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Gremlin Traction Woes

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Topic: Gremlin Traction Woes
Posted By: WesternRed
Subject: Gremlin Traction Woes
Date Posted: Oct/15/2020 at 10:50pm
We had our fist run of the new season down here in the southern hemisphere on Wednesday night and I couldn't get the car off the line all night, 60's times were 2.1 or worse. The Gremlin previously hooked up fine off the line with 60' times around 1.70-1.75. MPH is roughly the same (around 112), but ETs were way off due to the poor launches, high 12's vs high 11's previously.

The only thing I have changed on the car over winter is the ignition and I now have timing control via the Holley Sniper ECU and I can't see that making much difference unless something was seriously wrong before.

I'm running 275/60/15 Mickey Thompson ET Pro radial tires, hard to imagine they would go off over the winter?

The most likely scenario is lack of track prep as these are just street meets and the big events don't start for another month or so, then the track will be prepped a bit better, but you are still running on the dregs at the street meets anyway.

So the task at hand is how to improve traction/launch on a poorly prepared track? I even tried launching in 2nd for one run and still had traction issues. In the past I could just load it up on the convertor and release the brake with minimal traction issues. Looking for quick fixes and maybe longer term strategies to make things better.

For reference, the Gremlin is stripped out and runs a 360, 727 and AMC20 rear, no bumpers and weight is around 3000 lbs with driver installed.

Looking at moving weight around, about the only thing I can think of is moving the battery from the engine bay to the rear, but this would only be an incremental change.

Should I consider putting the rear bumper back on, the original is destroyed, but I have the front bumper, which is even heavier with the reinforcement and could be mounted on the back. Trade off between more weight over the rear tires helping traction vs more weight overall slowing it down.

Now that I have a fancy programable ignition system, should I look at retarding the timing at launch RPM? If this is a possible solution, where do I start? I can set it up for timing to be all in by say 5000 rpm, which is what it drops to on the shifts so it would only see lower timing off the line. Convertor stalls around 3000 on the brake and flashes to around 4000 rpm. How much timing would you take out and where would you start feeding it back in?

Suspension is essentially factory with slapper bars on the rear and competition engineering drag shocks all round, set 90:10 on the front and 50:50 on the rear.

I did change out the front springs last season for stock 6 cylinder ones reducing the spring rate from 350 lb/in (Aussie V8 Rebel springs) down to 260 lb/in, but I still feel they are too stiff to really help much with weight transfer. Where can I buy some dedicated drag springs to liven up the front end?

Rear would be tired 6 cylinder factory leaves plus the slapper bars. When it's stalled up on the line, the bump stops on the slapper bars would be hard up on the front spring eye. Not sure what improvements I can make here as I'm not convinced Caltracs would be a big improvement, stiffer or softer springs perhaps?

Technique, any thoughts here or anything else I can work on?


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I've finally given up drinking for good...........now I only drink for evil.



Replies:
Posted By: 6768rogues
Date Posted: Oct/15/2020 at 10:57pm
I would move the battery because weight you have to haul with you is better in the rear. I would not add weight, it might help the tires grab but you have to move it. You are on the bottom of the world, gravity works backward?

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Content intended for mature audiences. If you experience nausea or diarrhea, stop reading and seek medical attention.

Located near Rochester, NY


Posted By: Hogman
Date Posted: Oct/16/2020 at 7:32am
W/R, I Didn't Read anywhere in Your Post about the TIRES Going up in Smoke, so, this May be a Mute idea. IF they are Smoking, I Truly Have to rump U ME, You Have been Drag Racing for Some time, & KNOW How to get the Tires Ready to LAUNCH for a Run Down the Strip. IF they are going up in Smoke, OBVIOUSLY That Would be a Good Part of the Problem. YES, I'm SURE You Knew that...... Anywho, IF that's what's going on, COULD You Temporarily BORROW a FRESH SET of Skins for a Day/Night to Try? Tires going off seem to be a Common problem up here.........  JUST TRYING to Help Sir.
GOOD LUCK!!!!  Thumbs Up
Forgot to Mention PRESSURES As Well............





