PDA

View Full Version : How does a 4.2L Short block compare to the SC's 3.8L?



phils89sc
10-11-2010, 11:31 PM
I was just curious as to whether anyone had ever gone with a 4.2l from a later Ford pickup? Pros and cons? Any incompatibilities? I am thinking about building another engine for my 89SC. Would the 4.2l hold up to being supercharged?

Thanks

ironworker
10-12-2010, 01:12 AM
yes the 4.2 will hold up .... get a hold of victor at spinningwheels-sc and he can help u put one together

Regul8r
10-12-2010, 08:13 AM
heard it is better to use your 3.8 block and rods. Bore it out and add the 4.2 crankshaft for a power motor. Seen others mention the 3.8 rods are tougher than the 4.2. The 4.2 has a balance shaft too, not my idea of a good idea.
Hopefully others will chime in on this.

kenewagner
10-12-2010, 08:27 AM
I was just curious as to whether anyone had ever gone with a 4.2l from a later Ford pickup? Pros and cons? Any incompatibilities? I am thinking about building another engine for my 89SC. Would the 4.2l hold up to being supercharged?

Thanks

I would PM David Neibert and ask about his combination. He is running big HP numbers with his. He can share his opinions and suggestions. Makes sense to talk to someone who has one rather than getting opinions from those that dont;) I beleive Dave Dalke built his and a few others as well. Another source to ask directly

Ken

white95v6
10-12-2010, 08:28 AM
heard it is better to use your 3.8 block and rods. Bore it out and add the 4.2 crankshaft for a power motor. Seen others mention the 3.8 rods are tougher than the 4.2. The 4.2 has a balance shaft too, not my idea of a good idea.
Hopefully others will chime in on this.

the sc rods are too short to use with a 4.2L crank. unless you cut the counterweights down alot. why not use a good rod and be done with it. and rods are cheaper then machine work and mallory added back to the crank after you cut the counterweights down.

and balance shaft removal is very easy. just spin the bearing to block the oil passage holes and done.

the 4.2L crank has been beat on by turbo motors for yrs now. and a few have seen some abuse from some procharger d1s and some with the little eaton.

my car with a 4.2 crank and a 3.8 stang block has taken alot of beating through the yrs. and i make about 900 or soo flywheel hp with a turbo.

fturner
10-12-2010, 09:31 AM
Its one thing to do it with a turbo, its another if he still intends to run the m90 etc, as that will put alot of stress on the crank that it would not see with a turbo.

We've had cases where folks have twisted the crank trying to run alot of OD on the blower.

Fraser

kenewagner
10-12-2010, 09:49 AM
Its one thing to do it with a turbo, its another if he still intends to run the m90 etc, as that will put alot of stress on the crank that it would not see with a turbo.

We've had cases where folks have twisted the crank trying to run alot of OD on the blower.

Fraser

I think the bigger engine displacement will almost require a bigger displacement blower to make HP. Neiberts combination works well due to a increase of blower size 1.5 M90 vs a 2.3 whipple and of course its a twin screw. A turbo would also be the smart way to go on a stroker. I agree with you, the M90 wouldnt be a real good fit but some will probably do it anyway

I see a lot of stroked 3.8s in the future and a lot more turbos coming in the future as this year they have been shown that huge HP gains can be had with the turbo. Kind of sad to think that my 400 hp now will be enemic in comparrasion a few years from now:rolleyes:

Ken

Roadhawg
10-12-2010, 10:02 AM
I think the bigger engine displacement will almost require a bigger displacement blower to make HP. I agree with you, the M90 wouldnt be a real good fit but some will probably do it anyway

Ken

Like me....... :rolleyes:

phils89sc
10-12-2010, 10:03 AM
Well, to be honest with you, I just would like the extra displacement. I am not looking at all to build a street killer, just something with a bit more grunt than what I have. I am probably looking at want less than 400rwhp. I need to be able to drive this every day and still be very streetable.

