Topic: 2.5 Rebuild Q & A 's

[Gearhead 88]

I'm starting a rebuild on a spare 2.5 core I had laying around , for now I'm disassembling and evaluating what's here.

Based on the stamped code on the block , it's an 88 , built October 24th.

The bore is standard , the rod and main bearings are standard. 

I'll be having the block bored + .030" and the crank ground - .010" & .010"

I'm thinking this engine was in front of an automatic trans but not sure , there is no pilot bushing in it . The bore size where the bushing would go is 1.498" ,  is this common to all 2.5's  ?   or   would this be the size that would accept the nose of a torque converter ?

I would like to know if I can use this crank or look for another.  OR    am I panicking unneccessarily and the pilot bushing is pressed into the flywheel ?
I can't remember   

It's going into a 94 YJ w/ AX 5  for my sweetie , this Jeep being the little sister to my 88 W/ 4.7 stroker.

If anyone has a spare pilot bushing laying around could you please measure the OD and post up the size please.

Oh , just so this doesn't appear to be another newby request , it's not , this is going to be a performance build .

Hesco cam , Bank'sexhaust system ,  ported  & polished head , high flow valves to compliment the bolt ons and external items already done.

What's already done ? , cold air intake , 4.0 throttle body , electric fan , 4.88 gears , flowmaster muffler , MSD coil & wires.


The head .........................




Thank's in advance


I'll try to keep this updated , the block , rods and crank are going to the machine shop soon.


Oh , my 4.7 is getting some upgrades too , a ported & polished big valve head , like this .........





 

[chardrc]

  I love it.... sounds like the other high performance 2.5l build on this forum.. hopefully this one turns out as good if not better.

[Gearhead 88]

The brakes have been applied hard to this project.


I was in the process of striping the block of every last removable item then , noticed the ten inch crack , just below the freeze plug holes . At first I couldn't believe my eyes , then I popped out the freeze plugs and sprayed some penetrating oil into the cooling jacket , it weeped out 
The outer wall of the block is actually heaved out 1/8" !!!


Plan B is to freshen the engine that's in the 94 now and use the high perf stuff on that .


The reason I'm doing this to begin with is , the existing engine has nearly 100,000 on it since it's last overhaul , which was thorough , consisting of  new everything . It's "lady driven" , meaning the hood is rarely raised to check fluids and has been run low on oil a number of times . Recent compression and leakdown tests have shown the need for further attention.

Based on measurements I'll be taking when I tear into  it , it may  only need re-ringing and bearings , we'll see .......................

Such drama   

The crack .........



Bummer , I believe I'll pour a drink now. 


Yes I did promise  updates ,  this was not what I had planned as an update !

[czjeeper]

Pilot bushing/bearing is in the flywheel.

[Gearhead 88]

Pilot bushing/bearing is in the flywheel.

I kinda thought so ,  I'm old   

[TahoeYJ]

Sounds like you're set on what you want to do. I can't give you any advice really over what you already know (I'm a youngin' anyway :) )

Where did you find the high-flow valves? I've slowly started doing some P&P on my old cylinder head when I have the time, and was curious if there were any valve upgrades. I do not know at this time if I'll go as far as punching out my old block, but it's possible.

Everyone laughs when you say you're building up a 4 popper. I laugh when my 4 popper passes their lifted 4 liter, re-geared to compensate for 35" tires down the highway at 80. People with 6 cylinders don't like it when you're able to pass them 

[Gearhead 88]

Sounds like you're set on what you want to do. I can't give you any advice really over what you already know (I'm a youngin' anyway :) )

Where did you find the high-flow valves? I've slowly started doing some P&P on my old cylinder head when I have the time, and was curious if there were any valve upgrades. I do not know at this time if I'll go as far as punching out my old block, but it's possible.

Everyone laughs when you say you're building up a 4 popper. I laugh when my 4 popper passes their lifted 4 liter, re-geared to compensate for 35" tires down the highway at 80. People with 6 cylinders don't like it when you're able to pass them 

Set on what I want to do ? , yup ,  I've build many  engines , decisions on a build are based on what works , often good old hot rod techniques that have been used for years are what get satisfying results.

Valves can be sourced from several  suppliers , Hesco , Mopar and a few others . The valves I've chosen work well with ported heads and multi angle valve seats , the head of the valve is shaped to enhance air flow , stock valves are shaped much like the head of a nail . Some stock intake valves have a small 30 degree back cut , which helps with flow , as the valve initially leaves the seat , back cutting an intake valve that has a single 45 degree angle with an additional 30 degree angle improves the flow of that valve. This is an additional step that must be requested when a head is being re-conditioned , I do my own head and valve work so I just make it happen when I choose to , multi angle seats help alot , I routinely do this as well.

I happen to like these little engines , they have some desirable  features . I like the fuel economy , the ease of maintenance , the light wieght and reliability , all good qualities.

With the correct gearing  a 2.5 is a fine engine in a Jeep , combining gearing and performance work just makes sense. Swapping in a bigger engine ?   ppffffffff , I'd rather buy a Jeep that already has the 4.0 , than go through all the motions to convert a 2.5 to a 4.0.

[Mr_Random]

You forgot timing chain driven overhead valve non interference engine, with a low end torque oriented cam, and a short stroke for a decent power curve! It's unlike any other four cylinder I've driven, that's for sure... I love being able to pop the clutch and actually feel it go from the start, rather than "wait, wait, wait, 3500, almost there, 4000, THERE we go!" haha....

good luck on getting a block, if you were anywhere near arizona I would get you mine for cheap!

Wish I could have gone with your plans, my new engine got half of what yours did, Pistons .030 over, crank -.020 and -.030, port and polish, but no cam or valves... Don't worry much about the bearings, I got the engine not knowing it was rebuilt (half-assed mexican job) within 50,000 miles, and the machine shop said everything was fresh enough there was no reason to do anything but clean it up, so I left it with a weird bearing grind.

How much does a banks header cost? I know I've seen it before, just don't remember.