Forum: A while back some of the more experienced members pooled their experience on when things start to break.
How rear ends start to break sooner w/slicks.
How a 500hp 350 does not last long. lol

I did a search and couldn't find it.
I have said for years that we put as much into chassis as engine.

So how hard can I push before things begin to break?

TIA

R

 

If you know how to drive, parts will last a long time.

 

Well I guess YOU are the one who can only answer that question.

Reason being....if you have a high HP/torque engine and did not replace parts that can handle this increase in power....then...no on here has the 'crystal ball' to tell you how hard to can push it.

DUB

 

I can see this is going the wrong direction.
There are forum members who have spend more on broken parts than I have in my whole car.
At some point, stock parts fail.
Those w/experience know that point!
Gkull and Lars among others know what's up!
Sometimes they share what they know.

R

 

I suggest you contact Tracdogg2 on the subject. Mike has a pretty good handle on what parts can take before they break. He can also help with getting the parts and setting everything up or guide you thru the process
if that is what you want. He is in constant contact with the racers and knows what works.

 

Any individual will only have one [or possibly a few] episodes by which to judge vehicle 'reliability'. But, you need many instances, with similar conditions, to understand where the 'weak links' will be. So, no single person is going to answer your question.

The best you can possibly hope for from this Forum is for you to solicit ALL readers to report what piece/pieces broke on their stock car after installing an engine with similar power to yours. Then, YOU can accumulate the results and see what summary information you can glean.

You can start that process by sharing what model vehicle you have, what transmission, drivetrain components (stock or otherwise), and tires. Readers will need to have about the same vehicle for their info to be of any value to you.

On the other hand, if you want someone to 'wing' it, I will offer that for a manual trans car, the clutch, half-shafts and joints are the most likely to be destroyed first. With an auto car, the torque converter and possibly something in the engine broken from overrev...when the tranny throws craps...are possibilities, as well as the half-shafts and joints. This all assumes that you have installed some pretty sticky tires on the car. If you have just street tires on the car, then THOSE are the most likely items to get worn out first.

 

My 74 is nothing special. That's why I'm doing my research/homework. To do what I want to do safely, coilovers F & R will be necessary. I'm waiting to see what DSE has for a C3.
My car has sb w/218-224 HR w/1.6RRs. AG and Demon. Rotten 2.0 RH ex man, 2.25 duals. 3:55 gears, way too close M21 trans.
H pipe.
315 rwtq 280 rwhp
It fades quickly after 4K. lol

F/R sway bars, struts, bil, VB&P brakes. #330/#460.
Nice street car ride.

I am determined to do the SS.
Few other events and track days.
I can start in Touring Car Class 140 mph sustained.
I will need a .70 OD 5 sp trans.

At some point 1/2 inch wheel studs become necessary.
I have no idea when?

I want to optimise what I have.
The 2.5 in RH should give me 500 rpm and 20 rwhp?
We shall see about that?
LTH and 2.25 ex should have me ready for whatever is next for a motor.
I'm thinking 400 Dart w/AFR heads. Can't go wrong!

I can learn from the mistakes of others.
After all, I teach.

R

 

Half shaft u-joints will go first, likely followed by the shafts themselves. Next will be the outer spindles. After you break the outers, you will likely break the inner stub axles in the diff.

If all that manages to hold up, then you'll break the posi carrier itself, the spider gears and the clutches.

A lot depends on if the car is a stick or auto, and also the condition of the current parts.

Stick cars will break some drivetrain parts easily with minimal power, where as an auto car will usually have its drivetrains live a while even with decent power.

The key is limiting the squat on the rear suspension and don't let it wheel hop.

As a basic upgrade, at a minium, I'd put 3", .095" walled half shafts in it with solid spicer 1350 u-joints, and some QA-1 shocks set to stiff when youre gonna beat on it.

 

Note that I have owned and driven drag cars ranging from Top Alcohol Dragster to doorslammer "stock" cars, as well as A Production big block vettes.

First thing to consider is that 40+ year old steel is not as strong as 1 year old steel.

Second thing is to consider that when built, the GM engineers did de-rate parts so they would hold up under normal use. I would presume the percentage would depend upon the specific part and application. So a part designed for a 250 ft lb torque motor in 1969 might not hold up under a 500 ft lb load today. Tires were different, engine horsepower was different, and the parts were new.


Third thing to consider is that if you do plan on doing anything hard core (like dumping the clutch at 5000 rpm with slicks) expect things to break.

For shock loading related failures, start with the half shafts/u-joints, then the driveshaft / u-joints, then the differential and its mating components. Make them bulletproof, and your mechanical failures will be fewer.

Or, don't use sticky tires...

My rule of thumb when restoring or building a car is START WITH THE BRAKES. No matter how fast you can go, you always have to stop. Then do the steering, then suspension..in that order. Now you can spend some time on the motor.

Good luck, have fun and most importantly, be safe.

 

Rick, I think another way to look at this is to always ask yourself, what is my "weak link"?

