73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Members Rides => Topic started by: team39763 on March 11, 2008, 07:46:37 pm
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Here's a video we took today. It was a bit wet outside, but the streets were dry enough to drive on so I decided to take her out. I attempted a burnout to clean off the tires, but I suck at it....I need a line lock. Anyway, we got a shot of my usual launch method. I stall it up to until I feel a little kick(3500rpms), then I let loose. I noticed that back doesn't squat down, but the front does come up. I hate the way my truck takes off so mild and tame...I think my next truck build will have a bigblock.
Let me know what ya'll think of it.
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What's your actual stall speed?
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I have 3500rpm converter.
Here's another one. Again, you can see I have a weak launch when I do the usual. So I'm gonna try a different method that Lorne told me about. Maybe my launch method is what caused me to have bad 60ft's at the track?
I didn't stall it up as high on this one, but you can tell I didn't put my foot into it until it after it got going.
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Eh, sure sounds nice though. 8)
Mine stalls up to 2.5k RPM, the tires squeel all the time.
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Team, do you have a tach? If so do you know how to do a stall speed test?
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Yes, I have a tach, but it reads slow at times. I've had my tach/shiftlight set for 5500rpms, but somehow I hit my 7000rpm rev limit before the shift light came on.
No, I don't know how to do a stall speed test, but I'd like to know. I take back what I said about stalling it all the way up to 3500, I get it to 3000.
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I tried launching with Lorne's method, but I'm not sure if it made much difference. My truck is just slow off the line no matter what I do. I think I'm gonna need spray. 2nd gear is great, third gear is ok, but first just straight sucks. I think I do come off the line harder with Lornes method since I managed to smoke the tires pretty good the first time I tried it. But either way, my truck is just slow off the line. I don't understand how guys in ECSB's[new body style trucks] are cutting crazy low 60ft's and they weigh 1000pounds more, have a bit less power, and aren't using any suspension mods. I think there's even a few cutting 1.9's on 20's.
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How many leafs are in the rear of the truck?
What Rpms are you bringing the motor to before you launch it? If you are starting at 1200 that is your problem. Rev it to about 2500 and then hammer it when you let off the brake. If you got a 3500 stall take it to 3000 and see it if will hold. If you are launching at 1200, you are barely off idle.
Scratch that, saw the first one at 3500rpms. It sounded like it was struggling and then started moving on when you started rolling. Are you going full throttle immediately when you get off the brake? Have you tried a higher launch rpm? How high in rpms can you get the motor before it starts walking foward?
What happens if you just nail it from a stand still?
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Team, What gears/trans do you have? What are you getting for 60 ft. times? What do you have for tires? Did it spin at the track off of the line or just drive away? I was getting 1.71-72 60ft. on ET Street Radials for comparison, 700 trans/3.40 gear. Lorne
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CaptKaos: I have the full amount of leafs(stock). Yeah, I tried smashing it from standstill...it hesitated then just fried the tires. 1200 took off with no problem, but as you could see, it was still slow. 3000rpms were about the same as 1200. No, I don't go full throttle right away....maybe that's part of the problem? 3000 is as high as I've tried to get it, I'll try higher tommarow.
Haulin It: I have 456 gears and Rebuilt TH350 with shift kit. My 60ft's were in the 2.1-2.25 range. I have ET Drags @15PSI. At the track, it didn't feel like it was spinning at all(even with the open diff). At the track, I would stall it to about 2000 and hammer it on green.
