Milled 4.0L X heads

[Monzilla]

Im building a 4.0L X engine. 1994 short block with small OEM dish pistons. 1996 heads with small combustion chambers. I have non adjustable rockers. Comp cams custom grind with about .550" lift at vavle. I need to cut about .030" off the heads. If I cut the heads, I need to space the rockers back up. Are there rocker shaft mount spacers available? There seems to be a oil feed hole in the center shaft mount? It comes from the center head bolt hole.

On 90 degree V8 we loosen rockers to lessen then collapse of the hydrualic. Less horsepower used to collapse lifter means more at flywheel. Has anyone added additional shims to the mounts to loosen rockers? Or used old 2.9L adjustable rockers? Is the shaft size the same from 2.9L to 4.0L?

 

[MAKG]

I thought there were shorter pushrods available for this purpose.

 

[Monzilla]

I did not know this. I havent found them available when looking for rebuild parts. Do you know of a source?

 

[rickcdewitt]

whats your compression ratio going to be?
delta cams or another might have the shortened pushrods.

 

[Monzilla]

Im not sure yet. I think between 10.5 and 11:1. I have to wait until after I mill the heads and measure the volume of the combustion chambers.

 

[rickcdewitt]

what cpu are you going to use?i heard the early cpu(91-94) will burn up a motor with the late style fast burn heads?is there any truth to it?

 

[Psychopete]

I did not know this. I havent found them available when looking for rebuild parts. Do you know of a source?

Try these guys:
http://www.pushrods.net/

Pete

Edit:
They make custom pushrods, you will need to send them an email.

 

[Monzilla]

Its got the 1996 ECU, fuel injection and ignition on it. I am currently looking for 24lb injectors and a 66mm throttle body for it. Doesnt matter what the compression ratio is as long as I have hi enough octane fuel to run in it. Im going to try 93 with octane boost first. Then 110 if that doesnt work. The knock sensor should pick up any spark knock and retard the timing before piston damage occurs.

 

[Bird]

If you have to mill the heads that much, there's a good chance you'll have problems. These heads, unless they're aftermarket castings, have a very thin deck surface and the MAX recommended surfacing is .020" - otherwise porosity problems can (and usually do) show up.
The compression ratio of the early pistons with the late heads is nominally 10:1 - milling will up that a couple more tenths.
The 96's that I've worked on didn't have knock sensors............maybe you've got a special one.
Have run several EEC-4 setups with the fast burn heads - never burnt one down.

Sounds like you've got some head prep work to do to run that high a lift cam............


Bird

 

[Monzilla]

Im just learning about the 4.0L in the last year or so. Ive never heard of porosity problems with the 4.0L heads. Thats good to know. On the deck surface, do I have to worry about coolant to combustion, coolant to oil, an external oil leak or an external coolant leak?

The EEC-V wiring diagram lists a knock sensor for a 1996 Explorer. I didnt find it in the block. I wondered about it not having one. Thought maybe it was in the cam sensor or something wierd llike that.

Ive got several hours of port work in the heads, larger vavles, springs, and aluminum rocker spacers. Now im seriously contemplating not doing the mill work if im going to have leaks. I dont wanna ruin all the work Ive done.

 

[Bird]

Any one of those leakage problems could occur, not to mention the sealing problems with the intake manifold.

Another very common fault with the 4.0 heads is cracks that develop between the valve seats (sometimes aggravated by installing larger valves).

Hopefully, you cut down the valve guides to accomodate the higher lift cam - otherwise, you will be seeing problems there.

Port work - hopefully, you used a flow bench to verify your work - the intake side is very sensitive to any cutting and can really screw up flow without even thinking about it. The exhaust side is what really benefits as the exhaust port is pretty restrictive.

Bird

 

[Monzilla]

The intake side looks very nice from the factory. Some minor polishing and we are good to go. The intake ports needed hours of cutting. Almost 1/4" of material from side to side. I was impressed. The exhaust side needed major bowl work and casting removal.

I havent cut the top of the guides yet. I was told I would not have an interfierence problem. Should I assemble the engine and measure first? Or positive on the guide cutting?

 

[rickcdewitt]

Have run several EEC-4 setups with the fast burn heads - never burnt one down.


Bird

do you think i could run a fast burn long block in my 91 without much work other than a flywheel,exhaust manifolds and sensors?