I understand there were a few special order 3rd gen convertibles with 350's but generally GM didn't offer the 350 for these cars. Was that due to the weight & power of the 350 or only a fuel economy consideration?

Given how flimsy and flexible the unibody 3rd Gen convertible is with subframe connectors what's maximum wheel horsepower and torque for 3rd Gen convertible without getting into issues of overstressing the unibody?

Is 450 wheel horse power and torque too much for one of these convertibles with just subframe connectors?

I'm planning an LS swap for my convertible 450-500 rwhp is very doable NA and 650 rwhp on spray is as well. What's the limit for the convertible unibody without a cage?

Automatic, Street & strip use with sticky tires.

Your comments and opinions are appreciated.

 

I would say about 400 bhp with subframe connectors is safe. You could fit a mini-cage across the rear seats to reinforce and fabricate some better sfc's to support 450 +

 

Fuel economy is why. GM made no official 350 convertibles. All of the 350s are either 1987 (maybe 88?) Customer Converted Camaros or 87-89 Firebirds. It's the same reason you couldn't get 350 t-top cars off and on through the years.

 

I can hit 400rwhp easily with an LS1 with heads & cam.

I had planned to do an H&C LS2 or stroker LS6 but that's in 450-500 rwhp range and sounds a little to aggressive for this unibody.

 

There isn't going to be any number. It is all going to be dependent on traction and what bracing has been added. The more bracing the better
Do inner and outer subframe connectors. If you haven't already experienced it you'll be amazed at how much they help out. When I had my convertible stripped down to JUST the body (no doors and before SFC's) on four jackstands I could feel the body flexing when I climbed over the core support or fender.
If you don't need the rear seats and don't mind the look of a roll bar on a convertible then also throw in a a six point or a four point with the lowered door bars that don't "legally" qualify it as a six point.

Pics of the inner set I made with the UMI outer set.

 

Tibo thams for the pictures. Sunframes for sure. Roll bar is out because we use the back seats for girlfriend's grand kids to ride around in when they are with us.

 

Back in the day there was a 87 GTA vert in a mag and he was running pretty decent times. Thinking he was in the 10s or something

 

I'm thinking that without a rollbar in a convertible you are kicked out for running faster than 11.5 in the 1/4 mile. In these cars that's probably around 450 rear wheel horsepower. Maybe 500 if the suspension isn't great and the car is heavy.

 

AmorgetRS is spot on, the reason why the 350 was NA with the "Factory" convertible was due to MPG... Only 87 IROC-Z's and 89 Formula/GTA/TA had the 350.

I would personally think up to 250 to maybe 300 hp without significant issues, just make sure your doors close well. SFC's would be strongly suggested above that.

JOhn

 

10's impressive, I'm surprised!

Mid to High 11's are max I'd push the car, so 11.6 is a fair cut off.

Sounds like the 3rd Gen convertible with bracing & subframes will be good for the max hp I would build for the car - 400-450 at wheels. Thank you to all who replied.

 

Just looked at the story, its called deranged droptop. The car is a 88 gta vert. 1.47 60ft, 10.20s @ 134 mph 1/4 mile. He does have a 10pt cage in it, still, that's booking.