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4.3l sohc v6?


2000StreetRod

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crankshaft options

My engine modification budget limit on my Sport has been $100 per rwhp. It worked out close to that on my intake system modifications, my exhaust system modifications and now my M90 installation (includes the cost of PCM tuning software package).

I estimate the cost of a custom stroke billet crankshaft to be $3500 to $5000 depending on the quality of the steel, counterweight shape, machining tolerances and heat treating method. Added to that is the cost of new pistons, rods, bearings, head bolts and gaskets.

I suspect the cost of a custom stroke forged crankshaft would be even more expensive because of the special machines needed to pound the steel into shape during the forging process.

I think the cost of a custom stroke cast crankshaft would also be prohibitive because of the cost of developing the mold. I have not found any supplier of manufactured stroked cast crankshafts for our engine.

Since most OEM crankshafts are cast I assume that is the case for the SOHC V6. The only option that has a chance of satisfying my cost criteria is to modify the stock crankshaft. Offset grinding the rod journals to increase stroke decreases the journal diameter weakening the crankshaft. From what I've read on the internet the stock crankshaft can handle 500 bhp. If I reduce that to 400 bhp for the regrind and assume 50 bhp to drive the M90 that leaves 350 bhp or 300 rwhp. I'm currently at 237 rwhp so 300 rwhp would be a significant increase. With a stroke increase, cylinder overbore and the M90 boost I might get a 30 rwhp increase giving me a budget limit of $3000. There would also be a crankshaft safety margin of 30 rwhp for improved heads.

Obviously, getting 30 rwhp from the heads is less expensive than getting 30 rwhp from the crank/bore but if both are eventually to be accomplished it is less work to do the crank/bore first. Also, I'm more interested in low to mid engine speed torque increase than top end hp increase.
 


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Bronco2

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I talked yesterday to a Ford Ingenieur who was involved in introducing the New Explorer in the 90. After talking to him the goal was a new Engine because the 2.9 was good for Ranger but not for the heavier Explorer. So Ford outsource the investigation to an recommended German engine builder. Fact is 4.0 is the greatest low cost setup which the OHV and later the SOHC is usable. Thats only must be seen by Fords economic eyes, where engine must be ceap and holts at least 150.000 miles!
If the would again produce a 4,0 engine there are 20Years later better material and castings. So far, a machine shop could get more out of the engine by lowering the expected hold up time.

So What i figured out for now is for an SC'ed engine with 8,5:1
MAHLE PISTONS SBF165030I16 FORD SBF INVERTED DOME 331ci 4.030b 3.250s 5.400r
Rod1 Manley Performance SBC Chevy H-Beam H-Lite Rod 14036-8 6.000" 600+ HP
Rod2 BILLET H-BEAM CHEVY SBC 6.000 CH6000AZLB-L8

The Piston is 4-030" over and to prove if it will fit

Deck Hight Stock
Comp Height + rod Length + Stroke/2 = 224.9932mm
36.576mm+ 145,9992mm + 84.4/2 = 224,775
Setup Manley Rod
29.591mm + 152.4 mm + 87,6/2 = 225,791mm
K1 Rod Setup Honda Journal = 48.005mm (1.890)
29.591mm + 152.4 mm + 90,4/2 = 227,091mm

as rod 1 it would be 4.325cc
as rod 2 it would be 4463cc *my favorite

depends if deck hight is allowed .9over stock
the Crank Rod Journal have to be machined
Stock is 54mm (2.125-2.126) Opt1 50.8mm (2.0) Opt2 is 48.005mm (1.890)

i will talk to my machine shop in a few days...

to be continued


Helpful Links

http://www.cbperformance.com/v/enginecalc.html
http://users.erols.com/srweiss/tablersn.htm
http://users.erols.com/srweiss/calcci.htm
 




jd4242

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I talked yesterday to a Ford Ingenieur who was involved in introducing the New Explorer in the 90. After talking to him the goal was a new Engine because the 2.9 was good for Ranger but not for the heavier Explorer. So Ford outsource the investigation to an recommended German engine builder. Fact is 4.0 is the greatest low cost setup which the OHV and later the SOHC is usable. Thats only must be seen by Fords economic eyes, where engine must be ceap and holts at least 150.000 miles!
If the would again produce a 4,0 engine there are 20Years later better material and castings. So far, a machine shop could get more out of the engine by lowering the expected hold up time.

