4.0 SOHC Performance Motor Build

I've been helping the mustang crowd come up with a decent set of rods to use in place of the stock forged I-beam rods and I've found a couple different options out there. I want to use this thread for documentation purposes for all the options found and eventually, there will be info about all things needed to build this motor along with the estimated cost. Finally, after the research is done I'm going to put a motor together.


The Objective

A 4.0 SOHC that will consistently hold 500HP and 600HP at the drag strip. (for a decent cost) - in other words, if this can't be done for a certain price, then a different motor is a better option.


Stock 4.0 SOHC INFO

Deck Height 8.858
Bore 3.953
Stroke 3.31
Rod Length 5.748
Piston Pin Height 1.44


Cylinder Bore
Diameter 3.9530
Out-of-round limit 0.0010
Taper 0.0010


Piston / Rings
Standard DIA 3.9520 3.9528
.5 MM OS 3.9716 3.9724
1 MM OS 3.9900 3.9910
Piston to bore limit 0.0012 0.0020
Compression Ring end gap (top) 0.0080 0.0180
Compression Ring end gap (Bottom) 0.0180 0.0280
Oil Ring Snug Fit


Crankshaft and connecting rods
Crankshaft endplay 0.0020 0.0126
Connection rod journal DIA 2.1250 2.1260
Out-of-round and Taper limit 0.0003
Bearing oil clearance (desired) 0.0003 0.0024
Bearing oil clearance (allowable) 0.0005 0.0020
Connection rod endplay 0.0036 0.0106
Main bearing journal DIA 2.2430 2.2440
Out-of-round and Taper limit 0.0003
Main bearing oil clearance (desired) 0.0008 0.0015
Main bearing oil clearance (allowable) 0.0005 0.0020


Valves and related
Intake
valve seat angle 45 Degrees
valve seat width 0.0600 0.0940
valve seat runout limit 0.0020
Stem diameter standard 0.2740 0.2750
stem to guide clearance 0.0010 0.0020
valve face angle 45 Degrees
valve face runout limit 0.0010

Heads
68CC cambered

Camshafts
lobe lift (intake and exhaust) 0.2590
Allowable Lobe lift loss 0.0050
endplay 0.0003 0.0070
Journal DIA (ALL) 1.1000 1.1040
Bearing Inside DIA (ALL) 1.1020 1.1040
Journal-to-bearing (oil) clearance Standard 0.0020 0.0040
Journal-to-bearing (oil) clearance Service Limit 0.0060

Rods

Rod Option 1

The first rod option is a Forged H-beam Manley rod that states it holds 700-800HP on a 4.6 V8. We v6 dudes have to overkill here because 500 HP on a v8 is different for 500HP on a v6.

4.6 L Stroker w/ 22 mm pin and a 2.000" crank journal
Part No. 14044-8
Center-to Center 5.850"
Big End Bore 2.125"
Big End Width .940"
Pin End Width .940"
Pin Bore .8671"
Gram Weight 612


Here is the rod.



With this rod option, the rod journal (big end with the lip) will have to be narrowed by .064" per side. It should only be the little lip you see sticking out. The chamfer will then have to be re-cut and this should be it.

This rod is longer than the stock 4.0 SOHC (Stock is 5.748" and this one is 5.840") this means the custom piston being made needs to have a shorter pin height.

Custom pistons with floating pins will then need to be made to whatever compression you want. These rods go for around $579.50 for a set of 8. This means if you buy 3 set's for a v6, the fourth set is free. Furthermore this means the rod cost per rod will be $72.44 (Not counting the machining cost) If we estimate the machining cost, say 150.00 per set of 8, we come up with $91.19 / rod.

The H-beam rod option already available for the 4.0 SOHC is $125.00 per rod so you can see we've already beat that.

So, to recap this option.

Estimate $91.19 / Rod
Estimate HP the rod can handle is 700-800HP

This should be good for 500HP on the 4.0 SOHC


Rod Option 2

SBC rods.

UPDATE (9-5-2009) - I've decided to go this route for rods. The first option is still available; however, the cost was the deciding factor.

The second rod option is a SBC eagle H-Beam rod that is 5.7" long from center to center. The stock 4.0 sohc rod is 5.748" so this rod is .048" shorter. This means the custom piston being made needs to have a longer pin height depending on the compression desired. The rod journal bore on this rod is 2.1" where as the stock 4.0 SOHC has a 2.125" rod journal. This means the bore has to be opened up. The cost per a set of 8 is lower for this rod ($359.00) so this puts us at $44.87 / rod. The machining cost will offset this and I'll update the thread when I get the info.

The good about this option is the ARP rod bolts are 7/16" where as the first option has 3/8" rod bolts.



