Getting my new 406 SBC installed, running, and driving

[sweetbmxrider]

I was told rule of thumb is as soon as you see smoke in the side mirrors, release line lock and then let off the gas. Should continue the burnout just a few more feet.

Does the data log show when you start the shift and when it completes?

[IROCZman15]

that makes sense yup. I have not been able to see the smoke in the mirrors, but I will try to look harder. I cant say that I have actually ever seen the tire smoke, but I know the tires are getting sticky since I come back to the pits with rocks stuck to them from the return road after the pass, but without me seeing a video its hard for me to know that my current burnout process is the right one for my application
-a guy on thirdgen.org pointed me to this info from Mickey Thomspon:
https://www.mickeythompsontires.com/...fication-sheet
yet, I have an auto trans and drag radials, so it says long burnout for auto trans, and short burnout for radials. hm....

Not sure what ya mean about start the shift and when it completes? If you mean when I physically move the shifter vs when the transmission slides into the next year, then the answer to that is no, the sniper software doesn't have a feature that shows that. If you mean the length of time I am in each gear, that I can actually calculate using the start/stop feature of the holley datalog software. I can probably even calculate how long I am on the damn rev limiter and get a good laugh out of that number.
-- The shift kit that is in it, is apparently the best one to use for a performance built 700r4 and my shifts are indeed firm and quick without being too unnecessarily rigid. https://probuiltautomatics.com/shop/...ied-shift-kits fortunately, the only issue I have ever had regarding shifting, is not the transmission, but me not reacting to the shift light or timing the dash tach needle.

[IROCZman15]

Short Version:

- Drove car to Atco
- Made 5 passes, best ET was 11.845 (pass 1) best mph was 115.94 (pass 5) best 60ft was 1.667 (pass 5)
- I have WOT ignition timing and AFR dialed in and set to perfection
- still working on finding optimal 1-2 and 2-3 shift points.
- nothing broke, nothing weird happened, car did its job
- packed up car and drove it home



Long version:

I decided to take the car down to Atco Dragway on Friday night for the Test and Tune. Rumors are that Atco might be closing its doors permanently as a drag racing track at the end of this season so I wanted to make some passes there as kind of a bucket-list type thing for myself. Atco is 2+ hours from me with no traffic, and despite me leaving my house at 1:30 pm, I still hit a bunch of NJ Friday afternoon traffic. I sat in traffic basically bumper-to-bumper for a good 45 minutes on rt 287 in Piscataway and the engine temperature never went above 191 deg. Made it down there right around 4:30 and unpacked my hundreds of pounds of spare parts, tools, a wheel, and misc gear. Went through tech, which was super easy and effortless. Got the tire psi, shocks, tune file, and fluids all set.

Pass 1:
6:18 pm DA was 669 53% humidity and 67*F. did a decent burnout
Launched from 920 rpm idle, converter flashed at 2,861 rpms. Shifted 1-2 at 6,567 (rev limiter) and shifted 2-3 at 6,072, crossed the stripe around 5,831 rpms. Checked my AFR readings, CL comp, and learn numbers in the file and those were great so I re-saved the file and used it the rest of the night.
- Had hoped that I would simply improve upon my timeslip as the night/weather got better, but just like several previous drag events at Island.. my first pass was my best timeslip of the whole night.. I don't know why that keeps happening to me!

video: https://www.youtube.com/watch?v=IptrSp8nSKQ








Pass 2:
7:51pm DA 195, 66% humidity and 61*F
-same tire pressure, same shock settings, longer burnout. lowered my shift light so I could try shifting at a lower rpm
Launched from a 937 rpm idle and converter flashed at 2,975
short shifted my 1-2 shift at 6,096 and then really short shifted 2-3 at 5,765, crossed the stripe at 5,537 rpm
short shifting the 2-3 really killed me up top, but the pass felt solid and the datalog traces looked good despite the pass being my slowest of the night

video: https://www.youtube.com/watch?v=gr2-uTHJZ2s







Pass 3:
9:37 pm DA was -39 with 70% humidity and 58*F
left the front shocks the same but tightened the rear shocks half-a-turn since my 60foots seemed a little slower than last month at Island. rear tire psi had dropped to 18.4, so I left it there. raised the shift light up a bit and also moved my rev limiter from 6,500 to 6,700 rpm.
- launched at 921 rpm, flashed at 2,770. Shifted 1-2 at 6,648 (rev limiter kicked in for a split second) and then shifted 2-3 at 6,377, crossing the line at 5,777 rpm. Noticed on the datalog (upper green line) that I was not at 100% throttle until I got into 3rd! wtf!

