cam shaft swap help

[SappySE107]

It can't be a 98 then. 99 was rare but available in large port for the 3100.

[Rootie524]

ok good.
next questions are:
how do 3500 valves help? more lift and they are lighter? and will the increased lift cause it to knock pistons or its not that much of a lift?

and do i need to tune anything PCM wise because of my new cam and supporting mods? my air/fuel ratio should still be good, right?

and i plan to get 28lb injectors in the future..Ben, can you tune my PCM for them..or anyone else here?

[SappySE107]

I can change the injector size, but I don't have anything tuned for that setup. I hope to get tunes figured out for my parts as I have access to the vehicles.

[IsaacHayes]

If it had the large port intakes, then the valves should be large too like the 3400 and your 2002 3100. So if that was the case the heads are close enough. If it had the smaller valves then it's an older casting and wont flow as well as the other head, but won't blow anything up just wont be optimal for power/etc.

3500 valves are lighter. Lift is a function of your cam and rockers, not the valves. If the valves had more lift when open, then they would never seat all the way when closed... lol

Yes a tune is proper way to do it when changing the VE of the motor significantly like with a cam.

[Rootie524]

how do i get a tune? buy an HPtuner thing? because i need something. i just went driving today and first gear is amazing but 2nd gear acts like 3rd or 4th. its pathetic. it's slower than it was before.

im going to list a whole bunch of things i noticed..try to help me figure this out.
when i start the car sometimes out the tailpipe i see it spitting drops of liquid which i presume is gas. and it seems to be worse on gas (although expected..it seems worse than it should) so if im running rich, would that cause the complete loss of power im seeing? idk why i would be running rich..not a clue

also, when i rev it alittle i hear a squeal in the engine. it's sounding like a vacuum leak but i have no idea where from. i thought at first the heads but i torqued those puppies down and did the extra 90 degree turn or whatever it was..so im thinking possibly LIM? and i know leaks cause power loss..

and when i accelerate when its shifting gears it seems to pause for a second and slowly change gears. before it was super quick because i had my shift pressure adjusted in a PCM tune..so idk.

my theory is new cam..bigger lift..more air coming in..needs more gas in the mixture. also bigger exhaust lift so more air going out..needs headers to make it leave efficiently.

ill take a video when it stops raining of me driving so you can see the loss im talking about..and of the engine bay and the squeal. but i just want to thank you all for bearing with me and helping me out. i know i have a lot of problems and ask a lot of questions..but im learning so much and i thank you all.

[IsaacHayes]

The VE of the motor is totally changed, so it will run rich at idle and low RPM until the PCM tries to learn the differences, but it will never really "learn" just adjust as much as it can. It will run lean at higher RPM's where the power band has shifted... For a comparison my motor which does not have a cam change, but has large exhaust (no headers) and big port intakes, 3500 plenum and 65mm TB takes about 2 weeks of driving normally before MPG and power response is back to normal after disconnecting the battery.. If it was tuned it wouldn't be but a few hours if that.

[SappySE107]

hptuners would be the way to go to get it dialed in completely. I forget what cam specs you have now. Did you post those in this thread?

[Rootie524]

yeah cam specs are earlier in this thread

so your saying when ever i do any sort of mod like this or what you did i need to disconnect the battery and "reset" the PCM to have it learn the new mods. And when you say drive normally do you mean like i normally do (fast, quick accelerations) or like your supposed to (moderate acceleration, no racing, normal speeds) and by doing that it will better adjust my air/fuel mixture to something that works better?

but it makes sense that im rich at idle because of the gas that comes out..and it makes sense that im lean at high RPMs because of the complete loss of power. I'm definitely going to get the 28lb injectors though..so Ben, PM me or something and let me know how much it will be for you to change my PCM for the new injectors.

is there anything else i can do apart from getting a tune at a shop or getting VCM suite? or can you assure me it will learn the best it can and fix the sluggishness.

[SappySE107]

ive search for lsa and icl and got nothing.

The computer is not going to autotune itself. It will skew fueling but that is not going to be a good way to go. If you have raw gas going through the cat and out the mufflers, there is a serious issue. Having it tuned or getting the vcm suite are the best options.

[Rootie524]

i've only seen this happen once and it went away. ill go see if gas comes out again. when it did it wasnt much just some small drops came out for a bit then as the car warmed up it went away. vcm suite is pretty expensive so i might try to find a shop that can tune.

what exactly is it that i need to get tuned? what's off?

[SappySE107]

volumetric efficiency is off, and your power enrichment would need to be changed on a dyno tune. Spark and other modifications could also show some improvements. Without datalogs, its all just a guess at what all needs to be done.

[Rootie524]

well crap. sorry if this has already been made clear..but until i can make it to the dyno or get a tune..will the PCM fix itself a tad to make it at least alittle better?

and if i need a tune..im going to wait till i port my heads, get the 3500 valves, 28lb injectors and all that good stuff.

and when i get headers and exhaust..that won't need a tune, will it? the PCM can learn little stuff like that, right?

[SappySE107]

It adjusts fueling based on O2 feedback and adjusts spark via knock sensor feedback. At WOT, there is no O2 feedback. In open loop, there is no O2 feedback. I still don't know what cam you have to know how it should be acting right now. It is best to tune it when you are done if you don't have the ability to tune it yourself. You would have to tune it for injectors.

[pocket-rocket]

i've only seen this happen once and it went away. ill go see if gas comes out again.

Could it have been moisture in the exhaust from high humidity (you said it was raining) and not running for a while since you were trying to fix it? Or did you smell it and verify it really was fuel?

[IsaacHayes]

^^^ It could be water vapour. That is a by product of combustion.

If you put in bigger injectors you will have to have it tuned right after, as it will flood the engine if you don't. The computer won't learn, but it might get better as far as driving around like a normal person would. Don't go past 70% or so throttle as it stops reading the O2 sensor there and goes off the programmed tables, but since those aren't tuned that is bad... Drive it gently and normally without getting on it too fast and the PCM will adjust and be more driveable. It won't be right but as long as it's not off too much it shouldn't blow up but it's not good for it to just drive it untuned all the time...

And don't disconnect the battery, if you do then it has to start all over at trying to compensate.

You really need a tune, especially if the cam is a moderate or aggressive one. Drive it gently until you get a tune.