mcw0629

Hey guys, I have a 89 Iroc z28 Vert. I've had the car for a year, enough time to figure out all the problems an older car can have lol. Anyway I've got three questions:

1)My car has a aftermarket flowmaster exhaust and is very noticable through my convertible top (although I love! the sound of my chevy, I would like to be able to talk to someone in the car, while highway driving, without almost shouting!) Is there anyway to quiet the interior of the car?

2)Second my car rides very rough. I purchased the car with with low profile tires and 16 inch wheels. I am going to buy taller tires and hope this fixes the problem. But, I have no idea if the tires are the whole problem. Could it be that the Z28 suspension is much stiffer than the base model? I can't believe that GM would sell a car that rides so rough. Any thoughts?

3)My z28 has a 305 tpi with an 4 speed auto. I have a 350 block and various top and bottom end parts. This will become a carburated 377 or a 383 engine if it goes in the car. I just wanted to know from some people who have preformed the swap....Is the car's wiring a nightmare to get sorted out when taking off the fuel injection (I suppose there will be a lot of loose ends)? What needs to be done with the trans if the engine is in the 400-450hp range? What are things you can do to keep the swap trouble free?

Thanks for the help on any or all topics!

gray89vert

iTrader: (3)

its gonna be hard to talk to someone no matter what if you have the top down. you could dynamat the interior which would run you about 200 bucks i suppose. taller tires will def. help your ride but i would suggest getting subframe connectors. they stiffen the chassis a lot and make the car ride better as well. If you plan on building that motor def. go 383. It really shouldn't be too bad since your taking it out and not installing fuel injection. we all know its easier to rip stuff out of your car than it is to get it installed(not always true lol) everything from your 305 should bolt to the 350 block meaning the mounting brackets and everything on the front of the engine. you have a 700r4 trans. i was told they handle 300 hp stock but idk that might be . i would get a shift kit, trans cooler, and a 2800 stall or so.

okfoz

Because most of the noise is coming through the top you might consider getting a headliner... I know starting in 90 or 91 ASC added a headliner to the top. Apparently 89's use the same frame, so in theory it would be possible to add a headliner, although I am not sure how they attach, or I would do this to mine.

One thing that is NOT in your favor is you have a convertible. You can insulate and use Dynamat all day long, but with the top down it will still be noisy. If you want a quieter car buy a hard top, not being cold or flipant, just honest.

THat was the point of the IROC, it was meant to be a performance minded car. A GTA or Trans Am will ride smoother than the IROC, they used lighter springs but thicker sway bars to get the performance. Some things that will help with your ride...
1) Reduce unsprung weight, things like lighter wheels, Aluminum driveshaft, aluminum control arms and panhard bar, will help some. If you can find lightweight front A-arms that will help too... It will help with ride and performance. some things will help more than others.

2) Find springs from a base camaro or firebird, they should be softer, just make sure that they are for a V8 up front as the v6 should have used a different spring rate

I am not going to talk you out of it, as I suspect your mind is made up. some things to consider by going to a carb:
1) Drivability will go down,
2) it will start harder
3) Fuel economy will suffer, I suspect about 25% decrease as that was my increase when I went to TPI.

My suggestion is to get an LS1 with a trans, better power, better economy, its all around better.

John