Engine miss and back-fire

[hell chicken]

ok, so im new here and i am seeking advice from some of you seasoned veterans. i havent got my sig added yet so heres the scoop. i have a 1994 trans am lt1. the car has 117k miles on it. i got it about 8 months ago on a trade and car ran great. recently i have started experiencing some performance issues. car stumbles and studders and backfires when accelerating and just flat out runs like crap. it had a msd optispark on it and msd coil. the ecm has been flash tuned, no catalytic convertor, flowmaster exhaust. so i started by changing the spark plugs and plug wires...no help. i then changed the fuel filter....again no difference. everyone says its the optispark so i pick up a new one and install it to learn that the two year old msd worked just as well as the brand new one i just installed. im a diesel tech by trade and have been for 12 years. looking for guidance here...what am i missing? i havent replaced the coil and i havent actually checked the fuel pressure at the engine. is there anything else here that i may be overlooking? sorry for the long post and thanks in advance for the help.

[Mystery Bird]

Have you scanned it for codes? You could try and clean the MAF sensor for starters.

[hell chicken]

no i havent. after driving it up the road and back...i have now found that i have water in the oil. looking like its time for heart surgery. lol

[wdmickjr]

O2s need to be changed every 30k miles. even though it works it could be slow. i didnt ever believe a "slow" O2 would make the LT1 fart puke and almost at times just lay down. but how long have your O2s been on the car? and it gets worse if it sits a while.

but a scanner will tell you.

and water in oil means well you know.. head gasket and that probably ruined your O2s

[hell chicken]

ok, so my original plan with this car was to run a 150 shot of nos til she blew and then, during the build, upgrade the cam. so, im looking for suggestions on a cam. i have talked to a few guys who say run the lt4 hot cam kit with the lt4 intake. thoughts? i still plan on running a 150 shot and im also installing headers while its out. not looking to build a 600hp car...just a stout, better than stock street car. suggestions welcome. thanks

[hell chicken]

Originally Posted by wdmickjr

O2s need to be changed every 30k miles. even though it works it could be slow. i didnt ever believe a "slow" O2 would make the LT1 fart puke and almost at times just lay down. but how long have your O2s been on the car? and it gets worse if it sits a while.

but a scanner will tell you.

and water in oil means well you know.. head gasket and that probably ruined your O2s

thanks wdmickjr, i'll grab a couple o2's and put them in while i administering heart surgery.

[hell chicken]

ok so now that im building this engine, its time for some upgrades. so heres what im thinking. port and polish the heads, comp cam 503, new lifters and valve springs, upgraded throttle body and a set of headers. i want to do a mild build so am i on the right track here? anything else i need while im in it? do i need to change the injectors? advice and opinions welcomed. thanks

[wdmickjr]

there are people on here say that a bigger TB is not needed, that there MAY be a slight increase in air flow yet is not economical.

i am going to use Scorpion 1.7" rockers on my rebuild with the VooDoo 60102 Lunati cam..but I am building for torque.

More valve lift = torque
More valve diameter = HP


check with KW Barka and Dynamic396.. i am sure they steer you right with what you want. they know about dynamic and static compressions, quench area, and formulas that make the right combos.

also port your intake. to match your heads.

[hell chicken]

Thanks for the advice. I will deff. Port the intake to match. Im very familiar with the diesel performance industry but not so much with the gasoline...thanks for tue help.

[BALLSS]

hell kitchen

you might want to check out Advanced Induction or lloyd Elliot for a head/cam combo. Their packages yield better results than off the shelf cams.

You should consider larger injectors with a cam but either AI or LE can advise. larger TB, if you do, I would just have the stock one re-bored to 52. It will be more "plug & play" than aftermarket.

You will need to have the PCM tuned for all of this. Injectors will absolutely require tuning as will the cam and even a larger TB if you have a automatic

[wdmickjr]

Originally Posted by hell chicken

i want to do a mild build so am i on the right track here?

A stock 355 LT1 with some port matching, headers, cam, 1.6 or 1.7" rr, CAI and a tune is mild.
My opinion honestly.

Do you know what heads you have; casting numbers? You could send them to Lloyd Elliot and get your heads done to his LE1 package and then you'd be still on the very high end of mild; all things considered prior in this post.

LT1 is a mild screamer already, right out of box.