video: https://www.youtube.com/watch?v=OFhd0Bu5YmQ








Pass 4:
10:50 pm DA was -127 with 73% humidity at 57*F
aired up rear tires to 19.5 psi but had just a touch of tire spin off the launch. Tried launching at 1,300 rpm also. Did not get get a datalog this pass (must have not pressed "start"), but I know I short-shifted the 1-2 shift and revved out the 2-3 shift a little higher.

video: https://www.youtube.com/watch?v=38QnGeH7Y7s






Pass 5:
11:12 pm DA was -107 with humidity at 74% and 56*F
- launched at 922 rpm and converter slashed at 2,843 rpm. no tire spin off the launch and it was my best 60ft of the night. Short shifted the 1-2 at 5,902 and then shifted 2-3 at 6,353 which had me crossing the stripe at 5,641 rpms
- if you look at the top green line on the datalog, I was only at 76% throttle all of first gear and then i got out of the throttle a little bit for the 2-3 shift. Damn it Dave! somehow, this pass had my highest MPH of the night (and ever) at 115.94mph.
video: https://www.youtube.com/watch?v=JBTKBMuvggc









They shut off the track lights a few minutes after my last pass so I packed up my car of all the gear and aired up the tires just as they were shutting off the parking lot lights and closing the main gate. They had a track rental earlier in the day so I think everyone was just ready to close the gates and get done. Nice easy drive home on the highways with only a few weirdos pulling up next to me and trying to play around. The car ran great and simply put the torque converter lock-up ON and cruised on the turnpike for a long time doing 85 mph at 2,450 rpm and the engine temp stayed at 158-165*F the whole trip. Fueled up once on the ride home and pulled into my garage at 1:50 am. No leaks, no weird noises, no mechanical issues what-so-ever. Turned off the battery kill-switch, shut the garage door, went inside and passed out.




Overall, I am super happy I made the trip and got some timeslips at Atco before it potentially closes its doors for racing. It was well worth the trip and the fuel cost. I improved on my previous best ET which was 11.855 at Island last month, to 11.845 at Atco. I have the drag race tune file optimized for 35* timing at WOT and the target AFR for 12.5:1 at tq peak and then leaned out to 12.7:1 at the HP peak. The AFR is staying really dialed in (pink and light blue lines in datalog). The best 60foot times come from launching the car off of an idle and my drag radials at 19psi with a 2/5 or 3/5 rear shock setting. I would like to scientifically determine my optimal shift point. I am thinking about creating a separate forum post to discuss shift points and use science and math to help me (us) determine my target 1-2 and 2-3 shifts.

[The_Bishop]

Maybe check your throttle linkage and make sure you're getting WOT when you hit the pedal? Also check the TPS if the mechanical side of things is right.

[IROCZman15]

yep. its correct for sure. I just don't think I had my foot down all the way on some of those passes, like a fool. I went through a ton of the TPS and linkage checks during that few weeks in August/september when my MSD ignition took a crap. I made a few videos and stuff about it too, but the linkage and TPS readings are true. I've operated it by hand and watched the butterflies open to wot. Basically, I just wasn't on the floor with the pedal. you can see the upper green line in some of the other datalogs on this page (and previous pages) which will show my TPS gets to 100% pretty often.

But even if it didnt reach 100% apparently that is OK based on the way the Holley sniper is setup with a MAP sensor. According to Holley, anything over 85% TPS is considered full throttle. So in theory, if my throttle pedal is at 85% or 100% wide open, the engine/sniper would act exactly the same.

[The_Bishop]

True, but the airflow wouldn't be as the butterfly valve would be partially closed. In any case, now you know what to watch for next time around!

[IROCZman15]

Originally Posted by The_Bishop

True, but the airflow wouldn't be as the butterfly valve would be partially closed. In any case, now you know what to watch for next time around!

