4.0 rebuild question

By the way all you guys are great. Just wanted to say thanks to all for the advised and opinions. Its always good to bounce ideas off of trusted people that know there stuff!
 
84jimmy said:
By the way all you guys are great. Just wanted to say thanks to all for the advised and opinions. Its always good to bounce ideas off of trusted people that know there stuff!
Click to expand...

For what it's worth, you can buy a brand new Scat crank, Scat rods, and custom pistons for not much more than it costs to source and rehab oem parts.
 
a_kelley said:
rough price? I can get crank turned for $90.
Click to expand...

New Scat crank is $450. I would have had to buy one, turn it, and have it adapted to a late model balancer, so there was more involved. Rods were $325 and custom dish pistons were $500. I could have done it cheaper, but paid extra to specify the comp ratio and not have to dick with deck height and pushrod lengths.
 
shawn said:
For what it's worth, you can buy a brand new Scat crank, Scat rods, and custom pistons for not much more than it costs to source and rehab oem parts.
Click to expand...

shawn said:
New Scat crank is $450. I would have had to buy one, turn it, and have it adapted to a late model balancer, so there was more involved. Rods were $325 and custom dish pistons were $500. I could have done it cheaper, but paid extra to specify the comp ratio and not have to dick with deck height and pushrod lengths.
Click to expand...

Ok simply to prove a point... Yes scat crank rods pistons, new etc.

New custom pistons $250
4.0 rods - free from old motor to $100 plus $100 to recondition
4.2 crank - $150? $100 to turn
$100 bearings

Looks like $700 all in (and high side)
$1225 +/- scat route..

hardly, would i say it's as cheap as going the 4.2 route. And to further prove

4.2 crank and rods $200 + $150 machine shop (resize/recondition)
4.0 pistons $150 (guessed)
Decking block $125

That puts you at $625 all in.

Both those figures don't count (line/cylinder/cam) boring the block as that's the same across all three ways.

Sounds like scat still almost double the 4.2 route either way..... I'm not saying scat isn't good stuff. Just saying economy build, it's still worth going 4.2, for those of us without baller budget... Oh wait, that's LS territory. (In all reality, I bought a 87 yj for the crank and rods to build the stroker and drop the later model injection system in.. but that's a different story and a project I've moved on from due to life- it's in my driveway and no longer mine..)
 
My advise on a stroker is...
Watch out for the “if you”s and the “might as wells” .
They sneak up on ya.
If you went thru the expense to do .......... might as well do ........... if you did all that, it’s stupid to not do..........
Next thing you know you’ve got 2000+ in the most bad ass stroker motor that’s never been put together, and occupied a corner of the engine room for two years. One day that t176 will beg for mercy, one day.
Ask me how I know.


Sent from my iPhone using Tapatalk
 
josh m said:
My advise on a stroker is...
Watch out for the “if you”s and the “might as wells” .
They sneak up on ya.
If you went thru the expense to do .......... might as well do ........... if you did all that, it’s stupid to not do..........
Next thing you know you’ve got 2000+ in the most bad ass stroker motor that’s never been put together, and occupied a corner of the engine room for two years. One day that t176 will beg for mercy, one day.
Ask me how I know.


Sent from my iPhone using Tapatalk
Click to expand...
I'd assume since he has a Grand Cherokee. He's got a 42re, but yeah it'll beg mercy one day too.
 
a_kelley said:
Ok simply to prove a point... Yes scat crank rods pistons, new etc.

New custom pistons $250
4.0 rods - free from old motor to $100 plus $100 to recondition
4.2 crank - $150? $100 to turn
$100 bearings

Looks like $700 all in (and high side)
$1225 +/- scat route..
Click to expand...


If we're going to play that game, let's at least do apples to apples:

Pistons (KB421) $260
Rings $60
Reuse old rods $100 (to resize)
Buy, turn, and modify the 4.2 crank: $250 (highly variable, probably $150-350)
Mains: $65
Rod bearings: $35
Total: $770

All the above from Clegg with a Scat crank: $899

If you resize the rods and fit them with ARP bolts, it's going to cost you about $250. The Scats are $275 at Clegg

So, like I said, "not much more."

The "poor man" builds are cheaper, but come with compromises of their own.
 
shawn said:
If we're going to play that game, let's at least do apples to apples:

Pistons (KB421) $260
Rings $60
Reuse old rods $100 (to resize)
Buy, turn, and modify the 4.2 crank: $250 (highly variable, probably $150-350)
Mains: $65
Rod bearings: $35
Total: $770

All the above from Clegg with a Scat crank: $899

If you resize the rods and fit them with ARP bolts, it's going to cost you about $250. The Scats are $275 at Clegg

So, like I said, "not much more."

The "poor man" builds are cheaper, but come with compromises of their own.
Click to expand...


