Build questions from Alaska

[holeski]

New here and to building motors so I have lots of questions. I have been lurking for the last 2 days reading as much as I could. Of course I haven't read everything so if I ask something that has been covered before please direct me to that thread.

I live in Alaska so parts can be hard to find and good machine work next to impossible(big $$$$$). I run a small off-road fab shop and a club here, norakor.com. Motors are the one part I have never been good at, but hope to change this with all your help. I have two many Jeeps. 94 YJ on 40"s and lots of stuff to go with it. Motor is going to need love here soon. Everyone thinks its stroked now, just 40 over. Its all gearing in my case, but still sees 75-80 MPH.

More urgently is my 88 Comanche. The stock 4.0 was sick and I fed my old 88 XJ to it and swapped that 4.0L and NV3550 in. That motor sat for almost two years, but only had 60K from the last rebuild I had done in Ohio. Within a few months I was showing signs of Blow-by(bad blow-by) and coolant in the exhaust. I pulled the head tonight and no major failures I could see, but need to have it checked. Cylinders look a little scratched up.

So here starts the project. I stripped a 96 XJ that threw a rod. Head looks good. Assuming the 96 head is good can I run that and the intake/header on my 88 motor? If so what am I looking at gaining and is it worth it?

Parts I have:
2 complete 88 XJ 4.0L motors
Most of 96 XJ 4.0L HO
Access to 258 parts
Set of Eagle rods(need to look and see specs) given to me by someone for real!

What could I do with all this?
What other things can I do to bump things up while I have it in pieces?
How big is air temps in building a jeep motor/stroker? normal winter temps her are between -20 to -40, summer 70 to 90
Pros & cons of a snorkel and facing the snorkels mouth backwards?

Thanks

[Cheromaniac]

You can use the following parts to keep things nice and simple:

'88 4.0L block (overbored)
258 crank
258 rods
Speed Pro 677CP pistons
'96 cam
'96 head
'96 valvetrain
'96 accessories

Engines make more power in cool air and since you live in a wet climate where roads can become flooded, a snorkel is a good idea and it doesn't matter which way the mouth is facing.

[holeski]

Snorkels are a must for me now on everything I have. I have had two hydro locked/blown 4.0s in my YJ and one on my old XJ. What I was kind of wondering is at higher speeds running the mouth facing the rear of the Jeep, if it could act like a venturi effect(think that is the right term) pulling air out? With it forward am I seeing a ram air effect with high speeds? And if so are there any gains there?

On my Wrangler the route to the air box is more direct then on the MJ/XJ. This is one area I want to shorten the path on the Comanche. I am running K&N filters on both in the stock air box. Should I be able to get enough air flow for the motor when tuning for useable power?

With the 96 head intake/exhaust what am I looking at to make it run electrical wise? Building this thing is one thing hooking it back up to run right is another.

Port an Polishing the heads. Seems the more I read about this the more I am confused. From what I grasp we want to polish more then port or remove metal? Don't make a wide spot that will create turbulence? you want the air to flow into the head easy and into the exhaust easy, but leave the step on the back side so air can't flow back easy?

[SilverXJ]

Ram air is a myth on slow land based vehicles. The snorkel will hurt your performance to begin with due to its small tubing and all the cuves the air has to travel through. However, its more important to keep your engine alive.

On the port and polish, you shouldn't remove a lot of material. Just basically smooth things out and polish the exhaust side. Don't do like some people do and open up the exhaust port to match the gasket or even the header.

[omegatron]

What is the consensus for the P&P on the exhaust? Is there any benefit from opening up the port just a little bit? Maybe just a 1-2mm enlargement or perhaps shaping the port to more of a circle as apposed to the oval shape that was cast?

[holeski]

As I understand it you lose low end torque and usable power by opening the exhaust up.

Checked my block and found it didn't match what was in the FAQ.
8933002665 and 706M26. If I understand my searching this block corresponds to the 53005535 block. Build date of June 26, 1987. But according to the FAQ that the "M" would make that a 258 block.