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Team, What was your MPH in the quarter? Did I see somewhere you posted that it has gone high 12's? Or is this a " I beat a guy who says his... story?" Why don't you go straight to the floor all at once on the launch? Is this when you get the bog? If you have a non-posi rear & 4.56's & it doesn't spin something is wrong! Either the engine has no snort, the converter is too loose, the carb problem, something is a miss. You need to figure this out before you start spraying it, you'll just have a slow truck on spray or worse, you'll hurt the engine. Start with the basics & move on from there. Lorne
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My MPH was 107. Yes, I ran 12.8@107. I guess I don't go straight to the floor because I'm trying not to smoke the tires. Off idle to full throttle is when I get the bog. It's a posi rear, but at the time I raced at the track, it was only spinning one tire during burnouts. Since then, I have drained and replaced the fluid and also adjusted my traction bars...now the posi works everytime and I lay two identical patches of rubber. I'm pretty sure I can tune out the bog, but I don't know what else to do after that. I'm gonna try a few different launch techniques tommarow. I understand that I have a small motor in a big heavy truck so it takes some effort to get going, but my truck just seems crazy slow off the line.
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Well the 107 MPH is in line for the 12.80, the engine is making some HP to get it to 107 & considering that you should be .4-.8 quicker in the 60ft. the truck recovers good to go 107. It sounds to me, like your thinking, you need to work on the first 60 ft. If the converter was way too loose you would not get to 107 either because it would not be able to pull in high gear. What carb do you have? Is the bog right when you floor it or does it start to go & then bog? Do you know how much your truck weighs? And how tall are the tires?
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In the first video you can hear the motor stumble a bit as your brining it to 3000. Is this you doing that or the truck all by itself, and what was the RMP when it happened? If it's the truck, I think that may be the source of your problem.
Nice ride though. The motor sounds real healthy and I bet with a little fine-tuning and some practice with your launch technique you can post something in the low 12s. Just for giggles, what was your reaction time at the track?
Smitty
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Haulin It: I have a Holley 950DP(I know it's huge, but it runs 100% better than with my 750). The bog happens when I get on the pedal too quick and then it goes...Maybe I need bigger squirters? My truck weighed 4000 with 450pounds of driver and passenger, so I'd say it's around 3550-3600 without us(I weigh 220). My tires are 28" tall.
Smitty77: That was me trying to bring the rpms up. It seems like it struggles around the lower rpms, but when it gets to 3000, it seems happy. But it's not built for low RPMs anyway - large single plane intake, 3500 stall, huge carb, cam, so that's expected right? The bog usually happens if I don't stall it up at all, so I'd say it just off idle. I have a good video of it...you'll have to excuse my wife(if you listen closely you can hear her)...LOL. My reaction times were in the .8's. The first run I had was a 1.5 because the truck bogged on the line, but I still ran a 13.0@105 and I believe the 60ft was 2.1 on that run.
Here's the backroad run where it bogged off the line.
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What is Lornes method you mentioned a few times?
Stall speed is easily measured if your tires don't break loose. Baiscally stand on the brakes as hard as you can and accelerate to WOT. Your highest RPM is your stall speed. Don't keep repeating this test but do it for your own knowledge. When you reach your stall speed the fluid in the converter is essentially impeding on itself and that in it's own can cause a poor launch. Try seeing what it is if your brakes can hold it. If your tires spin the test is invalid. Have you considered a trans brake?
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Vile, I have never found a converter that wouldn't "flash" to a higher stall than it would go to up against the brakes. I bring The RPM's up just enough to know it will take off cleanly. A little playing to see where that is, but I spend many a minutes working the carbs. My 3900lb. truck is happy to leave on the last Yellow from 1200-1300 & flash on take-off. Some vehicles do take a little more. I've pretty much used this method in any auto tranny vehicles. The carb/engine has to be able to take instant RPM, any hesitation here & you need to work on the carb/ignition.This also limits the possiblity of "pushing through the brakes" once your staged. Just my two cents, Lorne
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I've considered a trans brake, but in the end, I didn't feel it was worth it. I'm not a serious racer and I heard that the TB was a little harder on driveline parts. + I see plenty of other trucks/cars just fly off the line without the T-brake. I'll try that stall speed test this afternoon. Yeah, Lorne told me about his method a while back(described above).
