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.

 

[rpcaster]

Jakee,
Thanks for starting this thread! I was just getting ready to start researching myself.

Did you calculate what compression ratio using option 2 would be, with std pistons?

Is there a HP rating for the option 2 rods?

 

[Jakee]

Jakee,
Thanks for starting this thread! I was just getting ready to start researching myself.

Did you calculate what compression ratio using option 2 would be, with std pistons?

Is there a HP rating for the option 2 rods?

The HP rating I'm shooting for is 700-800HP but I'm not sure of the rating for the SBC rod I posted; however, these rods are plentiful - there should be NO problem finding a good rod here.

I've actually just started researching option two pretty hard. There will need to be a custom piston made and you can state your desired compression ratio. The custom piston manufacturer will probably move the piston pin height up or down to get the compression ratio you want.

This is what I have for option two - a set of eagle I-beam rods (for measuring purposes) and I have a stock SOHC rod and piston on the way (I ordered from ebay for measuring purposes) After I get good measurements, I'll get a quote for a custom piston. This price should be very close between the compression ratios.

I'm currently having a quote done on pistons for option 1 and I asked for the stock compression ratio. Again, this can be changed during manufacture.

 

[CDW6212R]

Interesting subject Jake, I hope you find a great set of parts for it. LOL, you will need a new adapter plate to change the trans of course.

Seriously though, may I suggest that you consider using existing parts available commonly for other engines? The 302 is about .050" bigger in the bore, so if you can find a way to make the bore size 4.00", or if the 302 pistons can be had in the needed bore for the same cost, that is your best piston option. You can get all kinds of pistons in various piston pin heights etc, in any dome/valve shape you could ask for.

The best method I believe would be to find every important SOHC dimension for the shortblock, and right those down. Take those numbers and the research you do about the bore size, and contact a well known stroker engine builder. Those guys deal in lots of various odd sized pistons, rods, cranks etc. They can more quickly point you to the best path. As an example, if there are great rods and pistons available to use, but for a longer crank throw, grind the crank and make it work. You could end up with more displacement, and less expensive parts.

The pro engine builders are good at finding those nice parts combinations. That's how the 347 was born, and lately the 357/357/363 etc. Just maximizing the space and parts you can get. Try speaking with Woody of Ford Strokers if you get solid specs to deal with. He knows the aftermarket parts very well, he might have an idea or two. Regards,

 

[Jakee]

I've got the tranny covered.

I've got the specs and have been talking with piston manufactures. A few other guys are going to talk with the rod company to see about some other options.

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

 

[CDW6212R]

Those are good specs to work with to build a nice engine, given existing parts. Those are very close to the specs of the 302 and other smallblocks. I would find parts for their high strength and light weight, and that is what the common stroker parts are known for these days.

 

[Jakee]

We're more than likely going to have 4 test victims for rod option 1. The rods will be re-sized, custom pistons built, assembled and weight matched. We have one mustang owner that's going to push the crap out of the motor so it should be interesting. We may possible see a 600HP 4.0 sohc?

I've pretty much sourced the entire thing and once the testing is done, you others will have options other than what's available right now.

I'm going to be a little more conservative and shoot for the 400 range with 16LBS of boost. Who knows what the next weak link will be; maybe a split block? There's only one way to find out.

 

[CDW6212R]

For a high performance application, I would be meticulous with the valve train.

I would degree the balancer to start with, meaning use a degree wheel and piston stop to properly locate TDC. That is a critical check and step. You must know where TDC is, and the TDC "tool" in the SOHC kit is not accurate. Once you have located TDC and marked the balancer and timing pointer(mark the crank trigger or make one), then you never need the TDC "tool." Of course you should also degree the cams when you build one, like any newly built engine. Confirm the valve events carefully, and check the pushrod lengths. Those are big keys to big power and the valvetrain surviving.

I would test the two cam chain tensioners when brand new. Find out what the internal mechanical spring is when it's new and working properly. Then you have a baseline to test used tensioners. You can remove them at maintenance mileage points and test them. They only cost $30-$40 so replacing them is not a bad idea either. Those tensioners would be my biggest worry. Keep those good with plenty of oil pressure to them, and the valvetrain should do fine. Regards,

 

[Jakee]

None of the failures this far indicate valve to piston contact so it's not looking like this is a problem. There is; however, concerns about our timing gears not keyed and a chance something will slip so we're working on ideas for making sure nothing slips. The stock valve springs will not do good above 5200 RPM so there is a nissan spring that is looking good (still being tested but it's working out).

CDW - I have a bunch of turbo miles on my 4.0 SOHC and I have NEVER had a problem with the timing set. I know others have and I'm not sure why.

