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Discussion Starter #1
layed out my intersect today and came up with 66" out and 10" up. lower bar is headed up hill about .6 deg. i think thats a little long and high what do you guys suggest i shoot for?

1960 falcon chassis car
approx 2,500lb , 112" WB, 10.5" crank cl , #1 plug is 5" behind spindal.
i dont have acces to scales so just using what i have.

car seemed to leave the line a little sluggish. didnt even want to lift the front tires but ran 1.3 60'. then spun tires at 1/8th mile every pass but not 100% positive that wasnt water leak related.

 

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Discussion Starter #2
also 557 bbf approx 750-800hp , glide with a brake shooting for high 8sec ride.
 

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i'm at 56"out 6.5"up. 109wb with 605bbf and a 1.80 glide.my motor is back like yours too. it has 60'd 1.13-1.14 with loose converter and used up slicks,lol. i'd try to get that bottom bar flat as i could,jmo.
 

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Discussion Starter #4
ill have to see how much change moving the rear of the lower up a hole will make. maybe up it one and drop front of the upper one should drop me down and shorten it up a bit
 

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Discussion Starter #6
i was just thinking upping the lower wil get me lower but also a little further out and im already 66" if i drop the upper i should get closer to the general recomendations by most.
 

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be sure and do the math.you can find a few ways that'll work for you.you can play with the ride height some too.:D
 

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Embalmer
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Seems a little long for the power level...

Shortening it up a little should hit the tire harder... As well as keeping it planted down track...

We run long in our twin turbo car but we are constantly applying more power down track and it keeps it planted pretty well..


DS
 

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Where is your intersecting point in relation to your nuetral line and C/G??? I have a heavy front end and my inters. point is just above my nuetral line and just in front of my C/G and I ride my wheelie bar for about 75 feet or more, and although I could make it launch lower, I like the wheelie factor:cool: I hardly have any seperation or squat, and my ride just rides the ring gear and goes out and gradually moves up on the bar.

You just have to find your sweet spot.
 

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Go back to basics; flat bottom bar, 11-11.5" spread on the housing 56" out. The flatter bar will allow the shocks to compress after anti squat, and the upper bar angle (ic length) should still whack the tire.
 

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Discussion Starter #11
still having issues guys. i do know the car weighs 2800# with me in it. also motor is making 955 at the crank and no longer fighting water leaks also swapped to a 4.57 gear. i moved the 4 link to 49" out and 6 3/4" up. that left me with only 9 1/4" of sep at the housing. car is launching pretty hard wrinkling the slicks up a little and shooting straight out of the hole with no wheely (best 60' 1.24). i am still having traction issues down track. i plotted moving the upper bar up one hole up front and could get 65 1/8 out and 5 5/8 up. would that help?

most recommend more spread at the housing but the upper is already in top hole and to get the lower to angle down hill (currently 4.8*) i have to bring the lower up to its top hole. i could try dropping it one hole and lowering the car to get it sloping down but i only have 2.5" of fender clearance as it sits. it has never rubbed at this setting so dont know exactly how much room i need up there.
 

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Discussion Starter #12 (Edited)
So I went ahead and moved the upper a hole up and am at 65 1/8" and 5 5/8 up. First pass had a vibration in the seat like it was shaking the tires let out and ran [email protected] Next pass someone recommended stiffening up the rear shocks they were set full soft so we gave them 2 clicks ( single adjustable strange coilovers). Car spun the tires and got a little loose before the 1/8. Final pass I dropped 1psi to 9.5 and twisted the shocks to full stiff. Made it to about 1000' again and this time the vibration was much more harsh in the seat. Let out and stabbed back in it vibration came right back and went [email protected]

I'm really having a hell of a time figuring this out. I believe vibration is tire shake/spin especially since it has got loose on me a couple times near the 1/8. The tires were all balanced and there is quite a bit of lead on the back wheels I wonder if there balance is good at 130+ mph?? They are 32-14 MT about a year old and probably 15-20 passes on them. There very sticky the car never has a problem before the 330' and they drug a whole mess of rocks up in the trailer after I loaded up the other night.

