hi guys i beleive i have decided what i want to do to my 300 as far as engine mods go to start with.

#1 My engine is a 1988 efi 4.9 im going to put a crane power max truck cam 260/272 grind (as optikal used i beleive)

#2 Also im am going to port and polish my heads. I might also try to port match the manifold to them. Anyways the few questions i have to ask is about how many more rpms on the top end do you think i will have to play with? im hoping that i will be able to rev it to almost 5k with these mods. Also am i wrong in thinking i will get around 50 hp out of the cam and head work alone not on a top end but as a max somewhere in my power band?

#3 would i need bigger injectors with this added power and will my factory computer setting adjust to this modest build?

#4 If i need bigger injectors what should i put on #hour wise around 19#?

Sorry a lot of questions but, i do appreciate your help and replys as usual .

ps. be as detailed as you may because, i am quite new to engines so on so forth and only 16 so lack of experience can be an issue. although i will have help with these mods for sure.

 

Well, I can answer a few of your ?'s. I think that with head work and a cam you would see an additional 50hp. You don't need larger pistons unless you plan on overboring the engine. I think 19# injectors would work fine if your modifications aren't too wild.
I would convert from your speed density to mass airflow. This is how the computer dertermines air/fuel mixture by reading the amount of incoming air and adjusting the fuel flow accordingly. Speed density systems don't play well with modifications. Another thing you can do is put on a free flowing exaust. I would use a hi-flo cat as well.
I'm not sure about your rpm ?. 300's don't like to rev very high which is good because they don't need to. They make their power(torque) at low rpms. Torque is what you want. Your truck is heavy and torque is what gets it moving. Horsepower is a measurement of torque. Think of it this way- torque is the amount of work that an engine can do over a period of time. Horsepower is how fast that work can be done.

 

Aaaah t/y thought no one would have any answers on this efi is a touchy subject for 300s i've come to find. That would be nice to get an extra 50 hp outa it maybe 70 ft lb torque. probably would make me do quite a bit better.
I think my truck could use new injectors anyways so i will go with 19# injectors.
as for the speed density to mass air flow change up, do you have any details on this? What would i get the mass air flow system off of and how would i go about taking out the old and putting in the new?.
As for me wanting to put on a few rpms this is mostly because, my transmission is a double granny and i have a big gap between 2nd and 3rd and a decent size gap between 3rd and 4th. So when im in a hurry its tough to go fast shifting at just under 4k rpms. Im hoping on another 1k to play with.
Supposably the cam i picked is good 4 1500-4500 rpms i beleive the crane guys said. Im thinking opening up the heads and exhaust the small ammount extra should give me another 500 rpms. If not im sure it will lag less anyways. T/y for the reply and keep posting all!!!
ps. as for the freeflow exhaust it's not to bad i have no cats and a decent set of pipeing im hopefully going to have true duals with and x or h pipe cross over with a banks muffler soon t/y again.

 

I think 50 hp is rather optimistic for just cam and head work. Probably 25-30 is more reasonable.

 

I have a 300 backed up by granny tranny (NP435) and when I'm in hurry I usually just wind out second gear because of the wide ratio gearing.

 

Yah thats what i do to but, id like to have it so it keeps pulling when i wind it out steada falling on its face in 2nd. T/y guys.

 

that cam recamends a valve seat presure of 160psi closed and 315psi open. your stock springs are 77psi closed and 150psi open. you will experience slow throttle respons and your rpm wont reach 3800 with out vale float.

 

Yah i do the same with mine it helps but, when you wind it out it only helps in the next gear would be nice if you kept accelerating as you were winding it out. t/y for all the replys guys.

 

hmmm the user that recomended that cam to me said he had a few extra rpms to play with but, facts r facts you must be right. what camshaft would you guys reccomend?

 

talked to my performance teacher before i did the swap and everything was acceptable...i know i've takin mine to 4 grand and havent had any valve float or related problems...

 

Yah i've heard a few people with this cam since u optikal couldn't imagine they were all full of ****t ill check in to it more though. I like the fact that it will work with my stock computer settings or is suppose to anyways.

 

im not saying hes wrong or right, im just sayin thats the first i heard of that with the powermax 260.272 grind. the the lift is still ok with stock springs...

 

Crane actually says 110 and 312 for this cam. Those are valvespring forces usually used in much larger cams than this. Those specs are probably for the only spring they have for the 300. They say valve float won't happen until 6500 rpm with those springs and by 6500 you're probably going to have bigger problems than valvefloat. They list much lighter springs for bigger cams in different engines.

 

just another tid bit of info, when my old 300 died i tore it down to the head and yanked it off. no signs of wear or tear. and i really beat the snot out of that, especially when it came close to its demise. if ur worried about the springs then i would suggest getting stock replacements or if u feel the need, upgrade.

i wouldnt worry about it but if ur tearing down the head make sure to check the spring height and stenght while ur at it. dont forget the 3 angle valve job and new valve guides/seals.