Gearing a street/strip 500" BB

Thinking about pulling the 3.91s out of this thing & going 3.55. Has a 3500-stall converter. Makes enough torque that it seems a 2800 converter, 3.55s & 28-30" tire would work well.
With the 3.91s & 3500 stall, it would be pretty busy on the 65-70 MPH ride for 90 minutes to the nearest track. Swapping to 30" tires should help that, but maybe not enough.
Looked at several gear/MPH calculators, and accounting for slippage, I'm still undecided. Whaddya think?

3.23.

You have enough torque and converter to haul the mail any way you want and it will be more freeway friendly.

Kevin

I would think the converter would need tightening up...

It might depend on the torque converter? I changed from an older design 10" Dynamic 3,500 stall that was good, but on the loose side to where it slipped fairly easy below the stall speed. The new converter is a custom (and expensive) tight 9" from Ultimate. It flash stall speed is close to 5,000 RPM, but I don't notice any slippage (more than a stock converter) in normal driving. It's nice for the street, but maybe too tight at the track?

Has a PTC 9.5" converter, I should call them and see what they spec'd for the car.

Have 3.54 gears in an F body here with PTC 9.5, and with the 275.50r15's (around 26" dia.) drag radials, it goes about 3000 rpm at 65 mph. I would love to drop down to 323's if I could and try that. Even a 3.08 gear would probably work well.

Moparts member Prosport is running 10's with a 500" A body with 3.23 gear.
I believe he is running a 9 1/2" Dynamic converter.
https://board.moparts.org/ubbthreads/ubbthreads.php/topics/2416556/1.html

I have 3.54 gears in my '65 Coronet behind a 512 stroker and I'd go higher if I could. I think 3.20 would be good, maybe even a tad higher.

Good luck getting a converter that tight with a 500" BB.

I have had 2 PTCs behind my 540 Hemi. They would flash to over 4,000 with 3.91 gears. I had asked for as tight a converter as they could make for the same reasons the OP wanted a tight converter.

The car just felt "spongey" down low driving around. PTC said that they would try to tighten it up one more time, but didn't think they could get it much ,if any, tighter. Actually, they said send it back a third time and they would see what they could do.

Oh, and did I mention that the engine vibrated around 2,000 RPM when I got it back the second time?

So I called Lenny at Ultimate. He told me that the problem was the 9.5" cores just aren't big enough to hold our torque monsters. And that there aren't any of the good old 11" cores around much anymore.

But I sent Lenny my PTC converter anyway. He did as much as he could with it and suggested some other changes I could make on my end. It still flashes to 3,800, but is noticeably tighter and more responsive down low. And the 2,000 RPM vibration is gone.

P.S. I have several of the huge motor home converters laying around, but he said that he can't get any of the internals that he would need for them.

Talk to them before deciding on which gear ratio, I tried from 3:73 to 4:30 in my old pump gas Duster with a custom built 10 inch Contintental converter for that motor, 517 C.I., 612 HP at 5500 RPM with the low deck six pack with 440 six pack carbs.
That stupid car ran within .03 ET, high 10.40 E.T. in the 1/4 mile,and very near the exact same MPH in the 1/4 mile with the 315x60x15 M/T ET Street radials using all four rear gear ratios, 3:73,3:91,4:10 and 4:30
My message is those long stroke motors with small stock like heads on pump gas make so much torque and HP you may be very happy with 2.76 to 3.23 gears in the rear
I ended up using 4.10 after I bent the 8 3/4 housing bad enough to need replacing, I used a truck Dana 60 and had it cut down to replace the 8 3/4, no more problems after that

What might work well depends on the engine combo, especially cam. If the cam is in the 240 range (intake duration @.050") it should handle 3.23 gears just fine. Can't help on the converter to go with it... I run a manual.

This thing has Indy EZ-1s, matching single-plane, and hyd roller 236/241 @ .050 with .541/.544 lift. But the more I read & think about this, it seems like a lot of stall & gear in the car for 512".
I'm thinking 11" with around 2400 stall & 3.55s with the 30" tires. Called PTC but they weren't able to nail down any info beyond what I already "know" about this 9.5/3500.

