question about converters

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tom340

tom340

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New motor has been in @ 4 weeks now. Been driving the car around to get a feel for things etc.. We have an 11" Dynamic converter installed, and yes Im sure I made the wrong choice. The converter is basically "locked in" right from idle. You can hit the pedal to the floor from idle @ 850-900 rpm and barely haze the tires. Very odd, the motor just a few short weeks ago pulled 430HP and 440 Tq peak on the dyno at the crank with undersized 1 -5/8" headers and the carb a bit lean. (The factory 275 hp was enough to roast the tires..) Even from a roll, say at a road speed of 50mph you can mash it and the responce is poor. Anyhow, question about the converters, does anyone know what the factory rating stall speed was on OEM torque converter? Flash stall speed?? Any experience with comparisons to a modern Dynamics 11" to the stock Hi-po 340 converter '68-70?? Thanks tom
 
I called them earlier this afternoon. Spoke to Shawn. Im not 100% sure what the specs are on this 11"..Im guessing stall speed @ 2500 advertised, not sure what the flash stall is. Believe me, the question has come up if there is something not right about this converter. Shawn says, based on the cam specs and some dyno info the converter "is not matched up".. But to be locked up from idle? I saw in last months Mopar Muscle the guy with stroked 70 Duster running LOW 12's-NO traction at all with a "stock oem" converter.
Same distributor, coil, plug wires, harness and ECM used on Dyno thats in the Duster.. Only components added: full exhaust and trans/converter
 
Stock is low like 1500-1800. Sounds like something else isnt right though. Even with the wrong converter it should melt the tires.
 
Many of the old car ads indicated that Hi-Po motors with automatics came with hi stall speed convertors, but I have not seen any actual numbers. I finished putting my 69 340 Dart back together last summer. With 75k on the car, I thought about spending money on a transmission rebuild and a new convertor, but decided to just change the fluid, filter and the input seal and bolt it back in. The original trans and convertor still run great. It shifts firm and quick enough to chirp 2nd gear, break the tires loose, and kick car slightly to the right. In my opinion, the original setup was just right.
 
I think 1800 was considered the "high stall" back then LOL
 
If the advertised stall is 2500 then the flash should be around 2900. I'd say there is something wrong if it's as tight as you say. However, even if you had an old classic converter you should still be able to roast the tires unless you got some crazy gears like 2.92, actually what gears do you have.

Terry
 
demon seed said:
If the advertised stall is 2500 then the flash should be around 2900. I'd say there is something wrong if it's as tight as you say. However, even if you had an old classic converter you should still be able to roast the tires unless you got some crazy gears like 2.92, actually what gears do you have.

Terry
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Thats what I was thinking. I highly doubt your running tall gears, but that would be one thing to look at as well. Build your stall around your gears is what I was told.

My parts car has 2:73's in it. That poor thing has never spun a tire in its entire life!! Could you imagine:angry7:?
 
Tom340,
Not that you don't have a converter issue going on here, but I would be looking at my timing just to make sure something hadn't slipped and also make sure the secondaries are opening up all the way. If you "mash it at 50" and the response is that poor with those kind of Dyno numbers, something sure is wrong.
 
Mopar always had better converters than the average GM product. The typical OEM "high Stall" converter gave you about 2000-2300 RPM. A regular converter typically stalled at 1600-1800. By way of comparison, a TH400 behind a Buick stalled at 1200-1500. No wonder there is such an aftermarket for performance converters for GM engines.

I would consult your converter manufacturer if you are unhappy or feel they sent you the wrong part. any reputable convereter shop (and Dynamic is certainly reputable) should be able to identify the prob,em and make their product work as advrtized
 
{You guys came up with some good stuff..few answers in no particular order. GEARS: 3.55:1. Timing: the engine builder was over Monday and did a THOROUGH check of what he could. Total advance and idle timing are just fine. Compression check shows we are perfect on all 8 cyl. SECONDARIES: adjusted and working Ok. Primary metering rods changed to richer and lighter springs. Also tried 3 carbs, mine works best.} Some research from today: Again talked to them at Dynamic. (Im learning much about converters) They take the information provided-and you needs to be accurate-and they do the figuring. being this is a high torque stroker application and not a stock or "bolt-on" mod 340 the correct converter will ask to stall at a very very high rpm. By nature of their design-the 11" street converter (live and learn) is pushing the advertised 2600 rpm stall speed to its lowest extreme, if not lower . My motor, as built, is asking for 3800-4000 rpm stall. He says it will seem like Im losing 75-100 Hp. with the 11" street converter. My friend Greg's R/T Chally 383 (engine built by same guy, he uses the 9 1/2" Dynamic) can smoke them off idle. We virtually have similar HP/Tq figures and just 10 C.I. difference. Also: had 1/2 hr chat with a chassis dyno tuner/experience musclecar and drag racer today prior to scheduling an appointment. To summarize: after a give and take of detailed information like cam specs,compression, cubic inches, exhaust, weight, tranny, gear ratio, ignition etc.......he didnt even pause for a second and said I needed the 9 1/2" converter. He said with the 11" it "must feel like your towing a car on a trailer behind you". He uses the Dynamic converters exclusively for street/strip or strip only. He says mine is a worst case scenario for chosing an incorrect component. (Adam is right about the stock converter stall speed, 1800 RPM) However the construction is way different than a Dynamic due to the pitch angle of the fins internally. Thus the ability to spin wheels off idle and create at least a minimum stall. . However you suffer with slippage at cruising RPM, poor economy, heat buildup. My last potential issue could be chosing to use factory manifolds for a stock look. We couldnt test with them on the dyno due to fitment issue. I was figuring it would kill me by at least 20 hp & tq. (from what I have read from prvious test) and can live with 410 HP if thats the case. Chassis dyno tuner says at this level with some headwork and my cam specs like I have he has seen it hurt performance 25-50 hp from idle to peak rpm . He told me before I do this (chassis dyno) to swap converters at least because the chassis dyno results "will make me sick" . I should expect a 22% loss with auto trans and should be @ 345 RWHP if I used the way too small 1- 5/8" cheapo headers like on the dyno run. My current 11" converter and manifolds may limit it to 250-260 RWHP. :( Not good. So it looks like Im about to find out how important the correct converter is. $$$$$$ I may need to steal from the basket at a local church Sunday-keep an eye for my name in the police blotters!
 