So What i figured out for now is for an SC'ed engine with 8,5:1
MAHLE PISTONS SBF165030I16 FORD SBF INVERTED DOME 331ci 4.030b 3.250s 5.400r
Rod1 Manley Performance SBC Chevy H-Beam H-Lite Rod 14036-8 6.000" 600+ HP
Rod2 BILLET H-BEAM CHEVY SBC 6.000 CH6000AZLB-L8

The Piston is 4-030" over and to prove if it will fit

Deck Hight Stock
Comp Height + rod Length + Stroke/2 = 224.9932mm
36.576mm+ 145,9992mm + 84.4/2 = 224,775
Setup Manley Rod
29.591mm + 152.4 mm + 87,6/2 = 225,791mm
K1 Rod Setup Honda Journal = 48.005mm (1.890)
29.591mm + 152.4 mm + 90,4/2 = 227,091mm

as rod 1 it would be 4.325cc
as rod 2 it would be 4463cc *my favorite

depends if deck hight is allowed .9over stock
the Crank Rod Journal have to be machined
Stock is 54mm (2.125-2.126) Opt1 50.8mm (2.0) Opt2 is 48.005mm (1.890)

i will talk to my machine shop in a few days...

to be continued


Helpful Links

http://www.cbperformance.com/v/enginecalc.html
http://users.erols.com/srweiss/tablersn.htm
http://users.erols.com/srweiss/calcci.htm
No way would a 4.030 piston fit...thats almost .080 over stock bore..you do realize stock bore is 3.950.....
Also if I remember no way would a .900 taller piston fit..I believe the number were in the .00* like .003 or something VERY small..
 
Last edited:




Bronco2

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if not fit, there are another piston.. that truely fit...

have to be checked..
 




jd4242

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if not fit, there are another piston.. that truely fit...

have to be checked..
You would be looking for a bore around 3.990 MAX from what I recall..unless others chime in and have proof a bigger on fits..or unless I missed something. .which could be
 




Carguy3J

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You would be looking for a bore around 3.990 MAX from what I recall..unless others chime in and have proof a bigger on fits..or unless I missed something. .which could be

"Jakee's" motor build thread has lots of good info, though the last few pages went way off track, and is filled with a bunch of irrelevant ( to a 4.0L motor build) chatter http://www.explorerforum.com/forums/showthread.php?t=247561&page=15

A 4.0" piston will fit. The consensus was that early ('90-'94) blocks should hold the needed overbore, and that 347 stroker pistons were the way to go.
 




jd4242

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"Jakee's" motor build thread has lots of good info, though the last few pages went way off track, and is filled with a bunch of irrelevant ( to a 4.0L motor build) chatter http://www.explorerforum.com/forums/showthread.php?t=247561&page=15

A 4.0" piston will fit. The consensus was that early ('90-'94) blocks should hold the needed overbore, and that 347 stroker pistons were the way to go.
We all know a 90tm will hold a 4" bore..I run one..this is the sohc block and it wont..
 




Bronco2

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Is there any overbore failure message ... outside?
 




2000StreetRod

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Max overbore

I sent the following email to Tom Morana a while back:

"I've read that the cylinder castings are thinner on the SOHC block than the early OHV block and may not be adequate for a 4 inch bore."

His response:

"We can overbore up to 4". We can custom the compression to your application. That information is incorrect, and actually the other way around. The earlier blocks are the weaker ones. If you're uncomfortable going to the max (which is .050") than you could go with .040" or .030""
 




jd4242

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Hmmm well ive personally know thats not true..
 




2000StreetRod

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Super Six Motorsports" idea

According to the technical article written by Super Six Motorsports in Nov 2005 they were thinking about a 3.5" stroke and a 3.980" bore to achieve about 4.3L. They were concerned about the block's thin cylinder walls.

I wish I could find someone who has stroked and bored their engine and is willing to share what they did.
 




jd4242

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According to the technical article written by Super Six Motorsports in Nov 2005 they were thinking about a 3.5" stroke and a 3.980" bore to achieve about 4.3L. They were concerned about the block's thin cylinder walls.