So, I am glad you said that, and I fully agree with you on that. If the blades are not 100% open, there is a slight airflow restriction into the engine. I spent a lot of time reading how TPS, Map, and VE table info works for the sniper, ad while I understand the basics of it, I still have wondered about the butterflies. The more air in, the more fuel can be added and essentially the more volumetric efficiency and cylinder pressure I can make. Most people (my tuner in Texas included) have told me that WOT is WOT on a map system. I still think of it like you are, and that if my blades are not fully open, I am giving up VE. I am glad to be able to datalog and see it, otherwise without that, I would just "assume" I was at full WOT for every pass. The datalogs show that I was only at 100% TPS on pass 1, and pass 2, 3, 5 I had some throttle fluctuation. I probably also did on pass 4, but I didn't record a datalog during it.

-the more I look at the sniper tunes and datalogs, the more I want to get back out to the track and run the car again. I am probably going to type up a separate post/thread about scientifically mathematically figuring out my optimal shift points, so I will be asking for as much group input on that as possible. I know I am splitting hairs here in search of maybe shaving down another tenth of a second or so, but I am hoping for one more good track session before winter comes along.

[IROCZman15]

Finally getting a chance to sit down and type all this up. Too many other important things earlier this week, but the rainy day today allowed me to get this all typed up.

Had planned to go to Island on Friday night for TnT and had the car fully loaded and packed. All I had to do was throw some drinks and snacks in a bag and hit the road. A guy on TGO who was going to bring his thirdgen that runs 12.3s sent me a message saying Island was canceling due to impending fog. I was definitely bummed out because I planned on racing Friday night and then doing a big car show/fundraiser on Sunday. It did turn out that there was significant fog later at night and the DA was not great either, so Island was correct in decideing to cancel it. I decided to skip the Sunday car show and race at Island instead, so my Test and Tune happened Sunday, which was also the NETO, vs MANDRA vs Gassers event so there was a good amount of cars on the property. Weather was pretty good that day, slight wind with the occasional gust but it was crisp and cool so the DA was helpful.







On the way to the track, almost just as I was passing by Larry's shop, my speedometer went dead, so I checked the cable and without taking things apart determined that it was a cable issue, not a dashboard. turned out that I was right, the end of the cable broke off about 3" from where it enters the tails haft housing. Due to the trans tunnel of these cars, the area is tight and the cable bend is pretty sharp...even by nature from the factory. I'll get a new one. ATP-Y-814 like $10 at advanced autoparts. In fact I think I have the receipt from when I bought this exact cable in May of this year and it has a 1 year free replacement.





On Wednesday of last week I took out 30 minutes to wire up the 2-step rev limiter feature on the holley sniper just to see if it would help me launch at a steady set-higher rpm. Holley makes it super easy since it is a ground-trigger input and no relay is needed. Just wiring and a button. I will relocate my button over the winter, as its not in the most user-friendly spot being at the oem ash tray... more on this later.

testing 2-step at 2,500 and 3,500:
https://www.youtube.com/watch?v=B_vsvgeJJAw

and at 5,000:
https://www.youtube.com/watch?v=LsNEzd5cfiE


I had created a pretty good tune file for the day and was feeling pretty confident. New spark plugs gapped at .035 and I also took some time to learn how to "index" them with indexing washers. Kept the front struts at the low setting 1 out of 5 and the rear shocks at the 2/5 all day. Rear tire pressure was at 19 psi and the front drag skinnies at 38/37 psi. The plan for the day was to shift at 6,600 rpms because of some math and calculators that I discuss in my other "shift and launch" thread on this forum.


Pass 1:
Temp was 47*, 60% humidity, and DA was -447. Did a 4 second burnout and shallow staged. Decided to try to launch using the 2-step rev limiter which I had pre-set to hold 1,600 rpms. I wasn't concerned about reaction time, more about a clean launch, which did happen! Launched at 1,676 and Shifted 1->2 at 6,573 and 2->3 at 6,632 while tagging the rev limiter a bit, and crossed the stripe around 5,842. Checked the data log and the afr looked great but I am still getting a rich spot right after the launch when the converter flashes. it is the pink dip on the datalog right after the 80 second mark.. As usually seems to be the case at most of the dragstrip days I've done this last half of the yea... my best pass of the day was my first pass.

