Anyone on the forum dyno their engine and then take it to a chassis dyno to see the true powertrain loss. I have noticed that almost all the dyno numbers posted on forums for older cars are significantly less than the advertised HP/torque even on newly installed crate engines. I know that there are a lot of variables when a chassis dyno is done but with corrections for atmospheric conditions shouldn't a 355 hp engine at least put 300 hp to the ground? Just curious if the drivetrains on the older corvettes rob that much power and if so which component is it that is stealing the power. I took my 2002 Z06 and it made around 360 hp stock at the rear wheels which is what I would expect. I took my 1965 roadster with a fresh 327 with Performer RPM heads/intake and only got 259 hp on the same dynojet. Are the new vettes that much more efficient?

 

There are just so many variables. I once went around and pushed all the brake pads back off the rotors. We got five more horsepower on the next run.

Actually, if you get really serious you can find a lot of horsepower in places other than the engine. That's why people like a chassis dyno.

An engine dyno only measures one thing - flywheel horsepower and torque.

Richard Newton

 

The dyno operator generally can estimate pretty closely based on their experience.

Working it backwards, how do you know your 327 is making 355HP at the flywheel?

 

I don't know that the 327 was making 355 hp. I used that figure because I have seen numerous cars with a ZZ4 crate engine advertised at 355 hp put down dismal numbers on the dyno. In fact I dont think that I have ever seen a dyno sheet that was even close to being in line with what would be expected except on newer model cars. My point is that there seems to be something in the old setup that is killing rear wheel hp. Is it the transmission, the u joints, the differential? I am curious as to what needs to be updated/upgraded to get more power to the ground. What is the point of a 500hp engine if 30% of its power is leaked in the drivetrain. Seems like money would be better spent in the transfer of power than on a powerplant that is as efficient in delivering power as the government is in giving healthcare. I really don't care about the actual numbers but I want a seat-of-the pants thrill when I stab the accelerator! I got it in the Z06 and really want it in my midyear! These new crate engines are dyno tested before they leave the dealer and yet fail to deliver on the street. Do a search on dyno numbers and show me someone who says "Wow, that is what I expected!" on a midyear. They usually start with an intro like "Disappointing numbers today. Maybe I need to advance my timing or get a bigger aircleaner to retrieve that 100 RWHP that I am missing."

 

Not sure how to respond here. To net it out, properly run dynos put out relatively accurate results, with drivetrain losses in the 8-15% range. The simple answer is that you're not making 355HP at the flywheel with those results, and you're not going to find 100 RWHP in the drivetrain. There may be more horsepower in a tune, but without hard data on the engine you (and I) are just guessing at what it will put out.

I suspect this is not the answer you're looking for, so I'll bow out

 

Thanks for the input. Just curious if there is something else to change other than the engine/induction to get that lovin' feeling. I know they are just numbers but heck, we are paying out the nose for them!

 

You're looking to increase your RWHP with no change in FWHP? As noted, there might be some odd tweaks here and there, but in short - no.

Generally, you get what you pay for in FWHP - or at least, that's been my experience. I've never been disappointed at the dyno yet.

 

The C5/6 seem to have less drivtrain loss than the traditional trans/rearend setups.

Also the difference in tech (heads/cam/air and fuel management) is astounding between an old school Gen1 and the LSx series motors.
There are aftermarket parts that help close the gap some but overall Id say technology is your Z06s friend.

 

That is what I have noticed. The only numbers that I have seen that are in the 15% drivetrain loss range are on C5/6 cars or on older vettes with modern drivetrain setups (resto mods). Oh well, just curious if someone had flywheel numbers and then RWHP numbers to see the real loss in power in the traditional setup.

 

In my experience, the difference here is maybe a couple percent.

I recently dynoed a 1971 Chevy C-10 2WD pickup with a TH350 and aftermarket torque converter both on the engine and chassis dyno. I'll look for the sheets, but the 355 made 360 HP at the flywheel and 310 at the rear wheels - about 14% drivetrain loss on a well-run dyno with an experienced operator. On the same dyno with the same operator, my 2003 Z06 rated at 405HP (mine is bone stock) put down about 351HP on the dyno, which is in the ballpark for these cars...and 14% drivetrain losses if we trust the rated power.