ME


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Hogman


Posted By: WesternRed
Date Posted: Oct/16/2020 at 8:53am
Ah yes, tires going up in smoke, although maybe not literally, basically stepping out big time at the rear and having to get off the gas. I usually try to hold the burnout as long as possible to heat the tires, which may not be that long in the scheme of things, but start the burnout in 2nd and shift into top. Not having somebody outside of the car watching probably doesn't help with the diagnosis, but from my end, not doing anything differently, although I did try a few things to see if it made any difference.

Tires started at 17 psi then dropped to 14 psi, that didn't seem to help.

Was mention of others having similar problems, which adds a bit of support to the lack of track prep theory, but hey, no-prep drags are all the rage these days, so there must be ways to make it work.


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I've finally given up drinking for good...........now I only drink for evil.


Posted By: XJ6
Date Posted: Oct/16/2020 at 9:07am
Try a leaf spring clamp on the front halves which essentially changes them into ladder bars. Do you still have rubber bushings on leafs and control arms? Poly up front will increase quicker transfer aluminum out back in the eyes is better than rubber for racing. Cal Tracs work great with their mono leafs 


Posted By: WesternRed
Date Posted: Oct/16/2020 at 9:35am
Rubber bushings everywhere except the spring perches at the moment.

Also think it might be sitting a bit high at the front, I did cut half a coil off the new springs to bring it down a bit so that I now have about 2.5" of available extension at the wheels.



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I've finally given up drinking for good...........now I only drink for evil.


Posted By: WesternRed
Date Posted: Oct/17/2020 at 2:27am
So battery relocation would be a US$150 exercise but the time I buy a box, cable and isolation switch, worth it or not?

In the front suspension as a quick fix I could remove the spring isolators and add some spacers to the shocks for a little more extension potential, maybe another inch or I could cut another half a coil off the spring but that is obviously irreversible and would increase the spring rate a little.


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I've finally given up drinking for good...........now I only drink for evil.


Posted By: WesternRed
Date Posted: Oct/19/2020 at 9:18am
Since we were talking about getting rid of the rubber bushes in the front suspension, any thoughts on the Opentracker roller bearing conversion for the front control arms? The Control Freak coil over conversion is probably way beyond my budget and I'm not sure if it's more pro touring than drag orientated? 

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I've finally given up drinking for good...........now I only drink for evil.


Posted By: XJ6
Date Posted: Oct/19/2020 at 3:42pm
The opentracker control arm kits look nice but in addition to the price there is precise fabrication/welding involved and seem to be oriented more for road racing/handling. Maybe start with a full poly conversion including the perches and see how that works first if on a budget. Getting a Gremlin to hook is challenging but can be done. Here is a Gremlin that appears to have a Cal Trac setup and soft front springs running some impressive ET

https://www.dragzine.com/news/junkyard-amc-gremlin-gears-up-to-run-into-the-7s/" rel="nofollow - https://www.dragzine.com/news/junkyard-amc-gremlin-gears-up-to-run-into-the-7s/


Posted By: WesternRed
Date Posted: Oct/19/2020 at 4:48pm
Originally posted by XJ6 XJ6 wrote:

Here is a Gremlin that appears to have a Cal Trac setup and soft front springs running some impressive ET

https://www.dragzine.com/news/junkyard-amc-gremlin-gears-up-to-run-into-the-7s/" rel="nofollow - https://www.dragzine.com/news/junkyard-amc-gremlin-gears-up-to-run-into-the-7s/

Now that's what I'm talking about. I notice the front end actually squats on the line and it has way more suspension movement than mine. Would love to know what the suspension specs are on that thing.

And here they are:

Up front, the suspension is stock AMC with Viking double adjustable shocks. At the rear Caltracs traction bars, split mono-leaf springs, and double adjustable Viking shocks complement the Ford rear.




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I've finally given up drinking for good...........now I only drink for evil.