Cost to grind cranks is same whether 258 or 4.0, so add $100 to buy a 4.2 crank & Rods.

Add $20 to have new 4.0 pistons put on 4.2 rods.

4.0 overbore piston and rings price is same, so that’s a wash.

Cam cost is $179 + $20 for valve spring shims.

Gasket set is same for 4.0 vs stroker, same for bearings.

Yes it costs more to port the head, but can be done for under $200 plus some time. Biggest ROI found here for the stroker.

There is nothing that is that much more expensive about doing a simple stroker.

Now, going to offset ground crank, longer rods, custom pistons, ls-juan valves and springs, and aluminum head obviously pushes the price up substantially, but that’s not apples to apples comparison.
 
shawn said:
If we're going to play that game, let's at least do apples to apples:

Pistons (KB421) $260
Rings $60
Reuse old rods $100 (to resize)
Buy, turn, and modify the 4.2 crank: $250 (highly variable, probably $150-350)
Mains: $65
Rod bearings: $35
Total: $770

All the above from Clegg with a Scat crank: $899

If you resize the rods and fit them with ARP bolts, it's going to cost you about $250. The Scats are $275 at Clegg

So, like I said, "not much more."

The "poor man" builds are cheaper, but come with compromises of their own.
Click to expand...

Beat me to it. I forgot to hit reply earlier after typing ‍
 
Mac5005 said:
Beat me to it. I forgot to hit reply earlier after typing ‍
Click to expand...

No worries. It's one of those things - you can spend as much or as little as you want, and there are pros and cons to every build strategy. My only point from earlier was that the Scat stuff is high quality and fairly affordable, especially so if you're having trouble finding a crank.
 
So if I go with a cam that wont require me to change springs and retainers should I replace the old ones that are currently in? They are coming out of a motor that has over 250,000 miles on it. Not sure if they would be compromised. What about the stock valves? should I replace them or only replace the valves and springs if they are needed?

What it looks like im going with as of now. AMC 258 crank and rods, kb421 pistons (want to keep the 8.8.1 CR), new cam, heavily ported head and intake after being reconditioned with new seals and 3 angle valve grind.

I am trying to do this on a budget but dont want to cheap on things like valves and springs that could potentially have a failure and ruin my motor. I know you get what you pay for but I also know that after this more then likely I will blow my tranny and be replacing the 42re. There are two that I am looking at both around $1500-1600. So that extra cost is a factor. ( just incase anyone is curious or has opinions the two I am looking at are at https://www.bestbuytransmission.com/42re-transmission and 42RE Transmission For Sale, Rebuilt A500 )

again opinions are always welcome!

If I do replace the springs, retainers, valves and so on will it be cheaper to go through the machine shop I use or where I will order the parts?

Lastly (seems like this post has gone way to long) anyone have any experience with Prestige Motorsports machine shop located in concord NC (Performance Engine Builders | Concord | Prestige Motorsports) Was recommended to them by someone.
 
Replace the springs with OEM late model 4.0 ones. They upgraded them (stiffer) around 03.
But if it were me, I'd break in the new cam with the original, weaker ones (it'll limit wear on the cam during break in)
See how the tranny does after the engine rebuild. Tighten up the TV cable a click, add a cooler, replace the converter while the engine is out.
 
Jody Treadway said:
Replace the springs with OEM late model 4.0 ones. They upgraded them (stiffer) around 03.
But if it were me, I'd break in the new cam with the original, weaker ones (it'll limit wear on the cam during break in)
See how the tranny does after the engine rebuild. Tighten up the TV cable a click, add a cooler, replace the converter while the engine is out.
Click to expand...

Exactly what Jody said.

Break in cam with light springs, and add extra zddp to the oil for break in. I’d go with rotella white bottle oil for break in, then switch to blue bottle rotella after 3k miles.

Follow proper cam break in procedure.

I wouldn’t worry with new valves unless they are in bad shape. A good 3/5 angle valve job will be sufficient. I wouldn’t change retainers or keepers, unless you find issues with them.

Once you break in the cam and change the oil, swap to new oem springs.

Have machine shop get new springs and verify their pressures. This is the time to measure bind height and if you can/need to add shims under them to get spring pressure up a bit. This will ensure they are all good to go before install. If it were mine, I’d be wanting to get 105-110 lbs with the valve closed.

Have machine shop check installed height, spring psi, actual lift, etc when doing the valve/seat work.

Make sure to use clevite 77 bearing lube on all bearing surfaces during install.

Plastigauge everything during assembly.

Before you crank for first time, pull plugs, add some oil to tops of pistons, and use started to spin engine to verify good oil psi, before it fires.

Brings up the next point. Get a Melling high volume oil pump and put in it. Cheap insurance for long term.

Rotella oils have higher zddp than others, that helps the hydraulic flat tappet lifters and cam lobes stay alive. This is why you add extra zddp during break in. Just no synthetic oils for break in.

