4.3l sohc v6?

It's been several years since there's been any posts on this subject so I decided to start a new thread to discuss it. There are several ways to significantly increase the power and torque of the SOHC V6: supercharging, turbocharging and stroking. All three are fairly expensive modifications and many members would probably comment why bother when it's possible to upgrade from a V6 Explorer to a V8 Explorer for less money. Well one reason is the V8 was not available in the 2 door Explorer and another reason is I have become comfortable with the SOHC V6 in spite of its potential timing chain death rattle. I am approaching the end of what I hope to be a successful supercharger installation and for various reasons I am not interested in a turbocharger installation so I would like to limit this thread to discussing stroking (and possibly boring) the SOHC V6.

Tom Morana Racing offers a 4.3L stroker kit for $2,600 and a 4.3L short block for $4,550 with the short block requiring a $300 core charge. They claim an increase of 30+ hp and 30+ tq with no other modifications. Additional costs would be gaskets, TTY bolts, and probably a custom tune increasing the total cost of the stroker kit to around $3,000. That's about $100/hp which is comparble to other performance enhancements. In spite of the V6 use in the Mustangs I'm not aware of any other commercially available stroker kits.

I wonder if the Morana kit would hold up on a daily driver and if the pistons would provide adequate oil control. It's hard to determine from the photo of the kit components if the oil control ring is far enough above the piston pin for good oil control. I also wonder if the height of the piston is adequate to prevent "rocking" in the cylinder bore. There's no mention of clearance issues between the block and the crankshaft counterweights or rod caps. Maybe no modifications to the block are needed.

I have no experience with stroking an engine. I will appreciate your comments.

 

[2000StreetRod]

no documented installation

I have spent several hours searching the internet and while I found numerous posts discussing the possible installation of the Morana 4.0L to 4.3L stroker kit I could not find a single actual installation in a Ranger, Explorer or Mustang. Potential concerns expressed (may not be valid) were: reground crankshaft, weak connecting rods, exceeding block capabilities, high cost/hp.

 

[Dono]

Seems like a lot of cash for a relatively small increase. I'm sure the power increase would be compounded with a power adder. Not sure about oiling or other components for longevity. I can't see why there would be an issue there. Stroking is nothing new, but I'm probably over simplifying it.

 

[Dono]

jd4242 is stroking his 4.0 ohv. Lets see how he makes out.

 

[Carguy3J]

Is offset grinding the stock crank an option? I seem to vaguely recall reading, somewhere on here, that it wouldn't work because of the oiling passages in the crank or something like that. Anybody know?

 

[2000StreetRod]

reground crank

I asked Tom Morana if his crank was new or reground. His answer was it's a reground OEM crank. He also said they've sold quite a few of the Stroker Kits without any negative feed back, but he's not aware of any clients who have documented their installation on the internet. I followed up with questions about retention of the block cradle and if so does it need to be modified for crankshaft clearance. Haven't received a response to that yet.

My concern about oil control is that the original Cologne block only had a stroke of 60.14 mm which has increased to 84.07 mm for the current 4.0L displacement. Increasing it more may require placing the piston pin closer to the top of the piston. The piston pin bore could interfere with the oil control ring land like it does on the 347 stroker pistons.

I haven't kept tabs on jd4242 and didn't realize he was stroking his OHV. I know he has the block cradle installed so I'm curious if he has to modify it.

 

[Carguy3J]

Well, if that's the case, why pay so much for the Morana "name"? I think you can have a local machine shop do the crank grinding, and gather up the other parts yourself, for less then the kit.

Check out this thread started by "Jakee", wherein he did some extensive research into using "off-the-shelf" pistons and rods from other applications, including small block chevy's.
http://www.explorerforum.com/forums/showthread.php?t=247561

Maybe you could find a piston with raised ring lands and/or thinner rings, thereby avoiding having the oil control ring and piston pin interfere?

You may be able to get away with using a slightly shorter Chevy 350 rod, and leave the piston alone. You'd have to calculate the rod/stroke ratio, to see if you can come up with an acceptable combo.

Here's a decent article on stroking, via offset grinding the crank:
http://www.fordmuscle.com/archives/2003/09/stroker/

I think somone (maybe Jakee as well) was also looking into boring the block to 4.00 inches and using Chevy small block pistons, which are more readily available.

 

[2000StreetRod]

Excellent article

. . . Here's a decent article on stroking, via offset grinding the crank:
http://www.fordmuscle.com/archives/2003/09/stroker/ . . .

