8 inch converter questions...

[73Scamp318]

I'll just start out with the current specs:

74 Duster, unknown weight, probably 32-3400 race weight
full interior
subframe connectors
no heater

360 .060 over, 10:1
stock crank, rods, & Speed Pro hyper pistons
Milodon pan and windage tray
HV oil pump
OOTB Edelbrock heads
Edelbrock Perf RPM cam 7177, 234/244 int/exh @.050
1.6 Hughes roller rockers .520"/.544" int/exh
RPM Air Gap
Holley 750HP DP, 1/2" open spacer
Mopar Performance distributor, 18* initial, 35* total, all in by 2500
Taurus electric fan
1 5/8" cheapie headers to 2.5" exhaust dumping at the axle, Flowmaster 40s, and cutouts

9.5" PTC converter
rebuilt TF727 with TCI Street Fighter valve body
8.75 rear with 4.30 gears and Sure-Grip
Nitto NT555R drag radials, 275/60-15
small block torsion bars, 90/10 Lakewood front shocks
002/003 SS springs, snubber, CE adj 3-way shocks
Mallory 140 fuel pump, Mallory bypass regulator, 1/2" line to and from the tank

I am currently running 12.0-12.1 @ 110-ish with mid-to-low 1.6 60-foot times and am planning a cam change this spring. I'm currently leaning towards something [email protected] and .550-.600 lift. I have a ported Victor 340 that has been sitting on the shelf that might be a better fit than the Air Gap for the new cam.

While I'm at it, I'm considering pulling my 727 9.5" PTC converter that flashes to 4200 and going to a 8" converter that would be purchased after I finally buy a cam. I'm shooting for mid-11s with the new combo.

I have some questions, since this is unfamiliar territory...

The 727 is basically stock, other than a 5:1 lever, HD band strut, TCI Streetfighter VB (has the low band apply), and the converter. I haven't had any problems with it and it works well. Do I need to do any upgrades to safely run a 8" converter, like a bolt-in sprag, billet drum, trans blanket, or some kind of unobtainium widget I haven't heard of?

Has anyone run a 8 inch converter on the street? I'd like to be able to get out on the highway with it and be able to run between 3000 and 3500 RPM without problems. I have an external transmission cooler plumbed in after the cooler in the radiator.

I'd appreciate any input, since this may be a tall order. This is a street/strip car and I can tolerate quite a bit, but it needs to be able to get around on the highway without riding on a trailer.

 

[BVoelzke]

Years ago I broke my good 340 so I put in a 318 that a friend had ,put on a ld4B intake a mild cam and unported 360 heads with headers and mufflers it was going 13.20-30s with 3.91 gears. I had a 904 with a manual valve body and a 10 inch convertor. I put in a Turbo- Action 4600 stall 8 inch convertor and it started going 12.70s, I don`t remember the 60 ft times and it wasn`t driven on the street. When I fixed the 340 I put in a 557 lift M/P purple shaft cam, heavily ported J heads and a Victor 340 it went a best of 11.36 but with 4.56 gears. Same convertor and trans.

 

[flyfish]

I drive my car on the street with 8" PTC converter. It acts very similar to my old 10" converter just puttin around town...unless I smack the load peddle. Get a good trans cooler and you should be fine. A trans blanket would be a good idea for any car with decent power. I would definitely do that no matter what else you do just for peace of mind.

Just my 2 cents on going to a bigger/better cam (great idea by the way)...you may want to spend the money you have for the converter on porting those Eddys instead. That way you can really take advantage of the bigger cam...just something to consider.

 

[clinteg]

When I talked to Dynamic the other day, I was contemplating between their 9.5" and their 8". What they had claimed was that my car might be 1.5 to 2 tenths faster in the quarter but would probably run AT LEAST a few hundred rpm higher on the highway. They were unsure as to how much higher though. I guess it all depends on what you're wanting to do. They also claimed that their 9.5" would be 3 tenths faster than any other 4000 stall 10" converter out there. Is that true? I don't have any idea. Do you want the fastest converter you can put in the car? 8" is your converter but if you're running around town, make sure you have a decent trans oil cooler. I didn't want my car screaming at 60 mph so I went with the 9.5". It should run right around 3000 rpm at 60 based on another member's identical setup. I didn't see that the extra $300 for the 8" was worth it for what I'm doing with the car. But for you, it may be totally worth it.

 

[73Scamp318]

Thanks for the responses.

