2.5 / 4.0 l Performance

[Bnine]

Strange that they would walk and wear around the roller like that.

Might have to clamp them down in a vice and do an endplay check on those trunions.

Im going to have mine out by the new year when I do my head. I'll check mine and get you some numbers bud.

[Gearhead]

Bill  , the rollers can be checked for side play with a feeler guage .  I was ina hurry to leave town last week and never had time to be any more scientific than to yank out the old rockers and replace them , um ,  very quickly.


Some of the Mopar rockers had small nicks in them right out of the box , there's a possibility that failure could have been initiated by a microscopic stress riser.

I doubt there was any other fault in this valvetrain , it ran great before the roller rockers , I installed them and it  ran good for 5000 km , then one broke , I removed them and ran with stamped rockers. Later I bought a replacement pair and put the set of R R 's back in , several thousand km later a second rocker broke , they've been removed again and steel rocker arms are back in it. I should add , when they break , there is no warning , just a sudden loss of power accompanied by  some klacking.  No stuck or bent valves , broken springs , mashed valve seals or bent pushrods , fragments ? none , just a rocker busted in half and a bit of damage  to the rocker where the roller is moving laterally. This engine never see's high RPM , I do not beat on it , it's VERY torquey down low so I don't often get my foot into it very far.


Once I get the new cylinder head to a state where the valves and springs are assembled , I'll mock up some roller rockers as well as a pair of stock rockers , on the bench and get a real good look at a few things , till then this is all a mystery

[BlackYJ]

Some of the Mopar rockers had small nicks in them right out of the box , there's a possibility that failure could have been initiated by a microscopic stress riser.

Let me have a look at them and I should be able to tell you how and where the failure started

[Gearhead]

Let me have a look at them and I should be able to tell you how and where the failure started

You are welcome to look at them . It would be best when viewed while  I can do a bench top mock up.  The valve stem protrusion on this big valve conversion will be very close to  a stock 4.0 head enabling an inspection of where the rocker pad or roller would  contact the tip of the valve. I can use some light springs that are normally used for valve train set up to do a simulation of valve travel and how the rockers and valves interact together. There's still a bit of machining to do yet .

[Gearhead]

Since .......




Here's a couple of pics of those rockers

[Gearhead]

Some more machining done.

Did all of the spring pads today , easy once all of the fixturing was made  and the correct cutter in my hands.

[Gearhead]

More sanding n' polishing

A couple of views

[Gearhead]

Recent developments and observations.

I'm begining a 2.5  engine build  ,  starting with a spare cylinder head I had laying around.

I took the head apart for cleaning and inspection and noticed a few things............

The lifters can be removed without taking the cylinder head apart , the bores where the pushrods travel are not bores at all like on a 4.0 , they are openings that appear to be large enough to pass a lifter through.

The exhaust ports are somewhat restrictive on the casting I'm using , I'm not sure if this is common to all 2.5's or not , definately room for improvement , very encouraging , there are gains to be made.

The intake ports , although similar to a 4.0 head are positioned lower and do not have a trough that helps direct the fuel discharged from the injector , like a 4.0 head , still some room for improvment here  too.

The combustion chambers appear to be smaller than a 4.0 , not a big deal , I like compression any ways , what may be a problem is shrouded intake valves.


Why am I doing a 2.5 ? ?   , I need to do one anyway , so why not P & P the head and use a performance cam , a header and decent exhaust.

What has been done with this one so far has helped alot , a 4.0 throttle body , a Flowmaster exhaust , an electric fan , a cold air intake and 4.88 gears.The next phase is to freshen up the engine with whatever is necessary or required and prepare a cylinder head and cam upgrade , probably a Banks header & monster exhaust.

I'll be doing some research as I go , choosing a good cam and stuff .

There's no hurry with this , shooting for completion and install by spring.


Comments ?  criticism? suggestions welcome .

I'm looking for cheap , or free cores , donations to my research , 4.2   4.0   2.5 , I could use a 4.0 ( 91 & up ) core that needs rebuilding , or a 4.2 crank n' rods.
The 2.5 core I've got here needs to come apart before I can determine if it's worth rebuilding , plus It's been laying outside for several years ( rusty )

[Gearhead]

Update......

I'm 2/3's of the way done with the port work on the 2.5 cylinder head. The exhaust ports cleaned up nicely , the intakes were pretty good to begin with and are looking good too. I am fortunate to have this cylinder head , it's in great shape.  The end result will be a vast improvment to the stock 2.5 that's in the 94 YJ now. It was rebuilt in 2005 but recent compression and leakdown testing  showed  variances in compression and leakage that led to the decision to prepare a replacement engine. 
Lady driven means , the hood is rarely lifted to check the oil, it has been found to be run low on oil several times , shortening it's life.

When looking for a used vehicle , ....... BEWARE   of the "Lady driven" comment added to many for sale descriptions.