I'm gonna mess with the carb today and see what I come up with. The carb worked flawless when we first put it on a few months ago...no bog or hesitation. Nothing has been changed on the setup, so I don't know why it's doing that. But like I said, it's only off idle.
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Its a Holley, and the temperature changed that is why it runs different. ;)
I would experiment with different launch rpms. Once you get it stalled, hammer it, that is the point of the stall to get to where it makes power...
This is a video of my brothers 2000 RCSB 5.3L with an STS. This was one of its fastest times at 12.26@109.95mph in the quarter.. SRT10 Ext cab on the far lane was Sure he was going to blow him away at the beginning with his 500hp truck...
http://www.gracemotorsports.biz/video/JCfreakvsSRT10Extd.mov
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Chris, I'm assuming your kidding about the weather changing based on the wink? Holley carbs can be a little fickle when getting them dialed in, but really not that hard. The turbo idea adds a whole new dimension to the launch (getting the boost up). I love watching the turbo vehicles run, however allot of them seem to be a handful on the starting line. Lorne
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Not really, but I hate Carbs, Holley being at the top of the list. They are finicky and weather changes do effect them.
His truck is injected so dialing it in is simple as changing the variables in HP tuners, WAY more simple than dialing in a Carb..
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Goodness, I wish I had a launch like that. Yeah, I've heard that Holleys need to be adjusted for the weather. Maybe just richen the idle screws a bit?...that fixed the off idle stumble I had with my 750(only at part throttle though). I think I may go to that crappy track and give that guy a run on Sunday. I'll see if we can get some video of it for you guys.
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Team, It sounds to me that you need to work on the accelerator pump cams/squirters. The idle screws are not going to fix the problem. The engine is going lean when you whack the throttle open, there is not enough fuel to cover it up. Does it ever shut off clean when you go straight to the floor? If your going to play, just spend the bucks now for the Holley master kit # 36-182 & the cam assortment. From there you should be able to get the bog out. You need to work on the initial "flat to the floor" problem until the engine revs straight up from near idle, once you have this, your 60 ft's will drop. I don't feel there is much need to run a full trottle pass every time until you have the bog worked out, no sense in working over the engine until your on top of your game. Good Luck, Lorne
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You're right Lorne. I think my trip to the track will be strictly for tuning and dialing it the combo. It looks like I'm rolling solo on this trip, so I probably won't be able to film any of it....maybe from inside the truck. I know the truck has 50cc pumps front and back, the squirters are pretty small if I remember, but I have some 35's and 37's somewhere around here. No, it never shuts off clean, it recovers and goes. I have a few pump cams laying around, I'll see what's on there and what I have.
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The 50cc pumps can't hurt. Your thinking you have less than 35's in there? I would not be supprised if you needed some in the low to mid 40's, you gotta cover 475cfm per. I just went & checked, the other kit I have is Holley pt # 36-184, it has squirters up to 50 & the cams
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Team, What I was thinking & what my fingers typed last night wasn't really the same. The idea that you will need conciderably more pump shot is correct. Forget the part about CFM. What I meant was that a 600 cfm carb may work well with a 32 or so squirter, the 950 having bigger bores/throttle valves needs more fuel the cover the bigger opening holes, understand?
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Yep, I understand that. That makes sense too. It's funny, the "gearheads" down here think you can put smaller jets to make a carb smaller. I never believed that(especially after I learned how carbs worked). What you said earlier made sense too. Thanks.
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Would anybody happen to have any videos of their trucks doing a launch on the street? How much faster do you guys' trucks take off compared to mine? Am I asking too much from my combo? Tomarrow is raceday, so I'm gonna work on my launches and see what I come up with. I won't worry about E/T's because this track is crappy and they get the times/speed wrong all the time.
