Fast car, slow ET?

I have a buddy who has a really nice '56 Chevy. It runs 140 mph at the track which seems fast to me for a '56 Chevy, but the ET is slower than the charts say it should be. Car is a little less than 3000 lbs with driver, has ladder bars, big slicks, etc. I have one picture of the car leaving the line and the slicks have some wrinkle to them but it doesn't appear to be launching super hard. The nose lifts a small amount. The timeslips vary (which might be a clue) but typical numbers are 1.40 60 ft, 6.25 660 ft, 8.15 1000 ft and 9.75 or 9.80 for the quarter. MPH is in the 140 range.

Wallace says the car should run 9.50, Moroso says 9.60. Various calculators say the engine is making 600 to 650 hp to run those numbers in a 2950 lb car. The engine should be making more power than 650, It is a Dart 540 which the engine builder said made 850. The engine looks like it should make 850 hp, but I haven't had it on a dyno. But even if the engine is only make 650 hp it still should be quicker than 9.80 if it can run 140 mph.

So my guess is that there is more than one issue with the car. I'm thinking that it isn't making the power that it should and even with the power he does have it isn't running the times. Just not sure if it is a chassis problem or a transmission issue. The wrong torque converter could be costing a few tenths I suppose. The chassis builder says the car needs a four link which might be true but I'd think it could still get down the track faster even if the ladder bars weren't ideal.

Many people who don't test different converters will never go as fast as they could with the best converter for their combination.
Does this owner want to go faster and quicker?

Converter, converter, converter. I looked up a bunch of ladder bar cars that run in N/SS, 10.5" tire, foot brake. They average 139-140 mph running B/FX (9.50 index) should go around mid 1.3X 60ft, 6.05 in the 660
Doug

60’ is pretty soft for a car with big tires that goes 140mph.
Should be close to a tenth better...... low-1.30’s.
Plus, it’s a brick...... which should be negatively impacting the speed(so with better aero it would be even faster...... which would make the 60’ look even worse).

It’s an example of not having the “combo” right.

Converter/cam might be a mismatch....... by the looks of the headers, they probably weren’t used for the dyno test, so that’s an unknown variable.
Footbrake or transbrake?
Glide?

Since the speed is way down....... if the alleged dyno numbers are correct....... there could be some other issues in the car costing some power.

I have seen this type of situation play out before.
Car owner spends thousands on car upgrades(converter, fuel system, carb, etc) to no avail, then has motor dyno tested only to discover the car is going as fast as the hp it produces will go(motor doesn’t have what was expected).

I like to use 90% of the STP dyno power as a point of reference for how quick/fast the car “should” be able to run. Then add in any extra ET correction for tracks at higher elevations(over 1000’ or so).

So, working that backwards, 3000lbs, 140mph...... shows 630hp....... which is 90% of 700hp.

Frankly, with what’s available for BBC parts these days...... if one set out to build a “bracket race” 540....... it would be fairly hard to end up with only 700hp.

If nothing obvious in the car reveals itself, I’d put an engine dyno test pretty high on the troubleshooting list.

If the motor tested at 800hp, then the 90% number I’d be looking at is 720hp....... which “should” be going 146@3000lbs.

Sometimes the simple things can be revealing....... do a compression test and check the lash.

SO many things could be wrong.

BUT id start with the 60" seems light for that mph

Converter, and a car like this needs a data logger. Nothing will point you in the right direction like a data logger will. Racepak sportsman will more than pay for itself int eh info it will give you for getting the converter alone correct

They put the car on a chassis dyno a few weeks ago since they thought it was down on power. According to third hand info, the car made 850 hp on the chassis dyno. I've asked the owner if he can send me a copy of the dyno sheet since that doesn't add up. 850 on the chassis dyno would put the car up past 150 mph even if the converter and chassis weren't perfect. The 60 foot might be slow but with that much power on board the car could still get rolling past mid track.

This. How do you improve something if you can't objectively measure it.

I’m not saying this is the problem, just pointing out how sometimes it’s not anything you might expect.

