Ok, I need to rebuild the 351w that is in my truck, and like all the others, I'm lookin' for more power.
This is in a toy truck that I just use for offroading/weekend driving. I'm not sure of the overall weight of the vehicle.. but it's an 81F100, but it's got the D70 and D60 under it, which would add more weight.

I'm sure I wanna stroke it, but I'm not sure what variant to stroke it to. I tried searching for the info I want, but couldn't find it.
Anywho, from what I gather, these are the common options:
393, 408, 418 or 427

How much of a difference would be seen between, lets say, the 393 and the 427? And would stroking it all the way out to a 427 decrease the life of the motor?

I'd like to have a good ammount of low end grunt, as it'll be pushing fairly big tires w/ steep inclines and or through mud, etc. But I'd like to to have a good ammount of power high end as well, so an overall well rounded motor.

I don't know much about cams, and and all that, or how to calculate what I should be using as people have suggested in other threads I've read.
So if someone would be able to assist me in chosing a cam/intake/heads that would be greatly appreciated.

http://www.jegs.com/webapp/wcs/store...0187&langId=-1

I was looking at those heads, and the numbers seem to be pretty good as for the torque/HP on that 392 they tested them on, 586hp/487tq using an upped cam and those heads.

What do you guys think would be my best option?

Also, how do you calculate to figure out what size carb. would work best for your setup?

 

the 408 from what i hear has the best rod ratio going. which means a longer life, but really it comes down to the build itself. you can go cheap and question it or spend some money and never sweat it again. get the motor balanced, AFR 185 aluminum heads, you will probably need a 750cfm carb . not sure on the intake because i am more of an efi guy. once you got most these pieces figured out then call compcams and tell them the specs. they will recommend the best cam for your application.
by the way how big of tires and what gears are you running or planning to run?

 

Probably end up w/ about 38" tires, not sure on the gear ratio. There's 4.56s in there now, but I'm sure I'll swap that out for something lower.

Just curious, but, how come you chose the AFR 185 alum. heads over the ones in the link. Reading info on the AFR 185s, they say opperating RPM range from 1500-6500 RPM, which is good. But then they say that it's meant for up to a 351ci engine. Once stroked I'd be above that, and therefor wouldn't I be limited by the heads at that point?
(Copy and paste links, remove the space between the J and the E)
Heres where I got the info on the AFR 185s.
http://www.j egs.com/webapp/wcs/stores/servlet/CategoryDisplay?catalogId=10002&storeId=10001&cate goryId=26553&parentCategoryId=10187&langId=-1

This is what I was originally thinking about. It just doesn't say where it makes it's power at, and I'm not sure if it's meant for high RPM power or what, because I'm looking for something w/ a good powerband, like that of the 185s.
http://www.j egs.com/webapp/wcs/stores/servlet/CategoryDisplay?catalogId=10002&storeId=10001&cate goryId=22799&parentCategoryId=10187&langId=-1

 

to much head flow will increase were the power is made. thats why i said the 185's because they flow awesome but still restrict enough to produce good low end which is what you want especially turning large tires. i couldnt get the linke to work. why not just post the name of the head

 

The heads I was talking about are the SBF Jegs/Kaase heads.
This is the info listed for them on the website:

247cc intake runners
1.375'' square exhaust ports
60cc chambers
2.10''/1.60'' stainless steel valves
1.535'' springs w/.750'' max lift for Solid Roller Cams
1.460'' springs w/.610'' max lift for Hydraulic Roller Cams
331 cfm intake and 210 cfm exhaust @ .800'' lift

Another thing to take into consideration, is I'd like to supercharge the motor. I'm lookin' at some twinscrews that make consistant power from 2K RPM+, around 6-8 lbs boost.

 

if thats the case you will need to keep compression down to 9.0 or less. are those heads aluminum?

 

It's kind of a tough choice between the strokers.

I havn't looked at it yet, but there is a book out there (summit has it as well as other book stores) regarding ford strokers - how to build a big inch ford. It may help you in the decision.

I went with a 393. Reason? The 393 doesn't have the best rod ratio of the bunch but it uses 302 pistons and is the more popular stroker making it cheaper. The 408 was $400 more for me to get, and the 427 was even higher. The 393/408 is not going to have much of a difference, we're talking 3.85 vs 4" stroke. Here are typical tq figures from strokers...

A 393 can potentially put out around 475rwtq (even greater in extreme cases), but that is one with a 5200 RPM TQ peak.

RWTQ's should be at or greater thru a manual tranny about:

330rwtq for a 302-306
370rwtq for a 331
390 rwtq for a 347
390 rwtq for a 351
430 rwtq for a 373
460 rwtq for a 393
480 rwtq for a 408
500 rwtq for a 427
510 rwtq for a 434

If you're going to put a blower on it - it'll complicate the build but you'll have to specifically design the engine for it. You'll need dish pistons for a supercharger and your choice of heads may be different than if you were going NA. Definitely need lower compression like Travis said.

I talked to a guy yesterday with a 408 - running AFR205s instead of the 185s, carbed with .625 lift in the cam and around 240-260 duration running 525fwhp (engine dyno) n/a. With 6-8 lbs of boost you'll be adding about 100-150hp - running around 600-650 or so. That's starting to approach the limits of a stock 351 block...depending on budget you may want to look into an aftermarket block to ensure your investment doesn't go up in smoke. This could easily be a $10,000-$13,000 engine.

