Bolt-on Rant

[chuckspeed]

Awriight.

This has been buggin' me for a while.

When folks walk by yer car, they ask, Whatcha got?

They expect a whole buncha pieces parts - or some sorta listing of the bolt-ons ya got. They almost NEVER ask ET's or traps - which is the REAL indication of whatcha got.

Back in the day, I had a friend with a Torino he was gonna mod the snot outta. Bought ALL the bolt-ons available at the time - I mean ALL - and spent a month hangin' 'em on the car.

the result?

The car was SLOWER!

It turns out the guy bought too much cam and carb for a stock block, stock head motor, and the setup flat sucked since he couldn't get the air into the combustion chambers. He ended up sellin' all the stuff and goin' back to stock.

Here's the point:

Bolt-ons DO NOT make yer car faster - unless you take the time to sort out the setup. Yah - there are a couple of EZ ones like CAI's and catbacks which add HP - but for the most part, you're MUUCH better served figuring out how to get the power you have to the ground most efficiently. Our modern muscle cars post some fairly stout HP numbers (as compared to the silly-assed inflated figures from the SAE gross days) which means that a well-prepped nearly stock modern muscle car will benefit MORE from chassis and powertrain setup than ANY OTHER MOD - PERIOD!

An example:

Been researching the next round of mods for Max the Mach, was considering a blower to amp up RWHP to over 400. In researching ET's and traps of blown mod motors, I've found that a well-prepped N/A car is as quick or quicker than it's huffed counterpart!
Yeah - the blown car has a higher trap, but that ain't worth diddly when yer blowin' the tires over the first eighth of a mile!

You wanna go fast?

a) Upgrade yer rear end. That ring and pinion is selected as a compromise between fuel economy and performance. If you wanna go fast, the MINIMUM rear axle ratio you oughta be lookin' at is a 3.73 for pushrod motors and a 3.90 for OHC setups. Our O/D transmissions eliminate the 'busy' feeling of a short gear - I've been runnin' 4.30's for a couple years now with NO mileage penalty - 18-19 MPG city; 25-27 MPH hwy.

b) Get some sticky tires. Drag Radials will cut a couple of tenths off yer ET - and make the car much easier to drive, honest. The folks who complain about wet weather traction with DR's are obviously from California, as a DR in the wet is WAAY stickier than any tire on snow. Us northerners know how to adapt to changing weather...

c) Locate the rear end. Control arm upgrades reduce wheelhop, which is a prime contributor to lost time and broken axles.

d) If you have an auto trans - change the convertor. The Peebmonster's Mothership (LT1 Roadmaster) had a 1200 stall (!?) convertor; I went to a 1600 stall (which is REAL conservative) and it REALLY woke up the car! If it's a performance ride - consider a 2200 stall as a minimum.

when you're done, your car will *look* stock - but you will have shaved at least a half-second off yer ET. No, you won't win any parking lot underhood bling-bling sessions, but you will have a nose out where it counts!

[Katech]

Amen brother!

Aftermarket companies claim big numbers for bolt-ons. When we test them on the engine dyno (not a dynojet) we see small gains on stock engines. Definitely not where manufacturers claim. Bolt-ons work well in conjunction with more elaborate modifications because they all work together as a package.

[z28 justin]

Good post. I've been looking into finding some way to get power to the ground more efficiently, but I'm too scared to go with drag radials because I don't have $2500 for the 12-bolt or 9" and driveshaft needed to support them effectively without blowing up.

Has anyone here tried a girdle on the 10-bolt? I was wondering if it was worth the money to try or not

[chuckspeed]

Originally Posted by Katech

Amen brother!

Aftermarket companies claim big numbers for bolt-ons. When we test them on the engine dyno (not a dynojet) we see small gains on stock engines. Definitely not where manufacturers claim. Bolt-ons work well in conjunction with more elaborate modifications because they all work together as a package.

