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]

Factory overbore

Thank you for that very useful information! According to my workshop manual the specified oversize pistons sizes are +.5mm (.020") and +1.0mm (.040"). The stock cylinder bore is 100.4mm (3.953") and piston diameter is 100.380-100.400mm (3.952-3.9528"). If the min wall thickness is only 0.1777" with the stock bore then a +.040" overbore leaves only 0.1377". According to L.A. Sleeve's website their most popular sleeve thickness is .093" which allows for an overbore (I assume +.010"). But their sleeves are made from billets stronger than our cast iron cylinders. A 4.0" bore is a .047" overbore leaving only a minimum wall thickness of .1307". If Tom Morana's statement that the later SOHC blocks have thicker walls than the earlier ones is correct then a 4" bore might be feasible but I don't know how it would hold up on the street. I've been searching the Mustang forums for anyone who has bored their block and the largest I've found so far is +.020".

 

[Bronco2]

then a 0.15 should be enough in a sohc engine block..
as my machine sop told me

Thx for the Pic!! btw i have installed a UK Shifter, its same than a Australien.. only thing is the front is not straight, so there is a 20mm Gap to my dashbord...

 

[2000StreetRod]

0.15 inch wall thickness

Bronco2, thanks for posting that 0.15" wall thickness is what your machine shop told you. Unfortunately, that only allows for .1777-.1500 = a +.0277" overbore or a diameter of 3.9807". That's not even enough for a +.040" overbore.

 

[jd4242]

I figured this would be the outcome. I would have figured if a 4" bore would have worked, someone would have done it by now.im just praying that the 90tm ohv block can handle it like I've read/seen..makes me very nervous as my pistons are already paid for and being machined as we speak..

In my opinion the major benefit to going to a custom piston is the strength, not size..I dont think there would be much power gains over a .040 or say a .060!!! Personally if it was me, I would be looking at how big of a valve would fit or how big of a cam could be made..WAAAYYYY more power to be gained there, then trying to fit a HUGE piston in there..

 

[jd4242]

So, I took the SOHC block in for sonic testing today.

I have some sad and almost unbelievable information.

At its thinnest point, which is on the front cylinders and the lower water jacket quadrants the SOHC cylinder walls are only 0.1777 inches thick. Yes, that's only around 4.5mm in metric. I couldn't believe my eyes as he was testing it. We even double checked with an outside caliper to verify the readings.

This guy is an engine re-conditioner of 25 years and he said "That's already well within Tiger territory there".

In other spots around the block it is thicker 0.217 to 0.234. It's just at that point on the front cylinders it gets real thin.

Please Note: The SOHC engine I tested does need a re-ring kit and as a result there is a noticeable lip from where the rings have worn into the bore and where they haven't. So there may be a little more meat on a fresher SOHC block.

can you be more specific when you say ""front side" ??

I would think you mean the major thrust side of the piston wall??typically if its the ""front side"" that means the wall facing the front of the engine or left side if your standing looking at the engine from the driverside. .but typically if its the left or right side then typically the middle cylinder will be thin on BOTH sides between the cylinders(where I was told its to thin to handle larger than.040 bore)

Also where it was thin did you check the bore measurement to see if it was outa round?? ""If"" it was the major thrust side and not the ""front side"" then its very possible the thin wall is from wear...

 

[Carguy3J]

I figured this would be the outcome. I would have figured if a 4" bore would have worked, someone would have done it by now.im just praying that the 90tm ohv block can handle it like I've read/seen..makes me very nervous as my pistons are already paid for and being machined as we speak..

In my opinion the major benefit to going to a custom piston is the strength, not size..I dont think there would be much power gains over a .040 or say a .060!!! Personally if it was me, I would be looking at how big of a valve would fit or how big of a cam could be made..WAAAYYYY more power to be gained there, then trying to fit a HUGE piston in there..

Actually, I think you are overlooking a big benefit of a bigger piston / bore...... It helps to un-shroud the valves. In fact, smaller valves, with less shrouding can often flow better then cramming a larger valve in and ending up with increased shrouding, both in the chamber and from the top of the bore. Same thing with a "bigger" cam. It may or may not help to lift the valve higher, depending on chamber design and bore size. Now, playing with cam timing "under the curve" is a different story. Getting them on/off the seat quicker and earlier could make big gains.
http://www.eurospares.com/graphics/...tNews.com - All Racing News All the Time!.pdf

Also, on the wall thickness / strength issue, has anyone considered using a partial block fill? Its been proven to help retain bore shape/size and reinforce "excessively" bored blocks in many applications, both street and race. I just don't know if the SOHC's cooling system passages/design will allow for it? http://www.hardblok.com/

 

[jd4242]

Actually, I think you are overlooking a big benefit of a bigger piston / bore...... It helps to un-shroud the valves. In fact, smaller valves, with less shrouding can often flow better then cramming a larger valve in and ending up with increased shrouding, both in the chamber and from the top of the bore. Same thing with a "bigger" cam. It may or may not help to lift the valve higher, depending on chamber design and bore size. Now, playing with cam timing "under the curve" is a different story. Getting them on/off the seat quicker and earlier could make big gains.
http://www.eurospares.com/graphics/...tNews.com - All Racing News All the Time!.pdf