Video: https://www.youtube.com/watch?v=oKZCQUDu620







Pass 2:
Temp was 49* with 53% humidity and a -246 DA reading.
Moved the rev limiter up to 6,800 and moved the 2-step rev limiter to 1,800 rpm. a 4.5 second burnout and tried to launch off the 2-step again. Couldn't get the button and my foot on the brake pedal to release cleanly so I boogered up the launch pretty bad. Launched at 1,803 rpm and 1->2 shift at 6,597 and 2->3 shift at 6,612 crossing the line at 5,723 rpms. Pretty happy with my shifting being very close to my target shift point of 6,600 but bummed out that I ruined the launch. Noticed a lot of -CL comp on the datalog, as well as the rich dip at the converter flash point, but aside from that dip, the AFR was dead on.

Video:

https://www.youtube.com/watch?v=VK6bUgGbC8E







Pass 3:
It had sprinkled rain in between my last pass so they had to take some time to dry the track. At 51*, 52% humidity, and a -139 DA. Put the rev limiter to 6,800 and the 2-step to 2,000 rpms. Did a 5.5 second burnout and launched at 1,911. Boogered up the launch again, this time because I think the car started to creep and I didn't release the button/brake pedal clean also. First weekend ever using a 2-step, but it was worth a shot. Shifted 1->2 at 6,648 and 2->3 at 6,638 rpms so I crossed the line at 5,907 rpms. Cl comp was better after I had adjusted a little bit of the VE table up top and the learn table had all small numbers too. Still a momentary rich pocket at the converter flash in 1st gear.

Video: https://www.youtube.com/watch?v=_h2HqcdhsOc





learn table after 3 runs:




Pass 4:
Temp was 51* with 52% humidity and a -118 DA. Decided to go back to foot braking off the launch and aimed for a 1,200 rpm launch point so I wouldn't creep past the beam. Did a 5.5 second burnout and launched at 1,188 rpms. Shifted 1->2 at 6,361 (a little too early) and shifted 2->3 at 6,604 which put me crossing the line around 5,748 rpms. I had puled a little more fuel out of the area of the usual rich pocket and saw much less of a dip on the datalog (pink line). There were a few rain drops on my windshield at/during the run and I was super hopeful for one more pass, but sadly the rain came and the track closed for everyone. I packed up my gear and got the car setup for the drive home as is started to rain more.

Video: https://www.youtube.com/watch?v=ixV87rCIWsY







On the ride home I noticed the engine oil pressure on the oem style dashboad gauge was reading higher. Both at idle and while driving. I kept an eye on it and listened to the engine the whole way home, so no radio. The oil pressure gauge is incorporated into the tachometer on my car, and this tachometer I got from Cajun Tach supply back in the spring because it had a different redline and higher oil pressure gauge value readings. Since last week I have ordered a mechanical oil pressure test gauge online and it will be here in a few days. As part of my winter routine I also plan to pull the oil filter, cut it open and examine it along with an oil change. I now have +3,000 miles on this engine since it was installed back in February. I changed the oil and filter at 500 miles, at 1,500 miles, and now (soon) at 3,000 miles. I am hoping just the oil pressure sending unit or filter is having an issue, or even the needle on the dashboard gauge. Any thoughts?


That pretty much wraps up my racing for this year and car shows are done also. I would have loved to have an 11.7x timeslip and I tried like hell to get one, but the best slip of the year was the one from Pass 1 on this past Sunday.

[LTb1ow]

Can you show a plot of just the MAP values?

[IROCZman15]

yea, if you mean just a screenshot of a datalog with only the MAP reading trace? I can do that. Or do you mean the MAP values from my tune and the VE table?

