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.

 

[CDW6212R]

Find a machine shop which regularly builds the SOHC 4.0, and ask them if they ever sonic tested a block. The accurate way to over bore any block past the accepted limit, is to sonic check it.

Some blocks are known to be too thin to push the limit, like the 351 Cleveland. Those are no problem to go .020 over, but .030 is a risk, and past that is not smart. With a 429/460 block, you can bore those .080 without checking. With sonic testing, some of those can go as far as .160" over. That's a 4.52" bore compared to the stock 4.36" bore.


If the 4.0 block is that close to a 4.00" bore, I'd look into that. The available pistons for 4.00" is countless, including the light weight parts used in any small block kits.

If the stock crank is as good as almost all other Ford cranks, strength is not an issue. Ford stock cranks won in Pro Stock for years for Bob Glidden and the 351C. Those were not forged cranks, just typical Ford nodular iron cranks. Chevy has forever had weak plain cranks(most models), and only their "forged" crank models are worthy to race with. Obviously their later model parts have finally improved, they even use titanium in some LS engines.

If you are serious about SOHC power, contact Woody at Ford Strokers. He knows as much as anyone about aftermarket cranks/pistons/rods for small block Fords. If the bore size is that close, he may be able to quickly point you to rods and pistons which would be usable in the 4.0 engine. He needs to know the block deck height, stroke and bore sizes, and crank journal width at least.

A good stroker engine is just a wise combination of available parts that fit and lower the reciprocating weight, while displacing more volume.

I wouldn't race a stock weight reciprocating assembly if I had the choice of the wonderful light weight aftermarket parts. You would be amazed at how heavy stock pistons are, and stock rods etc.

Do not hold on so tight to the stock parts, if there's something available that's better, get it. Regards,

 

[Jakee]

Don't think anyone has tried it. To sonic a block is to measure the wall thickness of the cylinders.

"Sonic and Pressure Testing - It doesn't make sense to do machine work on a block that may not even be usable. That's why it's wise to sonic test the block before much effort is put into it. Sonic testing can tell you the thickness of the cylinder walls quickly and easily. Even on a new block, this is important because core shift can cause one side of a cylinder wall to be too thin. Engine builder Peter Guild of PME Engines says he likes to see the cylinder wall thickness at least 0.275 inch. A sonic tester is also capable of catching a block that's just too far gone to be rebuilt again."


Money money money...That's all it takes. The rest is just doing it.

 

[CDW6212R]

Yes, and not all shops can have sonic testing done.

Hunt around and see if others have worked on the 4.0 blocks to push them to 4.00" bore. The piston prices are way cheaper if you can use a common part, plus the aftermarket parts can weigh a ton less. You can buy a whole 347 reciprocating assembly for $750 or less. Just think of what the various stock type SOHC parts choices cost, and those are heavy and stock displacement parts.

I don't have a need to build a 4.0 myself, but I appreciate the interests of others who need to build them. Spend some time to investigate the chances of using aftermarket parts from other engines to make a much better assembly.

 

[Jakee]

I've spent many hours researching this. The first post has what I found to be the best options. It's not cut and dry but there is potential. I still can't dedicate money towards this but hopefully soon. Stroking is good but you can blow this motor apart with high flowing heads, cams, and a turbo. Somewhere near 500 HP is where the other built motors have failed. Keep in mind they all were using stock rods, which is why I spent so much time on the rods.

 

[Jakee]

Something EXTREMELY embarrassing - Having a mid-mounted turbo and the turbo oil pump stops when pulling into a gas station. Thought it was just a fluke, pulled out and got on it, and all I can say is those diesel smoking trucks have nothing on me. Quickly pulled over and started troubleshooting. It turned out to be a connection had corroded enough to lose contact. Murphey's law says this has to happen when pulling into a gas station full of people and not when you've drove the thing many times down country roads.

I can't tell you how tired I am of cleaning oil out of the air tract.

 

[Limited02]

That's a bummer! At least she's back to running again

Would there be any way to add an oil seperator or do I have the wrong thing in mind and it's not possible???

 

[2000StreetRod]

scavenge pump

Finally got around to installing this...

View attachment 64577

That looks like an oil scavenge pump by Exa-Pump. One of those might be suitable as an engine pre-oiler. They're rated for continuous duty, 50+ psi, with oil inlet temperature as high as 350 degrees. I haven't been able to find a specification on self-priming capability.

 

[Jakee]

No. The turbo is mounted under the truck and beneath the oil level in the pan. When this is the case, you need a pump to return the oil to the pan. (see above for that pump I just added). If this pump fails the oil will build up in the center section of the turbo. It will then find its way out of the bearings and into the exhaust. It will also find its way out the bearing and into the compressor side. There are no magic seals on a turbo. If you fill the center section up, it will find its way out the bearing journals. So for a remote mounted turbo it is extremely important to have a very good oil return system. I now have the best pump out there but I need to make sure all the wiring is up to par. Also need to make sure the relay I have is good. I’m thinking it was corrosion but it could’ve been the relay getting hot. Anyways, I need to go thru this and make sure. Also need to hook the warning light back up that tells me when there is no power to the pump. If this was there I would have caught it before it started smoking. So in short, I need a failsafe mechanism added.