Questions that I have would be:

Which cam would I use (4.2L or SC 3.8L (auto or stick, 89-93 or 94-95, ?)
Which heads (stock port SC, 4.2L stock ported, etc)
Will my Harmonic Balancer work on the 4.2L, or what has to be done to accommodate that?

I intend on using my M90. Kind of on a budget buildup. A turbo is really not in my future any time soon.

As for stress on the crank, why would it matter if an SC or turbo is used, boost is boost right? I could be wrong on that. I don't intend of overdriving the blower any more than 10%

Roadhawg
10-12-2010, 10:09 AM
As for stress on the crank, why would it matter if an SC or turbo is used, boost is boost right? I could be wrong on that. I don't intend of overdriving the blower any more than 10%

You need to compare Dyno graphs between the different style superchargers and turbos.

rzimmerl
10-12-2010, 10:16 AM
Well, to be honest with you, I just would like the extra displacement. I am not looking at all to build a street killer, just something with a bit more grunt than what I have. I am probably looking at want less than 400rwhp. I need to be able to drive this every day and still be very streetable.

Questions that I have would be:

Which cam would I use (4.2L or SC 3.8L (auto or stick, 89-93 or 94-95, ?)
Which heads (stock port SC, 4.2L stock ported, etc)
Will my Harmonic Balancer work on the 4.2L, or what has to be done to accommodate that?

I intend on using my M90. Kind of on a budget buildup. A turbo is really not in my future any time soon.

As for stress on the crank, why would it matter if an SC or turbo is used, boost is boost right? I could be wrong on that. I don't intend of overdriving the blower any more than 10%

What your are trying to do here is not a budget buildup, expect to spend $$$ for a project like this even with an M90 blower.

phils89sc
10-12-2010, 10:30 AM
What your are trying to do here is not a budget buildup, expect to spend $$$ for a project like this even with an M90 blower.

Well, I think everyone is under the impression that I am wanting to build a monster or stroke an SC 3.8L. Will the 4.2L, in its stock form, handle the M90 (10% OD) as well as or better than the 3.8L SC? Basically, I would like to get a 4.2L from an F150, rebuild at least the shortblock, put on whatever heads are suggested (SC or stock 4.2L), port whatever heads are going on (myself, I am capable), reuse what I can from my SC (intake, ported exhaust manifolds, etc). Like I said, basically, I am looking for extra displacement. I have questions like:

Will the SC heads bolt up to the 4.2L? If they will, I assume I can use my intake and exhaust manifolds right? We covered the balance shaft removal earlier.

I cannot go turbo as I do not have the fabrication facilities to do so.

Mike8675309
10-12-2010, 10:46 AM
As for stress on the crank, why would it matter if an SC or turbo is used, boost is boost right? I could be wrong on that. I don't intend of overdriving the blower any more than 10%

I'll humor you, but to be certain, you have a lot more reading to do if you are asking this question.

Superchargers are driven by the crank, usually a pulley bolted to the front snout of the crank. This pulley can pull tens of horsepower off the front of the crankshaft. This creates unique bending and harmonic forces in the crankshaft. Turbo cars do not have to deal with that.

phils89sc
10-12-2010, 11:13 AM
I'll humor you, but to be certain, you have a lot more reading to do if you are asking this question.

Superchargers are driven by the crank, usually a pulley bolted to the front snout of the crank. This pulley can pull tens of horsepower off the front of the crankshaft. This creates unique bending and harmonic forces in the crankshaft. Turbo cars do not have to deal with that.

Thanks for humoring me.. I understand that the SC has mucho parasitic drag on the crank because that is what drives it. My line of thinking was on cylinder pressure and the effects of it on the piston, rods, rod journals and mains... SC's do not seem to run as much boost as turbos, but boost....is boost!! Also, turbos use restriction in the exhaust to create power by spinning the turbine, more backpressure could lead to other issues. So I guess it is a give and take both ways, SC or Turbo....