This was several years ago(over 15).
A customer of mine builds a hot street/strip 496 BBC to put into his customers mid-80’s Monte Carlo.
Motor gets dynoed, makes what was expected(don’t remember the numbers.....650-ish?)

Car has some sort of converter and 4.10’s, 10X28” slicks.

They go to the track on a test and tube day, and there are hardly any cars there. They can make tons of passes.

The car is all over the place in the 11’s....... not super close to the 10’s.
My customer is asking about shift points, rpm thru the lights, etc...... not getting any useful data from the owner, who is unhappy that the car isn’t running 10’s.
My customer jumps in behind the wheel...... runs 3 10.8x’s in a row.
Tell the owner how to launch, where to shift, etc......... owner back behind the wheel....... a bunch more 11.xx’s.
I don’t think he ever got a 10 out of it that day.

Sometimes........ the problem is........ the driver.

Here’s another thought.......

Is the cowl hood the “correct” distance from the windshield?

Attach a piece of string to the inside of the scoop, long enough to easily come out beyond the edge of the scoop.
At the top end of the track, see it the string is sticking out of the scoop.
It shouldn’t be, but if the scoop is too far away from the windshield, the inside of the scoop can be a low pressure area, instead of a high pressure area.
If the string is being sucked out of the scoop, the scoop opening is a low pressure area.

Could be a fuel system issue , hood (as mentioned), converter, ignition,
Dyno helps but doesn’t simulate track conditions
Best money spent would be racepak sportsman . AF sensor, Fuel psi sensors . Etc
Data data data
Trips to the track could be 100.00 -400.00 with that type car . 5-6 wasted trips could pay for the data logger .
A good converter co will take that data and get it correct with less testing , less wear on the car, engine , tires , etc

That is something I hadn't thought of and could explain some of the things that don't add up such as the car making power on the chassis dyno but not running the number at the track. Most of the other systems in the car get fully exercised on the chassis dyno so fuel flow and exhaust and ignition and stuff like that should be good at the track if they are good on the chassis dyno. Airflow is a wild card.

That would not explain good mph. If the car makes the power on the chassis dyno that matches the actual mph, then the e.t. can only be explained by traction or poor converter choice.

The speed is way off for what the chassis dyno numbers were.


Hopefully Andy will get the dyno sheets to look at.

The hood scoop thing doesn’t explain the poor 60’ times though, as it wouldn’t be having any real affect at that point on the track.

An 850hp 540 in a big tire 3000lb car should be solidly in the 1.20’s for 60’ times.

Could be multiple issues with the car. Once I can confirm dyno numbers I'll know more where to look. Could be gearing, shift points, converter, or chassis causing the poor ET and the scoop costing MPH. The car once ran 143 mph at Yakima which is higher elevation. So I'm thinking there is a variable that we don't quite understand.

A lot of good ideas, and i bet more than a couple of things mentioned are at fault. A video of the launch might reveal poor shocks/ settings. Someone with a desktop drag strip program could compare differences due to the shoebox body. Other gremlins could be headers, collecter length, fuel system or carb, who knows what lurks undetected.

The first time I saw the car run it was going 10.20 at 142 mph. I was watching from the starting line and just wondering what the heck was going on. He adjusted the trans brake RPM and played with the shift points and now he runs fairly consistent 9.80 at 140+ but it still isn't fully optimized.

I tell people all the time....... the hard part about getting a car to put up a good number at the track....... is making everything on the car work together.
In many cases........ making enough power to reach the desired performance goal is the easy part.

Did he buy it or build it?

If he bought it, what was he told it would run?

Soft 60 foot. Car is relatively light. Good MPH
Sounds like
convertor might be knocking 60 foot out of it. Too tight?