Also, on the wall thickness / strength issue, has anyone considered using a partial block fill? Its been proven to help retain bore shape/size and reinforce "excessively" bored blocks in many applications, both street and race. I just don't know if the SOHC's cooling system passages/design will allow for it? http://www.hardblok.com/

I would have to look at the spare sohc heads again but if I remember correctly you can only go so big of valve before they touch and shrouding of the valve doesnt come into being a MAJOR factor..I know for sure on a ohv it doesnt..if the sohc valve size is anything like the ohv then they are WAYY undersized for the motor.your major power gains have come from head flow, obviously there is a fine line but its been proven on dynos again and again that most power has been gained with larger valves and cam design, not over bore

 

[jd4242]

Just double checked the valves and its not as big of an issue as it is in ohv...

Sohc has basically a IN 1.8 AND EX 1.5(surprisingly)..not bad for 4.0 but could still be larger especially on the exhaust side for a forced induction motor..just for comparison the ohv has IN 1.7 & EX 1.3....

 

[Carguy3J]

Just double checked the valves and its not as big of an issue as it is in ohv...

Sohc has basically a IN 1.8 AND EX 1.5(surprisingly)..not bad for 4.0 but could still be larger especially on the exhaust side for a forced induction motor..just for comparison the ohv has IN 1.7 & EX 1.3....

Huh.. That is pretty good for the SOHC. Chevy Vortec heads, capable of making 400hp on a mild 350, only have 1.94 in / 1.50 ex valves, and they are regarding as one of the best flowing oem iron heads GM ever made. I have a set on my currently disabled Chevy K30 pickup.

I do think that a larger exhaust valve would be a good idea on the 4.0-OHV 1.7 on the intake seems reasonable, but only 1.3 on the exhaust seems a little small, especially with a better cam, headers, etc...

 

[jd4242]

Huh.. That is pretty good for the SOHC. Chevy Vortec heads, capable of making 400hp on a mild 350, only have 1.94 in / 1.50 ex valves, and they are regarding as one of the best flowing oem iron heads GM ever made. I have a set on my currently disabled Chevy K30 pickup.

I do think that a larger exhaust valve would be a good idea on the 4.0-OHV 1.7 on the intake seems reasonable, but only 1.3 on the exhaust seems a little small, especially with a better cam, headers, etc...

Yea I was pretty shocked also..of course like I said its a fine line on size and even port work.I would like to see a 1.9 &1.6 for forced on the sohc.

Fyi I went with 1.8 &1.5 on my ohv and very nervous the 1.5 may not fit, definitely the max

 

[Bronco2]

got the SOHC engine drawings, 5,0mm is the cylinder wall thickness on the paper...theoretical

its from a 1L2E-6010 Casting

 

[jd4242]

got the SOHC engine drawings, 5,0mm is the cylinder wall thickness on the paper...theoretical

its from a 1L2E-6010 Casting

Where in the world did you get that? I would love to get a copy for the 90tm ohv block....

 

[jd4242]

Even at 5 mm thick, that still not enough for a 4" bore....5mm=.196 You take the minimum wall thickness of .15 and only leaves you a .046 over bore (4"= .047 over bore) I wouldnt trust it,especially for a boosted applications. ..

 

[Bronco2]

as i told before....

i know people who was involved in resizing 2,9 to 4,0 and to SOHC...

 

[Bronco2]

Even at 5 mm thick, that still not enough for a 4" bore....5mm=.196 You take the minimum wall thickness of .15 and only leaves you a .046 over bore (4"= .047 over bore) I wouldnt trust it,especially for a boosted applications. ..

my block will also been sonic testet before i start boring the hell out..

if its not possible.. i will stop by 4"
still waiting for sonic..

 

[2000StreetRod]

5l2z-6010-a?

Nice going Bronco2! What model and year is your 1L2E-6010 for? Any chance to find out the thickness from drawings for 5L2Z-6010-A? I think that's the block that was used in the early Mustangs. I suspect there were some changes in the block casting in 2004.

After doing a little searching I think you have a 2001 block. Is that what is in your propane powered 90 Bronco2?

 

[Sedition]

Maybe Bronco got it straight out of the factory in Cologne. It looks like I'm going to have to measure my bores after I finish honing. It's taking quite a bit of honing to flatten out that upper lip too.

 

[Bronco2]

Nice going Bronco2! What model and year is your 1L2E-6010 for? Any chance to find out the thickness from drawings for 5L2Z-6010-A? I think that's the block that was used in the early Mustangs. I suspect there were some changes in the block casting in 2004.

After doing a little searching I think you have a 2001 block. Is that what is in your propane powered 90 Bronco2?

Yes the Block i m in is a 2001 Explorer block

the Block in my Propane B2 is a 10/98Explorer ...
The Casting i asked for is a spare, which i will rebuild...

i will ask for another drawings (5L2Z-6010-A)but i think the a same..
i m waiting for another mate who work in the engine casting factory if he has more infos to me..

any OHV number to search for?

 

[Bronco2]

Maybe Bronco got it straight out of the factory in Cologne.

he did... but its under property of F...

 

[Sedition]

I just gave my bores a quick measure after honing them. They're 0.6mm over (.024")