1988 Jeep YJ Wrangler 2.5L TBI Cylinder Head and Block Casting Identification Issues

[Melchehabi1]

I'm replacing the head on a 1988 wrangler YJ when i noticed a couple odd casting +head numbers. If my research is correct, I have a 88 head (or possibly 84) on a 83 engine block...Is this ok??? 

 

What's led me to believe this?

Head #s are 3242 893. The 893 matches the Cast # that i looked up when ordering a replacement through Autozone. 

Though there is also the number 84 written on the block a little further down...making me think it may belong to a 1984 cj7?

 

The engine cast # is 312U07. The other number on the engine block is 3239448. Sources online say this was an engine built on 12/07/1983.

 

Very confused here. Can anyone shed some light? Is this engine ok to use with a tbi? Apologies if that's a dumb question. Any help is greatly appreciated.

[Moses Ludel]

There are no dumb questions, Melchehabi1...One of the best resources I've found around interchangeability of head or block casting numbers is major engine remanufacturers.  I took your question into the ATK/VEGE catalog and found this information:

2.5 / 150 L4 86-83 U CJ7, Cherokee, Scrambler, Wagoneer, OHV, 8 Valves, Carb, Naturally Aspirated, Gas, Complete with Valves & Springs, 7/16" Head Bolts In line 117, 403, 645, 684, 893 2A24

2.5 / 150 L4 97-86 E, H, P, U CJ7, Cherokee, Comanche, TJ, Wagoneer, Wrangler, OHV, 8 Valves, Carb & FI, Naturally Aspirated, Gas, Complete with Valves & Springs, 1/2" Head Bolts In line 117, 403, 893 2A27

[2.5 / 150 L4 02-98 P Cherokee, Wrangler, OHV, 8 Valves, FI, Naturally Aspirated, Gas, Complete with Valves & Springs In line 117, 403 2A36]

The catalog download in PDF is at http://atkvege.com/wp-content/uploads/sites/5/2018/12/head2016.pdf.  See page 53 and further.

The 893 casting shows up for 1986-97 engines with 1/2" head bolts, including your TBI 2.5L.  This casting number also shows up for 1983-86 carbureted and TBI/EFI engines with 7/16" head bolt sizing.  Head bolt sizing determines which replacement head you need.  It appears that AMC resized the bolt threads for the 1986 model year with some carryover of 7/16" block/heads that year (not unusual).  If the 893 was actually used as a 7/16" bolt size prior to the bolt size increase, 1/16" is slight enough to not need a new head casting.  The head could be machined for 1/2" bolts (a 1/32" or 0.03125" radius increase) instead of 7/16" bolts.  Presumably, the head-to-block bolts needed more clamping force, the reason for the size increase.

What this indicates is that the 893 head will work for either EFI/TBI engines or carbureted engines, and that's the real concern.  According to the ATK/VEGE catalog, this head casting can be used on any 1986-97 Jeep 2.5L engine with 1/2" bolt sizing, which actually surprises me.  If so, the head will work on a 1991-97 MPI engine.  The significant cylinder head change year group is 1998-2002, likely for emissions reasons. 

This 893 casting head is common and correct for a 1987-90 TBI 2.5L.  For ordering purposes, ATK/VEGE breaks out the head differences by 7/16" or 1/2" bolt sizing.  AutoZone and others order from ATK/VEGE and similar reman shops.  Their information would trickle down from the remanufacturer's references.  Is your block and head 1/2" thread size?  ATK/VEGE would supply their 2A27 cylinder head part number.  If 7/16" bolt size (1983 to 1986), the head would be the 2A24 part number.

The reman industry catalogs suitable interchangeability of parts, not pinpoint "factory" cylinder head and block part numbers.  Below are actual part numbers for the 2.5L carbureted and EFI/TBI engines.  Note that there is a distinction.  My guess would be that the 83502487 OEM Mopar part number is the 893 head, as it is shown fitting 1986 carbureted Jeep CJ engines and also the fuel injected (TBI) 1987-90 engines.  The block and cylinder head significant difference is the bolt sizing, which again shows up in the common 1986 and 1987 use of the 83502487 part number.  Part numbers and casting numbers are not the same thing, but these Mopar part numbers follow the pattern for the 893 casting.  These are actual Mopar catalog part numbers from that era:

1 HEAD, Engine Cylinder  1983-86 Jeep CJs with the Carbureted 2.5L Engine

83500254  1983
83500675   1984-85
83502487   1986

1 HEAD, Engine Cylinder 1987-90  Wrangler 2.5L TBI Engine

83502487 1 Injected #2403
83502488 1 Carbureted #2405

Moses

[Melchehabi1]

Moses- You’re knowledge and expertise is extremely appreciated. I’ve read many of your postings and the help I’ve received from them has been priceless. 
 

it looks like it’s the 7/16 bolts, verifying that it is indeed an earlier engine if I understood your post correctly. 
 

