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Old 12-02-2020, 02:31 PM   #220
11 Second Club / Meet Coordinator
IROCZman15's Avatar
Join Date: Dec 2004
Location: Roxbury, NJ
Posts: 1,850
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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: 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.


install kit:

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.
1987 IROC-Z - modified

Last edited by IROCZman15; 12-02-2020 at 02:35 PM.
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