I know of a guy with a Challenger in full street trim, pretty mild 505/727, 3.23s & 28" tire that runs 11.50s at about sea level (Sears Point), doesn't even shift the thing manually. Don't know what converter's in it but I'm gonna ask.

I bought a Hugh's 11" rated at 3,000 stall when I installed the Gear Vendor overdrive in my Coronet. Car weighs 4,175lb, 3.54 gear with 275 15 Nitto Drag Radials. The 540 HEMI has a 248/254 @ .050 solid roller. It would blow right through the converter, and felt mushy on the freeway in overdrive. I sent it to PTC and asked them to make it as tight as possible. It is much improved. The rpm will climb 300 on a long interstate hill @ 75 mph. Flat and level a true 75 mph is 2,500 rpm.

I think you are right. I bet the engine starts to wake up in the low 2000 RPM range... should be a very torque combo. 3.23 and a true 2400 stall would drive well I bet. I run a 496 with 243@.050 intake duration cam, 3.23 and manual transmission. The engine feels very strong as I get above 2000 RPM in any gear including overdrive... and I can always drop down a gear or two if I want to fly.

I had a PTC 11 inch 2200 stall behind the 511 in my 69 Supper Bee with a GV and 3.54 gear. I built the engine for low end torque, if memory is correct I believe the cam lift was in the .456 range. Sold the car in 2015 so can’t check the cam card to be sure. This is what Ken at PTC recommended based on my build specs and it worked great with all the the low end torque the 511 made. The car weighed just under 4,000 pounds. AC, PS, PB car with bucket seats.

That must suck to have these awesome big inch motors and can’t evem enjoy them on the street. That would be sad if a lonely little 446 would bust a stroker on the street because of the tall gears and big tall tires lol. Wait a minute, I’ve seen it before lol.

It's pretty obvious these combos mentioned above were built for the street, hence the highway gearing. Just because they're trying to make their converter more efficient doesn't mean they won't currently lay some smack down.



Topside, I've been extremely happy with my combo. It's 500" with the MP 557 lift cam, 9.5" Dynamic converter as KillerBee mentioned, 275/60(28") tire, and 3.23 gears. I can drive this car all day long and cruise down the highway at 2800 RPM or less.
I drove it to the track, went 1.51 60 foot, 10.69 at 124.65, and drove it back home smiling ear to ear. That's with zero tuning.

The converter is slipping 17.5% down the track, which is a lot to me, but a couple experts have told me that it is being caused by the 3.23 gears so I'm afraid to mess with it. A modern high dollar converter might flash better and be more efficient(more MPH) but it sure would suck to spend all that money and gain little or nothing.

I am very tempted to try a 2.94 gear with a 26" tall radial at the track, and use the 28" tires for the street/highway. That should net the same ET's and be even more highway friendly.
I know it's personal preference, but I can't handle 3500RPM's on the highway like a lot of guys can.

Thanks, ProSport. I'm not sure of this PTC 9.5's efficiency; car's been trapped in my shop due to winter, haven't driven it in a couple months. Yeah, the taller the gear, the less "leverage" so to speak, so the slippage & stall increase. Similar logic applies to shorter tires' grip vs input torque at the hit.
Funny thing is, my old 438" Hemi 4-speed car with 4.10s & 28" tire was happiest at & above 3500 and it didn't bug me to run it that way; it was like a ginormous SBC in that respect. I spun it to 7500. But in my mind, once the stroke hits 4", one can take advantage of the torque available at lower RPM. I think it'll last longer as well.
70RT: I've done a couple of 446s, one pretty stout & edgy on the street. My real racecar is a low-10s ex-SS/IA SB Duster. Of the 5 cars & 2 trucks currently, every one has a job, and this car's job is to drive to the track & have fun and be a bit more carefree.
I appreciate the info & comparisons so far, thanks!