For the first 3k miles, don’t run wide open, and don’t run steady state. A little more difficult to seat rings well with auto, with a stick I make long high load pulls by upshifting early, to slightly lug the engine, then let it rise in rpm slowly, but high load. This is exactly how we would seat rings on the dyno. High load, 2/3 to 3/4 throttle, long slow pulls.

As far as trans, do what Jody said, new filter and converter while the engine is out, and adjust the tv cable. Install a bigger auxiliary cooler to keep the trans cool and it’ll be fine.

Match cam and converter specs. If you want to optimize the setup while doing it.
 
84jimmy said:
So if I go with a cam that wont require me to change springs and retainers should I replace the old ones that are currently in? They are coming out of a motor that has over 250,000 miles on it. Not sure if they would be compromised. What about the stock valves? should I replace them or only replace the valves and springs if they are needed?

What it looks like im going with as of now. AMC 258 crank and rods, kb421 pistons (want to keep the 8.8.1 CR), new cam, heavily ported head and intake after being reconditioned with new seals and 3 angle valve grind.

I am trying to do this on a budget but dont want to cheap on things like valves and springs that could potentially have a failure and ruin my motor. I know you get what you pay for but I also know that after this more then likely I will blow my tranny and be replacing the 42re. There are two that I am looking at both around $1500-1600. So that extra cost is a factor. ( just incase anyone is curious or has opinions the two I am looking at are at https://www.bestbuytransmission.com/42re-transmission and 42RE Transmission For Sale, Rebuilt A500 )

again opinions are always welcome!

If I do replace the springs, retainers, valves and so on will it be cheaper to go through the machine shop I use or where I will order the parts?

Lastly (seems like this post has gone way to long) anyone have any experience with Prestige Motorsports machine shop located in concord NC (Performance Engine Builders | Concord | Prestige Motorsports) Was recommended to them by someone.
Click to expand...

Look up Newcomer Racing, no personal experience of with him but I've heard nothing but good things about him. He's in the Concord area.
 
I was thi king about having the machine shop put the short block together just for peice of mind. Didnt think it would be that expensive. Especially if they are resizing and checking clearances
 
Highly recommend Kanapolis Engine repair, and I would also highly recommend an Enginetech gasket kit, which can be had from them.

If I were going to have an engine done that’s where I would go and it’s not as close to me as it probably is for you. They helped with my last 4.0, and they also done a complete rebuild on my buddy’s Jeep with a 1 year warranty.
 
84jimmy said:
I was thi king about having the machine shop put the short block together just for peice of mind. Didnt think it would be that expensive. Especially if they are resizing and checking clearances
Click to expand...
the machine shop will check sizes and bearings, you just double check behind them. As far as assembling the engine, it's easy enough to do, just some details to pay attention to. As far as zddp in oil, use blue stp, it's got lots in it. There is also another zddp only additive by Lucas in a tall skinny bottle.
 
84jimmy said:
I was thi king about having the machine shop put the short block together just for peice of mind. Didnt think it would be that expensive. Especially if they are resizing and checking clearances
Click to expand...

The machine shop I helped at made the most money on assembly work, not actual machine work.

Nothing wrong with having them assemble it, but cost can be an issue.

It’s definitely not too complicated. Just take your time, check everything and torque everything to spec and in correct order.
 
I was only going to have them assemble the long block. Might be more open to doing it myself if anyone wants to help on here? Beer and food is always free! Just never done a complete bottom end before myself....well at least the putting ot back together part. Taken plenty of them apart
 
So I read somewhere on another forum that

"The early 258 crank was designed for use with the Borg Warner automatic, and requires an adapter to be used with a Torqueflite automatic"

What is my 42re Borg or torqueflight? Will I need an adapter?

I've also been heard that the earlier model cranks with 12 counter weight compared to the newer 4 are stronger and better, yet all of the new scat stroker kits for sale come with 4 weights. Why would they not be 12 if the 12s are better?
 
Some people prefer the 12 ctw due to its extra weight and therefore more inertia, which is more beneficial on a manual trans. A Lighter crank will rev up faster than a heavier crank (more HP but same torque, for no extra work other than lighter).

The early crank is one from way on back.. the crank from a later model 4.2 will bolt right up to a 42re with your existing flexplate (as the yj used it's little full hydraulic controlled brother 32rh)
 
a_kelley said:
Some people prefer the 12 ctw due to its extra weight and therefore more inertia, which is more beneficial on a manual trans. A Lighter crank will rev up faster than a heavier crank (more HP but same torque, for no extra work other than lighter).

The early crank is one from way on back.. the crank from a later model 4.2 will bolt right up to a 42re with your existing flexplate (as the yj used it's little full hydraulic controlled brother 32rh)
Click to expand...

So the one I'm getting from you will bolt right up to my 42re?
 
Back
Top