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So your mph will go up when you go back to the taller tire? Why is that?
What intake are you running, forgive if I've asked that before. Maybe a high ram or something would get the combo to make power higher? My build in progress has a Baker soft lobe hyd cam and high ram to spin 8K.
Because he is out of gear and hanging at 6600 rpm for a couple hundred feet at the end of the track. With a bigger tire he will still hit the 6600 rpm wall but at a higher mph and likely right at the stripe instead of hanging there for a while.
So your mph will go up when you go back to the taller tire? Why is that?
What intake are you running, forgive if I've asked that before. Maybe a high ram or something would get the combo to make power higher? My build in progress has a Baker soft lobe hyd cam and high ram to spin 8K.
The way I see it, depending on the “tightness” of the converter there will be a place where you can no longer accelerate efficiently based on power input and load. I believe the converter I have is so tight this point is about 6600 with my current load/power level. The older larger 370 engine hit this point about 6800. I was hoping with the shorter gear and tire it would put less load on the engine and allow me to go past this point at my current power level. It did not. I also tried bumping it to 24lbs to see if it would pull past. It didn’t.
So when I hit 6600 now I stop accelerating efficiently. The car still pulls, but feels like it drops 400 hp and accelerates very poorly. If I put the larger tire back on it will allow me to finish the ¼ before hitting that “Wall” at 6600 rpm.
Did the same on my 370. I tried a 28” tire and lost 5MPH.
Running the LS6 intake, stock 78mm TB.
FWIW a buddies 5.3 just made some great passes with a very simple setup. No intercooler VSR S480, LJMS STG 2 cam. With the LS1 intake he takes it to 7800 rpm. @ 24lbs it went 5.47 @ 129. Has the bargain 10” PTC converter. I don’t think the intake is holding me back. I’m sure it’s not optimal... but if an LS1 intake can go 7800... an LS6 should be able to do the same I’d think.
If I had it to do over, I’d def. go the route you are going.
What I've see locally most of the LS single turbo stuff (5.3-5.7 for example) made peak HP in the mid 6500 range with an LS6 intake.
I'm surprised your buddy's setup still pulls around 7800 with an LS1 intake.
I'm all over the place on gearing and tire size, I can run 275-60's and fit in some local stuff, or I can 31 x 18.5 x 15 QTPs which would look sick, or a 316/60 DR. Good chance I might run 3.70 gear because a buddy has a complete center section available.
Got to to thie track Friday night. They had just scrapped and prepped the track for the fall nationals. 30” MT pros stuck very well. (hope it’s the tire and not the prep job) Used my older 2-step settings of 3800 and it dead hooked and bogged. Bumped it up to 4000 and got a 1.45 60'. Then 4200 and 1.41 60'. Went 9.14 @ 150. 5.9 at 121 in the 1/8th. (20lbs and 14*)
I'm going to keep bumping the 2 step till it spins. If I could squeak out 1.3x it should be back in the 8's again! It felt "fast" again now that it hooked. Temp’s were in the low 60's as well. 105* charge temps at 20lbs ain't bad! 75% humidity killed the DA though.
Still at 4200. Going to see if it was the tire or the track prep that was working so well. I’m told the launch RPM can be super sensitive. Plan bump it 50 rpm at a time until it spins. They are having another event this Saturday night if weather holds. I’ve still got a serious amount of timing retard in it as well, but figure I’d like to get the rpm as high as possible if it takes it.
Doesn't look very violent yet, not even picking up the wheel.
Forgive if you covered this a few pages ago, but what shock setups you running front and back? For tires you have 315 Pro? And a ladder bar setup, are the bars even, up or down hill? What % weight on the nose?
16 way double adjustable summit shocks on rear, 125lb springs. 1 click away from full tight on compression and 6 clicks from full loose on extension. 15lbs in the radials.
Front suspension is OEM with OEM struts and strap limited.
Ladder bar angle is slightly down (not hitting tires near as hard as it should) Don’t have any more adjustment though. Ladders were not setup correctly.They are also pretty short. Bad deal all around for a great 60’.
I’ve never had it on proper 4 way scales. Just the DIY scale “pucks” that were made for me. I’ve made a few changes and shifted some weight around since, but was about 52% nose heavy. I need to scale it again. Its roughly @ 3100lb race weight with all the ballast and a full tank now.