Thanks for the link. An informative but concise article. Having never even installed a stroker kit before I would have to learn a lot before feeling comfortable picking my own components. With the 2005 Mustangs using the SOHC V6 I thought there would be multiple sources available but the trend for Mustang owners seems to be upgrading to the V8 rather than modifying the V6. So far I have not found a suitable performance engine machine shop here in Greenville. If I do find one, I doubt the shop will have any experience with my engine. I don't want to be paying the shop to learn on my engine. That's the main reason I was looking for a balanced kit.

 

[jd4242]

As far as I know the sohc block wont handle a 4" bore.only I know of is the 90tm ohv.I to have spoke to tom and he really doesnt release alot of info but pretty sure he uses sbc parts and machines the crank.ill know more in the next couple weeks tho

 

[2000StreetRod]

I'm confused

I'm trying to understand what your plans are but getting confused with what you've posted. Are you going to beef up the bottom end (new stock crank from Rock Auto and Manley rods) while increasing the bore (new Manley pistons) but not stroking the crank?

 

[jd4242]

I'm trying to understand what your plans are but getting confused with what you've posted. Are you going to beef up the bottom end (new stock crank from Rock Auto and Manley rods) while increasing the bore (new Manley pistons) but not stroking the crank?

Yes.only way to increase the stroke is to offset grind the crank which weakens it drastically. Im just going with the strongest and cheapest setup I can.im more or less just making everything forged and increasing the bore to 4", not stroking

 

[Dono]

Ah thanks JD, I was under the impression you had some sort of path sorted out for stroking. I was curious.

Streetrod, sorry for the bad info. I was mistaking. I really doubt that you want to consider boring an SOHC block out to 4.0.

 

[jd4242]

Ah thanks JD, I was under the impression you had some sort of path sorted out for stroking. I was curious.

Streetrod, sorry for the bad info. I was mistaking. I really doubt that you want to consider boring an SOHC block out to 4.0.

Sorry thats my fault.I did say stroke but meant overbore.I know at one time tom was running oversized pistons and less stroke change but thought he went away from that.thought he went to a 4.1 or 4.2 kit which wasnt that big of a change so made it pointless. But i see he list it as 4.3 still and for sohc, so he must be offsetting the crank and slightly larger pistons.I need to check my paperwork once I get to work and see what a 4" bore takes you to without a change in stroke.offsetting cranks I dont like to much and would make for oiling problems I would assume for the piston.I dont need all those headaches, just want a good strong forged motor that I can boost or spray the crap outa

 

[jd4242]

Ok now looking back over my info.the reason I went away from stroking was because of Manley. To get 4.3 you need to increase the pistons and crank to about a stroke of 3.5(im finding conflicting info on stock stroke, found three numbers so it will need to be measured in person.finding 3.307-3.310-3.320).this combined with longer rods would make the compression height of the piston very small.also at the time I was planning on running shaved 95tm heads(10.67:1) and was wanting to lower my compression, which means more dish.manley thought there wasnt enough or it wasn't safe to run that small of compression height.I assume if there was room that it would be to thin or problems with the rings.
they advised me not to stroke/offset the crank and get larger CC heads, which now I've got 93tms.4"piston,6.058 rods and stock stroke will get me 4.102 Liters or 250.322 Cubic inches.this should be a very strong setup and still gain alot.the piston will be much lighter/stronger which alone equals power.mainly going for the strength tho..

If you want more specs I would love for you to look at them and go over them.I know you have a very good eye for details and would love to see if you see anything I dont or any input.we can do it in my thread if you want, so we dont get to far off your main post subject

 

[2000StreetRod]

Summary of Jakee's 4.0 SOHC Performance Motor Build Thread

. . . Check out this thread started by "Jakee", wherein he did some extensive research into using "off-the-shelf" pistons and rods from other applications, including small block chevy's.
http://www.explorerforum.com/forums/showthread.php?t=247561 . . .

There's a lot of useful information in that thread contributed by a number of members. I'm going to go thru it in detail and summarize in this post which will be edited numerous times.

1. The SOHC V6 block has thin walls and can't be safely bored to a 4.0" bore without sonic testing. Max cylinder overbore may be .040". Sleeving is a possibility. The early OHV V6 block has thicker walls and may accept a 4.0" bore. Does anyone know if the SOHC and early OHV blocks are interchangeable without modifications?

