cam swap questions

[JaJa Jr]

Thinking of doing a mild cam swap to a 92' bronco with a 5.0 my first question is can i just by a cam and lifter kit and install it with out having to change anything else such as pushrods springs ect. i will do that but down the road its a slow process. which leads me to my next question i want a cam that i can run in an all otherwise stock motor but will be a good choice later when i do other upgrades. any suggestions on certain ones. i know a little about how a cam works but when i look at a cam and it has durations and lifts listed im lost. i understand if i increase the duration then the valves stay open longer leading to more fuel and air and more time for exhaust to escape but can i go to aggressive? to aggressive and i can actually starve my motor of fuel right? wat about lift i have no input here all questions. i would rather not have to swap to another one later so i need some help to not choose the wrong one. and last one can i swap the cam without pullin the motor is there enough space in front of the motor? ive never done this before so i have no idea wat toi expect. just tryin to do some research before i get over my head.

 

[Fellro]

If you stay injected, you will be limited by that as well. Computers don't like high lift long duration cams.The computer controls how much fuel the engine gets based on the sensor readings. If you were carbed, then the cam does have more to do with how much fuel the engine can draw. With injection, you can go a bit more performance, but not too wild. Otherwise you have to recalibrate the computer.

As far as the cam swap itself, if you keep it mild, you don't have to change everything out, just cam and lifters. If you go higher lift, it isn't a bad idea to change springs, but you wouldn't absolutely have to, that comes with moderate performance cams as a requirement.

 

[greystreak92]

Speed density EFI can be temperamental as Fellro suggested and your 92 is indeed SD injected. However, mass-air EFI does NOT suffer from these limitations at all. The computer is no longer limited to pre-programmed volume capacities when you make the move to mass-air injection.

Given that your 92 has a speed-density injected engine, you will want to make certain that when you select a cam you make certain the grind is speed- density friendly. With that said, there ARE cams out there that work well in this application. RV (Recreational Vehicle) cams are quite well suited for increasing performance while staying within the parameters necessary to keep the computer happy. And that makes sense since RV's are typically dragging around a lot more weight than a stock truck so the grind on the cam is altered to improve performance based on the increased weight of the truck it is being employed in. Put that cam in a lighter vehicle and you will see a marked improvement in performance.

As to the procedure for making the actual swap, in most cases you can retain the same rods, rockers, valves and springs. The cam manufacturer can give you better information based on the cam you select. Most cams come with all of the critical components to complete the swap successfully save the time, tools, and knowledge.

 

[JaJa Jr]

never would have thought of a cam from an RV. wat is the difference between speed density and mass air flow EFI? i know wat a mass airflow sensor is but then im lost.

 

[Fellro]

RV/tow cams just give more in the torque range, not necessarily actually from a rv, just called that. Speed density is based off of vacuum, while the MAF system is based on intake air velocity

 

[greystreak92]

Speed density EFI uses a predetermined set of programmed parameters to input the volume of air coming into the engine. Since this can be calculated mathematically based upon the known volumetric capacity of any given engine, it can be programmed into the computer to optimize engine performance based upon the known fluctuation of air volume at varying RPM.

Mass Air takes things a step further and leaves the calculation of the volume of air actually entering the engine to a sensor designed to do just that. (I won't bore you with how the sensor works).

Speed density EFI therefore, is limited by the predetermined values assigned to the air volume capacities in the computer's software. Mass Air is not limited in this way. So, if you change cam, duration, separation, and lift, mass air can readily compensate for the change in the amount of air being introduced to the system. Speed density has a limited set of parameters to choose from and no way to determine which ones to use except by making logical changes based on OTHER parameters such as RPM and throttle position.

From this, hopefully, one should be able to better understand that speed density EFI, while quite capable in stock format, is not as open to significant changes in air volume parameters simply because it cannot calculate beyond what is already programmed into the computer. Mass Air EFI has a MAF sensor feeding it the EXACT air flow information so it can easily make adjustments without a need for any pre-programmed parameters.