[LTb1ow]

Yea the best run's datalog with MAP and RPM only

[IROCZman15]

sorry, I never remembered to post that datalog, whoops






unrelatedly, I did an oil change a few weeks ago and figured it was a good time to TRY one of those oil sample test kits. I also was curious about if the oil/filter change would remedy that high oil pressure issue that I had last month on the way home from Island Dragway.. tossed in a bottle that of AMSOIL engine flush since I had it on my shelf and ran engine for 10 mins. I will post a separate thread about that oil test.. but for now the engine oil pressure is back to where it normally is 52-55 at hot idle, and about 75-80 under moderate load. I hooked up a mechani9cal oil pressure test gauge to the threaded hole in located above the filter on the gen 1 Dart SHP block. got the same readings. So my oem style dashboard gauge is accurate. I'm still VERY baffled by why the oil pressure was reading like 100 under load and 80 at idle back in late October.

figured a new/separate thread would get more eyes and opinions so here it is:
http://www.njfboa.org/forums/showthr...626#post955626





Unrelatedly, I decided to switch up my tail-lights. I had this set in storage for like 10 years. The ones on the car I did the red-tail light mod to back in 2007 and while it looked better than the orange turn signal lenses, I still wanted something more bada$$ and sleek and tinted. Took these out of storage and peeled them apart. painted the inner orange lens with the Testors translucent red paint. sealed them back up and they were the same as the ones on the car. Decided to bite the bullet and try to tint them. But first I painted the outside of the orange lens with the translucent red also with the testors. Then I sprayed a generous 2 coats of the VHT nightshade, followed by a gloss clear 2 coats. Let them cure for a few days then buff, polish, buff again, wax. installed them today. pretty happy with the sleek look. No more rainbow of colors. Not sure if I am going to leave the on/off killswitch handle red or paint it black. Plenty of light shines through, and they are just the oem style bulbs, nothign LED or anything fancy. If it looks too "ricer" or ends up being a problem, I can just swap back to the other taillights. For now, I am glad that the multi-color is gone.

[maroman88]

looks good, ive done both the red out and black outs in the passed also

[BonzoHansen]

Cop guy, is that legal? Lol

The real test is how visible are they in daylight. I always find tinted tails can be hard to see on sunny days.

[Joey D]

Originally Posted by BonzoHansen

Cop guy, is that legal? Lol

The real test is how visible are they in daylight. I always find tinted tails can be hard to see on sunny days.

Shhhh

[V]

Should just do export tail lights, be real different, lol

[IROCZman15]

Originally Posted by BonzoHansen

Cop guy, is that legal? Lol

The real test is how visible are they in daylight. I always find tinted tails can be hard to see on sunny days.

I haven't had a bright sunny day out yet to really see how they look, but they are not truly as dark as the photos make them look. The day I installed them was moderately sunny and I took this photo around 2:30pm and the sun was behind me facing the back of the car. (Just had the taillights illuminated and the hazards too, no brake lights activated) On the drivers side is the tinted tail light and the passenger side still had the old red tail light one.



I'll see how it goes though out driving around one day. if I need to put the old red ones back on I can do that in 10 minutes time. or I can tint those old red ones but with less coats of VHT tint. No matter what I am just glad to have less colors back there and more of a sleek look. I don't think they are much darker than those certain year tinted 3rd gen firebird lights that came stock. For reference, see the photo of the silver bird in front of me in the staging lanes at Island dragway in post #208 above. That's just a nice clean look with not too many colors, and that is stock! The look of the yellow license plate, with black housings, white reverse lights, orange turn signal lenses, and red tail lenses was just too much color-wise; not my style. .. and Certainly no euro lights or lenses will be happening V !

I will have to be more careful on the road and mindful of traffic laws in the future though, I have made a choice in life that will make me a "regular member of the motoring public" as I step away from my current cop job. All is well and I am good, so that is that discussion for now. Hopefully good/different/fun things are to come my way in the future with a different job and career. So some of the bigger projects on the car MIGHT have to wait a bit as I get life/budget restructured. Actually, not too many big projects remain for this car, and it is ok for them to wait a bit. Roll bar, big tube full exhaust, nitrous setup, new and improved subwoofer/amp setup, and some better Autocross/street tires too. I could probably tackle some smaller stuff like the electric vacuum pump for the brake booster, weight removal, and some new stripes on the doors in the meantime since that is lower budget stuff.

[BonzoHansen]

Really? Wow. Good luck!

[V]

Fair enough, lol. I just like things that are different.

One day ill have to buy a camaro again to put my set on.