Posted By: PHAT69AMX
Date Posted: Oct/19/2020 at 7:22pm
What P.S.I. hot in the tires?

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Link to a http://www.youtube.com/watch?v=MySiKQsmWxU" rel="nofollow - Short YouTube Burnout Video



Posted By: WesternRed
Date Posted: Oct/19/2020 at 8:39pm
I normally run 16-18 psi, did drop them to 14 last time when it wouldn't hook up and it didn't really seem to help.

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I've finally given up drinking for good...........now I only drink for evil.


Posted By: PROSTOCKTOM
Date Posted: Oct/19/2020 at 10:41pm
Originally posted by WesternRed WesternRed wrote:



Looking at moving weight around, about the only thing I can think of is moving the battery from the engine bay to the rear, but this would only be an incremental change.
That is the first thing I would change. That alone depending on the battery your using could be a 2% change in front to rear weigh bias. The other thing I would do if that doesn't yield you enough gain is re-install the back bumper. You cant go fast, and you cant be consistent if you can't hook it up. I have friend that has a Duster. One winter he decided he needed to put the rear of the car on a diet, so he bought aluminum center section (9" Ford rear), aluminum spool, light weight wheels, fiberglass truck lid, fiberglass bumper, lexan rear window, and a lite weigh battery. He worked at it and removed 150# of weight. The car slowed down .15 in the 1/8 mile. He bought new tries and tried everything to get the performance back to no avail. After a half of a season of banging his head on the wall he finally listened to an old racer that had 50-years of racing experience and brought the car to him. The next day he had the car ready for him to run again, but he wouldn't tell him what he did to it and told him to just go race it. Couple days later he took it to the track and amazingly the car ran the numbers it had prior to the very expensive weight lose program. So what did the old racer do to make to run again? He took the rear fiberglass bumper off and made a really thick steel plate that fit hidden inside the rear bumper. That plate weighed 150#. I've never forgot that story and I've never removed weight from the rear of a bracket car that didn't have a 4-link suspension from that day forward. 

Tom 


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1949 Ford Business Coupe
1969 AMC Rambler Rouge, Tube Chassis Race Car
1974 AMC Hornet Hatchback, Wally Booth Outlaw NPS Race Car Project
1980 Ford Fairmont Futura
1990 Ford F-350 Supercab Dually


Posted By: XJ6
Date Posted: Oct/20/2020 at 5:43am
Originally posted by WesternRed WesternRed wrote:

[QUOTE=XJ6]
Here is a Gremlin that appears to have a Cal Trac setup and soft front springs running some impressive ET

https://www.dragzine.com/news/junkyard-amc-gremlin-gears-up-to-run-into-the-7s/" rel="nofollow - https://www.dragzine.com/news/junkyard-amc-gremlin-gears-up-to-run-into-the-7s/

Now that's what I'm talking about. I notice the front end actually squats on the line and it has way more suspension movement than mine. Would love to know what the suspension specs are on that thing.

And here they are:

Up front, the suspension is stock AMC with Viking double adjustable shocks. At the rear Caltracs traction bars, split mono-leaf springs, and double adjustable Viking shocks complement the Ford rear.

The Viking shocks look like nice pieces. Around $200 a piece from what I can tell but might be the last set you will ever buy. I may switch to them on my Spirit which is running a similar setup as that Gremlin , Caltrac mono leafs and bars with a 9" Strange rear except Im using the Comp Engineering single adjustable shocks. In the front I cut a full coil off aftermarket springs and full poly bushings too


Posted By: WesternRed
Date Posted: Oct/20/2020 at 6:16am
From reading one of the articles on that Gremlin, the Caltracs made a big difference, so that’s probably a consideration.

Looking for alternatives to the Opentracker spherical bearing conversion, maybe just order some Heim joints from Speed  Motors. Does anybody make a tubular upper arm that works with the factory spring mounts?


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I've finally given up drinking for good...........now I only drink for evil.


