how crazy can I get?

[THE 580 Slider]

ok guys i have a 97 chevy (of course) reg. cab short bed. My truck recently started runnin like crap due to what i believe is a bad valve. So to make a long story short i am gonna rebuild at least the top half of the engine. So my question is if I bore it how big can i go, if i cam it how big of a cam, if i port an polish how much? simply put how far can i go before i need to dynotune my truck or have a custom tune wrote for it. The only thing i am set on right now is a set of longtube headers just not a certain brand in mind still shoppin. Any advice would be very helpful thank you in advance

[Chevy53]

How do you know its a valve thats bad? do you have any proof of this? have you actually diagnosed it as a bad valve instead of guessing?

port and polishing is a delicate procedure if you make it too smooth or take out too much material you can easily enough lose power and if you put longtubes on it your going to need a tune anyways to pass emissions so figure out what you really need since your deff going to need a tune of some sort and its deffinitly recommended if your going to do any major performance work to the truck

[THE 580 Slider]

How do you know its a valve thats bad? do you have any proof of this? have you actually diagnosed it as a bad valve instead of guessing?

port and polishing is a delicate procedure if you make it too smooth or take out too much material you can easily enough lose power and if you put longtubes on it your going to need a tune anyways to pass emissions so figure out what you really need since your deff going to need a tune of some sort and its deffinitly recommended if your going to do any major performance work to the truck

not 100% sure its a valve but after sinkin close to 500 bucks in it thats one of the last few things it could be not sayin for sure thats what it is but as of right now with out pullin my vavle covers an checkin rockers thats my guess but needless to say what ever it is i am goin to rebuild at least the top half of the motorwhen it goes in to the shop and the port an polish i was just throwin out there as an example of somethin to do as far as performance increase but here in oklahoma we dont have emissions testing so i dont have to worry about that. but with the LTs would i still need a tune to take full advantage of them? an i have some things i would like to do to the engine but instead of throwing them out there i am just seein what you guys have to say first

[Chevy53]

you wouldnt need a tune but you would want one wont run nearly as good as it could with a tune, put a peice of over exhaust and if the paper gets sucked in the you have a bad exhaust valve not sure how to quick test intake valve leakdown is probably your fastest option, id test em before you sink more money into it

[Low97tahoE]

i would tune it whether you do motor work or not, a tune is the best thing you can do, stock or modified

[SolMan98]

You've spent $500 and you haven't pulled a valve cover yet? What have you done?

[THE 580 Slider]

You've spent $500 and you haven't pulled a valve cover yet? What have you done?

Well lets see here its been on a tecII twice at a local chevy dealership, 2 new o2 sensors, new tps, new plugs, new wires, new cap ,new rotor, new thermastat, and has had a compression test done on all cylinders with between 155-180 on all 8 cylinders number 8 cylinder bein 155 psi. The dealership also said its not a fuel issue as he checked the fuel pressure also. This is why i was just gonna rebuild . to fix the problem an get a little more out of it

[Chevy53]

whats it doing when it runs like crap like hesistating off the line or what? does it get better as it warms up or better at cold or same?

how does it do on highway?

[hin532]

You will need a tune either way. Also may want to change tho the upgraded mpfi spider.

[THE 580 Slider]

whats it doing when it runs like crap like hesistating off the line or what? does it get better as it warms up or better at cold or same?

how does it do on highway?

its like i solid miss fire it dont matter if its cold or hot , in the city or on the highway it just straight runs like crap like a stuck valve. And my mpg went WAY WAY down went from 21 on the highway to i am lucky if i get 11 under the same conditions

[hin532]

its like i solid miss fire it dont matter if its cold or hot , in the city or on the highway it just straight runs like crap like a stuck valve. And my mpg went WAY WAY down went from 21 on the highway to i am lucky if i get 11 under the same conditions

Have you figured out what cylinder it is? You could have a leaking poppet in the intake Plenum causing that miss.

[THE 580 Slider]

Have you figured out what cylinder it is? You could have a leaking poppet in the intake Plenum causing that miss.

the dealership tech that ran the techII on my truck said the problem is either #8 or #2 . so not quite sure as of yet but my understanding is if one cylinder is goin crazy it has the abilty to mess with the cylinder oppisite of the problem cylinder?