BVoelzke, I'd love to see a half second drop in ET from just a converter change...it sounds like you just dropped it in an ran it.

flyfish, do you get out on the highway with it at all, say in the neighborhood of 60 to 70 mph? Does it run about the same RPMs as your old 10" converter? I've been real happy with my PTC 9.5 and I have a couple of guys lined up to buy it off of me if I change it.

I'm kicking around the porting idea now...I'm in a pretty good spot, less than 120 miles drive to either Mid America Racing Engines or Schurbon Engine Services, both of which have been competitors in the Mopar Muscle engine challenges. I think either would probably work well for porting the heads, though I may put this in the future upgrades category when I decide that I need to be able to run 10s

clinteg, that's what I was looking for, though Dynamic's responses were kind of vague. The trans cooler I'm running right now in series with the one in the radiator is no monster, but I haven't had any issues with trans temperatures. It wouldn't take much to get one about four times the size of the current one in the same space.

 

[DarrylsDart]

I have a 8" A1 convertor in my 70 Challenger street car and it works great!
At highway speeds It did gain 100 RPMs over the 9.5 convertor that it replaced.
The Challenger is a .030 over 440 with ported Indy SR heads, solid roller cam, 1050 QF carb and a DP intake.
I have a low first gear set in the trans but I only run a 3.55 gear.
The car weights about 3700lbs with me in it.
One Sunday morning last summer I jumped in the car put the top down and headed up I-17 from PHX to Flagstaff to see how the convertor would do.
I drove 50 miles north into the mountains running 65-70MPH, around 3000 RPMs.
The convertor had NO problem what so ever.

By the way I also have a 1969 Dodge Dart that is a SB street/strip car that runs very low 11s with a 9.5 convertor but A1 sent out my new 8" convertor today so I will be pulling the trans this weekend to be ready for the new convertor.

 

[Rob Eppler]

Thats a sharp challenger!!! Converters are VooDoo...what may be right for your engine will not be so good for another combination. I run an 8" in my Cuda, [440/Dana 3.54] It works really well. I have had it in the car for many years...trouble free. Wouldn't change it unless it broke...[Turbo Action] Just have fun...you will never figure it out unless a chassis dyno/drag strip is near by. And a few converter r & r's.

 

[BigWilson87]

Just my 2 cents on going to a bigger/better cam (great idea by the way)...you may want to spend the money you have for the converter on porting those Eddys instead. That way you can really take advantage of the bigger cam...just something to consider.[/QUOTE]

This is good advice from flyfish. You have a pretty well matched combo now. Although a cam change would help, I think I would reccomend only one change at a time. The 1.6 rockers are really helpjng that edelbrock cam. I think the first thing i would do is have a decent porting job done on the heads as well as a QUALITY valve job that includes backcutting the valves. That should put you solidly in the 11's. Next would be a well reserched step up to a solid cam. Sounds like a fun, low maintenance set up.

 

[flyfish]

Thanks for the responses.

BVoelzke, I'd love to see a half second drop in ET from just a converter change...it sounds like you just dropped it in an ran it.

flyfish, do you get out on the highway with it at all, say in the neighborhood of 60 to 70 mph? Does it run about the same RPMs as your old 10" converter? I've been real happy with my PTC 9.5 and I have a couple of guys lined up to buy it off of me if I change it.

I'm kicking around the porting idea now...I'm in a pretty good spot, less than 120 miles drive to either Mid America Racing Engines or Schurbon Engine Services, both of which have been competitors in the Mopar Muscle engine challenges. I think either would probably work well for porting the heads, though I may put this in the future upgrades category when I decide that I need to be able to run 10s

clinteg, that's what I was looking for, though Dynamic's responses were kind of vague. The trans cooler I'm running right now in series with the one in the radiator is no monster, but I haven't had any issues with trans temperatures. It wouldn't take much to get one about four times the size of the current one in the same space.

I don't get out on the highway much with my car. Most of my driving is in town, going between 35-50. I know going stoplight to stoplight it is not too different unless I lean on it a little. To be honest though, I drive like a grandma around town....my car is loud, purple, and practically screams PULL ME OVER. I learned about 20 years ago that in order to NOT get pulled over in this car I had to really be careful with the right foot :-D.

 

[mikedevore]

Any thoughts on switching to a 904?
Since you changing the convertor & the 727 valve body will work in the 904.
Also, the 904 isn't as prone to blow up as the 727.
You will also save about 35LBS of rotating weight plus the trans is lighter to.