Posted By: XJ6
Date Posted: Oct/20/2020 at 8:40am
Looks like Control Freak offers a control arm kit that includes the Viking shocks

https://www.freakride.com/product/amc-front-coil-over-conversion-systems/" rel="nofollow - https://www.freakride.com/product/amc-front-coil-over-conversion-systems/


Posted By: WesternRed
Date Posted: Oct/20/2020 at 7:20pm
The control freak setup looks nice, but maybe overkill for what I'm trying to achieve.

Roll on with the quick fixes for now, front shock spacers:



Gives me this much extension, which is about 1/2" more than before given other limitations that come into play. Hard to imagine it ever gets anywhere near this high on the track:



Probably going to have to lower the front and look at some options to get rid of the rubber bits to loosen it up a bit more in slightly longer term.

Also decided to knock out a new timing map to bring most of the advance in between 4000 and 5000 rpm, the boxed section is the only bit that really matters here. I can load this fairly easily on the night to see if it helps:



Battery location will be the next in order of priority. I have put an enquiry in with the Aussie Caltrac distributor to see if they can supply some before looking further afield as they are not really that expensive in the scheme of things.

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I've finally given up drinking for good...........now I only drink for evil.


Posted By: WesternRed
Date Posted: Oct/21/2020 at 5:02pm
And the outcome was pretty much no improvement. Did manage to get one run where it hooked up, ran a 1.76 second 60' and 12.04 second 1/4 mile, I think mostly from roasting the tires a bit more than usual in the burnout.

Here is the data log of that run, mostly to show that timing map worked as intended for anybody who is interested:


This one below, I tried to ease it off the line gently and it lit up the tires almost immediately:



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I've finally given up drinking for good...........now I only drink for evil.


Posted By: WesternRed
Date Posted: Oct/23/2020 at 5:53pm
Back to more mundane stuff, started work on the battery re-location, a mate at work is going to zip it up for me:



Off the shelf is just too expensive down here in Australia, would be $150 for the plastic Moroso box and $260 for the Taylor aluminum one.

I'm putting a rough plan together to build some front end components and will probably look at Caltracs for the rear.

Also noticed the the rear sits maybe 1/2" lower on the drivers side, so I'm going to have to look into that a bit more. 


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I've finally given up drinking for good...........now I only drink for evil.


Posted By: WesternRed
Date Posted: Oct/28/2020 at 3:56pm
Well, what difference a week makes, track was much better last night, no tractions issues whatsoever. Put my original timing map back in and actually ran a PB 60' time of 1.679, mostly 1/8th mile runs, we have a heads up radial thing that I'm running in, but did a couple or  1/4 mile runs in as well with a best of 11.84, which is about a tenth off a PB. Running 7.5-7.6 in the 1/8th.

I'd say the most if not all of the improvement was track related, but a few things I did were:

Roasting the tires extra hard in the burnouts, so maybe I've finally worn the winter crust off, my new benchmark for a good burnout is if the cabin is full of smoke afterwards. Sometimes it can be a tricky car to hold in a big burnout, but I'm getting better at it, having a rev limiter now it a bit of extra piece of mind.

Did cut half a coil off the front springs last weekend, which I can't see actually doing much in the scheme of things other than lowering the front of the car a bit, so it is a slightly more aerodynamic brick. Took the shock spacers back out too.

Battery relocation didn't get completed, so something to look forward to for next time.


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I've finally given up drinking for good...........now I only drink for evil.


Posted By: Rebel Machine
Date Posted: Oct/28/2020 at 7:24pm
My old Gremlin ran high 11s and never had trouble with traction even before I put Caltracs on it. 60' were 1.7xx but was banging on the pinion snubber. Those wide M/T Pro Radials you have should stick to about anything. Heck, my '69 AMX 60' went 1.424 on 255 60 15 M/T ET Street R DOT radials with 15lbs of pressure.

You said you've got the old slapper bars, maybe someone could take video of the rear when you launch it. Perhaps there's still some spring wrap. The Caltracs will stop that.

The big difference between slapper bars and Caltracs is the Caltracs put leverage at the front spring eye that transfer the weight rearwards. Slapper bars just keep the pinion from hitting the snubber.

