I pay another $1500 in shop fees/parts its still very worth it in my opinion.


When you say have the seats redone, what exactly do you mean? Are you referring to the valve seals that prevent oil into the cylinders, or the cavities in the head the actual valve stem goes through?


Thank you so much bud
 

myoung84

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2012 Power Wagon
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Hemi 5.7L
I had a 4.7 with 5 speed manual in my 2000 Dakota 2wd. That was a great combination. I traded that truck for an 04 Ram 2wd with 5 speed auto and was never happy with it. It was just OK when running empty but didn't tow well at all. It came stock with 3.92 gears and I eventually regeared to 4.56. That helped a little but still ended up trading it for a 2010 Hemi and it was night and day difference.

The 02-07 4.7 is only rated at 235 HP. I had the basic bolt on mods and a tuner as well. As far as gas mileage, I never got more than about 14 highway with the 3.92s or 4.56s. If the deciding factor for the 4.7 vs Hemi is fuel efficiency, then I'd go with the Hemi... If you like that truck and it's in good condition, buy it and drop in a Hemi...
 

john55

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hemi 5.7
I had an '02 QC 4X4 4.7, it wasn't that good on gas, probably not any better than a 5.7 back in the Gen 3 days and not as much power either :) I think the 235 hp. 4.7 works better in a Dakota
 

xb1230

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5.7 HEMI
Here is the deal with the 4.7L :

  1. Due some production shortfalls they sludge like hell
  2. MPG's are not that better than with the HEMI, if not worst...
  3. Not a lot of after-market parts to mod or upgrade the engine (This is probably a big one for the people here)
  4. Complex timing set-up, hard to replace. another production shortfall is that the tensioners are not holding up...
  5. It has a tendency to run a little hotter than other V8, making it more prone to overheating issues, head gasket leaks, etc.
  6. Durability has not been one of this engine's main characteristics because of all of the above

Many folks actually get better MPG's with the 5.7L Hemi because the engine has more HP and works less hard to get the truck moving.

That being said, if you are tight on maintenance, and monitor closely your engine, I do believe the 4.7L is a great motor if correct just a few small things.

You can read here how great of a design this engine actually is!

As for what to correct :
  • Valve seats (not valve seals) need to ahve new valve seats pressed and pinned as the OEM ones have a tendency to pop-out of their location creating major internal damages
  • Oil Drain Backs need to be widened and smoothed out to favor a better return of the oil from the Valve train down to the pan. That helps sludging by speeding up the cooling of the oil
  • MLS (Multi Layered Steel) Head gaskets will provide better seal as well as prevent potential head leaks
  • Pistons : There are newly re-engineered piston heads that help get the temperature in the combustion chamber under control to yet again minize oil sludge

That being said, if you are meticulous in your build, and take your time, you will get there. Then it will be up to you to properly maintain the engine. because the engine runs a little hotter and has the tendency to generate sludge, more frequent oil changes and close monitoring of engine temperature will allow you to keep it going for a good while.

Hope this helps.
 

hotkarl

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4.7 Semi-Hemi
Don't waste your time or money on a used motor or even rebuilding it yourself. The 4.7 is "special". Buy a rebuild from someone like Power Train Products or similar builder that corrects the OEM design flaws. Trust me.
 

john55

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hemi 5.7
BTW., 2002 is special, you can't use an older engine because of the reluctor on the crank...I can't remember the details at the moment...
 

justin13703

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Hemi 5.7
Xb1230 beat me to it but I was also gonna say that the hemi's do get better mileage than the 4.7s and that's why its not that popular of a motor
 

xb1230

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5.7 HEMI
I had a 4.7 with 5 speed manual in my 2000 Dakota 2wd. That was a great combination. I traded that truck for an 04 Ram 2wd with 5 speed auto and was never happy with it. ...ended up trading it for a 2010 Hemi and it was night and day difference.

...If the deciding factor for the 4.7 vs Hemi is fuel efficiency, then I'd go with the Hemi...

+1 on that. The Dakota was much lighter and the 4.7L faired a lot better in it. It is adequate for the RAM but nothing more.

If you like that truck and it's in good condition, buy it and drop in a Hemi...

Not a bad idea, however might as well start looking for another truck as the easiest and cheapest way to swap from a 4.7L to a HEMI is to have a donor truck next to yours as there are so many parts required for the swap... A wrecked 5.7 from 2003 to 2008, would be a good donor if that is the route you would decide to go.

Just saying
 

john55

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hemi 5.7
'02-'03 had JTEC computer, I'd look for a complete harness w/ computer if going to a 5.7..good luck...
 
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holicori

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Xb1230 beat me to it but I was also gonna say that the hemi's do get better mileage than the 4.7s and that's why its not that popular of a motor

I didn't know that. I didn't even look at the 5.7 on the mpg chart I had as I figured it would be awful!

So, now realizing the 5.7 hemi would get better gas, can I just drop a 5.7 hemi into a chassis that originally had a 4.7?

I would assume there would be some connectors or such that would be missing for the hemi. I would assume I have to trade over the ecm too huh?
 
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holicori

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Sorry, didn't see this went to page 2 and you already answered most my questions.

So if the 02-03 had a jtec....will a 2002/3 4.7 with a jtec mesh with a 5.7?

What if I bought a 2002/3 jtec harness/computer but it in say a 2004/5 5.7?

Sorry, I'm not experienced with the electronic and ecm side of things. Most all mechanical things I've done, but the electric throws me.
 

xb1230

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it is sadly more than just the PCM.

You will require a complete harness, and then some more parts.

As I said in my second post towards the end you are better off with a donor truck sitting nearby so that when and if you need something it right there close by.

The other thing is that with the introduction of the 5.7L, Dodge integrated the TCM within the PCM and moved to a drive by wire model, so you will also need the gas pedal from the donor truck...

And I am not accounting for the fact that you would probably need to go to a stealership to get the PCM flashed with the serial number of the truck. That is especially useful if you intend to use a tuner as they lock themselves with the serial number of the vehicle.

Better off looking for a truck with a Hemi that would suit your usage and your budget.
 

xb1230

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If I had the desire to do an engine swap, I would probably look at putting in a Cummins before giving myself the trouble of swapping in a Hemi... <

Just saying...
 

john55

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hemi 5.7
it is sadly more than just the PCM.

You will require a complete harness, and then some more parts.

As I said in my second post towards the end you are better off with a donor truck sitting nearby so that when and if you need something it right there close by.

The other thing is that with the introduction of the 5.7L, Dodge integrated the TCM within the PCM and moved to a drive by wire model, so you will also need the gas pedal from the donor truck...

And I am not accounting for the fact that you would probably need to go to a stealership to get the PCM flashed with the serial number of the truck. That is especially useful if you intend to use a tuner as they lock themselves with the serial number of the vehicle.

Better off looking for a truck with a Hemi that would suit your usage and your budget.


I agree, swaping in a 5.7 is doable, but it's not as simple as it sounds, '02-'03 should be a JTEC computer 3 connectors, which sometimes has an external Transmission control module usually located near the pcm, my '02 4.7 had an external TCM, then if you go '04 and newer, it should have an NGC computer, 4 connectors, different harness completely, internal TCM....

And we haven't even talked about emissions, evap. controls, or SKIM (security) yet....:)
 
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HemiLonestar

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5.7 hemi
If I had the desire to do an engine swap, I would probably look at putting in a Cummins before giving myself the trouble of swapping in a Hemi... <

Just saying...

Dunno bout that, a Cummins swap has been done to a 2002 that blew it's 360. Took a couple months to get it to fire, another 6 or so to get the other stuff (gauges, etc) to work right.
 
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