"The 258 can be identified by the 4th character of the engine build date code ("A", "B", "C" or "M"), stamped into the engine block below and between the number 2 and 3 spark plugs. An engine stamped with "B" is an early 258 with a 7.6:1 compression ratio. "A" and "B" are engines with 1-barrel carburetors, while "C" and "M" are 2-barrel. "M" originated in Mexico. Other codes ("E", "F", "K" and "L") are 232 engines."

I dubble checked this with the motor I took out since this one had been rebuilt before and came up with the same info with a slightly diffrint date. So are these 87 RENIX blocks a 258 4.2 block or 242 4.0L?

I have three heads, two 2680 that were on these blocks and the 96 0630.

The Eagle Rods I have are #CRS6150A3D and I believe comes with arp studs already pressed in
C-C Length: 6.150
Gram Weight: 660
Applications:
Jeep 4.2L, 258 c.i.- 2.095 crank pin / .912 piston pin / 1.063 b.e. widthNotes: +.025

[SilverXJ]

What is the consensus for the P&P on the exhaust? Is there any benefit from opening up the port just a little bit? Maybe just a 1-2mm enlargement or perhaps shaping the port to more of a circle as apposed to the oval shape that was cast?

Why? Do you have a flow bench?

[omegatron]

Just curious and in the P&P stage of my engine build. I didn't know if opening the port slightly or shaping it symmetrically would aid in better air flow ( & scavenging) for the increased displacement of the stroker engine. It seems there is a balancing act of preventing the back flow of exhaust by keeping a 'lip' from the cylinder head to exhaust header. Just trying to wrap my head around the process.

[holeski]

Pulled the head off since I noticed signs of coolant in the exhaust. I also had low compression on cylinders 3 &4.
#1~~~130psi
#2~~~130psi
#3~~~112/117/118psi
#4~~~117/117psi
#5~~~135psi
#6~~~136psi

From highest to lowest there is a 19psi difference. From what I have read thats out of specs..(120-150psi within 30psi of each other)
There are no water jackets on the block other then the front and rear. The head has them all around and the gasket just blocks them up. This seems to be where mine was leaking coolant into the cylinders. There was what seemed to be a grit or same in the water jackets also. The head gasket was pretty thick. I have seen where the JB weld them up to do a HO head swap on the 258, thinking this might be a good idea to do on mine too. Here are some photos, tell me what you all think.










Top head is the 87, 2680 casting, bottom one the 96, 0630 casting

[holeski]

You can use the following parts to keep things nice and simple:

'88 4.0L block (overbored)
258 crank
258 rods
Speed Pro 677CP pistons
'96 cam
'96 head
'96 valvetrain
'96 accessories

Engines make more power in cool air and since you live in a wet climate where roads can become flooded, a snorkel is a good idea and it doesn't matter which way the mouth is facing.

This block is already .030 over, should I go bigger?

[Cheromaniac]

Check the cylinders. You might not need to go further oversize but if you do, you can go +0.040" or +0.060".

[holeski]

So this is were I'm at with my Comanche,
87, block bore 0.030 over
96, 0630 head
96, valve-train
96, Intake
96, Accessories
96, cooling system
87, fly wheel turned and balanced with centerforce stage II
00+ NV3550 & NP231J with JB SYE

I know not a stroker yet, but I now have 5 complete motors and tons of parts to start building one soon as I get the hang of things. I need ideas for headers?? All the ones I have are cracked including my Banks which they wont warrantee since I didn't buy it direct from them. Should I just weld up the 96 header over the 87 or are there some truly good ones out there that wont brake the bank?

How do I get a ball park idea of the output, will all this give any real increases in power, torque or MPG? Considering I have the snorkel would boring out the TB be helpful at all or waist of time? Also which injectors would be better the stock 96 or the Ford multi hole ones?