Drag Racing Discussions > Front Engine Dragsters

violent shake middle of pass

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LaneM:
okay another note I am wondering if this too had any effects..well first bill perhaps you have something here..on my trip from getting the ride to Utah when I unloaded it here I noticed some lines cut into my lionaum floor in trailer...yep u guessed it..it was from the ribs on the tranny plate bouncing around from all the bumpy roads...this is where I learned folks support dragsters..no one had told me this prior and I being a door car guy had no idea..I looked things over 2 or 3 times from the time I got home til first on track and never found any damage..I have spent time there at the firewall/mount and the tabs where not broken like they are but perhaps where cracked just hadn't shifted from running yet. Thought two..my very first burn out..rolled through water mashed the gas and way violent shake..rolled past light started backing up(no help guiding)then was stopped by guy watching cause my shake was so bad it popped chute on line and I was about to back up over it....well I knew the timing was wayyyyy done here but my buddy thought I should licence with a slower ride first then get used to it and go faster ..more timing..well needless to say that low timing I believe was my reason for shake cause I had water...well after that first run I added more timing and never have had tire shake at burnouts again. Well it is more violent around 800 ft which is where I tend to get out of it..Im wondering if perhaps that low timing on first pass/burnout which had huge shake if that what broke my tabs and now when Im running then broken tabs and loose motor is my shake down the track..the first 500-600 feet feel totally great..no shake issues just pure acceleration..then shake..it is after I shift when this all happens..well a lot of ideas and I am going to be on the phone tomorrow calling around and see what I can do to get this covered..Im going to unhook all lines,wires,chute body tomorrow and if after talking to someone if they want to see it now with motor in I can show otherwise by wenesday it will be out then figure it all out then..I am really bummed there are no washers on bolts in alum. and I don't believe Loctite was used either..well it is a great way to become intimate with my new ride hope to figure it out and am excitied to see what a full pass feels like with no shake.

JrFuel Hayden:
Lane, if you are getting shake on the burn-out, you might be trying to make your burn-out too long. Just past the tree is plenty, unless you are John Force. BTW, if you stay in the throttle after the tires stop smoking, you could be hurting your converter.
Any way try Tim Moen, 801-231-9249, or Dean Averict [ phone ?] in Salt Lake. The important thing to find is a race car builder that has a chassis jig, not just a guy that will weld up your frame lying on his shop floor. You need to make sure your chassis is straight and true.

Jon

LaneM:
thanks jon I wrote that number down I will have to give a call..here is update..today all body is off ..belts that expire end of this month are on their way back to stroud for recert. I haven't found anymore issues or cracks the engine and trans will most likely be out this time tomorrow..another note..like I had mentioned earlyier I got this car from another guy who built her..he had claimed doing three passes in her and one at 7.29 in 1/4 at 195....I found a time slip from lebannon raceway in first of june this year just prior to me gettn it and it wasn't even close..it was a milder launch and slower 1/8 then topped out at around 90mph..could be a test..could've broke..now I suspect it shook the crap out of him and he got out of it..why I say..well when I pulled the wheels off they had no weights..I went and had them bubble balanced today and they both were almost a pound each off...a lot of stick ons now..they are hooiser 32x13x15 and with tubes,screws,two pieace welds its easy to see the balance issue.I talked to two of my buddys they say that is a common thing..is it?well maybe balance has been a lot of my problem all along...I know the tracks don't want clip on(nor do I)butyou do run stick on is that right?well I will have my frame checked when it is bare maybe this is a lot of it..I am loving all the ideas so thanks guys.

JrFuel Hayden:
Lane, when I have GoodYear and M/T mount my tires at the track they put duck tape over the stick-on weights.  If you don't have tape on the weights, do it before you run again.
Again good luck finding a shop that can put your chassis on a chassis jig, and get it straightened out. The shop that front halved our chassis and set it up to run an early Hemi or SBC, he told me when he front halved the car Don Enriquez drives, he found the rear-end was in crooked. Don later said how much straighter the FED went, he always thought, "well it's a dragster, I have to fight the wheel", not anymore.

Jon Hansen, Jrfuel

PSweeney:
I've had the same problem but knew it was as a consequence of damage, just struggled to find it.  My altered got out of shape in the traps, I wrongly stomped on the brakes and ended up bouncing around and landed from a considerable height.  I hit the trans pan off the floor which wiped out the belly pan, broke motor mounts, and flattened chassis rails. 

I fixed all the damage and re-installed the front brakes which is what caused the issue.  I then had the same problem as you, vibration and breaking traction at 1000ft.  It turned out bouncing around had buckled a wheel and bent a 35 spline half shaft.  When chucked up, the shaft had about 2mm eccentricity.  I replaced the shaft and wheels and it ran properly again and I had confidence in the car once more.

If the pan in your car is so low it's damaged the trailer floor, you will almost certainly be hitting the ground in the shutdown.  Repeated hammering of the mounts will cause breakages like that.

With regards to tires.  Don't go adding huge amounts of weight to balance them.  Bubble balance is fine but balance the rim first and mark the heavy spot then fit the tire.  Rotate the tire on the rim to offset any disparity between wheel and tire balance.  Then add the minimum amount of weight to get them balanced.  I don't use tape, I prefer to silicone the weights on, tape always lifts for me.

One more thing on the new car.  If I were you, I'd go over the entire car and check out every weld, nut and bolt.  Check the steering geometry, play in rod ends / thread engagement, tightness of jam nuts, play in steering / steering box etc.  Put right anything you don't like

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