2. There is concern about offset grinding the stock crankshaft to increase stroke due to:
a. Weakness
b. Reduced piston compression height
c. Lubrication

3. The stock SOHC V6 rods are the weakest link in high power motors

4. Head work and custom camshafts are needed to achieve the full performance potential of increased displacement.

5. For street driving higher compression ratio and less max boost is preferable to lower compression ratio and greater max boost.

6. To reduce detonation intercooling is preferable to water/methane injection because it provides lower IATs and doesn't affect air/fuel ratio.

7. SVO was able to increase the displacement of an SOHC V6 to 4.7L.

8. Stock valve springs are inadequate above 5200 rpm. Comp Cams 909 for Nissan are a possible alternative.

 

[2000StreetRod]

Engine specifications

Basic engine dimensions according to Ford Racing Parts.com in inches:
Displacement 4.0L, Years 1997-07, Bore 3.950, Stroke 3.320, Bore Spacing 4.760, Main Journal Dia. 2.244, Rod Journal Dia. 2.126, Con Rod Length (Mean) 5.748, Deck Height 8.858, Piston Comp Ht 1.440 (OHV 1.442)

Engine specifications from 2000 Explorer/Mountaineer Workshop Manual unless noted otherwise.

4.0L SOHC
Displacement liters (cubic inch) 4.0L (244)
Bore mm (inch) 100.4 (3.953)
Stroke mm (inch) 84.4 (3.31)
Compression ratio 9.7:1 (OHV 9.0:1) (from 2000 MY Explorer Owner's Guide)
Firing order 1-4-2-5-3-6
Minimum oil pressure at 2,000 rpm (engine at normal operating temperature) kPa (psi) 103 (15)

