There is a lot of conflicting info about whether or not to put high torque engines into our cars because of the body flex, especially the ttop cars. I would like to hear some experience and suggestions for running a 383 with between 400-500 HP in a ttop car and what it takes to do it without ruining a good body car. Or do I need to look for a hard top to build.

I appreciate the help and suggestions in advance.

Well, I'll let you know how mine is holding up in the rain when I get it out on the road. Rumor has it, from the previous owner, that the 350 in mine was upgraded to 383 when it was rebuilt. Hard for me to confirm without taking it out of the car, but there's a chance it really is. Here's to hoping he was telling the truth lol

Even if you didn't build a higher HP motor, these cars definitely need sub frame connectors. Especially the T-top cars.

I have a 383 in my T Top and totally agree with Red Rock. Subframe connectors are needed. Weld in are better than bolt in. I also put in a 4 point Roll Bar to stiffen and it seems to be fine. No twists or tweaks in the body.

I plan on subrframe connectors at the minimum on the car even if I dont go with the 383.

crazynights: would you mind posting a pic or two of the rollbar in your car when you get a chance? I'd like to get an idea of how it would look and fit in the car.

As well as a stock motor does.
I have had subframe connectors on for a long time. These cars need them no matter what size motor is in them.

I have the Autopower Roll Bar. I will get pics of it in the car.

Street-Sport Roll Bar
52150
82-92 Chevrolet Camero
Our Street-Sport bar is just what you need for your high performance street car.

Designed for high performance street use.
Bolt-in harness mount tube for easy installation of safety harnesses.
Bolt-In Removable horizontal harness.
4 point roll bar is made of 1.750 x .120 DOM mild steel tube.
All necessary installation and mounting hardware with back-up plates is included.
Street-Sport Roll Bar

Hope this works. First time trying to upload pic

I appreciate the picture, looks good from the side,

I looked up the roll bar info. It says that the crossbar can be unbolted and removed but do the mounting flanges create issues for utilizing the back seats? I wouldnt want to find out they're sticking out 1/4" from someones head in the back seat...

Them dang "383"s are rocket ships....

I know some people are running a heck of a lot more power in our cars, I'm probably wayyy over thinking a 383 with 450 HP

It certainly doesn't hurt to over think on these cars. They are fun cars, but just need some help in certain places. 450hp is nothing to sneeze at, these cars from factory were only designed for 225-250hp max. They need help in the sub frame area, along with brakes, rear ends, transmissions, all suspension bushings, and suspension parts, etc. Remember, these cars are 30 years old and older, and things wear out or deteriorate, or just were not built heavy. All you can do, is one thing at a time, but building the motor up first is like building the roof on a house first, and not starting at the foundation and working your way up.

I agree with you on building a solid foundation. The car I am looking to use is an 85 shell, no interior, engine, or trans. The only body work the car needs are 2 holes patched in the floor the size of a half dollar coin. Since I am starting from nothing and working up when I begin this build I want to see what I need to do to the body while I am working on the floors and etc, hence why I am here.

I appreciate the feedback and interested to hear more

https://www.summitracing.com/int/par...4365/overview/

This is a good book that helped me understand some concepts. You have to decide on your application before you start modifying. Chassis is your foundation. In my case, I wanted OEM look, TPI look, street application, strong enough for abuse on drag race track and around 400HP and 450lb-ft max. The weak link was the Tremek 6 speed rated at 450lb/ft. You don't necessarily want to overkill everything. It's going to depend on your application and amount of power you want.

I remember the first time I spoke with the performance shop and told them I wanted to put all around tubular subframe connectors. The guy looked at me in dismay and said "Are you going to put 800 to 1000 hp in this or what?". "Euuu.... Nope around 400hp" I said!!! So the squared basic subframe connectors were perfect for my application even if everyone said "use only tubular not squared". It's all about your application which depends on your budget too.

I did go overkill on the rearend though

Forgot to say that I still have to drop the 383 stroker in it!!! I am upgrading the fuel pump in a few weeks with a Walbro 255lph. Then finally, after all those years of prepping, testing and tuning, I will be able to get the mild 383 stroker built. I am confident the chassis will be able to handle it at 450lb-ft

I remember seeing one back in the mid 90s at the track with around 400-450 HP stall up, take off and busted the back glass out and a T-Top on its first run! Don't think they had bothered to go with SFCs.

