O.K. more numb nut newbie questions! I want to truly learn what it takes to build up a motor for more performance. The way I under stand a push rod motor is that it needs Air, Fuel & Fire to run. If you bore one out, does that alone give more compression ratio or is it in the design of the piston i.e. 10.5:1 domes, 11.5:1 domes etc. etc.? If it is in the design of the piston it self, can a guy tear his block down, have it mic'd and fluxed and guaged or what ever they do and all that good crap. If the block is not wore to much, could you simply put a piston of the standard bore size into the block for starters. I know you have to re-ring, rod,main and hone. I f the CR will increase from the stock sized piston in a different CR would the next step to getting more power be in the heads?

The way I'm thinking about this is this, If it takes air, fuel and fire to run, then by upping the CR you would need more fuel and air as well. Then the cam. Kinda like a drum, the harder you hit it the louder it is i.e. the harder the cam hits a lick, the more romp you have. Then the exhaust & intake again, the more air and fuel it gets into and out of the motor, the more power you get. But, if it can't get in or out of the compression chamber its usless as **** on a bore hog. so would the next step be milling the deck of the heads and having the heads cut out and fitted with bigger valves? And would roller rockers be needed to help it "flow" smoother to take power robbing friction out of the equation?

I know this probably sounds like the rambling disfunctional thoughts of a MAD MAN, but I just junked my jeep and now I want to get serious again. I have a 97 F250 HD 4x4. It has the zf 5spd. and a 351w. I want this thing to come alive when I'm ready to show the masses what time it is! Can someone please point me in the right direction for more power that can still be half way descent for a daily driver play toy?

Thanks, Danny.

 

Your best bet would be to get in touch with a local machinist/engine builder, that comes highly recommended, pay attention to the cleanliness of the shop, it can make all the difference. If the person you speak with sounds like they don't have a clue or refuses to answer a question you ask, walk out the door.

You need to take the block apart and have the bores measured, if all checks out then sure you might be able to get away with using a standard bore replacement piston. To increase your compression you can either use a flat top or dome piston, use a thinner head gasket, and you can mill the heads to decrease the cc volume, or you can use all three in combination. Increaseing the compression makes the motor respond faster and requires in some cases higher octane fuel. There is a lot more to it but to keep it simple, look around and find someone running a 351w efi and making the kind of power your after, in the application you plan to use your truck for, then find out what they have done to the engine and copy it....making X amount of hp isn't about any one part but the combination of them all. You do not need a roller cam to make power.

Define play toy? Easiest way to add power is forced induction, supercharge it or add some nitrous oxide...the key is to keep the boost or shot of nitrous oxide within reason and then you will have a reliable vehicle.

You might consider going to lower (numberically higher) gears for the front and back differentials and putting a shift kit in the tranny, you can also get a torque converter that will help with the torque production. The above aren't engine modifications but they will help the off idle grunt, if playing in mud is what your after, they will also improve your off idle to mid range performance on the street as well. I have only answered a piece or maybe none of your question, the question you asked has a lengthy answer, figure out what you wanna do with your truck and find a forum that talks nothing but modifiying the engine for that purpose, you will catch on in no time. Good luck

 

MASTER! GRASSHOPPER MUST LEARN THE WAY!

Well I don't like blowing smoke up my own ****, that's not me, but the year I spent loosing my mind in a 95 "4cyl" jeep, I have basically mastered gear & tire combo's. Those little 4cyl 2.5's don't make a lot of power! they are stout though. Rite now I am running 3:55.1/265x16/ZF 5spd. the ZF5spd. has granny low 5:72.1 combined with 3:55 & 24 gives me a final crawl ratio of roughly 59.6:1. Thats not bad for the low end. plus the motor really has a prety good romp and the Full Floater rear has a limited slip diff. the combo works o.k. I uasually take off in second on the street and most other places when I don't want to get down on it. I try not to punish the truck, but it's nice to here and feel the power every now and then! Shoot, it will drive in 5th at 35mph. The biggest area of consern is how to get it a little faster off the line and to hold the rpm's while towing? especially up hills. I tow an 18' pontoon boat alot. 30 miles one way. It just seems like under a load it needs about 1/4 to 1/2 throttle. Like something is holding it back. I was thinking of removing the cat because I don't have to go through emissions anbd give it a good tune up. I have noticed a little stumble, very slight, but I am intamit with my vehicles, I know when something is the slightest wrong.

 

There is, according to your post there is a 18' pontoon boat.

I may have become confused after reading your posts, originally I thought you were after more power in general, but seems from your second post, you feel you have actual problems with the engine as is. Pull the codes or go to autozone (they do it for free) and see what pops up and go from there.


Good luck

 

Well, there really is no problem with the stumble. It is extremely ever so slight. I am almost positive a tune up and quick code check so I can replace any sencors will make it go away. She really runs out real strong. Shoot, I can shift into 5th at 30-35mph. She probly just needs like an o2 sensor or something, plugs, button, wires. The wires look pretty good though, I am sure it needs a fuel filter and I might remove the injectors and clean them.

Would removing the catalatic converter mess up the computer? I don't have emissions around my place. and maybe a free flowing muffler and 3" single exhaust? I am seriously considering a 393 stroker kit. What is your take on something like that? Could you put a "small" RV cam with a 393 stroker kit and maybe bigger injectors, free up the air flow going in and the removal of the cat and the addition of the 3" single exhaust, would that be substantially more go-go? How would some mods. like that be on the wallet and gas tank mpg wise?

 

Check out comp extreme energy cams for your efi engine, they will have something that will work even better than a specific rv cam for towing, give them a call they will give you the right recommendation, but be sure you know what your end goal is and all the internal changes that it will include.

The exhaust modification you suggested shouldn't hurt anything. I have a 4.9 no cats and the egr tube is closed and there are no check engine lights and no changes in the performance. I might add, the closing of the egr tube was not to gain hp, another issue, nor did it gain any hp.

If you went forced induction there is a chance with a specific to your application chip you might improve your mpg slightly or leave it unaffected.

Call a local machine shop that comes highly recommended and see what they might charge to stroke your short block using a cast scat crank...you could always go to a 408 even more power. Might be a good time to have a three angle valve job and mild port work done to your heads, new cam, injecotors, throttle body and combo specific chip and you should be in business.

As far as what all this might cost, check around, you may find trading your truck for a diesal makes more sense.

good luck

 

Thanks brother!