At what torque level is frame stiffening needed

[Guest rick458]

I am considering a V8 swap, and was wanting to know what Torque/HP level

warrents frame stiffening? I want to try to keep the R 180, and I will NOT likely X-Cross the car. Opinions and experience Wanted.

[maichor]

Oh, boy. This one has been discussed a few times. You should be able to dig up a few threads by searching. Basically, I think most would recommend strut bars front and rear for any V8 swap. Your sig says Serious project car. If that means something above 400ft/lbs I would say do subframe connectors while the motor is out and before you start the swap. If it is a mild V8 you can get away with strut bars and perhaps a roll bar in a 260, provided that it is not a rusted out shell.

[Guest rick458]

The Serious part is that I have limited skills in Body work etc.

Over all the car is in pretty good shape, pan and frame are in good

condition, I have a little rust through on 1 rocker panel and one door,

 

I want a car with good performance, not a race queen, OR a money pit

I was thinking right at or below 400 ft/lb with a 350 or a mild 383, much more than that and I will need a much better suspension, new brake system, new rear end, Frame connectors etc..

 

So power wise what should I aim for to prevent that scenario?

 

I was planning on the tower struts anyway

[blueovalz]

I've always had a higher performing SBF (302 and 289) in mine, and never had any problems with the unibody. This included tower connectors to the firewall, I drove it a while (pre-cage era) prior to getting serious about the racing end and even without the cage, it did not seem to be overstressing any particular area of the unibody. My engines were near the 300 lb/ft of torque though.

[Guest rick458]

On the Cages, are we talking Toolbox back or A pillar/ firewall back?

and where is a good place to buy them?

[Guest Phil1934]

S&W makes 6 point. Bar and rear diagonals and two forward diagonals. Most mount the rear diagonals to the top of the strut housings and put the hoop as close to the seat bulkhead as possible and lean it back almost to the wheel tubs. You lose less legroom like that. Forward diagonals should be left to the truly serious.

[Clifton]

My 71' has a little over 400 rw torque, the 73' close to 500 ft/lbs. I don't run strut bars and haven't had any problems. A unibody is stiffer than most framed cars. People may recomend this or that but IMO most of it is not nessacery.

[Pop N Wood]

240 ft-lbs. 280's can go to 280 ft-lbs. Hence the names.

[dr_hunt]

Pop N Wood, really? I thought Datsun was what happened when the oriental CEO wanted to make a car for the market really quick like in 240 days and the oriental engineer said "Dat" "Sun". The upgrade took 260 days and so on, so forth.

 

JK, LMAO!

[Michael]

It all depends on your application.

 

For a street car, it's entirely possible to have a 400 ft-lb engine with no subframe connectors, no cage, and no strut tower braces - and not notice any problems - if the car's performance is never tested in a controlled situation.

 

On the other hand, skilled drivers will notice chassis flexure even at much lower torque levels, for example in road racing.

 

Probably the best approach is to build the engine and drivetrain, install everything in the car as-is, drive it, and then use your judgment on what structural improvements are required.

[datsunlover]

No no no, you guys got it wrong.. Nissan needed a name that sounded 'cool' and would sell in America. They asked a german VW exec what would be a good name to use? The german said "Yah.. we'll tink about it and let you know." The Nissan guys said, "No.. wee need name soon.. like by friday!" And the German said "Ahh.. Dat soon?"

 

Anyway.. as for strengthening, from all I've read the main usues in a Z are the front 'frame' rails and firewall. They flex/twist there, and can use a bit of braceing. Strut bars are a help to..

[Clifton]

It all depends on your application.

 

For a street car' date=' it's entirely possible to have a 400 ft-lb engine with no subframe connectors, no cage, and no strut tower braces - and not notice any problems - if the car's performance is never tested in a controlled situation.

On the other hand, skilled drivers will notice chassis flexure even at much lower torque levels, for example in road racing.

[/quote']

 

If there is flex how much is there? 400 ft/lbs really isn't much. I think people like to believe they notice flex. In a RR car there would be more flex from lateral load than engine torque.

[74_5.0L_Z]

400 ft-lbs of torque does not sound like much as far as twisting force on a frame, but when it gets magnified by the transmission and differential gear ratios, the forces get big fast.

 

For instance, my car has 330 ft-lbs of torque at the crankshaft, has a first gear ratio of 3.35:1, and a differential gear ratio of 3.545:1. In first gear (assuming that the tire don't spin), the frame has to react a longitudinal twisting torque of 330 x 3.35 = 1100 ft-lbs. The frame also has to react a twisting force of the differential around the axles of 330 x 3.35 x 3.545 = 3918 ft-lbs. This last number is the reason that Z's with big torque and big traction crack where the hatch and roof are joined.

 

To me, the best stiffening for a drag car is a six or eight point roll bar that ties into(and triangulates) the rear strut towers, and ties into the front and rear of the rocker panels.

 

 

[dr_hunt]

So, basically what you are saying is that the load should be spread out along the car for the forces acting perpindicular to the chassis's longitudional axis, but what about the rotational forces acting with the same axis?

[Guest zfan]

400 ft. lbs. of torque is nothing if it is not put to the ground and hooking up. Put 400 lbs of torque to the ground with some good sticky tires and suddenly it is a hell of alot.

 

I don't break anything or twist anything with street tires on my 383 powered Z but put some sticky tires that really hook and it is a recipe for disaster more often than I would like.

 

Mike

[74_5.0L_Z]

For rotational forces, it gets more difficult. Ideally, you would want to run a "Petty Bar" that runs diagonally across the passenger compartment (from the driver's side strut tower to the front of the passenger side rocker panel). Unfortunately, this isn't a good solution for a street or dual purpose car.

 

My car is now primarily an autocross car, but I still like to drive it occasionally. The chassis in my car was completely rebuilt after I wrecked the front end so my solution is a little extreme. I built a tubular front end, installed a square tubing frame, and mounted the engine using plates that tie the strut towers together.

 

 

[Guest rick458]

I just dont want to do all the work and crack the car at the A pillar

My ID wants to put a sb 427, a bullet proof tranny with a R 230,

Coil overs, meats, Brembos, Recaros, and a $15,000 paint job.

 

My brain wants a reliable, quick, flickable good looking car, that wont be side lined in the rain.

 

thats why I have to plan correctly,and gather info

[HeatRaveR]

From the looks of the V8 installation above, does having a V8 mean you can no longer fit a front strut bar? I've got a '82 280ZX that I'm considering installing an LS1, but I really dont' wanna give up my front strut bar.

[74_5.0L_Z]

I can easily fit a strut bar because the distributor cap is behind the centerline of the strut towers. I can fit it either between the intake and distributor or between the distributor and water neck. When I still had the stock strut towers, I ran a strut tower brace between the intake and distributor. I don't use a strut tower brace now because I don't need it. The engine plate ties the two strut towers together.