Stall on a Stock 904 Converter?

[318willrun]

Brake stall on my completely stock 318 - 1800 RPM. Same converter with a low compression 360 with a MP 268/272 - 450/455 cam - 2100 RPM brake stall

Yep, engine torque plays a big part of what the converter will stall at.......

 

[73Swinger18]

Stock 904/318 combo had two converts, a low stall and a high stall. Difference between the two of them about 3-400 rpm. Low stall typically around 1600 to 1700. From the photo, the converter you're showing is NOT an original converter, but a rebuilt. The factory does not paint converters. I don't know what it's like down South, but when I worked in the industry, two Mopar converters that were always CORE IN FIRST, HEMI'S AND 340'S.
Contact a builder of high stalls, give them all the information on your engine build and what you've put into it, rear axle ratio, tire size and what you will be mainly using your car for. This is the only way you'll get the converter that is best for your needs. Check with a number of these companies not just one to get their recommendations.

Remember, Summit, Jegs, etc. do not build converters. They buy them from a wide variety of converter builders, and at times they buy based on price. I'm not knocking these companies, but they may lack the knowledge to get you the converter for your application
At all costs, avoid used converters, as you never know of what they look like internally without cutting them open.

Thanks for the good advice! There is a reputable converter business near me I will contact once everything is together. I had the tranny resealed and a shift kit installed. That converter was the one that came with the tranny. It was rebuilt and repainted. I may wait to see if I can get a bigger rear end as well.

 

[AJ/FormS]

If it was mine,I would pull a head off and measure stuff. I have reused head gaskets two and three times.
But failing that, like T-N-T says,2800 will get you back some grunt.
And that rear has got to go. Someone said your car will be a turd to 30mph. I say more like 40.
The engine won't wake up until maybe 3500rpm.Those 205/70-14s are about 79.5 in circumference.
So
(3500x79.5)/ (1056x2.71x2.45)=39.7mph. Getting to that 3500 is gonna be the big deal.But I guess that teener might spin one of those skinny donuts, so it might not be so bad. At least until the spider-gears seize up...............
But, I can see the disappointment on your face already. So with the lack of compression,you are gonna need 4.10s to get going by 26 mph, and at least a 2400 to do so with any kind of authority.
3.55s will make it 30mph. But the loss of torque multiplication means you need more TC;perhaps 2800
Of course a DP carb, well tuned,might make the 3.55s move out a little better.... Oh wait, no compression,scrap that idea. No compression means, the engine will likely bog,perhaps big-time, with a DP,even with 3.55s and a 2400.
At this point getting the compression up to where it needs to be is still cheaper than all the other options. And waaaay more satisfying in the end. If you boost the Dcr up to 8 or even 8.2, you may get away with the stock TC. And I bet you were gonna put 3.55s in it anyway. And at that point,she will be ready to rock.
So, a Static C/R of 10.3 would get you a Dcr of 8.1 and 162psi; a really good start. This Scr, requires a total chamber volume of about 71cc. That is doable, with teener heads.But you are gonna need to get the pistons way up.Ima thinking Zero-deck.
So a new set of pistons,a bit of machining, plus 3.55s and a suregrip for that 7.25,and the stock TC(which will now stall probably up to 200 rpm higher); versus a big TC and 4.10s,and still the suregrip. Since the current pistons have never run, they are still worth good coin.In the end,perhaps a bit more money spent, but a way funner combo. And better fuel mileage to-boot.
I know what I would do. But I'm used to backing up and starting over I have made a lotta mistakes over the years. But one of the worst was camming up a stock-compression 73 teener with 2.73s and a stock TC. I must admit tho, it did have pretty good passing power................. at 70plus mph..............kicked down into second!