You've got a lot of homework to do

Edit: Here are some rod ratios...


Rod/stroke ratios:

347 = 1.58

393 = 1.54

408 = 1.55

427 = 1.47

I wouldn't worry about the rod ratios one bit, but I thought I'd post them.

 

Yes, those heads are aluminum.
And I knew I'd need to keep the compression down in order to supercharge it, I've heard that 9.0 would be good for 6-8 lbs boost.

This may sound like a dumb question, but what about the stock 351 block couldn't take that much HP? Is it not built as thick as an aftermarket block?
I can't quite afford or justify spending 10-13K on an engine at this point in my life, LoL so that would be out of the question. But I would like to get as much out of it as possible, staying w/in the safe range of the block.

So, as for the heads w/ a supercharger, since it's forcing more air etc. it sounds to me like it would help produce more power if the engine could breathe better. But at the same time, if it's breathing too much, will that power all be produced at a high range, or how exactly does this work?

 

The webbs and block will simply crack - the stock block can only handle so much power. I'd say you'd be safe with 600-650hp but the strength of blocks vary...some can stand 800-900hp some can stand 600...just know that it varies. I'm not exactly sure what the safe limit is - but I know you'd be getting close to it.

Aftermarket blocks are built stronger - Dart is one of them.

My 393 was about $6000-$7000...but I didn't build it paying attention to every penny. The shortblock was $2400. Performance heads run around $1000-$1400 and up depending on what you buy, I got cheap ones for now ($700). A supercharger alone is about $2000-$3500, and the best one for your application would probably be the KB twin screw at about $3300.

You're going to have to define your budget - and what you're going to be looking for in performance...then try to match the two. It can be tricky.

Horsepower isn't cheap

This is a very crude explanation, but hopefully it'll make sense to ya.

For an N/A engine, the displacement sets the torque level, more specfically the stroke. The bore in our case is going to stay about 4" but the stroke depends on what stroker you get. The longer the stroke the more torque it puts out, but also the more airflow in CFM it pumps per revoluion. A 393 will pump a lot more air at 2000 rpm than a 351 will, obviously.

So basically, the more stroke you have the more air is needed. And when we're getting into this, we need to think about air intake velocity. Say you've got a 393 for an example. You can put any head you want on it, including a stock head. The stock head has tiny ports on it and small valves. For that displacement, it's going to be like trying to suck air in through a straw. The velocity will be very high but you're limited on the CFM of air allowed to go through there. The supercharger will force more air in than what otherwise would be available through atmospheric pressure. If you put, say an AFR185 on there, with larger ports and larger valves, the CFM will increase and the velocity will decrease. The effect of the larger head is that it will allow more air to enter the engine and it will shift the torque curve up in the RPM range. You see, the torque level for both setups would be close to the same, there are no large increases in torque like there are for horsepower when making this type of change. As I mentioned, the displacement sets the torque...it'll make over 400 ft-lbs regardless of if you have the stockers or the AFRs. The horsepower and powerband will change significantly however.

A great example of this that I can use is a stock 302 vs ford's hipo 302 crate motor.

The stock 302 has 205hp/270ft-lbs with the tq peak at 3000 rpm, rev limit of 5500 rpm, power dropping off after about 4500 rpm. Their hipo unit has larger heads and a different camshaft to match. This engine runs 340hp but still only 310ft-lbs with a tq peak around 4500-5000 rpm. The tq peak shifted higher in the RPM range. The rev limit is moved up to about 6200-6400 and power doesn't drop off in the higher RPM range like the stocker. Notice how they picked up 135hp but only 40 ft-lbs? That's because the displacement didn't change - and other elements like higher compression added more power. If you lengthened the stroke (say a 331 or 347) the torque would increase, and horsepower would increase as a result of that.

The head choice is going to determine the general powerband that the engine will make - whether the power is high in the RPM range, in the middle, or low in the RPM range. You'd want an intake manifold that matches the performance of the head, and a cam that puts the finishing touches on the combo.

When you add a supercharger into the mix, you have to be more careful about what head size you choose. I'd say that in this application (truck) you'd want a smaller head with the supercharger to keep the velocity up which is different than what you'd do if the engine was N/A.

The supercharger pushes the engine to well over 100% volumetric efficiency. It is very useful to broaden the torque curve of the engine. An N/A engine can't make full torque across most of the RPM range. These strokers do pretty well N/A but the supercharger can help push that envelope.

You may want to consider whether or not the supercharger is going to be the right choice.

I chose not to go with a supercharger because I could get enough power out of the 393 N/A and with the added cost of the supercharger it was not within my budget. I havn't done a whole lot of engine building with superchargers - so all I can do is steer you in the right direction...but there's pleanty of info out there on how to do something like this. The supercharger complicates things and the engine needs to be built with that strongly in mind.

 

If you have any idea how much clearer that made me look at super chargers. I thought just bolt stuff on more power. Its all about ranges. Wow I feel slow now haha.

 

It's pretty involved.