Thanks, man!

I've been doing this a long time now (since the 70's) and it seems that a more accurate estimation of HP gain is to take the manufacturer's claim and divide by 2.

Another way to evaluate modifications is to look at $$/HP. A properly prepped car will end up costing $50/HP for the first 100 HP. The second hundred is a function of what platform you're on. Manufacturers build in a certain amout of safety factor in their designs; this is usally 25-30%. Since an LS1 puts out 300+ HP - 130% works out to 400-ish. Same holds for the Mustang crowd; a 300+ HP 4V motor will tolerate around 400 to the rear wheels B4 requiring additional structural upgrades. That next 100 HP can cost big bux, simply because you're upgrading stuff to help the setup live. You can drop 10 grand - and not pick up a single HP - but the money is well spent if you're thinking about 600+ to the rear wheels.

There are no shortcuts here, baby. Big HP gains result in hot oily parts on the pavement, unless you prep the car to handle the HP.

[lab1702]

Great post! So far I've done (a), (b) and (c). Currently thinking about (d), but not sure if that will be too much combined with (a)... I guess it should work fine since the converter doesn't change highway rpms?

[Bishopjay]

:))));

[chuckspeed]

Originally Posted by lab1702

Great post! So far I've done (a), (b) and (c). Currently thinking about (d), but not sure if that will be too much combined with (a)... I guess it should work fine since the converter doesn't change highway rpms?

Stall speed is defined as the speed at which the motor turns when the trans side of the torque convertor is locked. A higher stall speed means the motor can spool up further - thus releasing more power/torque to the rear wheels when the car requires it.

At highway speeds, two things occur in a modern auto trans:

1) You're most likely in overdrive, so the higher stall speed has minimal effect on steady-state operation. The only time you'd notice the higher stall is when you tipped *slightly* into the throttle - at this point there would be a couple hundred RPM increase above the normal bump in engine revs.

2) In reality - all modern O/D transmissions (and many of the non O/D automatics) have a torque convertor clutch circuit which, once certain speed and load conditions are met, locks up the torque convertor - effectively taking the convertor 'slip' out of the equation.
Hell - My kid's pimped-out '96 Geo with a three speed auto has a TCC circuit! Net effect is hwy MPG of a high-stall car is going to be roughly the same as a stock stall convertor...the only time you'd see a difference in MPG would be around town. If you're concerned about mileage - select a lower stall speed.

Convertors are pretty cheap - the rebuilt 1600 RPM stall convertor cost me all of a hundred bux; I could have had a 1750 RPM stall for the same amount.

[MxRacerCam]

there's nothing wrong with doing engine mods like bolt-ons first, it's just a different approach (and often, the intially slower approach).

you are definitely right, chuck. you can knock down better times by focusing on traction, lowering weight, and driving skill. but if you throw a ton of money at bolt ons while ignoring things like traction and driving skill, you definitely won't improve your times. but, on the upside, you've got those components out of the way, and you can move on to the areas that will truly improve your times.

[Bishopjay]

Personally I feel people buy bolt-ons to compensate for they lack of knowledge of engines. People(generally) say they wanna boost their impala from 300hp to 350hp and first thing they think is something simple yet effective(BOLT-ONS). What they don't know is that their car has the potential to get that horse power off of tuning the car.
You seen it before a guy has a bunch of bolt-ons sittin on 20's, because he don't know ride height matters and smaller tires spinning faster helps speed.

Hey But I can go on for hours, just my personal opinion. Bolt-ons are good too.

[lab1702]

Originally Posted by chuckspeed

If you're concerned about mileage - select a lower stall speed.

Not really concerned with MPG.. but I wasn't sure if the combination of higher stall speed and a first gear ratio of 3.22 and rear end ratio of 4.10 would be just too much gear and give me worse performance in the 1/4.

Sounds like a higher stall converter is still worth it, especially since I plan on staying n/a. :-)