For example, on a typical street driven performance (?) car (factory equipped), you might reasonably conclude that the tires are the weak link. "Typically" on a good, hard launch the tires will break loose before anything will break.

Add a set of drag radials and in all probability the tires will no longer be the weak link. The secret is to ensure that as you modify (add power potential) the car, the weak link remains something "reasonably" affordable and will not do too much damage if it fails.

When something does fail and you upgrade the component to reduce the chance of failure the next time, what now becomes the weak link? I think back in the 60's muscle car era, one of the first things folks added to help control the destruction, was add a rev limiter.

Good luck... GUSTO

 

Good way to look at the problem.
I would rather not find the weakest link the hard way. lol
Some things can be upgraded "While I'm In There"

In my lurking I notice power levels near Stk BB, do not seem to tear things up too much.
After 400 hp things can get fragile!

R

 

True - the un-prudent application of Torque will tear things up faster than almost anything!

GUSTO

 

Before you just start purchasing parts, I would contact the manufacture of the parts you are considering. Talk with the techs or the people who engineered the parts. Let them know what your ultimate plans are for your car, including hp/torque you will be installing, trans, rear end gears, style of driving, the type of racing and what class you hope to run in. Ask the manufactures as many questions as you can, and call more than one. Don't forget to ask how well parts and systems will work together in your plan. You will find some suspension systems may need to be modified to fit into your chassis or may not be designed to work with a particular brake system etc. You have to research and plan your project from the air cleaner to the rubber laid down on the asphalt. Engineer and design every inch, nut, bolt and cotter pin to be successful. Its time consuming and costly to do it right but the end result is a car that will perform as you wanted, will achieve your goals, with minimum maintenance and fewer repairs. I've always over built everything I've owed. If I'm designing a motor that will dyno at about 500 hp, I'll built it to take 850-1,000. I've found that my friends have snickered about the time and wasted money I throw into a project, but while they're home turning wrenches, I'm out enjoying my project worries free. Good luck and enjoy.

 

don't worry about it, it will make bad noises and tell you something is wrong.

In years past i was making a turn in an intersection and floored the gas, I heard a bang and then bad noises. So I just drove home easy. That was my second posi housing cracking. The cross pin elongates the housing holes and finally breaks the case. Then i found out about toms Stage 7 posi units and I've never had another problem

 

Well, I hate to state the obvious, but you ALWAYS want the tires to be the 'weak link'. The alternative is that other parts break!

How many strip cars have you seen that didn't rotate the tires? NONE.

You want to put as much power to the wheels as you can; but you never want the tires to just stick and break stuff. Shock loading is the primary reason for breaking metal parts. Beef up your hard parts to beyond what is needed for your torque capabilities. Then learn how to dead-start without shock-loading the drivetrain.

 

If a guy is prudent and checks components frequently you can usually head off a catostophic failure, but not always.

This points out an important area that some overlook. When the primary failure causes secondary damage than may be even more expensive.

Things like drive shaft and half shaft loops can limit secondary damage quite a bit. A rev limiter is gonna keep your 6500 RPM engine from seeing 8500 RPM when that drive shaft or half shaft ujoint gives out suddenly while launching. Loops can save one from severe body damage, to the car and you as well.

If you are going to push a mechanical device hard, plan for the worst and hope for the best.

I like high reving SBC's vs BBC's just due to the way the torque is delivered. Higher RPM and less sudden/shock loading.

 

Get solid motor mounts. I floored my vette on the way home from work and I noticed that the steering wheel locked. so I let off the gas and steering was OKay. I had energy suspension red poly motor mounts and the drivers side had broken and allowed the headers to lift up and wedge against the steering column.

When you road race if you are not braking you generally have your foot on the floor. Because of extended time with your foot on the floor the headers start glowing red-orange. My ER red poly motor mounts had actually melted and oozed down which contributed to them breaking.

I have 1320 drive line ujoints and greasless 1350 half shafts. I have the $600 pair midamerica yokes and Toms outers.

You need to remover the diff cross member and air chisel out the what is left of the 45 year old rubber damper inserts. I bought the aluminum disks. They actually do help prevent wheel hop.

https://www.vbandp.com/auto-parts/c2...it-detail.html

 

Thanks George: I knew the fast people would come out and help.
There is some very good info that needs to be saved and passed on.
I don't want to build my car in stages, each being more expensive than the last.

I like to overbuild things too.

R

 

If you are going to replace your outers you might as well just have the 1/2 inch studs.

My iron rear end is about 30 years old. just all good internal parts.

 

For your power level, stock stuff in good condition will be fine...Assuming you arent doing 5k dumps on slicks. I would put solid spicer ujoints in all 3 shafts.

FWIW, I ran 10.90s on a bone stock 71' rear diff with 150k miles on it with an auto trans. I did have upgraded half shafts and drive shaft. Stock stuff can hold decent power if its all in good condition. My diff was wore the hell out and the clutches were broken to pieces when I pulled it, yet it would still leave 2 nice black tracks.

FWIW, I'm on stock diameter studs with about eighty 1.5x 60' passes on them. No reason for 1/2" studs at your HP level.