4.0 HO head on a 4.2 block, cam question...

[Steve_gorak_69]

IF anyone can remember, I was trying to decide if I should put a 4.0 HO head on a very low mileage 4.2 block OR try to shoehorn in a 4.9 Ford six into my 93 XJ. After reading up on more and more things, the obivious choise is putting the 4.0 HO head onto the low mileage 4.2 block.

While I am sure I will have all sorts of questions as time progresses, the main one I have for now is the cam. Rather, which one for which block? Basically, I'd like to get is the best overall cam for more low end torque and more HP. Mind you, this will be my daily beater with 3.73 gears, AW4 (mated to a reclocked D300??), a MILD lift. NOTE: None of which are under the vehicle yet :d:

Let me know and thanks

[Steve_gorak_69]

OR, should I just get a rebuild kit for the 4.0, decent cam (again which one?), 4.2 crank and call it done?? Let me know what you guys think.

[Rescue35]

Put the 4.2 crank in the 4.0. About a year ago I could have given you lots of good info but ive been makeing plans for a V8 for to long now and dont have my notes handy.

[JeepinDoug]

Here's the cam I had ground. Power off idle.

Similar to the HESCO cam with a great vaccume signal.

[Jaffer]

Specs of the dyno proven HESCO grind for a 4.2L w/4.0 head and MPI:

Grind Type: H-264-14-B

Valve Timing
Int. Opens 18 Exh. Opens 66
Int. Closes 66 Exh. Closes 18

Duration: 214
Valve Lift: .470

It is one SWEET! cam.

[MellowYellow]

Jaffer,
Is that an off the shelf cam from them?
Can you expand on sweet?
What is it like at Idle?
At what RMP does it start to fall apart on the top end?

If my motor pings after I'm done with this swap I'm going to have a cow. So, I'm assuming a sweet cam doesnt' ping.

[JeepinDoug]

If you look at my spec tag you'll notice the lift is a tad smaller @ .435" lift and the dur is a couple degrees longer. This was as close as I could get through Elgin without going too big. Then if you notice the Int/exh timing are way off compared to HESCO's cam but IIRC HESCO reccomends changing the timing of the cam a few degrees. Rather than retiming the cam I had it ground into it.
Mine pulls strong up to 3500 rpms in final drive but I never go over that rpm. Power starts way early, under idle.

[MellowYellow]

Thanks for the input JeepinDoug.
I have a Mopar "RV" cam, but I couldn't tell you the specs.
The motor will pull well below idle (the tack reads down near 500rpm), but it sounds like it is going to come apart around 4000. It's like driving a diesle. My Gearing is so low that I'm at around 3000rpm at 55mph. Yet I still have pinging. I sure hope my 4.0 head fixes the pinging. I'm wondering if I should get a new cam at the same time. I'd hate to pull the head again.

[Jaffer]

Mellow, yes, that was an off the shelf cam.
Bennie at HESCO said, "John, don't look at the specs, just get that one and you won't be sorry." ... he was right ...
And I DID advance it 4 degrees as Bennie as well as Doug here has suggested.
Mine has a really nice 650 RPM idle, pulls like a mother bear up until around 3800 and red-lines at a little after 5000 ... been known to take it up there on regular intervals ... as anyone who has seen me drive will attest!
Unless your bottom end is shot and the tops of your pistons look like the hull of a barge you should have no pinging problems after you install a 4.0 HO head.

[JeepinDoug]

I can't believe the power I have in the elevation now, the MPI makes a BBD carb look like a gravity fed fuel regulator.

Mellow, you say your pinging. It that what makes the engine feel like it's falling apart?
If you're running a MPI kit and an aftermarket valve cover you need to remove the oil baffle under the CCV. It holds a puddle of oil and at higher rpms will draw oil vapore into the throttle body. Mine pinged like crazy at anything over 2300 rpms until I figured that one out.

[gripguru]

I got the clifford 272 cam. I really like it cause I daily drive my jeep. It pulls hard from 1K rpm but once it gets to 2200, the motor plants you to the seat and never gives up all the way to the MPI rev limiter ~6000 It is not a low end torque cam, but it holds its own and makes gobs of HP. Additionally I passed Sac County smog without a hitch. If I was to go back the specs on Dougs cam look fantastic.

[MellowYellow]

Originally posted by JeepinDoug
Mellow, you say your pinging. It that what makes the engine feel like it's falling apart?
If you're running a MPI kit and an aftermarket valve cover you need to remove the oil baffle under the CCV. It holds a puddle of oil and at higher rpms will draw oil vapore into the throttle body. Mine pinged like crazy at anything over 2300 rpms until I figured that one out.

I am running an aftermarket cover! oh man that would be a great quick fix. I'll give that a try. I have been wheeling more lately, so I hate to pull the motor apart before I'm really ready to finish it.
My best guess it the pinging is what makes it sound so bad. I sure hope it isn't the valves floating. The pinging is the worst under load over 2500, and the awful noise starts at 3500 on flat ground 4th gear.

I have the 4.0 head in the garage, so I'll be doing this swap in February. I hope my pistons look ok. If they look ok should I stick with the Mopar cam? Or would you recommend your cam? What does a cam cost? I can't remember. I guess I could go look it up.

[MellowYellow]

Sorry if I highjacked this thread and if I made it "newbie", but this is the first time I have seen someone point at the CCV baffel as a contributer to pinging. I have been reading about this for years and I know I would remember it. That didn't seem very newbie to me, but then what do I know.