Pistons

Compression Ratio for boost

UPDATE (9-5-2009) - I've decided to go with a 9.5:1 compression ratio (custom forged piston) and then get the piston tops coated.

Here is a formula for helping pick a compression ratio for a boosted engine. Anything between 16:1 to 18:1 is what to shoot for on a street set-up. Anything above 20:1 is race car country.

((boost psi / 14.7) + 1) x motor compression = effective compression.

Here is the 4.0 SOHC with 9.7:1 compression running 14 LBS of boost...

Effective Compression
18.93809524

Here is the 4.0 SOHC with 9.5:1 compression running 14 LBS of boost...

Effective Compression
18.54761905

Here is the 4.0 SOHC with 9.5:1 compression running 16 LBS of boost...

Effective Compression
20.25782313

Here is the 4.0 SOHC with 9.5:1 compression running 50 LBS of boost...

Effective Compression
42.69319728
(Okay, this is a little much)


A motor with 8:1 compression running 18 lbs boost VS a 9.5:1 compression motor running 12 lbs boost will have almost the same effective compression and about the same peak power. The big difference will be where you see the power, and how much of a demand will be placed on the supercharger/turbo. Obviously, the 9.5:1 motor is going to have far greater torque and low end power as the boost is only starting to come in. It is also going to be much easier to find a blower/turbo to survive at only 12 lbs of boost -vs- one that would have to put out 18 lbs of boost. It is now very easy to see why a higher compression motor with lower boost is becoming so popular.

Assembly Instructions

Download SOHC_Engine.pdf from FileFactory.com

There's still a BUNCH of work that needs to be done here so this should be considered "A work in progress" until I remove this line from the thread.

 

[Jakee]

Whoops....Well, let's call that post 50/50...LOL


"Hindsite is 50/50 when you still have your head up your BLEEEP"

 

[Jakee]

The RTV slowed the leak down but it's still there. I thought it did the trick but once the pan heats up the leak starts agian.

 

[Jakee]

The RTV slowed the leak down but it's still there. I thought it did the trick but once the pan heats up the leak starts agian.

Maybe it did work. After letting it cure for 24 hrs (opposed to 12) I'm not seeing anymore oil. This may of done the trick.

Rob - I know logging is the best way, but to tell the difference between spark blow-out and detonation, can you examine something (maybe plugs) or know which one it is if I describe the symptoms?

Basically, at around 3500 @ WOT it's starting to cut out and loose power. I ofcourse get out of it quickly but It doesn't sound like the detonation I've heard in the past. If it is spark blow-out, what would I look for?

 

[rocket 5979]

Maybe it did work. After letting it cure for 24 hrs (opposed to 12) I'm not seeing anymore oil. This may of done the trick.

Rob - I know logging is the best way, but to tell the difference between spark blow-out and detonation, can you examine something (maybe plugs) or know which one it is if I describe the symptoms?

Basically, at around 3500 @ WOT it's starting to cut out and loose power. I ofcourse get out of it quickly but It doesn't sound like the detonation I've heard in the past. If it is spark blow-out, what would I look for?

Yeah that RTV takes a while to cure fully.

To determine what you are encountering I would take your existing tune and drop a bit of spark advance out of it so you know it should not be detonating. If the engine doesn't cut out anymore then it is likely to be spark advance related. If it still cuts out then I would pull your plugs and gap them a bit smaller. If this takes care of the stuttering issue then you know you got it figure out. Then from there I would just methodically add spark advance back into the tune until you start to chatter the valves a bit and then back the timing off a few degrees and set it at that.

What hardware or software changed in your combo between when it was running well a year or so ago and now that could cause this issue to arise?

 

[Jakee]

Small changes only. The PCV system is now tied back into the intake pre-turbo in an attempt to create a vacuum to help rid the crankcase pressure. The actual PCV side of the system goes thru a oil-separator then into a oil catch can. The side that use to hook to the stock intake is now going into the same oil catch can. The catch can is connected to the intake pre-turbo. I don't see any traces of oil in the system yet; even the catch cans.

The pipe section that connects to the turbo was cleaned up (ported). It had a bunch of welds in the exhaust flow before, Especially the waste gate side.

The back wheels are wider and heavier…not sure if this changes the load enough to make a difference. I can say that it didn’t really help the traction problem. It’s now just a heck of a-lot louder spinning.

The gas may still be contaminated from sitting for so long.

Also, it appears I'm running 1 more pound of boost (for a total of 10). Either the crack in the intake (which I fixed) or the cold weather is causing it cuss I didn't adjust it yet.

I want to run 12 lbs in the future.