 


The port work will be done today , the valve job is next , I'll be using standard size valves , back cutting the intake valves and cutting four angle seats. I've got to clean up the valves , then decide if I'll buy a set of high flow , stainless valves or not.   A performance spring set is being used as will a Hesco cam & lifters.

I have a couple of options............

Plan A     
Build a fresh long block  with new pistons , bearings , oil pump & timing chain and drop it in shortly after it's ready.

Plan B
Freshen up the engine that was rebuilt in 2005  with whatever is required.

Either way , I should order one of those ridiculous windshield banner stickers , have it printed to say  CHECK OIL  , then apply it to the inside of the windshield.


Here's what the engine is going in.

[Gearhead]

A couple more 2.5 porting pics

[Gearhead]

Finished up the four angle valve seats on the 2.5 head today and dug the spare 2.5 core out from under the snow and drug it inside. , it still rotates ! after sitting outside for three years !





I'm disassembling the  short block I have to get an idea on what it's going to need to freshen it up. So far , I've discovered the bores are standard , the rod bearings are standard , the main bearings are standard. I've yet to take some real measurements , a visual inspection looks like rod bearing journals need to be ground - .010" , the mains look good.

There's a raised pad on the upper right  side rear area of the block , here there will be a stamped code , this one shows.........       810HX24

What's it mean ?   

1st # is the year  , this one's an 88
2nd & 3rd is the month  , 10 being October
4th & 5th is  a letter code   HX  ,  that breaks down into  150 cubic inch , 2.5 l , TBI , 9.2:1 compression ratio
6th & 7th #'s  = the day of the month , the 24th of October 1988 was when this engine was born.

The disassembly continues and  it's time to start a list of parts needed.

The head turned out so nice I'm going to order a set of stainless high flow valves ,  to go with the fancy cam I've chosen.

A call to Hesco  , to order a cam , lifters and springs is on the list of things to do .

I'll be dropping off the block ,  crank , rods to be hot tanked , checked for cracks , resize the rod big end bores ,bore and hone the block for  + .030" pistons , install cam bearings , press the new pistons to the rods , align hone the main bearing bores if needed and more .

I'll have them order me an oil pump , bearings , rings , gaskets n' stuff too.

EDIT........................ !!!!!


Anyone have a pilot bushing for a 2.5 laying around ?  I need to know the OD of it , I'm thinkin this engine was in front of an automatic ? , the bore in the back end of the crank is 1.498" , this seems large , like ........ large enough to have the nose of a torque converter stuffed into it !     OR   am I panicing unnecessarily and the pilot bushing is in the flywheel , I forget 

[Gearhead]

Whoaaa  !!!!!!


The brakes have just been slammed on the 2.5 build.

I have pretty much stripped the entire block , in preparation for the hot tank           BUT !!


THERE'S A TEN INCH CRACK DOWN THE LEFT SIDE OF THE BLOCK  , just below the frost plugs , the external wall of the block is actually heaved outward  1/8" !!!!!!!!!      :'(        I removed the frost plugs , sprayed some liquid wrench into the cooling jacket and waited , bummer ! it seeped out  :'(

The crack !!

  :'( :'(


I'm angry now    , off to pout , there's gotta be a bottle of dark rum around here somewhere .   

[hps4evr]

where do you get performance cams for the 2.5...

[Gearhead]

where do you get performance cams for the 2.5...

From HESCO ,  no one company has the selection of Jeep / AMC engine parts available that these guys have.

[Gearhead]

Some updates

The 2.5 build is on hold for now , the plan is to refurbish the engine that is running and currently being used as a DD. That will happen in the spring , unless I find another 2.5 core to build . I've ordered a bunch of parts to do a 2.5 rebuild , The head work is mostly done , I've ordered hi flow valves for it.

Any one have a 2.5 core laying around ?  a carcass , you may be tripping over and want it gone ? , cheap ? free ?


The big valve 4.0  cylinder head is progressing , today , I'm doing the final preparations to the valve seats with a fine set of stones , cut to four angles.
This is a precision valve job , precision means , the seat is exactly where I want it , the face of the valves  below show a dull area where the actual seat is and is positioned where I want it , to the outer edge of the valve is a shiny margin area , the dull seat area and above that , a 30 degree backcut. To achieve the dull finish , I use lapping compound , this is merely to confirm & get a visual on where the seat is and how wide , normally valves don't get lapped in  , it's not neccessary.

 


To back cut the valves , the valve grinding machine is set up  by angling the chuck portion to grind a 30 degree angle. That cut is above the 45 degree valve face cut .  Again , this 30 degree cut is to promote flow early in the intake cycle , when the valve first leaves it's seat in the head and begins opening.
Carfull measuring and grinding puts all of the angles where they are intended to be.



The exhaust valve are not being back cut , it's not necessary but an equal amont of care is taken to get the same precision and seat placement.