Cylinder Head and Valve Train
Valve guide bore diameter mm (inch) 7.00-7.018 (0.276)
Combustion chamber volume (cc) 65.197 ± 2.068-2.018
Valve arrangement front to rear LH=I-E-I-E-I-E, RH=E-I-E-I-E-I
Gasket surface flatness mm (inch) 0.08 (0.003) Total
Valve Seat
Width (exhaust and intake) mm (inch) 1.556-2.404 (0.06-0.094), 1.273-2.121 (0.05-0.083)
Angle degrees 45°
Runout TIR maximum mm (inch) 0.059 (0.002)
Valves
Valve stem diameter intake mm (inch) 6.965-6.98 (0.274-0.275)
Valve stem diameter exhaust mm (inch) 6.95-6.965 (0.274)
Valve stem to guide clearance exhaust mm (inch) 0.035-0.068 (0.001-0.003)
Valve stem to guide clearance intake mm (inch) 0.020-0.053 (0.001-0.002)
Head diameter intake mm (inch) 45.9-46.1 (1.807-1.815)
Head diameter exhaust mm (inch) 38.9-39.1 (1.531-1.539)
Valve face angle degrees 45°
Valve face runout limit 0.03 (0.001)
Valve Springs
Intake valve spring compression pressure at specified height (lbs) 275-305 Nm at 35.9-36.7 mm (202.84-224.968 lb/ft at 1.413-1.445 inch)
Exhaust valve spring compression pressure at specified height (lbs) 275-305 Nm at 35.9-36.7 mm (202.84-224.968 lb/ft at 1.413-1.445 inch)
Intake valve spring free length mm (inch) 43.1 (1.7)
Exhaust valve spring free length mm (inch) 43.1 (1.7)
Intake valve spring assembled height mm (inch) 39.86-40.86 (1.569-1.601)
Exhaust valve spring assembled height mm (inch) 39.86-40.68 (1.569-1.601)
Camshaft
0.472” valve lift with 116 degree lobe separation. (from Super Six Motorsports Tech note)
Intake duration @ .050" is 185 degrees (from Super Six Motorsports Tech note)
Intake lobe lift mm (inch) 6.584 (0.259)
End play mm (inch) 0.075-0.185 (0.0003-0.007)
Exhaust duration @ .050" is 193 degrees (from Super Six Motorsports Tech note)
Exhaust lobe lift mm (inch) 6.584 (0.259)
Maximum allowable lobe lift loss mm (inch) 0.127 (0.005)
Journal to bearing clearance mm (inch)* 0.04-0.095 (0.002-0.004)
Journal to Bearing Clearance Service limit mm (inch)* 0.152 (0.006)
*Tighten camshaft bearing cap bolts to 15 Nm (11 lb-ft) when measuring journal clearance.
Camshaft Drive
Journal diameter mm (inch) 27.935-27.96 (1.100-1.104)
Bearing inside diameter mm (inch) all 28.0-28.03 (1.102-1.104)
Maximum camshaft journal runout mm (inch) 0.05 (0.002)
Cylinder Block
Deck height 8.858" (from Jakee)
Cylinder bore diameter mm (inch) 100.4 (3.953)
Maximum cylinder out-of-round mm (inch) 0.025 (0.001)
Maximum cylinder taper mm (inch) 0.025 (0.001)
Main bearing bore diameter mm (inch) 60.634-60.620 (2.387-2.387)
Crankshaft to rear face of block runout. TIR maximum mm (inch) 0.127 (0.005)
Distributor shaft bearing bore diameter mm (inch) 72.43-72.473 (2.852-2.853)
Head gasket surface flatness mm (inch) 0.1 (0.004) overall
Head gasket surface finish RMS 60-150
Crankshaft and Flywheel
Main bearing journal diameter mm (inch) 56.980-57.0 (2.243-2.244)
Main bearing journal runout limit mm (inch) 0.05 (0.002)
Main bearing journal taper maximum per inch mm (inch) 0.008 (0.0003)
Connecting rod journal maximum out-of-round mm (inch) 0.008 (0.0003)
Crankshaft free end play mm (inch) 0.05-0.32 (0.002-0.0126)
Main bearing journal out-of-round mm (inch) 0.008 (0.0003)
Main bearing journal runout TIR maximum mm (inch) 0.05 (0.002)
Main bearing journal runout service limit mm (inch) 0.0127 (0.005)
Main bearing thrust face runout TIR maximum mm (inch) 0.0254 (0.010)
Thrust bearing journal length mm (inch) 26.39-26.44 (1.039-1.041)
Main and rod bearing journal finish RMS maximum 72 and 88
Main bearing thrust face finish RMS maximum 20
Connecting rod journal diameter mm (inch) 53.98-54.0 (2.125-2.126)
Connecting rod journal taper per inch maximum mm (inch) 0.008 (0.0003)
Connecting Rod Bearings
Clearance to crankshaft desired mm (inch) 0.008-0.061 (0.0003-0.0024)
Clearance to crankshaft allowable mm (inch) 0.013-0.048 (0.0005-0.002)
Bearing wall thickness mm (inch) 1.4-1.408 (0.0551-0.0554)
Main Bearings
Clearance to crankshaft mm (inch) 0.021-0.039 (0.0008-0.0015)
Clearance to crankshaft allowable mm (inch) 0.013-0.048 (0.0005-0.002)
Bearing wall thickness mm (inch) 1.8-1.806 (0.0709-0.0711)
Connecting Rod, Piston and Rings
Rod weight 587 gm (from Super Six Motorsports Tech note)
Side clearance (assembled to crankshaft) mm (inch) 0.092-0.268 (0.0036-0.0106)
Piston pin bore or bushing I.D. mm (inch) 23.958-23.976 (0.943-0.944)
Rod bearing bore I.D. mm (inch) 56.82-56.84 (2.237)
Rod bearing bore out-of-round mm (inch) 0.01 (0.0004)
Rod length center to center mm (inch) 145.965-146.035 (5.746-5.749)
Alignment (bore-to-bore max. diff.) twist mm (inch) 0.038 (0.0015) per 25.4 mm (1.000)
Alignment (bore-to-bore max. diff.) bend mm (inch) 0.0125 (0.00049) per 25.4 mm (1.000)
Piston Pin
Pin weight 156 gm (from Super Six Motorsports Tech note)
Length mm (inch) 72.0-72.8 (2.835-2.866)
Diameter (red) mm (inch) 23.994-23.997 (.9446-.9447)
Diameter (blue) mm (inch) 23.997-24.000 (0.9447-0.9449)
To piston pin bore clearance mm (inch) 0.01-0.016 (0.0004-0.0006)
To connecting rod bushing clearance mm (inch) Press Fit -0.018 to -0.042 (-0.0007 to -0.0017)
Piston
Compression height 1.44" (provided by Jakee)
Bore clearance selective fit mm (inch) 0.030-0.060 (0.0012-0.002)
Diameter — coded STD mm (inch) 100.380-100.400 (3.952-3.9528)
Diameter — coded 0.5 mm (inch) 100.880-100.900 (3.972)
Diameter — coded 1.0 mm (inch) 101.350-101.370 (3.990-3.991)
Pin bore diameter (red) mm (inch) 24.007-24.010 (0.945)
Pin bore diameter (blue) mm (inch) 24.010-24.013 (0.945)
Top ring groove width mm (inch) 1.64-1.66 (0.0645-0.0654)
Bottom ring groove width mm (inch) 1.79-1.81 (0.0705-0.0713)
Oil ring groove width mm (inch) 3.5-3.53 (0.1378-0.1399)
Piston Rings
Top compression ring width mm (inch) 1.578-1.598 (0.062-0.063)
Bottom compression ring width mm (inch) 1.728-1.74 (0.068-0.069)
Bottom compression ring width mm (inch) 1.728-1.74 (0.068-0.069)
Bottom compression side clearance mm (inch) 0.050-0.082 (0.002-0.003)
Top compression ring gap mm (inch) 0.200-0.450 (0.008-0.018)
Bottom compression ring gap mm (inch) 0.450-0.700 (0.018-0.028)
Lubrication System
Relief valve spring pressure lbs. At 35.3 mm (1.39 in) 61.3-66.3 Nm (45.100-48.730 lb/ft)
Driveshaft to housing clearance mm (inch) 0.02-0.031 (0.0007-0.0012)
Relief valve to housing clearance mm (inch) 0.015-0.03 (0.0007-0.0012)
Rotor assembly end clearance max. mm (inch) 0.014-0.044 (0.0006-0.0017)
Outer race to end clearance mm (inch) 0.06-0.12 (0.0002-0.0004)
Engine oil capacity liters (quarts) 3.8 (4) with filter