16 way double adjustable summit shocks on rear, 125lb springs. 1 click away from full tight on compression and 6 clicks from full loose on extension. 15lbs in the radials. JR: Wouldn't you run the compression softer if the track is jank and you are spinning at the hit?
JR: One guy I know who is a bit of a chassis guru said that if you spin at the hit, adjust compression, if you spin as the car is moving adjust rebound. Like slow it down if you have to.
Front suspension is OEM with OEM struts and strap limited.
Ladder bar angle is slightly down (not hitting tires near as hard as it should) Don’t have any more adjustment though. Ladders were not setup correctly.They are also pretty short. Bad deal all around for a great 60’.
I’ve never had it on proper 4 way scales. Just the DIY scale “pucks” that were made for me. I’ve made a few changes and shifted some weight around since, but was about 52% nose heavy. I need to scale it again. Its roughly @ 3100lb race weight with all the ballast and a full tank now. JR: 52% nose is nothing crazy so that's not hurting you.
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It usually doesn’t spin on the hit. Seems to spin about 1 second in like clockwork. Regardless of the timing pulled. (at least with the old tire setup) I’ve pulled it down to 0 degrees 1 second in and it still spun. Pulled no timing... does the same thing. Currently pulling about 8* .6 seconds into the run and ramp it back out over 3.5 seconds. I’ve tried tightening up the extension as well, but looking at the videos it really doesn’t separate much, so I feel like I need the extension loose’ish. 6 clicks is still pretty firm I’ll try more and see if it changes anything.
I feel like alot has to do with the nose falling back down and unloading the rear tires. If I can keep it planted and ramp in power fast enough, it *should* keep the nose up and be at least semi happy. That’s how it acted in the past when it would stick anyway. Also feel like a lot has to do with these damn finicky radials and track prep. Seems like the first 15-20 passes are great. (really great if tracks prepped well). Then they go to crap and it’s hit or miss for the next 20. 50 passes in they have like a 10% chance of hooking even with great track prep. My slicks lasted for 5 years! And that’s with street driving. I had planned to run the radial slicks but these new pros came up local for $400 so I had to give them a shot.
I’d be thrilled with a repeatable 1.3X 60’. Assuming it was setup correctly with a decent FWD ladder mounts and adjustable front struts I’m sure it could do 1.2x 60’s semi easily. Been fighting the urge to correct this chassis. It’s already “unsafe” IMO so I don’t want to sink a bunch of money into it. It’s a great 130 trap chassis. Not so much at 150+. Been waiting on the perfect roller deal to jump on for a few years now. Big surprise... cheap well built 2200lb street cars aren't all that common!
How long are your ladder bars? Room to move the bar and run longer bars? Just curious.
One way to tune the chassis is to slow down how quickly the back rebounds. Junk track, if you slow it down you keep the weight transfer going. If the track gets tight the thing to watch out for is wheelies.
People do work on getting the rear tires to seperate, like 3 inches or more, but if you do it too fast for your chassis you spin.
-Street driving dries out slicks and drag radials... lots of street driving or just a little? Maybe the tires were just too shot, because I don't see how a 30" tire in your combo doesn't go A to B in the low 9's.
Not too street time, just to and from the track (about 8 miles) and occasional car meet.
To be fair, it did work initially. With the 370 engine it clicked off multiple 8.xx passes @ 159ish with 1.3x 60’s. Sat for a winter, then sat for 3 months (always garaged) while I put the 4.8 in. No other changes and it never hooked again till I replaced the tires. Of course I’m assuming it’s the tires. I’ve only had 1 race and they scraped and prepped the track really well I’m told.
Been raining a lot here so most of the events have been cancelled. Our local 1/4 track was closed this weekend so a friend offered to tow the mazda to a new (newly reopened anyway) 1/8th mile strip in Ark City Kansas. "Mid America Dragway"
Gotta say though It seems like tires alone did the trick. No real changes and it's back to dead hooking 1.3X 60's. Only a few runs but basically all the same. 5.7x- 5.8x @ 120-122 mph. Got to run a few other really nice LS swapped vehicles in the vids below. The Chevy II was running 5.5x @ 128 with twin S366's at 25lbs with nice heads, intake, cam setup. Chevelly was a SBE stock headed 5.3 with a baby cam and LJMS S480.
09-04-2018, 02:02 PM