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Well, Dude didn't bring his truck to the track, so I didn't get a chance to race him. Instead, I ended up racing a Shelby Cobra and beat him by 2-3 cars. Then I raced a Z28. Here's the video of it. I was taking it easy off the line because this track is very slick. Then I backed off before the finish line because the track has huge bumps and I ended up scraping the lower control arms on the ground.
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Bumps at the end of the track bad enough to scrape the control arms!!! I wouldn't race there either, sounds like a death trap for really fast cars (and trucks). But then again I gather from the video, this isn't an NHRA-sanctioned track, LOL. Any idea what your trap speed was?
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team39763 where do live?
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I have 3500rpm converter.
Here's another one. Again, you can see I have a weak launch when I do the usual. So I'm gonna try a different method that Lorne told me about. Maybe my launch method is what caused me to have bad 60ft's at the track?
I didn't stall it up as high on this one, but you can tell I didn't put my foot into it until it after it got going.
http://s46.photobucket.com/albums/f143/team39763/?action=view¤t=730313f8.pbr
what gears do you have???? and how are you not even smoking the tires
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I have no idea what my time and speed really was....they told me I trapped at 97MPH, but they were getting peoples' time and speed wrong all day. They told one guy he ran 15.8@115mph and on his other run 13.4@78mph. Yep, it's a crappy track and I won't be going back.
Red4WD - I live in south Texas. 76 K10, I have 456 gears and I have no clue why it doesn't spin. I just noticed this afternoon that my posi isn't engaging(once again).
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In my professional non-professional opinion :P it just looks like a lot of slippage. Either from high-stall converter, trans slip or slipping converter (malfunctioning). I agree with Lorne though that converter slip might be ruled out because you're getting very good MPH on the top-end. That's excellent MPH for 4.56s I'd say. What's your tach say when you're crossing the line? It looks like the motor is revving up fast in 1st, but you're only getting thru it moderately fast. Looks like 2nd and 3rd gear really rip. So that only leaves me to think that at WOT when the slicks are hooked, the 4.56's are providing a ton of torque multiplication and that 6.0 is pushing the power thru, your 1st gear is becoming the weak link and slipping? I would also think that with that kind of power and those gears, you should melt the tires but then again, maybe those gears are a little too deep for tire burning and the motor revs past the torque point where the tires would want to break loose. Perhaps that doesn't make too much sense. Might sound weird, but maybe something like 3.73s could make better use of the grunt your motor makes and would yank it thru the lower revs faster.
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My tach doesn't read correctly, I'd say I was between 6000 and 6800rpms(judging from shiftlight and revlimit). I'm gonna try taking my truck to the real track where it actually hooks up good. I think my problem is that I'm too soft on the pedal, I don't mean to be, but in my head I'm picturing the tires going up in smoke and me not going anywhere at all. When I get to the real track, I'm gonna put it on the floor and see how it reacts. Everything you just said made perfect sense too. I may be looking to get a few different sets of gears to test soon, 373, 390, and 410's are on my list.
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I took the truck out to the backroads today just for fun(by myself). First I did a little burnout(first one ever in this truck) to clean the slicks. Then I stalled it up to 1400 and made sure I had traction before putting the petal to the floor, so probably about 5 feet before I floored it. Shortly after I floored it, it felt like it was free revving or trans was slipping or possibly the tires broke loose. I usually can tell when the tires break loose, but it felt different this time. I shifted to second and slowed to a stop. I tried it again, but this time I shifted to second right after I went WOT. I'm starting to suspect my trans. What happens if your converter is not fully seated? Would I have known by now? What if my trans cooler lines were backwards, wouldn't my fluid smell/look burnt?
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I think if you didn't slide your converter all the way home and still managed to bolt it up to the flexplate. You would know as soon as you fired the motor. I'm sure there would be an unpleasant noise to accompany the subsequent pump damage. And I wouldn't think that if you had the cooler lines attached backwards it would affect the way the fluid smells. But if you have any significant slippage, that would definitely cause the fluid to smell burnt.