 

[l8psiExplorer]

hey jakee I sent you pm

 

[CDW6212R]

None of the failures this far indicate valve to piston contact so it's not looking like this is a problem. There is; however, concerns about our timing gears not keyed and a chance something will slip so we're working on ideas for making sure nothing slips. The stock valve springs will not do good above 5200 RPM so there is a nissan spring that is looking good (still being tested but it's working out).

CDW - I have a bunch of turbo miles on my 4.0 SOHC and I have NEVER had a problem with the timing set. I know others have and I'm not sure why.

I'm not concerned about P/V clearance as that should be part of the piston and camshaft design. The cam designer controls P/V clearance as part of the cam design, another huge reason to only use a custom cam. A custom cam can be made to utilize big duration and/or lifts and stay far away from the pistons. An OTS cam is a crap shoot at best.

The bolt on the end of each cam is sufficient to hold the cam in place. There are no splines at all, the one bolt on each cam holds the chain sprocket securely to the cam. I doubt anything would be affected unless you got the rpm's really high, say 8000+.

I've hinted as gently as I can, the valvetrain is critical, and a custom designed cam for a specific engine and vehicle is the best way to succeed. A top level custom cam will include valve spring specs that you can trust to work with the rest of the engine. Selecting each valvetrain part separately is very risky, and it does not save much money.

You do have the benefit of the SOHC stock parts, many of which are great for your intended usage and rpm range. If you don't alter the rpm greatly, you can rely on the OEM followers and lifters, and all of the chains and sprockets. Just by maintaining the rpm range you cut down on custom parts to worry about. The pushrods need to be measured for and custom ordered(new cam specs). But the rest has proven itself well in the stock rpm range.

That's why I went into detail about the cam chain tensioners. Those are the source of most chain looseness which people have in their SOHC's. The mechanical spring inside weakens over time. How many times people hit WOT shifts affects that life span for sure. That's another reason to keep the rpm reasonable, to help that spring in the tensioners. The other chain tensioners also don't look like they would be happy with a higher rpm band.

I know, it's a big subject. If you or any builder will concentrate on the main things that I listed in my last post, the engine will start out stronger and last longer. I personally would work very hard to get a pair of custom cams made. I would as best I could sweet talk Jay into designing me a pair. I don't know if he can make those, but he has done countless other cams/applications. If he would I'd make a big bet that the power would jump a bunch from that alone. Regards,

 

[Jakee]

CDW - I appreciate your expertise and I do not doubt what you say. I'm just working on one thing at a time and right now I'm concerned about getting the rods / pistons worked out. After that will be a good head gasket. Then look at the girdle supported pan to make sure it's up to par. Once the bottom end is secured, I may hit you up on the valve train some more. Just give me some time to get the bottom end squared away.

 

[CDW6212R]

That's good, it's a very big puzzle so make all the pieces fit.

 

[jah81592]

You won't split the block at 450 whp, I can attest to that. As far as the valve springs, I have dealt with that for a while. You will get float after only a few miles, I am interested in what type of Nissan springs you are looking at? I have sourced a couple of different types but my engine project has been shelved until I am completely out on my own. I have even considered turning my truck to stock and installing the stock tranny. What type of trans are you looking at? I'll give you a smokin' deal on a controller,trans and driveshaft.-j

 

[Scott B.]

Subscribing...

 

[Limited02]

Any updates?

Have you looked into the Comp Cams Beehive spring? Seems like a decent spring for mild-rev applications? Looking forward to updates.

 

[Jakee]

The Nissan springs being used are comp cams 909. If you search for that you should find them. All dims are the same but the seat pressure is a tad higher than stock and seems to work well.

I'm still waiting on some parts to come in.

 

[aniljohn2000]

When A/Con is turned on explorer 2006 ( 70000 mile) the power feels less and up the slpoe is difficult and stop & go traffic becomes a pain as engines revvs more than the vehicle moves forward.
Do you think that a change of rings on the engibe will solve the problem? will valves also need changing? how do I kno that both rings as well as valves change will fix the problem

 

[Limited02]

You are saying that when you run the AC that you have less power? This is normal, takes power to run the AC. Like 15-20hp I think and when you go WOT, the AC will shut off until you get out of it.

When you are sitting in traffic and the AC is on the engine revs higher, causing it to move forward unless on the brake? When you turn the AC on, it produces a load on the engine and the engine will rev a little bit to make up for it.(I assume)

So no you don't need to change the valves or springs. The AC just uses some power and makes the car feel sluggish. Get a CAI, catback exaust, UDP's and tune

 

[Jakee]

Since this is up top, let me give an update.

I've done nothing but tear the engine down. Everything went on hold right before I went on vacation in California and spent all my money - I'm broke and I'm nervous about spending this sort of money with the way the oil field is right now. I'm not sure when I'll get the opportunity to do this and have considered canning this project and starting a more cost effective approach.