The thing I like best about the SC over turbo is the undeniable lack of lag with an SC. Although they have gotten better, turbos have lag. They may make up for it in the amount of boost they make, but they still lag and run extremely hot.

just my 2 cents.

rzimmerl
10-12-2010, 11:19 AM
Just to get this straight, few of the turbo SC's are running less boost then the twin screws and making more horsepower. Boost from a blower is not the same as boost from a turbo. Turbo outlet temps are much lower then any blower being used.

fturner
10-12-2010, 11:23 AM
If that is your goal, the cheaper route to go and get the same is to stick with a refreshed 3.8L SC block and just run a 94/95 blower at 10% OD with a snow kit with a good intercooler. The displacement factor isn't going to net you anything worth mentioning.

Fraser

old_coot
10-12-2010, 11:27 AM
The biggest impediment to just using the 4.2 from a truck is the rods---the 4.2 uses powdered iron rods (late model 3.8's also)and while they are fine for normally asperated applications forced induction of anytype would destroy them almost instantly...so good rods are necessary as a minimum. Late model 3.8's and the 4.2s use 6.090 rods while the Super Coupes use 5.956 rods I believe. I had a 4.2 liter crank cut to use the SC rods and with the late model 3.8 pistons it made for a 9.4 to 1 compression engine....a bit too much for a boosted engine but If I had gotten some forged pistons for it it would have lived longer...I cracked a piston due to detonation (i'm nearly deaf and couldn't hear it). sure ran good as long as it lasted though. the crank didn't need any mallory metal to balance so it was a 1500 dollar build for the engine. I have redone the engine with 6.090 H-beam rods and forged pistons making a little less compression (9.2to1 static). A lot more money and we will see how it fares. I winged it at the shootout but haven't opened it up to see what it is this time. On a positive note the crank seems to take the lick just fine...............Dan

Shinerstang
10-12-2010, 11:35 AM
It is really hard to compare a turbo to a supercharger. Turbo's are more efficient, thus creating more hp per pound of boost. We have a couple of 600rwhp turbo V6's with only running 17.8 and 20psi. Matt(white95v6) runs 30psi at 660rwhp?

4.2's are primarily stronger due to better webbing of the block, and the ability to increase the bore/stroke to make more hp. Let alone that the scat h-beam rods we use are pretty much indestructible. Custom forged pistons are not cheap by any means, but they are the best on a forced induction application. Compression height and pin offset are most important to avoid side-loading the pistons. I'm not sure how many really have this info, but there are a few of us.....

PDQ SC
10-12-2010, 11:41 AM
Wouldn't everyone agree that forced induction is akin to "artificial displacement?" I think putting that little blower on a bigger displacement engine would be futile. I agree that underdrive and snow is a better choice. From what I have seen, and i'm no expert, the stock blower you refer to does not have the capacity to provide the needed boost to get the grunt you are looking for. I don't think you would see any benefit unless you went with a larger displacement supercharger. Good luck and, unless it disappeared yesterday, Ricardo has an autorotor he's looking to sell.

phils89sc
10-13-2010, 01:41 PM
the sc rods are too short to use with a 4.2L crank. unless you cut the counterweights down alot. why not use a good rod and be done with it. and rods are cheaper then machine work and mallory added back to the crank after you cut the counterweights down.

and balance shaft removal is very easy. just spin the bearing to block the oil passage holes and done.

the 4.2L crank has been beat on by turbo motors for yrs now. and a few have seen some abuse from some procharger d1s and some with the little eaton.

my car with a 4.2 crank and a 3.8 stang block has taken alot of beating through the yrs. and i make about 900 or soo flywheel hp with a turbo.