[IROCZman15]

long post of text, sorry,
I might start a new thread about future car upgrades/plans, since this thread was based mostly on the getting the engine in the car, getting it running, and sorting out everything during its first year of use.

This upcoming year will probably include a bit less activity, but I still hope to race it and attend events when i can. my budget is going to be much lower than it was in 2020, so I have to pick and choose what projects I do in a smart manner.

I still hope to do the roll bar, and there is a local fab shop nearby that will do it for about $2000 including swingouts, nice welds, and setting up the 5-point harness. I hope to do that in the springtime, maybe.

however, over the winter I might want to spend a small amount of money while the car is off the road. I do want to do an electric vacuum pump setup. I do not want a mechanical one with an extra pulley and plumbing on the engine. I do NEED more vacuum to my brake booster because 7" of vacuum made things a bit sketchy during autocross, drag racing, and street driving. No hydroboost, no way. A small self-contained electric vacuum pump that I will tuck under the nose of the car, hidden from sight makes the most sense. While drag racing I can also put a T-fitting into the vac line and then connect it to my crankcase to pull some vac on it and gain some more horsepower.


I also have been tossing around the idea of a rear gear switch. In the effort to make the car quicker off the line and more seat-of-the-pants faster, I could either reconfigure my 3,400 converter and leave my 3.55 gear ratio, OR leave the converter as is and change out the gears. I am actually happy with the torque converter, and it was built with nitrous hits in mind. Having it configured with a 4,000 stall would probably make autocross very difficult, and start to also get away from the true street-based nature of the car for routine driving. I cant think of a good reason to leave the 3.55s and change out the converter. So, when I had moser build the rear (february 2019) I could only hypothesize about how the new engine would pull and what gear ratio would be best for this street/strip/autox setup. I went conservative with a 3.55 ratio, and I am glad I did. The car worked great with the 3.55 ratio with the old engine on nitrous, as well as with this current 406. I just am itching for a but more low end pull, more energetic launch, and faster acceleration.

for details on my 12 bolt setup (with photos) check page #2 at post #48 at this link: http://www.njfboa.org/forums/showthr...t=68229&page=2 which was posted on 5/8/2019

On Mosers website, I have the choice between 3.73, 3.91, 4.11, etc. I don't think it would be worth it for my to pull everything apart and only go from a 3.55 to a 3.73. I think a 3.91 ratio would be better. I played around with several of the online gear calculators and the numbers seem to jive about where a 3.91 ratio would put me at for peak rpm/mph crossing the finish line. My motor makes peak hp right around 6,000 rpm, but holds similar hp between 6000-6400 rpm....on an engine dyno, so obviously no load on the engine. Using a 26" tall mickey thompson ET street SS tire, I am pretty sure it will be able to hook/launch well enough with the 3.91 ratio to get my a wheels up launch and a low 1.5x sixty foot time. As for a 3.91 ratio in autocross, I actually think it would make the car more responsive. a higher torque converter would mean I would have to come out of the turns revving the engine to the moon in order to start pulling in between cones/turns. A 3.91 ratio would just mean I would have to be more careful with the throttle input in order not to blow away the tires. That's fine, I can work on that.

As for street use, I don't think a 3.91 will make the car un-drivable on the local streets, nor on the highway. I have a 700R4 with overdrive, and I have wired up my torque converter clutch to a lockup toggle on/off switch that I can turn on and off in 2nd,3rd, or 4th gear. So for highway cruising, I could just lockup the converter and travel along the highway at 80 mph around 2,900 if my math is correct.


gearset: https://www.moserengineering.com/12-...r-us-gear.item

install kit: https://www.moserengineering.com/12-...hevy-car-.item

Thoughts on a 3.91 ratio gear swap? it would cost about $400 in total including fluid and I would have to borrow a micrometer, dial indicator, and pinion depth tool from somewhere. I could pull the axle out of the car completely, or get the car up in the air in the garage and do all the wrenching with the axle in the car still.


The full blown exhaust project will probably not happen this year. I might plumb up the nitrous, but probably not until the roll bar setup is done. I am thinking that if I can shave a few thenths off my 11.82 et and maybe run an 11.5, it would justify my need for the roll bar. After the bar is in, I would be able to start dabbling with small nitrous hits without having to worry about getting kicked out of the track for no-bar rules.