I do have one more question....it looks like my valve cover may not be correct. I’ve been looking through pictures of 2.5 tbi engines and it doesn’t seem like mine is correct. The pcv on in front is on the side, not on top. Is this a newer valve cover? Is it ok to use.

i found the plastic valve cover replacement on rock auto and the front pcv but can’t find the taller rear one. Any idea where there’s one or an alternative available? Can I use a ccv instead?

[Moses Ludel]

You're welcome, Melchehabi1...Yes, you do have an '83-'85 (possibly early '86) block and head assembly.  This "long block" should work fine with TBI despite the 7/16" head bolt sizing.  If you have run the engine a bit, I would recheck the torque on the head bolts.  Do not overtighten, just verify the torque to factory specification...The change year and engine group with 1/2" bolts was 1986-97.  1998-2002 is also 1/2" head bolts with a different cylinder head configuration.

As for the valve cover, the picture below is my son-in-laws original engine in his 1987 YJ Wrangler.  Note the PCV, oil filler and Ventilation Valve Filter at the rear (Mopar Part Number 53002466).  This would be "stock" on your original engine.

Below is 1991 2.5L with MPI...Note the fill cap at the front and two rubber grommets (#14) front and rear.  (This is similar to the 1987-90 design.)  The grommet part number is 53004721 for this 1991-93 valve cover.

Below is 1994-96 2.5L MPI design...no grommet, just a fill cap near the middle.  The same illustration applies from 1997-2002.

So, I'm unclear about the Rock Auto valve cover and use of CCV, which was common on later 4.0L engines.  Can you post some photos?  The concern with CCV is to make sure the valve cover has an internal baffle or plate to prevent sucking or blowing oil from inside the valve cover area and into the air cleaner box.  Some photos of the valve cover, inside and outside would be helpful.  Also, where did the hose from your original Ventilation Valve Filter attach?  Does the tube run to the air box?

Moses

[Melchehabi1]

Perfect! 53002466 is exactly what I was looking for. The rock auto cover seems to be correct. It’s the current cover with the CCV that seems to be incorrect. I’ve attached a photo of it. I did have oil and what seemed to be coolant in my air box so I’ll definitely switch covers in that case. 

[Moses Ludel]

Yep...That would be the wrong cover if the CCV tube wafts oil into the air box.  Is there emulsified oil (milky mix of oil and water or coolant) under the valve cover or at the upper valvetrain?  If not, the water or coolant in the air box could have gotten into the air box during parts fitting, from a seeping hose or a possible radiator leak.  Hose or radiator leaks can spray coolant into the pickup tube for the air box.

Causes of emulsified oil would usually be a head gasket leak or a casting crack that allows coolant to get into the lubricating system.  Without the original Ventilation Valve Filter and a properly working PCV/closed crankcase system, condensation from the crankcase could pass through the CCV tube and enter the air box as water rather than coolant.

So, are you replacing the cylinder head only or the long block (block assembly and head)?  Do you have a complete replacement engine, or are you working with the engine shown in the valve cover photo?

Let us know how this all turns out...

Moses

[Melchehabi1]

Had a bad manifold gasket leak and was planning on just changing that but when I started it seemed like most bolts were pretty loose on the manifold. Changed the gasket and as I was tightening the bolts down I realized that one of the bolts just kept spinning. I’m assuming PO tried to change and stripped the threading. Decided to just change the entire head given autozone had one for $280. 
 

PO seemed to have changed a majority of the cooling system(hoses, radiator, thermostat) so I don’t think it was that.
 Took off the heads but the gasket looks intact. Are you saying there could be a crack in the old head of block that would cause coolant to leak in there. 
 

looked like the emulsified oil was coming in there from the direct ccv to air box hose.

The new head came in last night. I’m trying to find replacement bolts for it but am having trouble online. I can find a ton of 1/2 inch ones but never any 7/16... Any recommendations? 
Do you recommend changing the push rods and rocker arms as well? 

