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post #31 of 90 (permalink) Old Jun 8th, 20, 10:27 PM Thread Starter
 
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Re: My first ever dragstrip experience/timeslips

Quote:
Originally Posted by pockets View Post
Your gears are fine considering the torque your engine makes. You have a great all around gear now.
If you didn't have the engine on an engine dyno, then you don't know the true peak hp rpm. Chassis dyno is not correct in giving peak engine power rpm. Post what your engine combo is and we can give you an idea.
What timing are you running?
Have you had someone confirm with you that when you floor the gas pedal, the carb actually goes full open?
It's a BluePrint Engines 540 and it came with an engine dyno sheet so I know the numbers are correct. I can check exactly where the peaks are. I actually haven't verified my throttle is fully opening that is a great idea. Running 35 degrees total timing.

Quote:
Originally Posted by Georgia69 View Post

In any event, before spending any money on gears or converter or anything, get more practice with what you have, and work on getting the launch down perfect, IMHO. Can't legally go any quicker than 11.50 on an NHRA track without a roll bar anyway.
This is true and I was told as much pretty quick after my 11.50. Planning on a rollbar this winter.

Quote:
Originally Posted by mr 4 speed View Post

Also,surprised at the [email protected] 120 MPH..the 60 ft. was 1.58 on that run?
With that MPH and 60 ft. it should more like [email protected] MPH
the 60' was 1.67 on that run. My 1.58 60' was actually on a 12.19 run where I had to lift at the end because I was worried i'd break 11.50 and get the boot.

Quote:
Originally Posted by Ericnova72 View Post
Something is off....that MPH and ET don't show anywhere near 680 Hp unless the car weight is 5200 lbs.

At 4000 lbs for a fully loaded '72, it is only showing you 540 Hp flywheel, maybe 470 Hp at the wheels.
if it really is 3600 lbs, its even worse....465 Flywheel Hp and 435 wheel Hp.

Gearing will effect ET, but it won't effect MPH much....MPH is almost completely dependent on vehicle weight vs power regardless of gearing.


the 60' id good for a street driven car....but total HP is sorely lacking somehow. Time to do some serious carb, ignition tuning. seems to be WAY down on power unless the dyno was a lie.

What size/brand carb, and what are your ignition timing specs...initial, total mechanical advance, what RPM is total advance reached??

what's the exhaust system consist of?? Header primary tube size and length??
See above about legit dyno sheet

The tuning comments may be true, though it does start and run beautifully with no backfiring, bogging, breaking up etc. It's only got about 600 miles on it since I installed it last year.

I'm running an 850cfm Holley 4150-style. Running an MSD Digital 6AL. Initial timing is 14 degrees and total timing is 35 degrees.

Exhaust is 3" all the way back but I have cutouts for race time. headers are mid-length 1.5" primaries.

Quote:
Originally Posted by Lew540 View Post
What fuel pump set up are you running? I think you got some more potential mph there but wanted to see if anything might be holding you back.
Running a Holley Ultra HP billet mechanical pump rated at 170gph

Quote:
Originally Posted by blue_69_malibu View Post
Folks...it was the OP's first time out. Let me him breathe a little bit.
thanks man but I can take it! i just want to get better at figuring this stuff out.

Quote:
Originally Posted by pbcbob View Post
121 mph with 28" tire and 3.50 gear is less than 5600 rpm even with 10% converter slip, you need to raise your shift points up as you said, you might want to raise the fuel levels in the bowls and use a pump cam that delivers later as you are at part throttle when you leave. 680 HP needs fuel volume I assume you have some type of upgraded fuel pick up from the tank?
I'm running a 1/2" sending unit from RobbMC and -8 lines/fittings all the way to the carb

Last edited by JamesH; Jun 8th, 20 at 10:36 PM. Reason: adding info
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post #32 of 90 (permalink) Old Jun 8th, 20, 10:34 PM Thread Starter
 
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Re: My first ever dragstrip experience/timeslips

Here are my slips. I'm left lane every time as if you can't tell from my hilarious reaction times.
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post #33 of 90 (permalink) Old Jun 8th, 20, 11:14 PM Thread Starter
 
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Re: My first ever dragstrip experience/timeslips

Here's the second run

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post #34 of 90 (permalink) Old Jun 9th, 20, 1:14 AM
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Re: My first ever dragstrip experience/timeslips

Great experience and times for your first time out. Very clean car


"headers are mid-length 1.5" primaries"

This is the one thing that glaringly jumped out at me. You are choking that engine. You should be running minimum 1 7/8 or even better 2 inch headers. You can hear it in your video that it is not breathing.. Proper headers and I bet you hit low elevens possibly and most likely high 10s.

Very solid motor. Let it breath
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post #35 of 90 (permalink) Old Jun 9th, 20, 6:02 AM
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Re: My first ever dragstrip experience/timeslips

Quote:
Originally Posted by JamesH View Post

Exhaust is 3" all the way back but I have cutouts for race time. headers are mid-length 1.5" primaries.

