4.10 Gears vs 3.91/3.73/3.55 - effects on 1/4 times

This winter I am thinking about setting up different rear axle gears for my '67 383 Barracuda w/ a 727 & 4.10 SG. I am not sure how taller gears vs shorter slicks at the track would perform.

Here's how it's set-up
68 383 B motor w/10:1 compression
Edelbrock E-Street heads
Cam - Comp XE274H
230/236 @ 0.50 duration
LS of 110*
Intake CL 106*
.510 lift @ intake valve
.523 lift @ exhaust valve
Holley 850DP
Edelbrock performer RPM
Stock style converter (1800 rpm)
8.00/8.50-14 (27.5") M&H Racemasters
Weighs 3,090#

My best with this set-up is
R/T - .059
60' - 1.969
330' - 5.442
1/8 - 8.303
MPH - 85.52
1000' - 10.787
1/4 - 12.883 @ 107.81 mph

So with all that said, I have been told I could go faster with a 3.73 gear. I always thought the 4.10 would get it going quicker out of the hole. I always thought you set it up to go redline @ the end of the 1/4.

As it is, I'm @ 5,500rpm at the stripe.

I have thought about maybe a 3.55 or 3.73 & a 26.0" slick. Then I could run 28.0 tires still on the street & reduce highway RPM. That change on the track with a 26" tire (3.55/3.73) puts me at 5100/5350rpm at the stripe.

I am considering a better converter, maybe a Dynamic Converter, to get it off the line & get my 60' down. I just want it to be a fairly tight because it's my daily driver.

Faster, a little, but quicker no. You're probably making 350-375 HP. If it hooks and goes then maybe a 26" tire might hook, but I'd say no. You want the largest contact patch that you can stuff under the wheel well. 9X29X15 will give you the best grip for a standard wheel well using a 10" wheel. Run a taller street tire to keep the R's down,cheaper than a gear swap. 3000-3500 stall converter built to your cars specs. That should get you to 12.5's . Look up Richmond gear calculator and plug in the numbers. This is only a guide

I'm sure you could do something like 3.73's and a T/A "tight" 10" converter, or a Dynamic tight 9.5" and not lose any ET.

I would go 9x28's>9's keep the 4.10's and get a purpose made converter that flashes to at least 3000 for a 383, that 1800 verter is killing your 60/ET. Your mph/weight shows you are using around 307hp of whatever hp that motor is making which should be 350+?, its just not being allowed to unleashed itself early enough...you got a low 12 potential car there.

Here's a handy formula that will tell you all you want to know.

(MPH in 1/4) x 17.6 (constant)/ (Tire diameter x 3.14 (Pi) x 60 (constant) x gear ratio.

Your current combo would look like this:

107.8 x 17.6 / 28 x 3.14 x 60 x 4.10 = 5308 RPM


I did this for an old combo on my RR and it helped.

Want it to go faster, work on the 60' as it's REALLY soft. You've got a 12.00-12.20 MPH in a 14.00 chassis... 14.00 cars go 1.95 60's. You should be in the very low 1.7x range or even high 1.6x for that MPH if the chassis is good.

Gears won't do much when the chassis and converter aren't helping you at all.

I'd spend money on a good converter that flashes at least 3500. That will wake it up a bunch! New converters aren't the marshmellows of the old days either.

I agree. Spend the money on a good converter, as that will get you the biggest gains. Call a good converter builder and ask them what they recommend for their converter, and what gear would so suit you best.

Just did a quick calc, if we assume you have 350hp at the crank and keeping those slicks/gears you have now, with the right converter this is possible if it still hooks with the added hit>

60 Foot E.T. : 1.67
1/8 Mile E.T. : 7.60
1/8 Mile Trap Speed : 89.48
1/4 Mile E.T. : 12.04
1/4 Mile Trap Speed : 111
1/4 Mile Trap RPM : 5,580+slip or 5300+ w/9x29" tyres

From what I have seen the better the converter the less the rear gear even matters. With the stock converter a change to a lower gear usually shows big gains. When a good converter is in place before the lower gears those gains are usually much smaller. My car picked up .7 going from a 3.23 to a 3.91 when it had the stock converter. A friend of mine with a similar combo did the converter first before the gears, his car picked up zero ET going from a 3.23 to a 3.91 because the converter was doing all the work.

I ran my 340 Cuda with 3.55's 8x26" slicks, a B&M s/holeshot verter and went 13.31@101. I added a better cam/carb/intake, 4.30's, T/A 4200 verter, 10x28's and went 12.39@108.5, weight stayed the same at around 3550. Using weight/mph shows I added approx 50hp to the motor and thats not a 1 sec gain in ET.

Optimal 1.72 60 ft. Would yield a ~12.38 according to the wallace calculator using your mph.

I switched to a 4.30 from 4.10 when i had a 408 and seen nothing on my slip. I did have a 8" Lupo convertor as well. I did pick up rpm at the strip thou which was something. Went from 6800 to 7100. Now need to put the 4.10 back in for the 511.

I agree with those that say look to The converter if you are trying to be quicker in any meaningful way. The 1.7 and 12.4 would be realistic.