I wish I could find someone who has stroked and bored their engine and is willing to share what they did.
Like I said personally know a 90-94 tm block will handle a 4" bore and from what I know the sohc can only handle a .040 MAX
 




Carguy3J

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According to the technical article written by Super Six Motorsports in Nov 2005 they were thinking about a 3.5" stroke and a 3.980" bore to achieve about 4.3L. They were concerned about the block's thin cylinder walls.

I wish I could find someone who has stroked and bored their engine and is willing to share what they did.
You could have a block or 2 sonic checked. I believe its about $100-$150 for that process. It might be even less for a V6. That would give you a definitive answer as to what overbore your block can handle.
If you're willing to spend the money, you could test several blocks, and have a good "average" as well, to see what is generally possible with a SOHC block.
 




2000StreetRod

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cylinder sleeves

Another possibility to achieve a 4 inch bore and a longer stroke is to install sleeves in the block. As I recall my 2600 cc Alfa Romeo engine came stock with a sleeved cylinder block. To increase the bore it was possible to purchase new sleeves and pistons. One of the issues with stroking the SOHC block is the length of the cylinder bores. It may be possible with sleeves to have a longer stroke. I may contact L. A. Sleeve to get an estimate.
 




jd4242

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Another possibility to achieve a 4 inch bore and a longer stroke is to install sleeves in the block. As I recall my 2600 cc Alfa Romeo engine came stock with a sleeved cylinder block. To increase the bore it was possible to purchase new sleeves and pistons. One of the issues with stroking the SOHC block is the length of the cylinder bores. It may be possible with sleeves to have a longer stroke. I may contact L. A. Sleeve to get an estimate.
Ive seen a couple blocks and pretty sure the problem comes because the cylinders are so close together. .there is not room between the two to sleeve or over bore..as you know this block started its life as a MUCH smaller bore then was over bored to get 4.0
 




2000StreetRod

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bore spacing

According to Ford Racing the bore spacing on the 4.0L V6 is 4.760 inches. According to L.A. Sleeve the most popular cylinder sleeve thickness is 3/32" (.093") which allows for an overbore. There should be plenty of room for a 4" bore if the walls were thick enough.
 




jd4242

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I have a spare sohc block..if you all want to start a fund, I can drop it off at my machinist and see if he or it can be bored to 4" safely. ..
 




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the question is.. how much meat has to be leave to be a good cylinder...

how thick is the material and how much have to stay to handle the detonation

sleeve needs material to keep it round not to shape it like an egg ...

btw .. the ingenieurs build up a OHV engine with dohc cosworth heads .. there was only one cast and build which had 300hp .. in he 90'
SOHC wont fit the heads because of the water passage in the block..


.080 are only two mm thats one per side.. not so much .. ;)
 




Bronco2

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btw .. someone now the ford OE Number of a SOHC engine block?

need it for more details on it.
 


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2000StreetRod

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displacement change vs cost/rwhp

Again according to Ford Racing for the 1997-2007 4.0L SOHC V6:
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 Height = 1.440
The only difference for the 1990-2000 4.0L OHV V6 is Piston Comp Height = 1.442

Using the above the total stock displacement = 244.10 cu. in.
Increasing the bore to 3.990 (+.040) = 249.07 cu.in.
Increasing the bore to 4.000 (+.050) = 250.32 cu.in.
Increasing the bore to 4 inches only matters if it makes pistons readily available at a lower cost.
However, increasing the stock stroke to 3.5 with the stock bore = 257.34 cu.in.
A bore of 3.99 with a 3.5 stroke = 262.58 cu.in.

With 6 psi of boost I've got 237/244 = .97 rwhp/cu.in. Assuming the same ratio with 262.6 cu.in. yields only 250 rwhp or a 13 rwhp increase. If I could get all of the work done for $3000 (unlikely) that would be a cost of $231/rwhp - more than twice my criteria. If I were racing and 13 rwhp made the difference between winning and losing it might be worth it. However, for the street at this time I just can't justify the cost unless the short block needed a rebuild.
 




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