Never even knew they made a 1.5" primary tube header for a big block.
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post #36 of 90 (permalink) Old Jun 9th, 20, 6:41 AM
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Re: My first ever dragstrip experience/timeslips

Your not running the 850 vac sec Holley by chance are you?

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post #37 of 90 (permalink) Old Jun 9th, 20, 8:04 AM Thread Starter
 
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Re: My first ever dragstrip experience/timeslips

Quote:
Originally Posted by Badd64 View Post
Great experience and times for your first time out. Very clean car


"headers are mid-length 1.5" primaries"

This is the one thing that glaringly jumped out at me. You are choking that engine. You should be running minimum 1 7/8 or even better 2 inch headers. You can hear it in your video that it is not breathing.. Proper headers and I bet you hit low elevens possibly and most likely high 10s.

Very solid motor. Let it breath
sorry about the mistype, they are 1 3/4" primaries. One of the few holdovers from the previous mild 454. I know that findings off-the-shelf big headers that don't hang are the bane of big block Chevelle guys and I tried a few different long tube sets on my previous motor before I settled for these smaller guys. I've considered something custom (ie Lemons) but maybe it's time to bite the bullet unless someone has a part number that isn't going to hang 2" below my already super low oil pan.
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post #38 of 90 (permalink) Old Jun 9th, 20, 8:49 AM
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Re: My first ever dragstrip experience/timeslips

The 2 inch will get you at least 30 hp and 30 tq back there was a good header article on a 540 and they went from 1 3/4 all the way up to 2 1/4 and the summary of the article said the 2 inch or 2 1/8 were equal on a 700 hp 540. One thing the 1 3/4" might be even doing is blocking the port as with some of these after market heads they mention you need at least a xxx inch header tube. The rest of the exhaust and fuel system sounds good. The Lemons are nice, I have them very expensive but nice and fit great they are 2 1/8 and on a 1965 that size can be a challenge. They also custom tailor it to your head so if you got a head with a raised exhaust port they have it covered they tuck up great. That being said the 2 inch would be a good choice to and Hedman makes a nice header too, though not sure how they are with the raise exhaust ports but many guys on here have them and can chime in. What heads are you running?
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post #39 of 90 (permalink) Old Jun 9th, 20, 9:01 AM
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Re: My first ever dragstrip experience/timeslips

11.5 in the 1/4 mile is a really good time slip for your first outing! You have a fast car there. Your 60 foot is pretty good.
I watched your video - Improve the way you leave. There is probably .1 or more there. Leave off idle and you'll pick up. As previously said every tenth at the 60 is about .3 at the 1/4.
I wouldn't change a thing (other than remove sway bar) until you have at least 12 consistent runs. Then you have a baseline.
Go Pro is a great tool to watch your tac and how well your are shifting points.
A couple of things...
Always do exact (timed) burnout, always have engine temp at same temp, stag exact same place every run, shallow for now, your not John Force, leave on last yellow, shift at same rpm every run, Consistency is king!
AND ... have a blast!!!
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post #40 of 90 (permalink) Old Jun 9th, 20, 12:44 PM
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Re: My first ever dragstrip experience/timeslips

Quote:
Originally Posted by JamesH View Post
Today was a great day. I'm 36, have had this car since I was 17 and today was the first day I felt it was both fast enough to be fun and safe enough to pass tech and make some passes. I had a great time and, of course, have the bug now and am trying to decode my runs and timeslips to see where I can shore up inefficiencies and shave time. My goal with this car is to be able to drive to the track, make a few relatively small adjustments and go.

Here are today's specs:

-'72 Chevelle, lowered 3", suspension set up for aggressive street/pro touring. Around ~3600 pounds?
-540ci BBC, 680hp/680tq
-TH400, 3000rpm stall
-9" posi with 3.50 gears
-28x10.5 radial slicks at 18psi

ambient temp was about 85F and sunny, track temp probably 95ish?

Drove an hour to the track, did nothing to the car other than bolt on the slicks, uncork the exhaust and rip it.

I made 3 runs. Average ET was 11.50 @ 120mph. Slowed down video shows the car rearing up a few inches and my sidewalls wrinkling with no sign of spinning so I think I hooked pretty well. 60' improved every run and got "down" to 1.58. Averaged 7.40 in the 1/8th. Launched and ran dead straight.

I don't have a trans brake so I was just foot braking and trying to launch around 3000-4000rpm and planned to shift around 5500 but I had actually set my rev limiter there (engine is 6000rpm max) so I bounced off it a few times. I might bump the limiter to 5800.

Obviously my main issue (besides my driving) is gears. 3.73s would likely immediately shave several tenths but man I love going 80mph at 2900rpm and I'm not sure I want to give that up.

Does anyone have any suggestions based on my setup and results for fairly quick things I can do when I get to the track to shave some time? I have front and rear sway bars and adjustable everything on the suspension.

Thanks for reading this. Damn today was fun.
Having fun should be the priority your first time there. There is plenty more left in that setup. I'd suggest launching from an idle next time. Pre-loading a four link like a Chevelle never works as well in my experience.

Quote:
Originally Posted by Ericnova72 View Post
Something is off....that MPH and ET don't show anywhere near 680 Hp unless the car weight is 5200 lbs.