-Steve-



Posted By: WesternRed
Date Posted: Oct/28/2020 at 11:21pm
Here is a quick video of the slapper bars in action, they seem to be working as intended:

https://www.youtube.com/watch?v=YYx_JhVWRGE" rel="nofollow - https://www.youtube.com/watch?v=YYx_JhVWRGE

I had the driveshaft hitting the floor before I installed them.

As you said, it seems the Caltracs offer some additional gains by shifting the instant centre for the rear suspension (I read that on the internet).

Looking at my timeslips from last night, and comparing them to the Wallace calculator, it seems that everything lines up pretty well and there is not much to gain in the 60' if it actually hooks up.

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I've finally given up drinking for good...........now I only drink for evil.


Posted By: WesternRed
Date Posted: Oct/31/2020 at 6:13pm
I’ve posted in the suspension section as well, I’m trying to find some details or specifications of the small car 4 cylinder front springs? Can’t seem to find anywhere to buy them, only 6 cylinder and V8 springs. Even the 6 cylinder springs seem to be the heavier duty version, that’s what I have in the car now. I’m thinking to get some made if I have to, but can’t do much without specs to work to.

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I've finally given up drinking for good...........now I only drink for evil.


Posted By: rcabt
Date Posted: Oct/31/2020 at 10:51pm
Have factory 6 springs in mine with 90/10 shocks and they have worked fine for 18 years. Had stock rear suspension, clamps on front part of the spring none on back half, slapper bars with snubber up against spring eye, air shocks with 5 lbs. in right left was 0. pinion angle was 3 negative, ran 1.42 to 1.45 60's with Hoosier quick time pros on a good track. Went to Calvert split leafs, bars and Rancho shocks with same tires, after a lot of tuning, same 60's, but about a thousand dollars lighter. Car left hard on both set-ups. 3000, footbrake, Ati converter, 400 turbo, 4.30 gear.  A lot depends on converter, launch rpm, gearing and track conditions. Have never ran radials so don't know about them, but the Quick time pros work well.11.50 x27 x15.


Posted By: WesternRed
Date Posted: Nov/01/2020 at 1:04am
Nice to see the back to back comparison of Caltracs to slapper bars, I've got a bit of work to do to get my 60' times down to there.

I'm playing is a bit of a series we have running here at the moment, which requires radial tires, but realistically they should be more than good enough to get the job done at my level.

I've finished off the battery relocation, so hopefully that will help a little. Currently looking at options to get rid of the strut rod bushed up front.

I've butchered my 6 cylinder front springs to get the ride down to a acceptable level, so I sort of have no confidence in them now.


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I've finally given up drinking for good...........now I only drink for evil.


Posted By: WesternRed
Date Posted: Nov/19/2020 at 7:06am
Feels like I have gone full circle and I am back to square one in more ways than one. ran the car last night and traction was again a massive issue. 5 runs with 60' times of 1.93, 1.73, 1.88, 2.04 and 2.07, so one good run with a lot of rubbish thrown in. By comparison, the previous time out it was 1.77, 1.75, 1.72, 1.68 and 1.71.

Lots of complaints about the track, particularly towards the end of the night. We have a theme night each week with half price entry and last night it was "Euro Night", so we had a whole bunch of late model Euro Trash running and the story was that these cars all running on street tires basically strip off whatever traction compounds has been laid down on the track. 

I didn't help the situation, even though the battery re-location is now complete. With all of my messing around with front springs, I ended up back on my original 350 lbs/in large car springs with the front end stuck up in the air, so that didn't really help at all.

The only positive outcome of the night was that there was a McLaren 720 S there running slower than me.

Anyway, some coilovers for the front are now on order, so hopefully they will help a little when they get here in a couple of months time.

In the meantime, I will put the cut down 6 cylinder small car springs back in and I have purchased some Opentracker Delrin strut rod bushings, which should be here in the next few days.  

 


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I've finally given up drinking for good...........now I only drink for evil.


