I just bought a convertible z28 with a 5.7L I asked the guy selling it why the 5.7 and he said that it was a LT1 out of an 03 Z28. The car runs great now but feels bendy in curves. Any comments on Subframe connectors and basic mods to the engine would be welcome.

 

Dave,

There were no 03' LT1's or z28's for that matter unless thats a type-o and you meant 93'. As far as SFC's Topdownsolutions, Spohns and Mac make some that will really stiffen the body and reduce all the flex. Are far as mods first do a tune-up then try headers and an exhaust if you don't already have that stuff.

Jay

 

I forgot to mention the took the heads out of the 305 and put on the LT1 and you were correct in assuming I ment 1993 not 03. it is tuned great now just seems sluggish compared to my 02 SS.

 

Thats because it has most likely 273:1 rear gears, which most ragtops did without a disc brake rear, which I dont think was available on convertibles.

 

It is is an lt1 motor (SBC Gen 2) in the car, I'm pretty sure 305 (SBC Gen 1) heads wouldn't work because of the reverse flow cooling, and probably some other things. Anychance we can get a picture of the motor?

-Jim

 

I will take one in a hour or so and post it.

 

Sounds like you were fed a bunch of bull.

 

Could be I am not familiar with that era of cars. I always wanted one just could not justify the 200 per month insurance payments (I was 21 in 91). Car looks great and runs good and I got a convertible for under 5k.

 

do that... I wonder what you have... the seller sounds confused at best...

 

 

Well, At some point the 305 may have been swapped for a 350.

It is beyond a doubt NOT an LT-1!

Most likely explanation: The motor was replaced. The person doing the swap ordered a 350 replacement shortblock and put the 305 heads and top end on that new engine. That is what the seller may have been trying to convey.

 

def not an LT1

 

There is a very common mistake with people who own 3rdgen Z28s. Alot of them assume if their Z28 has a 350 that is is an LT1 because they hear people say "its the same motor that was in the Vette". Some of them honestly dont know any better. Now in this case it could be one of the old school LT1s from the late 60s early 70s, but then you run into the problem of having to switch from the one piece rear seal to the 2 piece and then ofcourse you have to get a new flywheel also. Probably was a 305 that was replaced with a 350 and kept the original 305 heads on it because alot of backyard mechanics know this bumps the compression up "and compression means monster HP" lol not really, but those 305 heads wont flow enough air for that 350 if you plan on using bigger cam and upgrades.

 

Since it runs fine now I will wait until winter to tear into the engine. Any suggestions on vendors for subframe connectors and suspension would be appreciated thanks for the help.

 

- Wrong. 3.27 9-bolt with PBR discs factory here. Actually a lot of convertibles got 3.27/3.23(9-bolt/10-bolt) gearing and disc brakes. It was an option on them just like a hard-top or t-top car.

- anyhow, I'd deffinitely start with sub-frames, then look into new struts, lower control arms(relocates if needed), panhard bar, and a torque arm. Find the options codes and see what suspension package the car came with. You may then want to get different springs and sway-bars. If you do the chassis mods first, you won't end-up with a pretzel, and then you can throw anything at it you want to for power.

 

I have drums in the back was looking to do a swap out for discs but seems a little pricey for that right now. Any suggestions on a bolt in SFC I do not weld.

 

The alston's that TDS sells are great.

-Jim

 

DD72,
I have a 91 vert Lo3 and love it. (24mpg) I had the same flex problem with my car. I got hold of Lon @ Top Down Solutions and picked up the SFC. They fit like a glove and took all the yaw out of the frame in turns. I also got the "wonder bar" or steering box Bar and new sway bars with grease fittings from him. The wonder bar and SFC are a must on the verts. I felt that I needed to get the car's foundation ready first, before I started to try to make more power. Any way...I installed them my self. The SFC come with a bolt on deal but I welded mine on. Some of the welds are tight to say the least, it was worth it. Next was Adj. trail arms and adj panhard bar which made the whole suspension come together. The car is sooooo much more stable and the ride is more smooth and responsive in turns. I'm working on a new rear end and disk brake setup on all 4s next. I am driving the car this summer like you and getting parts for modifications to the motor later....
Soak it up....
dirt

 

I've heard that some guys go this route (350 block with 305 heads - and it's even more common now with 305 vortec heads) to have their cake and eat it too.... You get the larger displacement, but at the same time can potentially be a.o.k. when the time comes for emmisions. Anyone know if there is any truth to this? One other thing though, when you throw those 305heads on, don't you have to take the shortblock apart to run appropriate pistons?
-Andrew

 

It works OK for a mild motor. It bumps the compression, but you can quickly run out of flow. No, you don't change pistons, if you did, you'd gain nothing. As I said, mild 350.

 

there was no 03 z28, and no lt1 past 97