Thunderboy

Hey people, help me out with this question. I have a '90 RS L03 TBI /700R4 with close to 89k miles, in excellent condition. However, I would like to improve the power. I know it's no use to port the stock heads. However, I can get from a friend, the heads off an '85 or '86 (not sure about the year of the car) IROC 305 TPI, 'cause he's swapping in a 350.

Are these heads any better, and would it be worthwhile to buy them, and do the traditional improvements, like porting, polishing, 3 angle valve seats, etc.? are there any guides as to how much to take off these heads?

would I need anything else off the IROC engine, if I change the heads?

will my TBI manifold fit those heads?

Thanks for your help,

Thunderboy

Dewey316

anything is better than the swirl ports that are on your L03,

the only thing i woudl warn against is spending too much money on those TPI heads, there are alot of good aftermarket heads that can be had for very little money.

and you intake manifold will not "bolt on" to the 85-86 heads, but you should be able to modify it to fit. you can also pick up a cheap 4bbl intake manifold for pre87 heads, and then use a TBI adaport plate, that should give you a good power increase over the factory manifold.

iroc22

Those should be the 416 castings. Nothing wrong with them, and many people are running those heads on high horsepower engines. Sitting Bull has a good thread on the General Engine board with pics of his 416 porting progress.

TBI305Camaro

They are definetly better than the lo3 heads. Since they are also 305 heads you shouldn't loose much compression if any while running them. Hopefully hes a good friend that will just give them to you. If so stick them on your car. You cant go wrong that way,

Dennis91RS

waste of time change out to carb 350 and be done with it trust me

iroc22

That's the worst advice I've heard yet.

1MEAN92RS

Even if you didn't touch the 416s as far as porting, they will still outflow the LO3 swirl port heads. If you are uneasy with porting then you could only go as far as gasket match porting the intake side and polishing the exhaust port. Not difficult at all, and they would flow great! (compared to the swirl ports)

Later,
Harry

Thunderboy

Well, I considered swapping in a 350, but I have the following issues:

-It would have to be a late model block, with a mount for the knock sensor. I would have to get also a 350 knock sensor, chip and injectors for my TBI, not easy to come by here, and would increase the cost. In that case, If I were spending that much money, probably a complete 350 TPI would make more sense.

-If I install a carb, and eliminate the computer, my 700R4 would not shift properly, and I don't want to be manual shifting the tranny, as I once saw somebody here doing in another car.. That would thrash the tranny easily.

- in that case, I would have to remove the tranny as well, and replace it with something like a TH400 (and a new crossmember for it)

But the car is so nice and complete, that I would like to improve what is already there, not take it all apart, but thanks for the input.

Thunderboy

Dennis91RS

why wouldnt it shift fine the only thing the computer controls on the transmission is the torque converter lock up

camaronewbie

If they are the 416 castings - they are what I'm working on now for my LO3. I was scared to try the port/polish job myself, but I figured I had nothing to lose. I've put about 5 good hours into it, and I'm very pleased with my work so far. And it hasn't been hard to do, actually quite fun.

I'm a newbie - never went farther than a disc brake job until this year. Now I'm in deep, and having the time of my life. No camera here, so I won't be able to show progress pics - but anyone interested in my budget job feel free to PM or email me.