 

[jd4242]

What I will point out and seems everyone forgets about is the bearings in the rods....both the rods he posted will have to be machined on the big end and the sbc will have to be machined even farther...rods are measured without the bearing in them,""big hole dia""more you machine the weaker the rod

If you got a crank rod jurnal of 2.125" how do you think your use a piston with the big hole dia of 2.125 for the 4.6 or 2.100 for the sbc..where the bearing gonna fit???

Stock is 2.237ish why I chose the xr6 rods.yes they are longer but will be wayyyy stronger than milling the crap outa the rods or milling the crap outa the crank..

Stock rods, no bearings

 

[2000StreetRod]

rod bearing bore

What you posted seems reasonable. However, in my case of interest, if the crankshaft is to be stroked by offset grinding then the rod bearing bore will have to be smaller than stock by the amount of the stroke increase.

By the way, your rod bearing bore measures exactly the same as what I found specified for my engine.

 

[jd4242]

What you posted seems reasonable. However, in my case of interest, if the crankshaft is to be stroked by offset grinding then the rod bearing bore will have to be smaller than stock by the amount of the stroke increase.

By the way, your rod bearing bore measures exactly the same as what I found specified for my engine.

Aww very true.I wonder if you can get custom bearing sizes made or would you have to offset to basically a stock size?

 

[Carguy3J]

http://www.circletrack.com/drivetra...opments_race_engine/crank_journal_sizing.html

327 Chevy rods have a 2.00" journal size.

1.888" so-called "Honda Journal" rods are widely used in NASCAR and other high-end racing application. You can easily spend $2-$3,000 on a set of these rods. But, you can also find reasonably priced ones as well.

Its not uncommon for daily driver / budget racer guys to buy "used" engine parts, including rods, when they are sold off by the top-tier race teams. Its not the bad idea you might first suspect. Think about it. Dale Jr., Jeff Gordon,etc.... These guys are sponsored for millions of dollars. They HAVE to win races. They aren't going to risk losing a race over a set of $3,000 connecting rods. One race, maybe only one practice session, and they yank them; whether they are perfectly good or not. These parts are designed to make 800-900hp, running WOT all day long. Running them in a 400-500hp street car is way below their limits, and they have many, many more miles of that lower-stressed use in them. You can get the stuff for pennies on the dollar. Research it a little. Look in the circle track "world". You'll find the stuff, and many reports of successfully long-term street use.

Here's an ebay search, from Google. There's some irrelevant stuff to wade through, but also some good examples. http://www.ebay.com/sch/i.html?_kw=honda+journal+rods

Here's an auction for what used to be a very expensive set of rods, until they misplaced one somewhere along the way. They are now $99, for 7 rods. Perfect for a V6 guy.
http://www.ebay.com/itm/PANKL-RODS-...Parts_Accessories&hash=item20de97c303&vxp=mtr