My kids first hot rod was a Dart Sport street/strip car.
3.91 gear, 904 w/9.5 Dynamic convertor, 360 with KB107's OTB Eddy's, Hughes solid cam.
The car ran 11.80's with full exhaust.
The Dynamic seemed to lock up better at cruising speeds than others that I had used in the past.

I currently ran 904's in both race cars that I have, no concerns with them, just free horse-power.

 

[73Scamp318]

I'm lucky enough to have a 1/4 mile drag strip right on the edge of town, so I get to flog my Duster at the track quite a bit. I've had two goals with this car from the get-go with no power adders or transbrake, I want it to run solidly in the 11s and I want daylight under the front tires.

I have tinkering I'm planning on doing with the suspension yet, which may get me both of these goals, but I want to do something a bit more drastic and change up the combo. It sounds like the 8" converter should be pushing it, but still streetable...though I'll have to weigh it against getting the heads ported.

I had considered the change to a 904, but it'd open a new can of worms, requiring another transmission, converter, and driveshaft, putting me way over what I have to spend. I'd like to, but it's going to cost quite a bit more than I've got.

Anyone have a rough guesstimate on HP gain going from OOTB to ported Edelbrock heads? I'd probably be staying with the 2.02/1.60 valves and however far I can get with around $1000 worth of work.

 

[70aarcuda]

call Modern Cylinder Heads in Michigan and see what their going rate for CNC the eddy heads....you might be pretty close ...and that includes the valve job...setting up the springs ...etc.

 

[clinteg]

Does anyone have any in car videos of how an 8" converter acts driving around town? I searched youtube but couldn't really find anything.

 

[mshred]

I am not so sure why everyone hears 8" converter and then thinks "how streetable?"

8" is just the size...although 8" converters by nature do create more heat and flash stall quicker then larger diameter converters, that does not make them unstreetable. How tight or loose the converter is will effect the cruise rpm's the car sees and transmission temps as well, but even with a loose converter, you just aren't going to have a bear of a time on the street like everyone makes it seem. Comparing other peoples cruise rpms with a similar size converter will also be misleading- every converter is going to slip slightly differently, and that will effect cruise rpms.

I street drive my A1 8" converter with 5500 stall EVERYWHERE...Drives like a regular car, that is until I stomp the gas to make a stop light or play around with it and it flashes to 5k in a hurry, which if anything is fun, not bad lol. I run a B&M trans cooler in front of the rad (fluid does not pass through the rad) and my trans temps have NEVER gotten over 180 on the hottest of days. On the highway I cruise at 3200rpms around 60mph with a 28" tall tire and 4.10 gears...My limiting factor is my half filled block and oil getting too hot, not the trans at all. Even at the track, back to back passes in very hot humid weather the trans never gets hot (I have trouble putting temp into it!)

I also wouldn't go through the trouble of switching to a 904- I usually build my stuff "strong once", but I chose to go 904 when I went auto thinking it would hold my power goals...well I am about to surpass those goals this season, and am wishing I had gone 727 to start...just my 2 cents.

Not sure why all the converter companies make 8" race converters sound like the death of a street driven car, or why people think "high stall converters" are un streetable...Its a regular car until you mat it, and it sure is fun to smash the gas and fly past everyone around you (while also at the same time having them **** their pants). Put a good cooler on it and you'll be fine.

For the record, I wouldn't use A1 again, but thats just my personal preference. I have a 9.5" nitrous converter on the way from another company. As was mentioned, getting a converter right is like voodoo.

 

[mshred]

By the way, Rob Eppler and Darylsdart, your challenger and cuda pictures look BADASS! Nice rides!

 

[clinteg]

I am not so sure why everyone hears 8" converter and then thinks "how streetable?"

8" is just the size...although 8" converters by nature do create more heat and flash stall quicker then larger diameter converters, that does not make them unstreetable. How tight or loose the converter is will effect the cruise rpm's the car sees and transmission temps as well, but even with a loose converter, you just aren't going to have a bear of a time on the street like everyone makes it seem. Comparing other peoples cruise rpms with a similar size converter will also be misleading- every converter is going to slip slightly differently, and that will effect cruise rpms.

I street drive my A1 8" converter with 5500 stall EVERYWHERE...Drives like a regular car, that is until I stomp the gas to make a stop light or play around with it and it flashes to 5k in a hurry, which if anything is fun, not bad lol. I run a B&M trans cooler in front of the rad (fluid does not pass through the rad) and my trans temps have NEVER gotten over 180 on the hottest of days. On the highway I cruise at 3200rpms around 60mph with a 28" tall tire and 4.10 gears...My limiting factor is my half filled block and oil getting too hot, not the trans at all. Even at the track, back to back passes in very hot humid weather the trans never gets hot (I have trouble putting temp into it!)