I was kinda thinking the gear should go the other way but a great converter can make up a lot. If it were me, I would use a 4.56 and shift it at your 5,300 and hope it goes 6,500 through the lights. It probably won't though. Most Stockers are in high gear before the 660 but 4.88's and 5.14's probably are a bit much for most guys. It's expensive to really optimize 60' times. Guys have 4-5K of converters laying around. Center sections are not cheap either.

Thats what I would do is get a good converter for the combo and work on the 60. The gear in it now should work fine.
My old 383 Dart years ago was a 452 iron headed 383 with the MP .484 cam and stock 9.5 comp. I ran a tight 3000 Turbo Action converter in it with 26" tires and 3.91's. It would 60 in the 1.70's with about a 1.76 being normal. And it ran a best of 12.31 @ 110. Get a good converter built for the combo and get that 60 down. Good luck , Ron

383 motors need to rev to go fast at the 1/4 mile tracks Short stroke motors need all the help you can give them
That being said what RPM are you shifting at now?
Did you degree the cam? If so is it straight up, advanced or retarded?
If I was you I would work on the 60 ft. times, carb. squirters and traction first Is it spinning or dead hooking?
What size squirters are in the carb now and are you still using the 50 CC rear pump? If you have # 35 or bigger squirters try some # 33 or smaller and if your still running the 50 CC pump swapping it out to a 30 CC pump.

It's got a fast rate hyd cam in the motor....... So it's not going to rev real high, whether there is potential hp up there or not.

The OP wants to take gear out of it to make it more street friendly, but doesn't want to kill the ET.

With those variables in place, there aren't a lot of options.

The motor should easily make 400hp, if the valvetrain will stay happy high enough in the powerband to let it.
The RPM heads would certainly provide enough flow to facilitate a hp peak of over 6000rpm, but I'm not too confident the lifters will allow that to happen.

This is one of those situations where the intended use of the car, and the overall combo in general would make it difficult for the engine hp and the on track performance to coincide very closely.

EXACTLY......at 400hp? that car has 11.5 potential then, I don't think that is going to happen from 12.8's though with just a converter change.

A friend asked me to tune his carb on a chassis dyno on sat. I picked up 113 hp. 50 hp in it wasnt going full throttle 63hp in the carb tune. Just pointing out that sometimes there is more in it

I would put in a 3500-4000 9.5 converter with 3.73s if it was me

Considering his question, I wasn't going to go there.

Can't remember my Comp Cam part numbers, but I bet their 282 solid (xs282?) would put some power/mph in it, not to mention rev to the moon. Seems like smaller engines with short strokes that like to rev a fast rate cam is like a double wammy.

Russ, the xs282s cam is a real revver in a 383.
IMO, it's really a bit big for the rest of the plans for the OP's car.

Although, a small mid-230 solid single pattern on a 108 would likely do everything better than the xe274.

Several years ago when I had the 340 in my Dart I switched from 3.91's to 4.30's. The car averaged .006 better in 60' and carried it through the 1/8. There was no change in mph. A lot of money and work for so little gain.

At the time I was running a 9.5" converter from Edge Racing Converters that was built for the car. Very good converters for the money IMO.

3090lbs, is this correct or a miss print? with all those power adding parts to that 383 and 108mph @3100bs makes me think "where's the extra 60hp gone"? that thing should have 375hp or more, which should be around 113-114mph. before I spent a nickel on gears and converters i'd look for my lost power.

With that list of parts it should be making better power, from the parts list it should be a 425hp motor

Can you elaborate on this a little Dwayne? What do you normally see with these XE cams? Do they start to break up in the higher rpms or what happens exactly?

My experience with fast rate hyd cams is...... The lifters collapse more than "normal" on the opening side, and when the rpm reaches the point where lofting starts to occur, the lifters "pump back up", and if there is any appreciable preload, the valves hang open, and the power drops like a rock.
More spring pressure just exacerbates the situation.

What is required to get this type of cam to turn any real rpm are lifters with extremely tight internal clearances, and a very low quantity of oil below the plunger(limited travel), so enough spring pressure can be used to properly control the valvetrain, without worrying about how much collapse the added spring pressure brings.

Lobes that use longer, slower ramps have less of a tendancy to collapse the plunger on the opening side, so that's one plus if you're trying to achieve a higher rpm, plus the slower overall action requires less spring load to maintain control at any given rpm.

My personal experience is, I have never gotten any fast rate hyd cam to rev very high....... In any brand of motor.
I'll admit, I have zero LS or Gen3 experience though, and those platforms seem to not suffer from this situation as much as the old school stuff does.

Thanks for all the input/suggestions. Lots to consider & I think I will do 3.73 & a good converter & work on my 60' this spring. I will, down the road, think about making a cam/lifter change to get everything out of this set-up. The intake is good for up to 65oo rpm & I'm running a '65 steel crank, stock '65 rods & ARP rod bolts so the bottom end should be able to handle the higher rpm. I want to get all I can out of this combo but not get it too out of line for daily use since I drive it 75 miles a day.