I will definitely look into the book at the link you posted SbFormula.

I am looking to work on this car to be a combo track/autocross, I know that it won't be exceptional in both but I would like to build something competitive and to have fun.

Book covers 3 applications: High Performance Street Use, Drag Racing and Autocrossing


Good luck

Its not the hp that twists the body its the torque.I'm sure these cars are fine with those small high rpm japanese engines that have 450hp.The problem appears when you install a big american engine with high torque at low rpm ...that twists everything.It kinda annoys me when people say these cars are soft...no they are not ,the engine people install in these are not normal.I'm sure a 383 in a Renault (yes they don't sell in US but cost as pretty much as a Trans am) would total that poor thing.

With the T-Top, before I reinforced the chassis, I would put a floor jack behind the front wheel and jack the car up until the front wheel would lose contact with the ground. The door would be offset by 1 inch and would not shut. Now I can jack the car up the same way to a point that the back wheel starts to lift and the door shuts properly. I suspect that's what people mean by "soft". It's all a matter of perception. Imagine what the car does when you corner hard! It's not all about torque but also about handling and rattles! For what ever reason GM did not connect the front and back with reinforced structure... The floor pan is basically holding it together.

On my 150 hp Honda Accord I could jack the same way with the back wheel off the ground and the door would shut properly... That's not soft ;-)

Food for thought

That's because that honda has the frame through the rocker panel..all cars have that since late 90's when IIHS moved to offset crash tests.Be sure that honda would twist with a high torque engine inside it.Also having smaller holes for doors (2 doors per side) it reinforces the side of the car.

True! She would twist all right. She was a 2 door though

Those cages are really meh imo.I'm sure in this day and age there are ways to make your car really stiff and safe without ruining the interior.Modern cars have those cages build inside the shell ,don't know how much that would cost for these cars but it can be done since all cars on the road today are unibody.

I looked thru the link and if the car would be stiff from the inner and outer sfc's I would likely do without a roll bar for now. I don't think the engine I will be building is going to break 500 HP (budget limited) so I may go that route when I fix the floors and suspension.

There is also a difference between 500 hp at the crank, vs., 500 hp at the rear tires. Some may argue what percentages, but I'm a firm believer you lose 20% through the drive train especially on an automatic transmission.

I would like 500 at the wheels but realistically it will likely be around 500 at the crank

Mine comes in at 385 hp at the rear tires, which would put it approximately 462 hp at the crank, which also really means nothing to me, because it's all about the power to the tires. My torque is 377 @ 6000 rpm. I also have a real flat torque curve running from 3000-6500 rpm. I have a TPIS Mini Ram intake, which has a little less torque, but carries it through a longer range. There is always going to be give and take building a motor depending on what you want it for. The cam i had built is a custom made Comp cam that is border line for vacuum for the brakes. I still had to add a canister and maybe i will need a vacuum pump also, I only pull 10 in hg of vacuum. Any way, I will quit rambling now.

Think of it this way, put a T56 transmission, steel driveshaft and ford 9" in the car and leave them in for all of our engines. Put in a stock 305 TPI engine (200hp), then put in an LT1(300hp), then put a supercharger on that LT1 (400hp) Then put on a twin turbo (600hp). The amount of power needed to turn that driveline doesn't increase. It may have a direct proportional relationship with RPM though.

Higher horsepower in these cars is not all the same. A 383 engine with stock suspension that is only street driven will last a long time and may never cause any problems but taking that 383 to a dragstrip may wreak havok on the car. Put on sticky tires and you may really start to see the problems. I never installed connectors in my RS because I always knew I would be buying another Camaro to build properly since the RS had rust in the body seams, all of em. Even with all of the 350's and 383's I've had in the RS the doors still close perfect, panels still line up, no cracked tops, etc., It just comes down to what you do with the car and the tires you run. I drove within the legal limits and autocrossed and in never saw ill effects. Subframe connectors should be added and will make a huge difference but it's a myth that cars will die without them.

The camaro on roadkill survived quite well considering the abuse it got.