[Moses Ludel]

Melchehabi1...If the oil in the air box is emulsified, that could be a casting crack or head gasket issue.  More likely, if the cooling system has not been losing coolant, the emulsified oil is just crankcase condensation.  As you share, the closed crankcase system needs restoration. 

To keep condensation from forming in the valve cover area, the closed system consists of the PCV valve (creates low pressure/vacuum) and a breathing source (the Ventilation Valve Filter intake of fresh air).  If there is no PCV valve and vacuum hose, there will be no low pressure source to draw out condensation.

When you restore this system with the new valve cover, you will need a PCV valve attached to the correct vacuum source:  This will draw.  The vent filter side will be the fresh air intake:  Fresh air drawn through the engine and crankcase will pull out crankcase fumes and condensation. 

 What is the application (year and model) for the 53002466 valve cover?  If you run an '88 air intake and 1987-90 style valve cover, the Ventilation Valve Filter and a PCV valve would be required.  CCV valve covers use the flow-through elbow at the valve cover.

As for pushrods, it's a good idea to check the pushrod lengths.  Use a CompCams gauge like we discuss regularly at the forums.  Since you are installing a machined cylinder head, you will not know how much the head deck has been surfaced, the height of the valve stems or the amount of valve seat grinding.  Checking pushrod length will determine whether new pushrods are mandatory.  (See our many posts and replies regarding the use of a CompCams pushrod gauge.)  

Rocker arm replacement is elective unless there is excessive wear or roughness at the valve stem tip-to-rocker arm contact point.  If there is wear that can be felt with a finger, shops will either surface the original arms or replace them.  If arms are inexpensive and there are signs of wear, consider replacing the rocker arms.

Head bolts should be available from ARP (spendy but superior quality) or through Pioneer (https://pioneerautoinc.com) and Dorman.  You would need to match lengths if there is not a direct listing.

Here are the OEM Mopar head bolt part numbers for 1984-85 7/16" 2.5L head bolts.  Determine how many need an attachment stud at the top.  Order accordingly, there may be superseded part numbers for each type:

BOLT
J4006593  1984-85 shorter conventional head bolts without stand-up threaded stud for attachments
BOLT
J4007170  1984-85 longer conventional head bolts without stand-up threaded stud for attachments

BOLT, Stud
J4006955 [As Required "AR" quantity] 1984-85 with stand-up threaded stud for attachments...these are longer bolt length like J4007170

Moses

[Melchehabi1]

Thank you for the notes on the pcv system. Parts come in late this week and I travel for work until the following week so I won’t have an update for a little while.  
 

Will review the CompCams in the meantime. 
 

Going ahead and will order the bolts. Thank you for the ARP recommendation. They didn’t have a kit but I was able to find the bolts separately on their site. Well none with the stand up threaded stud but there was only one ground connected to it. (Picture below) I’m sure I can find another place for it so it should be fine going with all regular bolts.

However I did run into a possible issue...The bolts are all 1.25 in in thread length. The PO replaced one of bolts with a 2.00 in thread size. Since the overall length is still the same, my initial thought was probably no damage was caused but wanted your thoughts.

Are the valve cover bolts reusable or should I replace as well?

 

Im ready to get this back on the road!

[Moses Ludel]

Melchehabi1...Make sure you wind up with a solid engine to body ground, using either the existing ground strap or a battery grade cable.  The ground circuit is important:  battery ground to engine, frame and body.  They need to each handle the same amperage as the battery cable to starter.  On magazine project vehicles, I would use 1/0 welding cable with professional grade crimped terminals.  That's overkill for a stock electrical system with or without a winch.  I did this on 4x4s equipped with an onboard frequency welder. 

The shorter thread length is better as long as the threads are not below the cylinder head bolt holes.  Simply put, when you clamp the head and head gasket into place, there should be a few threads still up in the head holes.  You don't want to run out of bolt threads before the head clamps in place at full torque.  You're better off with the shorter threads if they work, as the un-threaded bolt shank is stronger than the threaded portion.  More shank, more strength.  Measure the bare head's bolt hole depths.   There should be two distinct hole depths.  You will be ordering two bolt lengths.

Reusing the valve cover bolts (if OEM) is perfectly acceptable.  The normal torque figure on these bolts is well below the point of stretching the threads.  If you are concerned, take a new bolt with the same thread pitch and align the threads with the OEM bolt threads.  The threads should mesh with no daylight.  If there is misalignment, the OEM bolt threads have stretched.

Moses