That is correct, it was 3090# at Tulsa Raceway Park. I weighed it with open header(the exhaust pipes off) & 3/4 of a tank of fuel.

[quote=grancuda
I am considering a better converter, maybe a Dynamic Converter, to get it off the line & get my 60' down. I just want it to be a fairly tight because it's my daily driver.


[/quote]

The Stock type converter is your Main problem. With the 383 go with Dynamics 9.5" vert. They are Very Tight verts and work very well. They are reasonable as well, around $600 bucs or so. With the 383 Id probably go with the 4500 stall 9.5"

Leave the gear alone for now, but I do like your thinking on the 3.73 gear and 26" slick for the track and 28,s for the street.

That's a far more technical explanation than what I was going to say, which was the valve train comes effing unglued beyond a fairly moderate RPM.

I hate those hydraulic Xtreme cams... noisy, sh!tty valve train control at higher RPM... everything I DON'T want with a hydraulic cam. I went to solid lifters years ago and haven't gone back.

As did I back in 1984 with the 340 car, the .484 hyd. purple was ok but when I stepped it up from a street car to S/95% Strip it had to be an sft cam. the old DC. 590, which also ran great on the street on the few times I took it out.
I think the OP would do very well with doing the same thing and let that motor rev freely to 6k+ with a decent tight 4000 flash verter, then we would see how fast he could go as its capable of much more with the hp people say it has.

Thank you and BRADH for the input. This conversation couldn’t have been more timely. I have an XE cam in my car. I just switched to a different set of heads with different valve springs and when I’ve taken it out to dial it in, at around 5900 rpm or so, the car feels and sounds as if it’s breaking up a little. I had no issues before with my old heads and springs; everything was smooth up to 6300-6400 (as high as I’ve ever revved it). The valve train noise sounds louder than what it was with the old heads and springs too.

In regards to it breaking up at higher rpm, I’m not saying there isn’t possibly something else going on because I’ve only had minimal time to mess with it but, the cam did come to mind. I added about ¾ turn of pre-load when adjusting the valves this time; next year when good weather comes back, I think I’m going to go to a half turn.

The car has always performed well with the cam but, I cannot stand the noise it makes. It always sounds like something is wrong but, every time I’ve adjusted the valves or had things apart for whatever reason, there is never any issues. The noises are variable too (sometime I’ll have X ticking and or ext. but, sometimes I don’t). Again, I don’t think anything is wrong but, it drives me nuts. I’ve got probably around 2000 miles on the car and 15-20 passes. I’m going to keep plugging along with this combo but, when I freshen the thing up, I will definitely be going with a different cam.

FYI- Not that it was apples to apples given I re-curved my distributor at the same time but, I changed from 4.10's to 3.73's and picked up a tenth and a half in the quarter.

6200 is about the best I've ever gotten out of one, and that was a SBC with factory(pretty light weight) stamped rockers.
On the BB motors, they've never made it to 6k.

I did some experimentation on the dyno years ago, playing with different spring loads trying to see if I could get more out of one. Increasing the springs from about 120/310 to 145/370 netted maybe a 100rpm gain..... And when the valvetrain got unhappy with the higher spring loads, it happened even more abruptly.

I ended up swapping to a solid lifter cam, put in springs that were 135/345, and it would rev cleanly to 6500(as high as I was comfortable with on that short block) with not even a hint of a stability problem.

The one time I recall seeing this phenomenon play out in a magazine was in Mopar Muscle 2005 with that EZ headed 446 Dulcich built.

I had already been through what he was experiencing and knew how that was going to turn out.

About 20 years ago, before my friend was running Schubek lifters in his Stocker we were trying to find some upper rpm stability out of his motor.
The cams that showed the most promise just wouldn't rev high enough to be usable.
Around that time we had also played with spring loads, and got basically nothing out of that.
We swapped some solid lifters into it one time to see if it was lifters or spring load.
Set them at .004 lash....... And the motor would go almost 1000rpm higher before getting into some float. The problem was the lifters all along.
The next year he put Schubeks in it...... And that was the end of the rpm problems.

I do like the way you said it.

Mike I was anxious to try your 26" slicks but the 275 pro radial worked so good I'm just gonna stick with it. Thanks for the offer though.

This cam/valvetrain is really noisy, I have adjust & adjusted thinking I did something wrong but no, it's just loud. I would run a solid lifter cam but really unsure how often I should do valve adjustments on a daily driver. I know some factory Mopars had them like the higher performance 273 so they should live day to day.

I had an old Toyota pick up with a mechanical cam that went 200k and never had the valve cover off.

Slant 6's were all mechanical cams up until the last one or two years of production.

For a modern high performance street friendly mechanical cam in a traditional v8 platform, I'd say popping the valve covers off for a look-see every 3000-5000 miles is probably a good idea.

The right type of solid cam wouldn't be any noisier than what you're dealing with now.

my experience has been frequent adjustments are more due to the person doing the adjusting than anything. you can buy solid cams that are pretty quiet.

Been awhile. Welcome back.

yep. we need to catch up sometime.