3.42 Vs. 4.11

[69NovaKid]

Looking to put a new ring pinion in my 10 bolt 8.5 ring gear 3.42 ratio running at 50 mph on the street at 2,500 rpm - with this rear and a th350 trans i am running a 14.4 on street tires at the track- NOW over the winter im looking to throw on 25 inch street slicks - and a 4.11 gear ratio - what can i expect out this ratio? will the car still be streetable?

[silicon212]

Put a big radiator on it, keep up on the oil changes and be prepared to stop at every gas station you happen upon.

It'll work, about 20 years ago a friend of mine had a '69 Malibu with 4.11s and a TH350 in it - it got about 8MPG downhill. Engine RPM was 2600 @ 45. But it sure was fun to drive!

As far as ET, I can't really tell you, but we used to get 11.8s with a 350 powered, M22 shifted Datsun 280Z.

[69NovaKid]

thanks man- thats nuts on the datsun haha light cars man- -- do you think the 3.42 will really bump the take off to an extreme degree? Or would you spend the 500 bucks elsewhere on power?

[silicon212]

Originally Posted by 69NovaKid

thanks man- thats nuts on the datsun haha light cars man- -- do you think the 3.42 will really bump the take off to an extreme degree? Or would you spend the 500 bucks elsewhere on power?

Going from 3.42 to 4.11 might, MIGHT get you into the high 13s at the most, but I'd think you'd still be in low 14s. Work on reducing weight where not necessary but do NOT remove something that might compromise safety!

Tell us what you have under the hood.

PS, are you SURE that's an 8.5 in there? If it's a 10 bolt, and it's original, it's likely an 8.2 and these were pretty weak without support.

[69NovaKid]

Under the hood im working with a 355 sbc - edelbrock performer rpm heads-air gap intake - fueld by a holley 4150 -850cfm carburetor - Lunati hydraulic cam 480/480 lift - 292 duration 109/107 lobe sep. 9:5:1 compression pistons - im thinking im around a 14.3 or.2 at the moment considering the last time i took it down the track after changing the ignition and and gapping hte plugs i bent the push rods in the 3rd cylinder in the first 60 feet and still ran a 14.5 on seven cylinders - but who knows 14.4 is best so far.. goal is a 13.6

[69NovaKid]

anyone got any ideas?

[silicon212]

I actually think you're a little overcarbureted. You might get FASTER ETs by dropping down to a 700-750. The cam is pretty lumpy in the idle - does that thing have to idle at least 1200 RPM to keep from stalling?

That's where I'd start working - better matching the engine. 4.11s definitely won't hurt and when you get that thing singing where it wants to, the engine tuning plus the 4.11s might get you where you want to go. Degree the cam if you haven't already done so, go with a 700-750 SCFM carb, play with engine tuning - you want as much advance as possible WITHOUT detonation - not only can detonation kill your engine, but it also kills performance. Also, run with the LOWEST octane gasoline you can get by with - the higher the octane rating, the lower the overall energy level.

[69NovaKid]

Good things-thanks for the advice -id like to keep discussing the matter if you dont mind? - I thought about the carburation i ran a edelbrock 750 on there and it was only getting a 15.8 until i switched over the 850 holley and dropped to a 14.4 - the plugs are all a grey/white in color it idles in park at 1100 or so and in first it drops to about 900 i had it professionally tuned by a 45 year vet racer -if anything i thought possibly under carbureted? I havent degreed the cam not exactly sure how to be honest and what would that give me? the timing is advanced as possible without pinging on 93 octane fuel-- would you recommend any other options to spend 500 dollars on besides the 4.11 ratio which may help my situation any better? Besides the roller rockers im looking to put in and street slicks by MH

[GeneralNutt]

i would change out that rearend. i had that same exact rearend and it is an 8.2 10 bolt and i put 4.11s in it and i have only a 350 with 335 horse and about 340 torque and i was in a flatspin and when i hooked it broke both axle welds. i went to a 12 bolt but that is just me maybe you can keep what you got on there and i also had to much carbeuration. i would suggest what has already been said down to at least a 750. also you have to remember that the whole engine has to work as one. it cant have various pieces and parts or else you will just end up not gaining much. that cam is a beastly cam and a little to big for what you got in that engine. but just suggestions

Good Luck

[MrPbody]

The Edelbrock carb is not a good indicator, as they're quite troublesome and not good performers. A 700 or 750 Holley would certainly show better. 850 is too big for a 355 that doesn't rev at least 7,500. A hydraulic cam won't go there without "issues".

If the engine is "happy" at 6,200 RPM, the 4.10 gear would really wake it up. Small blocks aren't noted for high torque, so the taller gear is a liability, not an asset. As others have said, be prepared to stop at most gas stations, and make sure your fillings are "tight". A 3.73 might be the best compromise.

Jim

[waupachino]

The vehicle is definitely over carburated for the motor. I had a 350 with Dart 202 sportsman heads and a comp 270 duration 470 lift cam with 10.0 compression 3.42 rear and a 2500 stall speed in a 79 Z28 running 12.8-13.2 all day long with a 650 double pumper. I think if you don't have a stall converter at this point, I would keep the 3.42 gears and get the converter along with a smaller carb tuned to the vehicle. This would help the car to rev quicker and definitely improve your 1/4 mile times.

[69NovaKid]

thanks for the input fellas- yeah ive been told its over carbureted too- i was also just told that the carb is a 750 but race tuned and came off a 396 bored to a 408 or somewhere along those lines basically a 12 something second car- without changing the ratio and keeping the carb considering re-jetting it - does anyone have any suggestions on what i can do to get this thing down into low 13's? i just recurved the distributor- im putting in roller rockers this winter and trying to keep it on street tires - waupachino -what are you workin with to be in 12.8s? slicks?