At 4000 lbs for a fully loaded '72, it is only showing you 540 Hp flywheel, maybe 470 Hp at the wheels.
if it really is 3600 lbs, its even worse....465 Flywheel Hp and 435 wheel Hp.

Gearing will effect ET, but it won't effect MPH much....MPH is almost completely dependent on vehicle weight vs power regardless of gearing.


the 60' id good for a street driven car....but total HP is sorely lacking somehow. Time to do some serious carb, ignition tuning. seems to be WAY down on power unless the dyno was a lie.

What size/brand carb, and what are your ignition timing specs...initial, total mechanical advance, what RPM is total advance reached??

what's the exhaust system consist of?? Header primary tube size and length??
Nothing is wrong other than you seem to be missing the difference between corrected and observed HP, and the fact that it's not an optimized drag car, but a normal street car. That's 98% of the cars on this site.
I'd bet it's an easy 3800lbs with driver, if not more.
85°F air temp at Byron is easily 2500+DA, so that's an easy -50hp.
1 3/4" headers vs 2" kill 30hp at that power level.
(120mph x 3.50 gear x 336) / 28" tire is 5040 rpm, maybe 52-5300 rpm with converter, not his 5900 rpm peak power.
Moroso Slide rule is rough 520hp @ 3800lbs @ 120mph.
I'd be interested to see the Observed/Corrected numbers from his dyno sheet, but doubt he has both.
PipeMax rough calculations below.
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post #41 of 90 (permalink) Old Jun 9th, 20, 12:57 PM
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Re: My first ever dragstrip experience/timeslips

Good point about the air - DA. Need to factor that in.
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post #42 of 90 (permalink) Old Jun 9th, 20, 12:58 PM
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Re: My first ever dragstrip experience/timeslips

Quote:
Originally Posted by bradley67 View Post
11.5 in the 1/4 mile is a really good time slip for your first outing! You have a fast car there. Your 60 foot is pretty good.
I watched your video - Improve the way you leave. There is probably .1 or more there. Leave off idle and you'll pick up. As previously said every tenth at the 60 is about .3 at the 1/4.
I wouldn't change a thing (other than remove sway bar) until you have at least 12 consistent runs. Then you have a baseline.
Go Pro is a great tool to watch your tac and how well your are shifting points.
A couple of things...
Always do exact (timed) burnout, always have engine temp at same temp, stag exact same place every run, shallow for now, your not John Force, leave on last yellow, shift at same rpm every run, Consistency is king!
AND ... have a blast!!!
Always shallow stage if you are making passes at a T&T or grudge night. You only think about bumping if you run, or plan on running eliminations where reaction times matter.

Steve R

Last edited by Steve R; Jun 9th, 20 at 1:01 PM. Reason: Z
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post #43 of 90 (permalink) Old Jun 9th, 20, 1:52 PM
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Re: My first ever dragstrip experience/timeslips

Are you using vacuum advance? What advance springs? Put the 18 degree bushing in the dist so you can run more initial. Possibly look at one of the 14 or 10 degree bushings depending on the cam specs, and if you use vacuum advance. Definitely make a change to 2"x3.5" full length headers. I used American Racing for my Nova, with raised exhaust port heads. They tuck up nice, they fit very tight to the block I had to put slight dents to clear the block in a couple places, and trim the motor mounts. In your Chevelle may be different. I used Flowmaster tapered reducers 3.5"to 3" so they help make the collector act longer.
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post #44 of 90 (permalink) Old Jun 9th, 20, 8:47 PM
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Re: My first ever dragstrip experience/timeslips

Byron Dragway timeslip. I'm in Illinois too. it was muggy today, especially with the remains of that tropical storm blowing in. Your going to pick up ET and MPH with better air.


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post #45 of 90 (permalink) Old Jun 10th, 20, 10:47 AM Thread Starter
 
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Re: My first ever dragstrip experience/timeslips

Quote:
Originally Posted by pockets View Post
Are you using vacuum advance? What advance springs? Put the 18 degree bushing in the dist so you can run more initial. Possibly look at one of the 14 or 10 degree bushings depending on the cam specs, and if you use vacuum advance. Definitely make a change to 2"x3.5" full length headers. I used American Racing for my Nova, with raised exhaust port heads. They tuck up nice, they fit very tight to the block I had to put slight dents to clear the block in a couple places, and trim the motor mounts. In your Chevelle may be different. I used Flowmaster tapered reducers 3.5"to 3" so they help make the collector act longer.
I am using vacuum advance. I'm using whatever springs come stock in an MSD Pro Billet. I should probably know though I'm not super keen on messing with what *seems* like a pretty well tuned motor.

From doing a little digging it seems like the best fitting full-length headers least likely to scrape are the Hedman's which are 1 7/8" and the American Racing which are 2" but only have a 3" collector. I will likely go with the latter

Unfortunately I don't think I can hit the track again without a 6-pt roll bar which really sucks. I love my stock-ish interior but you can't have it both ways.

Everyone has been great here with their thoughts and suggestions.

Last edited by JamesH; Jun 10th, 20 at 10:59 AM. Reason: typo
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