I just ordered a set of scales so I will be able to give those readings before to long.

Any suggestions I'm at a total loss here?? the car is completely set up by me and I'm just trying to follow similar setups and tuning from there.
 

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So I went ahead and moved the upper a hole up and am at 65 1/8" and 5 5/8 up. First pass had a vibration in the seat like it was shaking the tires let out and ran [email protected] Next pass someone recommended stiffening up the rear shocks they were set full soft so we gave them 2 clicks ( single adjustable strange coilovers). Car spun the tires and got a little loose before the 1/8. Final pass I dropped 1psi to 9.5 and twisted the shocks to full stiff. Made it to about 1000' again and this time the vibration was much more harsh in the seat. Let out and stabbed back in it vibration came right back and went [email protected]

I'm really having a hell of a time figuring this out. I believe vibration is tire shake/spin especially since it has got loose on me a couple times near the 1/8. The tires were all balanced and there is quite a bit of lead on the back wheels I wonder if there balance is good at 130+ mph?? They are 32-14 MT about a year old and probably 15-20 passes on them. There very sticky the car never has a problem before the 330' and they drug a whole mess of rocks up in the trailer after I loaded up the other night.

I just ordered a set of scales so I will be able to give those readings before to long.

Any suggestions I'm at a total loss here?? the car is completely set up by me and I'm just trying to follow similar setups and tuning from there.
My first suggestion.....don't change more than one thing at time.
You've got something else besides tire shake causeing the sudden vibration around 1/8 mile.....that's way out there.
Could you not drop the front of the bottom bar instead of raising the back?
 

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Discussion Starter #14
I'm in the lowest hole on the front bracket. I thought about cutting my brackets off and getting some with holes further down below the main rails so I could get a lower intersect without shortening my spread at the housing. Of course I'm hoping that's last resort.

It doesn't really seem like a vibration when it does it near 1/8mile it just smooth smokes the tires and gets loose. Now when it makes it on down the track closer to 1k' that's where I'm getting the vibration.
 

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Which manufactures fourlink are you using? I've seen this problem quite a few times when the front bracket was mounted to high in relation to the housing bracket. The problem comes in when trying to get an acceptable lower bar angle you have to raise the rear of the bar decreasing the rear spread thereby losing leverage causing spin down track.
Happens mostly when either the car was built for a different diameter tire or it just wasn't built correctly using the manufactures setup specs. Fixed a number of these. But it sounds like to me you have a couple of issues going on. Do you now if your driveline angle is correct or at least close?
 

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I'm in the lowest hole on the front bracket. I thought about cutting my brackets off and getting some with holes further down below the main rails so I could get a lower intersect without shortening my spread at the housing. Of course I'm hoping that's last resort.

It doesn't really seem like a vibration when it does it near 1/8mile it just smooth smokes the tires and gets loose. Now when it makes it on down the track closer to 1k' that's where I'm getting the vibration.
Lowering the car (if possible) will give you some adjustment .I'm like you....sure wouldn't want to cut and lower the brackets.

Wow, hard to believe your breaking the tires loose that far out...although the smoke proves that's what it's doing. Maybe a soft shock setting would help that. I'm wondering if a converter going bad would cause that vibration? Seems anything else like would vibrate all through the run.:confused:
 

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Discussion Starter #18
There s&w brackets. I believe I just stuck them up to high. This was my first time building a drag chassis and was doing what I thought was right. The more I read it seems having my lower bar the way it is makes it prone to tire shake. After some thought I. Believe I can either buy another set of brackets and trim a couple holes off the bottom and weld to the bottom of my current setup or make some templates and just cut my own. I can wrap them around the main crossmember and I believe make them plenty strong.
 

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Discussion Starter #20
heres a couple shots of what im working with. im really thinking it has to be a bad 4 link combo causing the problem. theres no other reason that i can come up with for this car to be loosing bite. its naturally aspirated not like im still turning up the power i should just be cruising toward the stripe.



 
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