So I could use either the 4.2l crank, 4.2 or 3.8l sc block. What rods would you suggest? It seems the 3.8l's require crank modification. I have read about using 351w h-beam rods or possibly stock 351 Windsor rods. How about pistons? ThNks

Shinerstang
10-13-2010, 02:37 PM
So I could use either the 4.2l crank, 4.2 or 3.8l sc block. What rods would you suggest? It seems the 3.8l's require crank modification. I have read about using 351w h-beam rods or possibly stock 351 Windsor rods. How about pistons? ThNks

The main journals are the same size on the 3.8 and 4.2 blocks. You can go with a 3.8 crank with Windsor rods(5.956) and taller compression height pistons, or a 4.2 crank with scat h-beam rods(6.125) and shorter compression height pistons. They can be mixed/matched between the 2.....

fturner
10-13-2010, 02:58 PM
Ok, its time to get realistic. If you are only intending to run the M90 with 10% OD, and lets say that is a gen III 94/95 blower with some good porting work, you'll hit 300rwhp with a cam and heads, or pretty darn close to it.

If that is all you are after, then forget about the 4.2L and just refresh the 3.8L SC block etc you have and you will have a very durable, good fuel mileage motor than can get you close to 12's in the 1/4 if you ever raced it, without

The 4.2L build will not be cheap at all to do, and the 3.8L short block has been proven time and again to be very solid and capable of handling ALOT more HP than what you are targetting.

Honestly, do the refresh thing with the 3.8, get the cam and heads done properly and get yourself the MPX setup with a good FMIC and you'll easily be making 330rwhp reliably, because the stock internals can take that including the pistons.... and that will still be cheaper than getting a 4.2 stroker built up enough to handle the above setup.

Fraser

phils89sc
10-13-2010, 03:45 PM
Ok, its time to get realistic. If you are only intending to run the M90 with 10% OD, and lets say that is a gen III 94/95 blower with some good porting work, you'll hit 300rwhp with a cam and heads, or pretty darn close to it.

If that is all you are after, then forget about the 4.2L and just refresh the 3.8L SC block etc you have and you will have a very durable, good fuel mileage motor than can get you close to 12's in the 1/4 if you ever raced it, without

The 4.2L build will not be cheap at all to do, and the 3.8L short block has been proven time and again to be very solid and capable of handling ALOT more HP than what you are targetting.

Honestly, do the refresh thing with the 3.8, get the cam and heads done properly and get yourself the MPX setup with a good FMIC and you'll easily be making 330rwhp reliably, because the stock internals can take that including the pistons.... and that will still be cheaper than getting a 4.2 stroker built up enough to handle the above setup.

Fraser

Ok, you talked me into it. Let me ask one more question concerning our SC 3.8L engine internals...

Are there any weak point or common failure points in our stock short blocks short of the head gasket problems?

BLOWN38
10-13-2010, 03:52 PM
Ok, its time to get realistic. If you are only intending to run the M90 with 10% OD, and lets say that is a gen III 94/95 blower with some good porting work, you'll hit 300rwhp with a cam and heads, or pretty darn close to it.

If that is all you are after, then forget about the 4.2L and just refresh the 3.8L SC block etc you have and you will have a very durable, good fuel mileage motor than can get you close to 12's in the 1/4 if you ever raced it, without

The 4.2L build will not be cheap at all to do, and the 3.8L short block has been proven time and again to be very solid and capable of handling ALOT more HP than what you are targetting.

Honestly, do the refresh thing with the 3.8, get the cam and heads done properly and get yourself the MPX setup with a good FMIC and you'll easily be making 330rwhp reliably, because the stock internals can take that including the pistons.... and that will still be cheaper than getting a 4.2 stroker built up enough to handle the above setup.

Fraser

What he said.

Get some 94-95 SC rods and get the forged factory replacement pistons from wiseco. And put MLS head gaskets on it.

fturner
10-13-2010, 06:37 PM
Ok, you talked me into it. Let me ask one more question concerning our SC 3.8L engine internals...

Are there any weak point or common failure points in our stock short blocks short of the head gasket problems?

Nope, other than the front crank bearing will wear a bit faster than normal because of the blower load, but we're talking over 100k miles before that is even worth considering to be an issue.

