4.2 Engine replacement stay '05 or go '06?

[5xBuckman]

I have an opportunity for a 2005 TB 2wd for $500. It appears that it needs a valve job, according to the mechanic that has it. After read the enormous amount of work involved with R&R a head on this, I'd rather just swap the engine.

The question at hand is this. I can source 2005 4.2 with 98k miles for $750....or I can source a 2006 4.2 with 115k mile for $1300. Is the 2006 engine worth the additional $550? @limequat

 

[HARDTRAILZ]

Dont think the computer will let you interchange

 

[Mooseman]

No advantage even if it did work. There was a change around 06 or 07 on the crank reluctor and sensor so it's iffy. Stick with the lower mileage 05.

 

[HARDTRAILZ]

2006 got the changes for the bump in HP

 

[Sparky]

Mostly the head change IIRC, which you can put an 06+ head on an 02-05 block, but, that would be doing exactly what he's trying to avoid doing.

 

[HARDTRAILZ]

What I saw was a bunch of little changes to get the 20 HP and not a simple head swap. i think its a matter of it all meshing correctly.

I do not think its worth the hassle to swap from an 05 though.

 

[Sparky]

I would agree with that. Get the 05 engine. Cheaper, lower miles, direct fit.

 

[5xBuckman]

I was really hoping you guys would say, "GM made some changes in the head/valves that should hold up better than the pre-2006 design."

 

[Sparky]

Head problems are not that common on any of them, really.

My 02 got 215k out of it easy, still ran great, just the frame rusted away.

Lots of people with high miles on them. A few have cooked valves, but not that many over all.

 

[limequat]

I vote for the 2006. After you figure in the amount of time required to do the swap, what's an extra $500 bucks for a better motor? Also, call the yard and tell them the situation. They may split the difference with you.

 

[Sparky]

Are the electronics not an issue going from 05 to 06? That was my concern.

 

[Mooseman]

Were there any other changes like the exhaust manifold? That could be an extra expense.

I'm still not convinced the newer higher mileage more expensive engine is worth it.

 

[Tiggerr]

Were there any other changes like the exhaust manifold? That could be an extra expense.

I'm still not convinced the newer higher mileage more expensive engine is worth it.

I'm with you on that one... I'd go for the lowest mileage I could find from any compatible year...

 

[limequat]

Electronics are not an issue. Use your existing PCM and harness. Everything plugs in, except for the coolant sensor. You'll need to reroute the connector.

 

[Sparky]

Oh ok. So the reluctor/sensor changes occurred the next year?

 

[limequat]

Actually not until 2008.

 

[Sparky]

OK. Wait, that's when they went to separate ECM and TCM vs the unified PCM, isn't it?

Seems a bit odd how they went through those changes just to then axe the platform the next year.

 

[Mooseman]

Probably was planned years ago and in 07 when they went to build, cancellation wasn't known yet.

 

[limequat]

Yes, and also the Delphi bankruptcy. GM was heavily dependent on Delphi for sensors. They started to resource things to Bosch to limit their exposure including just about every sensor and actuator on the engine.
Also interesting, the 4 cyl and 5 cyl atlas engines were always 58x even though they had the P12 computer through 2007.
Speaking of 2007...in 2007 all 3 engines used the same OS. In theory you could tweak one of those PCMs to run a 2008 engine in a 02-07 chassis. They changed the PCM for 2007 to double the memory. Why? Who knows. One year only PCM, not used for anything else.