1986Z28OWNER

iTrader: (1)

Ive got a 86 v6 auto thats getting a 305 TBI and a 5 spd in the near future, what im trying to do is, take the stock engine out of my Z28 already own it, dont tell me to buy somehting else, this is on a very VERY limited budget. i want to put the TBI setup on the LG4 but i want to change the cam. my question is what cam, i dont want to do alot of tuning but im willing to learn to do it myself. any suggestions?

slow_90firebird

Thats gonna be a kinda hodge-podge swap, because the LG4 uses a flat tappet cam, and the LO3 is a roller block.

You would probably wanna keep the LG4 heads, and just throw on a TBI intake manifold, and throttle body. Also, steal the computer and all the wires and sensors out of the TBI car too, because you are gonna need them to run the car.

I'm not too sure, but you are probably gonna want to do a fuel pump. The TBI probably needs alot more fuel pressure than the carb did. Also, probably need to swap in V8 springs in the front to handle the extra weight.

As for the cam, I am not really smart at them. I know summit sells alot of "Summit Racing" brand flat-tappet cams, for really cheap. You dont wanna go to radical because you will end up re-building the heads. But there should be some cams in there that would be significantly better than the LG4 cam, and probably still real mild for tuning. Ur gonna need lifters too...

Good Luck!

1986Z28OWNER

iTrader: (1)

ive got all that kinda stuff already, changing the fuel pump is easy but i can regulate the stock v6 but im going to change it(v6 was MPFI) springs are already v8, when i did them i planned ahead and got base model v8 springs, so it sits high with the v6 but should sit nice with the 305, ive looked for a cam, but dont know if a mild perf carb cam will work with the TBI or not, like i said, i will have very little into this swap by the time its done( all the swap parts cxame from my Z28)
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also, ive got a edelbrock performer intake with a TBI adapter plate which im going to use, and im most likely going to get a set of headers. (depends on the funding)

slow_90firebird

Well, I dont see why the TBI ecm wouldnt run a motor with a flat tappet cam. What you are gonna want to do though, is try and find one that is similar to the stock LO3 cam.

I have read, that the main difference between them, is that even if you used cams with the same exact specs, a flat tappet setup will provide different lift and duration characteristics at the valve, than a roller cam will. Therefore, we need an expert to chime in, and say what size cam you need to find that will provide similar lift and duration at the valve to an LO3 cam with rollers.

If I were you, I would try and use a cam that would even be a little better than the LO3 cam. Because there are people with LT1 cams in their LO3, driving around on a factory tune. Now, it supposedly runs kinda crappy like that, but I imagine if you found a happy middle ground between the LO3 cam and the LT1 cam, the car would start right up on the factory tune for you.


Like I said I really dont know alot at all about cams, but I was just looking and saw maybe something like this:
http://store.summitracing.com/partde...2&autoview=sku

I dont know if that is too much lift, I believe the stock heads can hold like .45 or .46 so I am guessing that would be safe. However, people say you wanna keep the LSA around 114 however that one is lower. I am not sure if that has to do with it being a non rolller either.

1986Z28OWNER

iTrader: (1)

im in the same boat, ive got a good idea of what i need, but i need someone that knows TBI better than i do to chime in, im thinking something around .440 lift, 112 LSA, and under 210 duration, am i crazy or does that sound good?

vipershark11

iTrader: (6)

why put a tbi setup on a carb motor? thats asking for a headache. unless youre looking for fuel economy. other than that youll make more power with a carb and itll be easy to tune. also the parts for a carb are a lot cheaper. change the jets and adjust the screws on the carb youre ready to go now with tbi you have to data log burn a chip try it datalogging and redo as required thats if you know how and have the tools.