I have searched posts for any info on this but couldn't find any.
I have a 83 z-28 with the underpowered LG4 305. I have 350 on the engine stand which I'm going to build over the winter.

How much HP can this car handle without breaking the t- roofs or twisting the roof ? I hear lots of people talking about this but I cant find any stats at all.
I want to build the 350 up to 325 to 350 hp.
Any help or a point in the right direction would be appreiciated.

Thx..

 

Welcome aboard thirdgen.org.

IMO, subframe connectors are a must-do for these cars, regardless of T-top or hardtop, regardless of power. Put $200 in your budget for them right now.

350 HP would be a cakewalk with SFC's. Of course, 10-bolt improvements are always in order, and poly engine and transmission mounts are superior to stock type rubber. After that, it's more about making it work better, not so much making it capable of handling the power. Along those lines, poly suspension bushings make a huge difference in the way the car behaves, as do boxed or tubular lower control arms and aftermarket torque arm.

 

Agreed, I've seen box stock 350 TPI cars put cracks in the roof's at the back of the passenger and drivers side windows. The more power you put out and the stickier the tire you use, the worse you make the problem. Get the subframe connectors in there first before you start doing power mods.

 

So if I put in a good set of SFC's and poly suspension upgrades the roofline will not tweak enough to cause t-roof breakage?. I understand that the car will handle much better withthe SFC's , and the rear end is making noise anyway so I will replace it with a positraction. The car currently has a THM 350 in it. I will be replacing with a 700r4 at the time of the engine swap.

I have had some 350 hp to 400 hp cars in the past 65 chevelle ss, and a 66 Pontiac Tempest with a 302 Zapper. Both of these cars had lots of torque and twist through the frames. I just don't want to spend the cash on the motor and have the roofs breaking!!!! :-)...

 

The ONLY car that I ever bought without those cracks was an 85 4 cylinder automatic car.

Even my V6 engines break the top without subframe connectors.

GET THEM!!

 

The cracks are common regardless of motor or trans.

JamesC

 

Thanks guys.....My car has no cracks and I want to keep it that way!!!!