Converter could be too tight, I don't really know how to figure that out given the info I have. He has the transbrake set at 5800 which seems like an okay number. Once I see the dyno sheets I'll have a better idea of where the torque curve is but 5800 seems like it should be in the fat part of the curve for a 540 engine. The car doesn't push thru the lights so the converter isn't super tight. I'm not sure where the stall speed is since the car doesn't have a driveshaft speed sensor. I think he shifts the car at 6600 rpm which seems a bit low for a 540 with good parts but once again, I haven't seen dyno sheets so I don't know where the power peak is. He did say the car went faster when he shifted at 6300 so maybe 6600 is a touch too high.

60ft is def slow compared to E.T. Get the 60's where it should be which I'm guessing should be like high 1.2's and I think the car will preform like it should. My guess is maybe convertor. One thing I don't think that was mention is the car getting full throttle? I know some racers that cars will dip into the 9's so they slow them up to run 10.00's since they aren't certified or have their NHRA lic. By doing this they slow down their E.T. but they have good MPH for their E.T. Also I know a guy that has a car that runs consistent 5.2's in the 1/8 with ladder bar...so needing a 4 link is total BS.

5800? sounds like the converter is way too loose , just from that. If this converter was too loose, it would pick up in the 60" AND MPH.
Get with a good converter company.
My deal is totally different, but my converter goes to 2900-3100 with NO chip or limiter.
What size is the converter and what company??

My buddy has a nova, 3600lbs. With a 565 it goes 9.30's at 142-144. 60' are in the 1.30 range
Heck, my sons car going low 11's 60 in the 1.40's

Almost any change I make to my car...I get the converter looked at and sometimes changed.

If nothing else I'd buy or borrow a LM2 and set it up to record rpm's. At least you could see the fall back rpm's on the shift and get an approximate rpm at the stripe to see if it's driving through the converter. Not near as much info as a Racepak can provide but a lot better than guessing.

I would've never bet my car needed a converter as loose as it is. 15-1, 572, 3300lbs, 4.30 gear, 10.5x31, 727 , 2.45 1st gear. It's been quickest with 6000-6200 fall back.
Doug

Are the engine build specs/details available?
CR, heads, intake, carb, header size, cam, etc?

See if the combo makes sense that it “should” be making 850hp.

What transmission is in it? Assume its a glide. For 140 the car should be much quicker than it is, easy 9.50's and if everything worked right 9.40's. Which makes that 60' even more horrific. A converter in a glide is a pretty critical part of the equation. I would also want to look at what shocks it has and how that ladder bar is installed. Maybe the car is just fighting itself off the line, but I would be VERY surprised if that converter was even close for the combo.

It does have a glide in the car. I talked to the transmission builder and he said they aren't shifting the car high enough. He said the stall speed is around 6200 rpm behind that engine and they are shifting the car too low and so they are staying in the converter all the way down the track. He said to raise the shift speed to 7200 and let it fly. He also said that they had the two step set too high. He recommended setting the two step at 5300 so the converter will flash at the line. I'll pas the word on to the driver and see what happens.

I picked up the build sheet from the engine builder. It doesn't have all the specs but it fills in a few blanks. Dart aluminum block, Dart Pro 1 heads CNC, 4.500 x 4.250, Manley 697800 pistons (should be 13:1 compression) Comp 1302B/4247B 112 solid roller with 4/7 swap. Dart intake,1250 Dominator carb. T&D 1.70 rocker arms. Peterson 5 stage dry sump. Engine builder said it made 880 hp on the dyno with a wet sump then they changed to a dry sump and it wasn't put back on dyno but he assumes it makes roughly the same.

Cam is a 4/7 swap so I want to confirm that the spark plugs wires are correct. Easy mistake to make that costs a bunch of power.

Exactly! Done this a few times before on different cars and always conclusive. This can speak to a good bit of what's missing but still there is something else major wrong if that's real the power/weight.

I agree with Al ! Probably a spragless too. He needs Data

Car is kinda heavy for a glide + wrong converter + wrong launch RPM + wrong shift point = PIG

Disagree about a big inch motor in a 3000 pound car with driver being even remotely too heavy for a powerglide. I just think in this case the guy missed on the convertor and maybe, as has been pointed out, launching the car, etc
Heck they put stock glides in ultra heavy Impala’s and Caprice’s from the factory

Not running hard enough to the 330'..... I think it needs a 400 and a different convertor.... Think it will pick up all the way around... Just my 2 cents..

that car is slow every where that horsepower and weight should be running easy 150 in the 1/4

Agreed.