I'm interested in some other specific situations, but the 25-30% losses noted just don't happen in my experience. I guess with an automatic and a downright broken torque converter you might see more than average - but what I see more commonly is complete guesses on FWHP and then blaming missing the numbers on the dyno

A little detail on the 327 in this case (cam, CR, etc.) would help put this to bed pretty quick.

 

No idea what that 327 made but I would guess it was more than 300hp. The engine was a small journal 327 with a comp cam 224/224 cam, Keith Black hypereutectic pistons which would give about 9.5:1 compression with the 64 cc chambers on the Edelbrock Performer RPM heads, Performer intake, holley 650 cfm carb, MSD ignition with 6AL box, headers, roller rockers, 4 speed Muncie, 3:70 rear end. Felt strong but only made 259hp/312ftlbs to the rear. Again, I don't know that this engine was all that. Those numbers for the truck are good and that is encouraging. Anyone else with this experience?

 

FWIW, a bit over 300 FWHP at around 5000-5500 RPM would be my estimate if all the specs are right. If you're guessing a bit over 300 as well...then aren't those dyno results about right?

Also FWIW, GMPP crate engines are dyno'd with open headers and no accessories. As installed the ZZ4 will make around 320 FWHP

 

Funny story about that 327. I sold the car to another fella who decided to drag race with that setup. He told me that the engine really "came alive" over 6500 rpm. I explained that the dyno showed peak power at about 5800 rpm and then dropped like a rock. He didn't listen. Needless to say, that engine no longer exists!!!

 

Had my car dynoed before & after putting my muffler eliminators on (straight pipes)

I actually lost power in the process.

What's that tell you?

 

many of you guys spend far to much time worrying more about paper hp and torque numbers vs the cars ability to be fun to drive and reasonably fast, if the car will run mid-low 12s at about 110mph and stop on a dime your far faster than most cars on the road, in a 3500 lb vette that takes about 380 rear wheel hp
heres some calculator links

http://forum.grumpysperformance.com/...hp?f=69&t=1814

I get guys in the shop all the time that think they want and need 550-600hp, what they really want is the ability to destroy rear tires at the flick of the throttle and to run mid 12s or slightly faster because that's all that's required to amaze and impress their friends 90% of the time.
any decently researched and built 383sbc or 396 BBC car produce those power numbers and performance matched to a 3000rpm stall converter and 3.73 rear gears

 

OT, but Numbers mean nothing, and HP=racing, torque=fun on the street!

 

IMHO there's gonna be no way you're gonna get 2002 Z06 performance out of a 327 unless you put the pistons, heads, cam, intake, and carb on there to do it and your combination isn't even going to come close. And after you do that, you'll find you've built an engine that's only going to be happy in the 4k and up rpm range. There was a guy who built a 327 with over 500HP on an engine dyno in one of the mags I read but I doubt that it would be much fun on the street. And he didn't build it for the street, he built it for the strip.

Also, IMHO those Performer RPM heads do not represent state of the art for SBCs.

Get a decent tuner to tune you 327 on a dyno and you'll probably see a few more horses.

Comparing a high horse fuel injected LS engine to a carbureted 327 is comparing apples to oranges anyway.

FYI, the September Super Chevy compared 3 blueprinted Chevy classics on an engine dyno. The 302 Z28 made 356HP/332TQ. The L76 (327/365HP) made 352/363 and the LT1 made 353/391. Not exactly awe inspiring by modern standards. But, hey, they were state of the art for 1968, 1964, and 1970, respectively!

 

...not what the OP was asking. OP was asking about classic vs. late-model drivetrain losses.

...and power is the all the same, regardless of the packaging

 

As noted a considerable amount of the loss between crank HP and RWHP is in the all the differences in pumps, fans and exhaust not counting a motor that in a car may be starving for fresh air and/or cool fuel.

That being said I would not expect the difference between a transaxle and a early model drivetrain to ever exceed 5% absolute max.

There are some services available to have gears coated to reduce friction aka power loss from specialty companies like Duntov Lightweight Corvette...... but it is expensive and a lot of labor is still involved when you get your parts back.

Doug

 

Have always understood there was app 100 HP loss in my stock midyear drivetrain. The 1/4 mile numbers supported that theory. The 65 now has a T56 6SP which uses AT fluid. The old Muncie used 90 Weight. I gained RWHP with the T56. Trouble is, Borg rep says only rated for 350 ft lb. He said if you put the slicks back on, your 454 will shell the T56. The 11.95 with the M 21 will have to stand.