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Ok, I checked and my lines weren't backwards. The reason I was worried is because I have a remote mounted filter and if installed backwards(reverse flow), it would damage the trans. The truck used to make a very high pitched whine at low speeds, but now it's gone. I was unclear on whether I needed shims between the flywheel and converter pads, none came with my converter, so I didn't use any. But I heard of others that used 1 or 2.
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Someone can correct me if I am wrong but I believe the only time you would need shims between the flexplate and the converter is if you were running a midplate.
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Not to sound like a jerk but are you sure your throttle is opening up all the way? I had a similar problem on a Camaro I had, put a new carb on and the cable would not let it open all the way.
Just a thought, sometimes the simplest things can haunt us.
With your setup you should be roasting the tires, I don't have near the setup you do and I can fry the 35's on my 81 K10.
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I didn't really think to check the throttle...good call. I noticed that sometimes when I drive my truck, I find a little extra bit of pedal sometimes...as in I can stick my foot in deeper. My pedal is really stiff, so it always feels like it won't go much further. If I loosen the throttle return springs, it will idle too high. Maybe I have them setup wrong. How do I tighten my cable to make the pedal bottom out/go WOT sooner?
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Team, We were just talking about that. Check the Engine/Drivetrain section. Everthehorizon started it, I believe. Lorne
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Team, We were just talking about that. Check the Engine/Drivetrain section. Everthehorizon started it, I believe. Lorne
Way to hack up my user name Lorne. :D
But seriously, team39763, why would the tension of your throttle return spring affect your idle? I can disconnect my return spring and it idles just fine.
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My throttle never returns to the idle I set it to. If I set the springs any tighter, the gas pedal is too firm. If I set it more loose, the throttle will get stuck and it'll try to idle at 2000. I went out and added a few shims on the pedal to make it hit WOT for sure. LOL. I wish I would've seen that topic earlier. Thanks guys, I'm gonna give it a try tomarrow.
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Team, Please stop & figure out why the engine will not idle with the spring removed. As was mentioned, the spring should have NOTHING to do with the idle. Something is wrong here. Try to figure out what it is. This could be unsafe to you & anyone around your vehicle. It would be a shame to crash your truck over something like that. Try unhooking the cable from the carb. Is the pedal/cable free? Does the throttle plate open & close free? One of them has to be the problem. If you need help, Ask, Lorne
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I'll check it out today. I had never seen/worked on a carburetor setup before this truck, so I didn't know how things worked. I did have the same problem with my other carb, so that makes me think maybe it's my cable/bracket setup. I'll take some pics to show how I have it hooked up.
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Does anyone here know, what is the best lubricant to use on a sticking throttle cable or as preventative maintenance? I think I've heard graphite spray before.
Not to hijack the thread, team, but I figured the answer would help you too.
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I used powdered graphite before, anything greasy will collect dirt and tend to stick. Takes a while but it did help.
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I guess I should try that too. I was trying to fix my tach today - it reads too slow when I'm racing. It reads fine if I drive normal. So I read the online directions for it and also checked out the Autometer website. According to the website, I needed to set it for a 4cylinder motor. And that's what I did, but it read about 800rpm too high at idle. So I tried the 6cylinder setting and it's only 300rpm too high, so I figured I'd stick with that, since it should turn on my shiftlight sooner. I think I'm just gonna buy a new tach. All my connections look good, so I don't understand why it does that when I'm racing. I've hit the 6800rpm rev limit with the light set to come on at 5500(light never showed). Then I hit the 7000rpm rev limit with it set to 6500(never showed). I know the light works because if I set it for 3000 and rev, it'll light up. Sometimes it does come on, but I don't know exactly what rpm I'm at until I hit the rev limit.
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I donīt think your cable is getting stuck or anything, the idle problem could be just a bent accel cable bracket or that the throttle carb shaft is worn out and air is getting in (vaccuum leak).