11" 2800 rated stall here. 3.54 gears in the Dana.

That combo works perfect with my 505" stroker!

Gotta love that torque

Yeah a street car that pulls the front wheels at the track leaving off idle! LOL

My rev limiter is set at 6400.

Hopefully the addition of adjustable rear shocks and relocated upper mounts will get us into the 10's n/a this spring.

This combo is so much fun to drive!

GY3 - whose converter? model# or name? flash RPM?

Turbo Action 11" 2800 stall is all I recall.

I bought it brand new 8+ years ago so I don't recall much else.

I don't run a tach so no idea what it stalls. LOL

LOL.

everyone is all about the latest greatest smaller converters but the old school Turbo Action 11" seems to still work ok huh?

how does the converter do with putting around? is it mushy feeling or pretty tight with little to moderate throttle input in high gear?

Come to think of it, I'd really like to hear from you guys with similar combos about:

Whose converter/name/model #
Advertised stall
Actual stall & slip driving
Flash stall
Cost

Might be good info for the Archives.

Until that stroker drives away from you because you run out of rpm.

Very tight. Love driving it around town and in traffic. I tried a 4500 stall and it simply did not work!

Post up some timeslips, Skippy.

I think Ehrenberg did a series in Mopar Action with a 500 cubic inch wedge. This was a 1969 Roadrunner. He was running 2.94 gears, and a Turbo Action Hemi converter. I believe the car was running low 12's. The big inch engine has so much torque it is easily able to overcome the tall gearing and the looser converter allows some rpm's at low speed. I run something similar to this in my 1968 Charger. While I don't have timeslips, I can tell you this is a fast combination and is very sweet to drive on the highways.

My Duster ran 10.49 at 126 MPH with a the original Contintental 10 inch custom built converter, it went low 10.30s at 127.+ MPH with the Turbo Action 8 inch SS/AH Hemi converter in it and it was way easier to drive on the street and at the track The Hemi 8 inch race converter acted like a stock 11 inch street hemi converter until I hit it to WOT My message is buy a really good high quality converter built for your engine and car combination for the type of driving YOU DO

Another interesting thread I need to be watching. I have the cubes and the high gear, I just have a choose-your-own-stall-speed in it.
I love seeing these good times with a streetable gear. Although most are lighter than my boat.

Your Probably right but I’ve got 6 gears and a magic button just Incase lol.

You know what we do with time slips on the street? We use them to wipe our ars with them.

Most of the poser car show guys say this so their 800 hp and 9 second quater mile claims can never be disputed.

Make sure and stay way from the track so you can keep bragging about your car's performance.

I'd like this thread to be more technical and an actual source of specific info, rather than a wiener contest.
Haven't heard back yet from 3 converter guys I've sent info to; since I don't know the true HP/TQ #s (no dyno/ET-MPH info), maybe they're reluctant to get specific.

Pretty hard to build a good converter without a dyno sheet.

Have you plugged your engine build specs into a dyno simulation program? That could get you close.

Kevin

Topside, I think you'd be happy if you call and talk to ATI and order a custom built converter from them.

There's also ALOT of local racers using Perfect Converter Company in Ohio with great results. If you call them ask for Bubba. He lives around the block from me.

The "Bold Beeper" ran a 3.23 in an 8 3/4" axle for awhile. It ran "Mid 11s" with that combo according to them. They then pulled the 727 and swapped in a "Kiesler 4L60E" 4 speed auto trans. I don't recall that they ever had any gear taller than that 3.23 but I do recall that they had a 3.55 for a short time.

Personally, I have ran several ratios in my 70 Charger. I have a 440 based 493 in the car.
I loved the 4.10s for snappy response at low speeds but 3850 rpms at 70 mph made it a pisser for the freeway. I've ran 3.23s for road trips and was pleased with them for the most part. I went with a 3.91 when I installed a Gear Vendors unit. That was a great combo but the GV had a few quirks so I pulled it out and sold it to a Moparts member that is quite happy with it now. I currently run a 3.55, a 28" tire and an 11" Converter from Ultimate Converter Concepts. Aside from gas mileage, the combo runs and performs great. I'd love to install a 4L60E 4 speed auto from SST but I'll have to save up a bit to get there. Lower freeway RPMS are not just a matter of better mileage, it is also much more comfortable. Lower RPMs= quieter, less vibrations and less wear on the engine.