I also wouldn't go through the trouble of switching to a 904- I usually build my stuff "strong once", but I chose to go 904 when I went auto thinking it would hold my power goals...well I am about to surpass those goals this season, and am wishing I had gone 727 to start...just my 2 cents.

Not sure why all the converter companies make 8" race converters sound like the death of a street driven car, or why people think "high stall converters" are un streetable...Its a regular car until you mat it, and it sure is fun to smash the gas and fly past everyone around you (while also at the same time having them **** their pants). Put a good cooler on it and you'll be fine.

For the record, I wouldn't use A1 again, but thats just my personal preference. I have a 9.5" nitrous converter on the way from another company. As was mentioned, getting a converter right is like voodoo.

Thanks for the info mshred. Now I'm debating calling Dynamic back and telling them I want the 8" instead. lol

 

[mshred]

Honestly dude, if you car is on motor and the stall is right, the 8" will be the ticket at the track...and with a good cooler that gets sufficient airflow (which imo you would need with ANY aftermarket converter, whether it be a 3000 10" or a 6000 stall 8") you will be fine! In fact, I LOVE smashing the throttle on the street and getting it right up to 5k...Never forget the first time I did that because I couldn't stop at a yellow the chick beside me in her car nearly shat herself! LOL

Just my opinion, but some good companies for converters- Ultimate, PTC, Pro Torque, ATI, FTI....they all seem to make a good converter, you will pay for it, but they will work with you to get it right (and don't be surprised if it has to come out of the car a time or two to get it RIGHT)

Good luck!

 

[BVoelzke]

I agree there is more to it than just putting a convertor in, many factors are considered when building the convertor for your application, rear gear size, cam lift, carb size, trans brake or not etc. I use Lenny at Ultimate for my convertors he has done the T/A 8 inch in my car now, my spare 8 inch and the lock up convertor in my D150 and all are excellent! Quick story.... about two years ago I was considering a store bought 11 inch convertor for my low 15 second 5.2 D150 I called Lenny and he said send me your stock lock up convertor, I did , he redid it and i picked up over a tenth in 60 ft, now going 2.0s in 60 ft compared to high 2. teens it used to .

 

[DarrylsDart]

By the way, Rob Eppler and Darylsdart, your challenger and cuda pictures look BADASS! Nice rides!

Thanks for the kind words mshred. Your car looks to be a real nice ride also.
Well I just spent the last two nights installing my new 8 inch A1 convertor in the Dart, just took it for a ride around the block and it seems way to tight. Guess I should have not told them it was going in a street car.
I am going to drive the car to work tomorrow maybe it will loosen up some. LOL.
This weekend NHRA is in town so I will not be able to test it for a week or two.

 

[mshred]

Thanks for the kind words mshred. Your car looks to be a real nice ride also.
Well I just spent the last two nights installing my new 8 inch A1 convertor in the Dart, just took it for a ride around the block and it seems way to tight. Guess I should have not told them it was going in a street car.
I am going to drive the car to work tomorrow maybe it will loosen up some. LOL.
This weekend NHRA is in town so I will not be able to test it for a week or two.

Thanks for the kind words as well! I like to think she isn't the ugliest duckling lol

Hopefully A1 gets it right, or it acts different at the track. I had a problem with my converter being made correctly to fit right off the bat, the stall was too tight...I got it re-stalled (although I really don't feel like they listened to me and the data I had) and it was still too tight for my car (it only loosened up by maybe 200 rpm). After all the money I spent on it, and the back and forth shipping, I would go elsewhere next time personally.

I hope you have better luck than me. Even though my car is street/strip, whenever I get parts for it like converter, cam, etc. I always tell them make it like its a race car, and I'll deal with the street manners lol

 

[flyfish]

............ Even though my car is street/strip, whenever I get parts for it like converter, cam, etc. I always tell them make it like its a race car, and I'll deal with the street manners lol

This is SOOOOOOOO VERY TRUE......been there, done that, had that headache too many times....lol.

 

[mshred]

This is SOOOOOOOO VERY TRUE......been there, done that, had that headache too many times....lol.

To be honest, I don't mind race car manners on the street...keeps it interesting, otherwise it would be just like driving any other car