ReBuild it right, and get a good tune on it and your good to go :).

Fraser

Shinerstang
10-13-2010, 08:44 PM
Ok, its time to get realistic. If you are only intending to run the M90 with 10% OD, and lets say that is a gen III 94/95 blower with some good porting work, you'll hit 300rwhp with a cam and heads, or pretty darn close to it.

If that is all you are after, then forget about the 4.2L and just refresh the 3.8L SC block etc you have and you will have a very durable, good fuel mileage motor than can get you close to 12's in the 1/4 if you ever raced it, without

The 4.2L build will not be cheap at all to do, and the 3.8L short block has been proven time and again to be very solid and capable of handling ALOT more HP than what you are targetting.

Honestly, do the refresh thing with the 3.8, get the cam and heads done properly and get yourself the MPX setup with a good FMIC and you'll easily be making 330rwhp reliably, because the stock internals can take that including the pistons.... and that will still be cheaper than getting a 4.2 stroker built up enough to handle the above setup.

Fraser

That is very true. I wasn't doubting that most would just go with an upgraded SC on a 3.8 block and call it a day. However, there are some who prefer to make very high hp, and with that comes the expense of going fast-thus the 4.2 turbo setup......

Regul8r
10-13-2010, 09:15 PM
What he said.

Get some 94-95 SC rods and get the forged factory replacement pistons from wiseco. And put MLS head gaskets on it.

Difference in the rods 89-93 vs 94/95?

fturner
10-13-2010, 10:12 PM
That is very true. I wasn't doubting that most would just go with an upgraded SC on a 3.8 block and call it a day. However, there are some who prefer to make very high hp, and with that comes the expense of going fast-thus the 4.2 turbo setup......

Yup, and the 3.8 block is still a viable option... we've just had a guy hit 600+ at the wheels with that block and a turbo :)... the SC 3.8 block is not the same as the N/A 3.8 block.

Fraser

XxSlowpokexX
10-13-2010, 10:24 PM
Nope, other than the front crank bearing will wear a bit faster than normal because of the blower load, but we're talking over 100k miles before that is even worth considering to be an issue.

ReBuild it right, and get a good tune on it and your good to go :).

Fraser

I still believe a high hp supercharged 4.2 motor with the factory crank will have durability issues in the end. I'd personally stick with the nice sc steel crank and block. I know with my 400rwhp roots blown factory shortblock (HO) engines I used to twist and snap cranks snouts for the heck of it. It was cheaper to replace the short block than build a stout one. I have however had 700+ rwhp out of a stock sbf (HO) block and crank turbocharged.

Bottom line is ford used a steel crank in the sc for a reason. just my 2 cents

David Neibert
10-14-2010, 12:08 AM
I still believe a high hp supercharged 4.2 motor with the factory crank will have durability issues in the end. I'd personally stick with the nice sc steel crank and block. I know with my 400rwhp roots blown factory shortblock (HO) engines I used to twist and snap cranks snouts for the heck of it. It was cheaper to replace the short block than build a stout one. I have however had 700+ rwhp out of a stock sbf (HO) block and crank turbocharged.

Bottom line is ford used a steel crank in the sc for a reason. just my 2 cents

I used to be concerned about the cast 4.2 crank, until seeing the mustang guys blowing up motors and cracking blocks, trashing pistons and all other manner of carnage time after time, with no damage to the crank.

New cast crank, with prep work and balancing cost around $500-$600. Billet crank was going to be around $2500. Don't think I'd trust it with an M90 and nitrous using a manual transmission, but I think it will hold up fine with a twin screw and non locking auto.

David

XxSlowpokexX
10-14-2010, 12:46 AM
Im just worried about the snout more than anything. Then again..I cant even make enought powwer to spin tires let alone destroy a crank steel or otherwise..:mad:

shoalcracker
10-14-2010, 12:55 AM
If its meant to be.................

Paul