You seem to live around the block from nearly everything cool.

Yes, lots of racers and fabricators right around me, Summit Racing is a few blocks away, and several dragstrips within 45 min. Plus there are local car shows every day of the week.

Recently I went to Perfect and I could not get what I needed to clear the nose and the pump so I sent my PTC in to get adjusted instead.
ps: don't get me wrong there are people with good results using their Vert.

Well, I think I'm gonna step back, swap in the 3.55s first, drive the car when the weather's decent, and see how it behaves.
Anybody got a desktop dyno program I can "borrow"? Last one I bought uses a floppy disc and I have nothing nowadays that accommodates a floppy.

’67 Coronet

505 with Eddy head std port

Flat tappet
.585/600
260@50
268@50

28” tire

With 3.23’s
11.50’s
Trap RPM about 5700-5800 @116-117
And 2900-3000 @ 70mph on the highway

With 3.54 in Dana
Trap RPM about 6000-6100 @120-121
11.0’s when exhaust is off
3200-3300 @ almost 70mph on the highway

9-1/2 convertor is more street friendly
8” convertor is obviously more loose and you have to think about pulling out of a parking lot or Dunkin to accelerate

Doesn’t matter which gear or convertor is in the car……..@ 45-50 mph in manual 2nd it break the tires loose

No doubt! I occasionally replace the Drag Radials with regular 275 street radials for a true radial class at our track. It is downright scary when you jump on it at the top of 2nd gear on the street!

I'm about to find out how a Dana with 4:10 is going to be like in my Challenger. Most of the shows are close and I trailer to the track.
505 low deck stroker
Trick Flow heads.
Solid flat tappet cam. Sorry, don't have the spec in front of me.
Comp Cam 23-232-4
26 inch tall Mickey Thompson in the rear.
727 with a converter with around 3,000 flash.
Calvert leafs, bars and adjustable shocks.

Right now I have the stock 8 3/4 with 2:76 gears.

I have a feeling I'm not going to want to do much highway driving...

4.10 gears with a 26" tire is gonna make some RPM's.

How does the car run and handle on the track with the 'regular' radials? One of my local tracks has a class like that and everyone wants me to run in it. Seems to me like it would be an ice skating rink.

I run a Dynamic 9.5 converter that will flash about 4200 at the track. And I use 4.30's with a 30" tall tire. I will say it drives great with that converter as it has no slippage driving around even on back roads at 2000 rpm and in that area. I honestly feel like my car may go faster with less gear as I trap about 6400 and it pulls real hard from 5000 to 6200. I just don't think I need that much gear with my 493 eng. I would be very curious to see how the converter works and drives with say 3.91's in the car as the converter was actually built for my old 440 and I just put it back in behind the 493 and it has worked nicely. I really hope to maybe swap in a 3.91 or 3.73 pumkin into my 8-3/4 rear and try it. But I will say I really like how nice the Dynamic converter works and how it drives so nice even at lower rpm's without it sounding like it has any slippage to me. Good luck with yours , Ron

I think that higher gear ratios will make the converter feel a bit softer down low on the street. And may impact the flash at the track, too.

But there won't likely be a huge difference just going from 4.30s to 3.91s.

Silver67,

Just curious your results for;

-3:23 with the exhaust off.
-3:54 with exhaust on.

Not bad at all. I run Mickey Thompson Street Radials and they like 20-22psi. I leave in 2nd gear and put 100+ lbs.in the trunk over the rear bumper. Managed 1.72 60 ft. on a prepped track and got runner up in the last race. Typically runs about 11.70's on that setup so I dial a 12.0.

The car goes straight as a string and works really well leaving off idle.

Here is a pic of the launch: