4.6 crank/rods+4.0 pistons?

[Abran]

I helped a friend get some parts machined for his engine build on his D2.

He went with 4.6 crank/rods and 4.0 Pistons. The thinking was a 4.6 with higher compression.

The machinist says it's actually a 4.2 with higher compression.

Anybody have some insight?

 

[ptschram]

Your machinist is an idiot and you should run away from him.

 

[Abran]

Noted.

So it's still a 4.6 but with higher compression?

 

[robertf]

is he asian? for some reason they sometimes include cylinder head cc in the displacement over there

if not, hes a moron

 

[Abran]

Not Asian, as white is the rice the Asians eat. And as American as can be, But apparently a moron.

Now that we have his race cleared up, are we talking about a 4.6 with higher compression?

 

[discostew]

The cylinder bore is the same on the 4.0 and 4.6 . The difference in displacement is from the longer stroke . Not sure why he would be confused on that . The pistons having higher compression is what these guys on the DWEB say . I think these guys are a normally reliable source of information . I plan to do it with the truck I'm building now , still on the fence about what cam I'm going to run .

 

[Abran]

Thanks Stew.

I'm about to do the same build and am contemplating the entry level Crower cam.

My only concern is California emmisions. Do you think I will have issues?

 

[discostew]

Thanks Stew.

I'm about to do the same build and am contemplating the entry level Crower cam.

My only concern is California emmisions. Do you think I will have issues?

I don't know . I think someone could get you thru it .

 

[ptschram]

It is my opinion that unless you are using an aftermarket EMS or have a distributor, the gains are limited by the existing EMS' ability to retard timing to combat knocking.

The wrist pin height is different on the 4.6/4.0 resulting in the slightly higher compression ratio.

 

[robertf]

the wrist pin is the exact same height

4.6 pistons are the same part as 4.0 low compression pistons

 

[discostew]

I agree with PT about the pinging . I can't remember who posted it but they claimed there was no knock sensor activity that was abnormal with the crower camshaft . I would like to see it on my own equipment . I think it would have to be retarding the timing some . But I have no experience with aftermarket cams in this engine .

What I do know is instead of an EGR valve this engine runs valve overlap to bring exhaust gasses back into the cylinder to lower combustion chamber temps . Pinging and the exhaust gas called NOX should increase . If it becomes an issue I plan to run some octane booster , also wonder about machining an intake manifold to accept a EGR valve and run ported vacuum to it . But guys are saying they have no trouble so I plan to do it .

 

[Abran]

I think I'm going to go for it and look into ECU programming down the road.

 

[discostew]

As far as programming I have an unproven theory about the prom I plan to run .

I understand that in Australia they don't have catalytic converters on there GEMS trucks . If in fact that IS true . I should be able to get rid of catalytic converters and rear o2 sensors . The prom is easily replaced and anyone who's had to drain the water out of an ECM should be able to replace it . But it looks like there's a kink in the higher compression piston thing .

 

[ptschram]

the wrist pin is the exact same height

4.6 pistons are the same part as 4.0 low compression pistons

Not according to the copy of Microcat that I have.

There are four different part numbers, ERR5553 through ERR5556

 

[discostew]

Not according to the copy of Microcat that I have.

There are four different part numbers, ERR5553 through ERR5556

I wonder if some of the special edition trucks got higher compression pistons . Is there any description with the part #s ?

 

[group captain mandrake]

So what is the difference between the 4.0 blocks and the 4.6 blocks?

 

[discostew]

As far as I know nothing . What does microcat say about blocks PT ?

 

[ptschram]

I don't know.

Or as the cool kids would say IDK.

 

[ptschram]

Cylinder block, Engine.

No differentiation, just some minor part number variations for years.

It looks like they all supersede to the 2003 model year block part number.

 

[group captain mandrake]

I've heard the cool kids take the rotating bits from their 4.6 and put them into a known good 4.0 block.
I never really knew why they would do such a thing. Then my 4.6 engine committed hari-kari.
It is now starting to make sense to me.