 

[Limited02]

Can the factory fuel system support what's needed for your current turbo setup? As in, do you think maybe it's starving of fuel when you go WOT around 3500rpm? Just a thought.

 

[Jakee]

Can the factory fuel system support what's needed for your current turbo setup? As in, do you think maybe it's starving of fuel when you go WOT around 3500rpm? Just a thought.

Naw, I'm running a walbro pump and 42LB injectors.

When I get off my rear and log, i'll figure out what's going on.

 

[Limited02]

Naw, I'm running a walbro pump and 42LB injectors.

When I get off my rear and log, i'll figure out what's going on.

Well get off your rear and getting to logging darnit!!!

Once you get it running good, I'm going to take another stab at what you'll run I'm thinking 13.1-13.3's with the little work you've done, but I'm not sure what all you've done.

 

[Jakee]

I got 4 idle logs and 2 no load rev logs done yesterday. The LTFT was greater than 25% off. I'm not positive why cuss I didn't think the changes I made had that much of an impact. I'm thinking It had to of been the PCV being in a metered system before and now completely separated from the MAF metered air. That and I probably tuned to the intake leak before.

It's good now and I'm going to spend a lot more time getting the tune nailed perfectly. Not just the WOT part but fast revs, drivability tuning, and more tranny tuning. There’s almost always room for improvement in a tune.


HAPPY HOLIDAYS EXPLORER FORUM!!!!!!!!!

 

[Jakee]

Another 8 logs done and it's dailed in pretty well. But I most say, when the pump stopped, oil got in the piping, which then got into the intercooler, and I refuse to take all that piping back off to clean. I've had to clean the MAF 4 times and I think most of the oil has blown out. It's just a pain when you get oil in the cold side cuss of it getting on the MAF wires and skewing the numbers.

I'm getting some weird readings up high at WOT...For a minute, I thought I had pegged the BA2600 Meter but found out it was a skewy number. I'd like for someone more experienced to view it if possible. Let me know and I'll post it.

 

[rocket 5979]

Another 8 logs done and it's dailed in pretty well. But I most say, when the pump stopped, oil got in the piping, which then got into the intercooler, and I refuse to take all that piping back off to clean. I've had to clean the MAF 4 times and I think most of the oil has blown out. It's just a pain when you get oil in the cold side cuss of it getting on the MAF wires and skewing the numbers.

I'm getting some weird readings up high at WOT...For a minute, I thought I had pegged the BA2600 Meter but found out it was a skewy number. I'd like for someone more experienced to view it if possible. Let me know and I'll post it.

My suggestion is that you take the time to clean your piping out. After all, how long is it going to take? Probably a few hours at the longest. At least that will eliminate one more factor in what could be causing your skewed readings.

 

[Jakee]

You're right and I'm being lazy

 

[Jakee]

I'm fine tuning the timing curve, and during this process, I've for sure made the valves cladder. The first time I tuned, I never got the valves to cladder before calling it quits. This time I kept going until I got the noise, then backed out.

The AD counts are running up higher than ever (900 range). The load is reaching 1.8 to 1.9

It's running good. The drivabilty is great. It feels as if it pulls all the way thru the RPM range and doesn't feel like it's falling on its face above 5000 RPM.

 

[Limited02]

That's good news!!!

Wish I was closer, I'd love to go for a ride!

Also, any pictures of the new wheels?

 

[Jakee]

I've only got the back ones on at this time. Money was low so I skimped and purchased used tires for the front. Went to have them mounted and found they were dry rotted. So, i'm waiting for the right time to buy the front tires.

I'll see if I can get a quick video up soon.

 

[Jakee]

Just had a coupler blow off @ WOT. Imagine trying to listen for ping and then hear a burst sound. Excuse me while I change my pants.

 

[rocket 5979]

Just had a coupler blow off @ WOT. Imagine trying to listen for ping and then hear a burst sound. Excuse me while I change my pants.

Are you running t-bolt clamps? I thought you were.

 

[Jakee]

Yes, there is one place where the end of the pipe doesn't have the rolled lip to stop the coupling if it starts slidding. This is where it came off but an easy fix. I was up around 11 lbs when it blew so that's part of it. No problems

 

[fishy2k8]

so what did you end up doing for a bottom end? did you go with the custom pistons and sbc rods? im looking for a budget way of building the bottom end of my 94

 

[Jakee]

so what did you end up doing for a bottom end? did you go with the custom pistons and sbc rods? im looking for a budget way of building the bottom end of my 94

The bottom end is still stock. I wound up putting it back together to try and blow it up first, before I rebuild the motor. (j/k) Plus it cost alot and money is allocated elsewhere for the time being.

I'm not sure there is a budget way of building this motor; it's going to cost. But I've managed to get it in the low 13's as is.