 

[Limited02]

Makes sense, now get to work!!!

 

[Jakee]

Hey, that built in cabinet is nice! Good work

 

[Jakee]

That looks like an oil scavenge pump by Exa-Pump. One of those might be suitable as an engine pre-oiler. They're rated for continuous duty, 50+ psi, with oil inlet temperature as high as 350 degrees. I haven't been able to find a specification on self-priming capability.

It is self priming and it can run dry. However, it is recommended it gets a splash of oil every minute to keep the worm gears lubricated.

 

[CDW6212R]

You will get it worked out and reliable I am sure Jake. The electric fan is the same way, it has to have dead reliable power feeds so it always runs. I've had my fan to not get juice once, and it ruined the T-stat and overheated.

For that pump, I would install the heavy gauge wiring you are etc, but how about two relays. How about installing two power feed circuits in parallel. Feed two relays that are both capable of powering the pump, and route them two different ways, if heat is an issue along the path.

 

[Jakee]

Good suggestion. I'm not the best when it comes to technically correct wiring so I could use all the help.

 

[Limited02]

Hey, that built in cabinet is nice! Good work

Thank you NOW GET TO WORK ON THE WIRING!!!

You will get it worked out and reliable I am sure Jake. The electric fan is the same way, it has to have dead reliable power feeds so it always runs. I've had my fan to not get juice once, and it ruined the T-stat and overheated.

For that pump, I would install the heavy gauge wiring you are etc, but how about two relays. How about installing two power feed circuits in parallel. Feed two relays that are both capable of powering the pump, and route them two different ways, if heat is an issue along the path.

That's actually a great idea!!!

Here's a question(Hope it makes sense!)

Let's say the pump requires a 30amp fuse...

-Do you use a 30amp fuse on each line or a 15amp fuse on each line?

-Would having two 30amp fuses make it seem like one 60amp fuse and not give the pump a chance to "blow the fuse," then causing harm to the pump?

-If no fuse is required, then nevermind:

 

[CDW6212R]

Thank you NOW GET TO WORK ON THE WIRING!!!



That's actually a great idea!!!

Here's a question(Hope it makes sense!)

Let's say the pump requires a 30amp fuse...

-Do you use a 30amp fuse on each line or a 15amp fuse on each line?

-Would having two 30amp fuses make it seem like one 60amp fuse and not give the pump a chance to "blow the fuse," then causing harm to the pump?

-If no fuse is required, then nevermind:

For a circuit that has more than one path like that for it, I'd use one fuse that feeds the whole thing. Take the power from one point or wire connection, and have the fuse or circuit breaker in that sourced power.

I haven't begun to add any new circuits to my truck, but I'd like to begin with a battery which has dual terminals. Has anyone here discovered what batteries can go in the Explorer and has side terminals? I'd prefer to leave the stock battery cables in place on the top posts, and add cables to the side terminals for new circuits. I hate cutting main battery cables, having the engine start reliably is the biggest priority.

 

[Jakee]

I found a site last night madelectrical.com that explains the double relay suggestion. I'm going to do this.

 

[Jakee]

By the way, I found this too, for anyone going through the same problems...

http://www.turbowerx.com/Scavenge_Pumps/page37/page37.html

 

[rocket 5979]

By the way, I found this too, for anyone going through the same problems...

http://www.turbowerx.com/Scavenge_Pumps/page37/page37.html

That's nice but a bit overpriced. Get a $20 low pressure hobbs pressure switch from Napa and a $10 12vdc piezo buzzer from Radio Shack, $5 in electrical wiring crap and about $10 in brass pipe fittings.

Adjust the Hobbs down to 1 psi, install it into a brass tee between the turbo oil outlet and the inlet of the pump and wire the piezo buzzer and everything else together. That piezo buzzer is loud and annoying so it will be able to get your attention if the pump fails. No need for the tactile warning device unless you just absolutely blast the hell out of your stereo all the time.

 

[Jakee]

Yes, I have all the stuff needed, pieced together just like you suggested. I've had it for a long time but haven't hooked it up. Just need to check the hobbs setting and make sure it's around 1 lb.


I'm going to use a red warning light in place of a buzzer. And a green or blue light letting me know there's power.

 

[rocket 5979]

Yes, I have all the stuff needed, pieced together just like you suggested. I've had it for a long time but haven't hooked it up. Just need to check the hobbs setting and make sure it's around 1 lb.


I'm going to use a red warning light in place of a buzzer. And a green or blue light letting me know there's power.

I thought about using a warning light as my indicator but then decided against it since it could be missed when I am in that "highway zombie mode" while driving to work at 0500 in the morning. :