Any thoughts on the camshaft choice? It seems "in the neighborhood" to me. Might not be perfect, but i don't think it is the problem or even part of the problem.

Until the question about just how the converter is behaving is answered......it’s a little hard to gauge the effectiveness of the cam.

I’d say if the 60’ was noticeably worse foot braking vs the transbrake, then the cam and converter may not be on the same page.

The car performance is so far off the dyno numbers of the motor, it’s hard to know what to look at first.
But that test might be revealing.

Be nice to see a dyno sheet to see how the curve looks.

Using my 90% rule....... at 880 STP corrected HP, it should be running 10mph faster.

The 140mph is showing what works out to a 28% loss.

It hasn’t been mentioned, but I’m assuming these runs aren’t being made at a higher altitude track.

One other thing..... does the car roll easily?
No dragging brakes or trans binding up?

I guess if I had to start somewhere, I’d see about borrowing a known good carb and see if anything good came from that.

Do the footbrake vs trans brake test.

Then look at those results and see if it makes sense to try a different converter.

If after all that it was still showing way low on power, I’d have the motor tested somewhere else.

On my post about the slow car of my friends, the carb we took off was the carb used to dyno it, but it sure did not work on the car at the track, & the 1st converter was WAY off. we still have a ways to go but it is MUCH better than it was

Everything is pointing to the converter being the issue IMO.

If you could grab a video of the car launching it would tell a lot of what's going on. Data from a logger would be even better yet or just some time slips. I've seen a slow reacting transbrake play havoc on stuff like this before, worn out button or dirt in the solenoid, but you would see some inconsistent 60' and reaction times as well. Like a 1.40 on one pass and a 1.47 on the next. If it's all consistent, then the converter is wrong. A chassis dyno won't tell you what's going on at the launch

Pulled the valve covers and found a broken rocker arm. Got it fixed but it hasn't been back to the track yet.

Well....... that’ll certainly numb it up.

Yeah, one dead cylinder will turn 800 hp into 700 hp pretty quickly. Could lose even more. We had a blown 454 on the dyno once and it dropped 250 hp from pull to pull after one of the rockers pulled the stud out of the head. It dropped from 800 to 550 hp with one dead cylinder so it really didn't like having the dead cylinder. Once the head was repaired it went back to 800 hp.

I"m not at the track this weekend but I got a text from the chassis builder and he said the car ran a 9.36 with the rocker arm fixed. I still think it should be a high 8 second car if everything is working properly, but 9.36 is a lot better than the 9.80's it was running.

He's lucky he didn't blow it up. Couldn't hear that?

Time slips don't lie. If the thing is anywhere close to the right RPM in the lights, MPH/weight equation works.

What did the 60' do on 8 cylinders?

The pushrod was wedged into the head so there wasn't any rattling or banging noises. Open header car so couldn't really tell that it was running on 7. I've run engines on the dyno before that had a pushrod out and the engine might sound a little flat but it doesn't sound like it is coming apart. We see the dead cylinder on the EGT display but you don't usually hear it. I don't have any track data other than the 9.36 that the chassis guy texted me. I might get a look at the time slips next week.

This is why after every outing I do a compression test , check valve lash , and check valve spring seat pressure .

After adjusting the launch RPM and shift RPM the car is running 9.50 @ 145 so that is closer to what it should be doing. I still think the engine is down on power from where the engine builder says it should be but that will have to wait until winter time.

145@3000lbs shows 705hp on the Moroso chart.
Still pretty far off being within 10% of the dyno numbers(“supposedly” 880hp).

A motor that was dyno tested here a few weeks ago, making 728hp STP...... yesterday went 9.03@147, at 2875lbs.
147@2875lbs also shows 705hp....... which is within about 3% of the dyno numbers.