[Joey D]

3:91's sound like a good choice to me.

[TaKid455]

Dave - Pay the extra coin & get a GM gear set if you can. Yukon/ US Gear would be 2nd choice for a street car. While you are hitting the strip, majority of driving is street.

[IROCZman15]

cool, if anyone else has more feedback, feel free to chime on in. Would 3.91s be too non-street friendly? I kinda don't think so. I mean I used to run the 3.73 gears with the old TPI engine (and 700r4) from 2004-2019. The 3.73 ratio was never bad on the highway, and I was never looking to blast across the interstate at 90-100 mph anyways. I think anything in the 4.11, 4.xx range might be a little too much, but a 3.91 coupled with the 700r4 overdrive plus locking up t he converter would be just fine.


Larry, i did a quick search for the GM made gears, nobody seems to be selling those. would that be something I would really have to seek out or where can I find them? I was probably going to go for the "lightning finish" on the gears, and I don't think a GM gearset would offer the lightning treatment that Moser/Us gears does. Apparently it helps with break-in and stuff? Can the GM gears only be found used or new-old-stock ?


As for the 3.91 gear with nitrous, I am struggling at how to mathematically determine how my current 3.55s would work with nitrous too. If I were running a 100 shot I would probably be at the very top of 3rd gear crossing the finish line. However if I were to run the 200 or more shot I planned on running, I am pretty sure I would have to shift into 4th gear (overdrive is a 0.70 ratio) before the line so that is not optimal. If I ran the 3.91s I'd hope to be able to stay at the top of 3rd gear while crossing the line when running no nitrous (current setup), and on a small shot I'd be into 4th gear, but on a bigger shot I would be into the meat of 4th gear. Since I have no idea how to use math to figure this out, I am just doing my best guess.

Basically, I want the car for feel more alive and woken-up not only on the dragstrip, but especially on the street. I want to take people for rides and have that killer instant acceleration. It is pretty good now, but thinking the 3.91s would really deliver the "pinned in the seat" experience.

[TaKid455]

With a 700, you have a 0.70 OD yielding you a 2.73 equivalent final drive with 3.91. With 27" tires, thats not bad. It comes to RPM *3 = MPH . Its your 1st gear that is a bit steep at 3.06. Coupled with your rear, thats a product of 11.96. I try to keep that number between 9-11 depending on combination. With 3.55, your at almost 11 . You could run the 3.91 w/ the 2.86(?) 1st gear in the 700. That would mean opening up the trans. Would also make the gear splits more even.

Blasting across interstates at 90-100...isn't that normal traffic?

[IROCZman15]

haha, in New jersey on route 80, you are right...that is the norm sometimes!

So another friend of mine and I were chatting tonight and he enlightened me to exactly what you are talking about. Prior to two hours ago, I had never looked into this "starting line ratio" SLR math. I definitely trust you for tech advice Larry and my buddy who was explaining SLR. Using those Wallace Racing calculators I did exactly what you explained.
http://www.wallaceracing.com/calc-slr.php
You are right that the steep 1st gear of the 700r4/4l60 is a big factor. What you said about swapping out the 1st gear in the trans could be an option, but I was hoping not to have to pull the trans out of the car this year, or for a year. I could always do that 1st gear swap next time it ever comes out.










As for highway cruising, I have noticed that when I activate lockup on the torque converter in OD on the highway, it usually pulls the rpms down about 400ish rpm.
So, for example, I took this photo while speedily-cruising on an open stretch of rt78 out in Pa on the way back from the UMI autoX event. I am used to locking up the converter and usually will coast at 85mph and be right at 2,500 rpms with these 3.55 gears. I think I did my math right?? If I were doing 85 mph with 3.91 gears and locked up converter... I would be at 2,753 rpms? If that math is right, thats not bad at all. (cross multiplication and such)






Eventually I would like a set of stickier/taller tires, but for 2021 I am going to use the current 26.1" tall MT ET Street SS tires. If I could find a deal on the old style Centerline Convo-pro wheels, thats what I would drag race with and that would have a tall slick on it. Just not for 2021.