By the way-if I do a "brake stall" as much as the cars suspension and brakes will allow the car will ROAST the tires and I can feather the gas pedal for literally an eternal burnout-or until im out of gas or the tires melt which would be more accurate.
 
A good converter is money well spent Tom. Did Mike build your motor ? I know he did Korrys.
 
The other Mike. Not Pettit. Hes next door. I tell ya what, a bunch of machinist talent in that little corner of the world! Mine was dyno'd on the pettit machine- I wound up buying a nice set of heads from him too, the older style swirl port MoPar perf. heads. All the drag and circle track guys have scooped them up and wont part ways. My Mikey is, well much more detail oriented :) Precise, deliberate, neat and organized. Spent 3 hours at the house Monday just to be absolutely sure everything is the same as 4 weeks ago with the motor.
 
One more day-more BS. Im DONE with these guys at Dynamic. Attempted to negotiate a fair swap on this 11" converter they claim on their internet site has a stall speed of 2600-3200 rpm (which would work just fine) Afterall, they GAURANTEE their product for 1 year and WARRANTEE for 5 years, right? After 11 phone calls since Wednesday, they insult me by offering $100.00 off towards their 9 1/2" and I would need to ship the 11" converter TO them at my expense. Thats $40.00 for 3-5 day, nets me $60.00 off a $600.00 converter. Their net profit would be a total of $1,000.00 for one converter sale, and then he'll RESELL my 11". They wont take my credit card- certified bank check OR money order only.. Credit card purchase offers the consumer protection-they claim its a "problem" to credit an account $100.00. My *** it is, I own a small business and its easy. I'm steaming over this company and their smug attitude. My engine builder invested a considerable amount of time with them trying to fit a converter that would work for me into my budget and this 11" was ONE of the recommendations. What kills me is how Dynamic "can diagnose" from Delaware that the converter "works fine", just the "wrong choice"....The 9 1/2" they make is the solution to all of lifes problems.
Mancini racing sells these converters-AND they have a slight problem with these guys! Dynamics specs are a conflict with real world findings-flat out FALSE ADVERTISEMENT. Go check out their website yourselves. Mancini does not advertise the 11" street as a 2600-3200 stall speed, instead they use a 2000-2200 rpm spec. A call to them reveals the 11" street converter is not as good as advertised and is one tight *** converter!
I would have considered a full refend, I'll pay to ship their lump of crap to them to pawn off on someone else, and eat the labor , then purchased the expensive 9 1/2" from them and been done with it. Based on their "GAURANTEE" and falsely advertised converter specs I believe I was being more than fair.
 
My motor, as built, is asking for 3800-4000 rpm stall.
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that sounds like a big problem. if your getting 2600 out of the converter and the motor doesn't make power till 3800 thats is not good.. suprised it even idles below 1300 rpm . i run the dynamic 9 1/2" converter and man its incredible. it woke the car up big time.
 
abodyjoe said:
that sounds like a big problem. if your getting 2600 out of the converter and the motor doesn't make power till 3800 thats is not good.. suprised it even idles below 1300 rpm . i run the dynamic 9 1/2" converter and man its incredible. it woke the car up big time.
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I take that back partially. Flash stall is what I meant. I would be happier with 2600 stall and 3400 flash, at least I could live with it vs. what I have now. The motor made gobs of power below 3800, over 400 tq at 2800 rpm but the cam duration is over 272 and the car is barely 3100 lbs. (not one single power robbing option) My setup is asking for 3400-3800 rpm flash stall.
If these guys at Dynamo didnt piss me off so bad I would use their converter again. Their mis-advertised 11" which fit my budget would have been at least adequate...maybee not the "best" option, but adequate had it worked like they claimed before ditching me.
 
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