Posted By: Steve Obertanec
Date Posted: Nov/20/2020 at 6:56pm
No matter how much time & effort you put into it, track conditions will almost always have you leaving the track scratching your head.

An area I see some economical improvement would be Calvert 9 way adjustable rear shocks. Another thing may be the slapper bars. We have always had good luck with the old Southside Machine bars. They bolt on the rear with the U bolts & bolt to the front of the springs with a square U bolt.      

Real slicks make a world of difference as well. 

Good Luck! 


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Steve Obertanec
www.stevandracing.com


Posted By: WesternRed
Date Posted: Nov/20/2020 at 7:06pm
I currently have Competition Engineering hocks on the back, but haven't actually played with the different settings, maybe I should give that a go.

Home made slapper bars on the back, was thinking to go to Caltracs, but have just spent all of my money on the coilover conversion for the front, so that would be something to revisit in the future.

I have the Summit Racing 3way adjustable shocks on the front at the moment, they are supposed to be 90/10, 80/20 and 70/30, but the human shock dyno suggests the they just have soft medium and hard with the the same rate on bump and rebound, they are set on the softest setting. The front end still feels very stiff to me, hence I'm hoping the coilovers will make a difference. I was having a bounce on a mates Valiant (Dodge Dart) and that is way softer in the front than my Gremlin.


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I've finally given up drinking for good...........now I only drink for evil.


Posted By: Steve Obertanec
Date Posted: Nov/20/2020 at 7:15pm
The Southside type bars are way cheaper than the Caltracs. Competition Engineering sells almost the same thing. We buy them cheap at swap meets. We get anything close then modify to fit. Southside is back in business but not making AMC bars anymore. I have been 1.36 60' on this set up. I have a stack of 5 leaf springs, pretty stiff & the Calvert shocks were a million times better than the Summit 3 ways. The  Calvert shocks are 9 way adjustable Rancho shocks & adjust with a knob. They really slow down the separation which tends to pull the rear tires off the ground. Your rear shocks could be too short as well? 

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Steve Obertanec
www.stevandracing.com


Posted By: WesternRed
Date Posted: Nov/20/2020 at 8:19pm
Sounds like I’ll be trying the rear shocks on the hardest setting, nothing to loose there.

There is a video earlier in the thread of the slapper bars in action.

I also have a feeling the rear springs are a bit tired and it seems to sit lower in the drivers side, I have been thinking to swap left with right.


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I've finally given up drinking for good...........now I only drink for evil.


Posted By: PROSTOCKTOM
Date Posted: Nov/21/2020 at 6:13am
Originally posted by WesternRed WesternRed wrote:

I also have a feeling the rear springs are a bit tired and it seems to sit lower in the drivers side, I have been thinking to swap left with right.
Do you have all the leafs strapped together? We machine little steel clamshells and bolt all the ends of the spring down tight to the main spring.

Tom


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1949 Ford Business Coupe
1969 AMC Rambler Rouge, Tube Chassis Race Car
1974 AMC Hornet Hatchback, Wally Booth Outlaw NPS Race Car Project
1980 Ford Fairmont Futura
1990 Ford F-350 Supercab Dually


Posted By: WesternRed
Date Posted: Nov/21/2020 at 11:01pm
These are the runs from a couple of weeks ago with a good track, also had the cut-down 6 cylinder front springs installed, which gives me a lot more extension in the front:



60' times were 1.75, 1.72 and 1.71, manages 1.68 on one of the other runs that wasn't in the film, which is a PB.


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I've finally given up drinking for good...........now I only drink for evil.


Posted By: Rebel Machine
Date Posted: Nov/22/2020 at 7:35am
Awesome! Looks like your shifter is the same as the one in my Machine (console shift automatic).

-Steve-



Posted By: WesternRed
Date Posted: Nov/22/2020 at 8:11am
That’s the that shifter was used in the Aussie Hornets, I did file the gate to make it work with the reverse pattern valve body. Had a lot of trouble with shifting straight from 1st to 3rd before that.

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I've finally given up drinking for good...........now I only drink for evil.



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