Edit- just got of the phone with the owner of the car with the 728hp motor.
Said he added an anti-roll bar to the car this past week...... adding 50lbs to it.
So, 147@2925lbs shows 715hp....... which is within 2% of the dyno numbers.

Yeah I agree. I think the car had multiple problems. It is down on power and it wasn't getting the power that it did have to the track. Now it looks like they are running close the correct ET for the MPH but the power is less than they thought they had. Fixing the power issue will be a different task.

They took the car to Bakersfield and it went 9.28 @ 151 mph. No changes to the engine or car. Just went faster for some reason. I always thought the car should be able to run 8.90 at 150 mph if the engine was making the power it was supposed to make. So it seems like that car can run the MPH, now they need to figure out the ET side of things. The car is in the chassis shop at the moment being converted to a four link setup. It is also getting double adjustable shocks at each corner. So we'll see how it does next year.

Curios on the rest of the drive train setup trainee/rear ?

151mph@3000lbs is showing 800hp....... so if it really makes 880hp, there’s still some room for improvement.

But...... they’re sneaking up on it.

Bakersfeild being in the middle of a bunch of orchard has a lot to do with the quality of the air, this time of year it is usually cool and DAMP though
I'm thinking it might be a tad on the rich side of the tune up being it went faster and quicker down there

Found out what the cam is I-284@.050 E-296@.050 pretty mild but should be easy on parts. I'd say he needs 6400 stall convertor to get that heavy car moving. shift to 7500-7800 and see what it falls back to.
Should nose over on the dyno around 7300-7400 (but my experience is with BB block mopar) not Chevy should be close same CI as mine

Was that in October at the WCHRA race? If so the air certainly wasn’t stellar for Famoso. But my lil Duster went 9.16 @ 145 in some 1800DA

Yeah, I think I know what is going on with the car. I was wondering about the odd numbers for a while but now that they ran 150 mph I'm pretty sure I know what the deal is.

Dyno shows 880. Car shows 800. What was the correction factor the day it ran? Add in drivetrain loss. The MPH may be close. The ET is weak. I’d try a converter before I went to all the work and cost of a 4 link.
Doug

If it was my car I'd have the engine on the dyno over the winter so I had some data to work with. But it isn't my car and they don't want to pull the engine to put it on they dyno. The last time I was over at the chassis shop they were finishing up the four link install. It is probably finished and on the trailer by now. They are headed back to Bakersfield for the March meet so we'll see how it does there. For some reason it seems to run the best down there.

20-ish years ago we had a motor(BBC) come to the shop that had a main bearing problem.
It had been run in the car(S/G Roadster) for about a season and a half.
It was built by one of the big name engine builders that used to have big multi-page ads in the National Dragster.
The car never went as fast as it was supposed to go, based on the numbers on the dyno sheet.
And thousands of dollars had been spent on “upgrades” to get the car quicker. None made any real difference.
The dyno sheet showed 812hp.

After the motor was torn down, and things evaluated...... it didn’t really seem like a combo of parts that would make 812hp.
I looked at the cam specs, and flowed the heads........ and it really looked like a pile of parts that would make about 725hp.

Block got line honed, crank ground, valve job refreshed...... new rings/bearings/gaskets..... and back on the dyno.
Made right about 725hp with the timing/jetting/lash set the way he had been running it.
We messed with those adjustments a bit...... found less than 10hp. Iiwii.
So, it goes back in the car with supposedly about 85hp less than it made before.
Ran .03 quicker.
That car was running as good as 730hp was going to push it.

A couple seasons later we made some big changes to it(heads & cam)....... and then it was making a bit over 800hp....... and then it ran like it had 800hp.

March Meet pushed to Memorial Day Weekend

Yeah I know how it goes. But this engine should be making 850+ hp unless something was put together wrong. It has 24 degree heads, good compression, big cam, big carb, big headers, etc. Trick Flow says their 24 degree heads make 1000 hp with a similar short block. But without having it on a dyno I can't say for sure what it makes. The fact that it ran 151 mph one time means it does have at least 800 hp.