 

[73Swinger18]

If it was mine,I would pull a head off and measure stuff. I have reused head gaskets two and three times.
But failing that, like T-N-T says,2800 will get you back some grunt.
And that rear has got to go. Someone said your car will be a turd to 30mph. I say more like 40.
The engine won't wake up until maybe 3500rpm.Those 205/70-14s are about 79.5 in circumference.
So
(3500x79.5)/ (1056x2.71x2.45)=39.7mph. Getting to that 3500 is gonna be the big deal.But I guess that teener might spin one of those skinny donuts, so it might not be so bad. At least until the spiders seize up...............
But, I can see the disappointment on your face already. So with the lack of compression,you are gonna need 4.10s to get going at 26 mph, and at least a 2400 to do so with any kind of authority.
3.55s will make it 30mph. But the loss of torque multiplication means you need more TC;perhaps 2800
Of course a DP carb, well tuned,might make the 3.55s move out a little better.... Oh wait, no compression,scrap that idea. No compression means, the engine will likely bog,perhaps big-time, with a DP,even with 3.55s and a 2400.
At this point getting the compression up to where it needs to be is still cheaper than all the other options. And waaaay more satisfying in the end. If you boost the Dcr up to 8 or even 8.2, you may get away with the stock TC. And I bet you were gonna put 3.55s in it anyway. And at that point,she will be ready to rock.

Thanks for the in-depth let down haha. No problem. Was planning on getting a bigger rear end sometime anyways. Not cool with one tire roasting. I talked with the machine shop and they shaved off 0.005" on the block and heads using stock size gaskets. Not sure if that would do anything though. Thanks again for all the help.

 

[AJ/FormS]

Hey, here's an idea; since the engine is assembled, you can run a compression test. You are looking for pressure in the 160 to 170 zone.
I'm gonna suggest;
-Over 160 can use 2000/2200 (like a stocker),and maybe as low as 3.23s. Strong runner, with good fuel mileage.
-Under 150 needs 2400 and 3.55s. Still strong but down on mileage.
-Under 140 needs 2800 and 3.91s. Not so good for street
-Under 120 needs 3200 and 4.1s;needs a rethink; kindof terrible for street.
-Under 100 needs a tear-down, something is wrong.

 

[T-N-T]

Unless my math is off, that's only 0.09" shorter than the Keith Black pistons. That doesn't seem like a lot. I wonder what the stock piston compression distance was in 1973?

Your math is right but you need to consider the actual deck height of the block. Most are at least .010 taller then the stated deck height of 9.6(9.599). I have seen blocks that were .030" taller. .010 to zero deck height is what I shoot for normally. A piston at .010" down is pretty easy to compensate for with a thinner head gasket.

 

[T-N-T]

Thanks for the in-depth let down haha. No problem. Was planning on getting a bigger rear end sometime anyways. Not cool with one tire roasting. I talked with the machine shop and they shaved off 0.005" on the block and heads using stock size gaskets. Not sure if that would do anything though. Thanks again for all the help.

Whatever you do don't waste your money on doing anything to your 7 1/4" rear end. Find at least an 8 1/4" sure grip rear end to replace it with.

 

[73Swinger18]

Whatever you do don't waste your money on doing anything to your 7 1/4" rear end. Find at least an 8 1/4" sure grip rear end to replace it with.

I just posted a wanted ad for a 7.25 Sure Grip....you must have seen it.

 

[T-N-T]

I just posted a wanted ad for a 7.25 Sure Grip....you must have see it

Yup... Save your money and buy a stronger one. I have exploded three 7 1/4's over the years, one on the first test drive after replacing a slant 6 with a mild 318. It lasted for about 10 minutes or one hole shot depending on how you look at it. I broke the pinion and locked it solid. I've replaced about 10 other 7 1/4"s over the years that failed on other people too. A built motor with a stall will make them go boom.

 

[73Swinger18]

Yup... Save your money and buy a stronger one. I have exploded three 7 1/4's over the years, one on the first test drive after replacing a slant 6 with a mild 318. It lasted for about 10 minutes or one hole shot depending on how you look at it. I broke the pinion and locked it solid. I've replaced about 10 other 7 1/4"s over the years that failed on other people too. A built motor with a stall will make them go boom.

You had issues with the Sure Grip ones too?

 

[T-N-T]

You had issues with the Sure Grip ones too?

Most of my issues have been with the ring and pinion, Being open or a sure grip won't change these failures. I did buy a car that needed a 7 1/4" replaced because the spider gears failed. I was too broke and busy to replace it so I welded the spider gears into a Lincoln locker. I put some bigger tires on it and broke both axle shafts a few days later when it wheel hopped racing a friend.

I normally use 8 3/4" diffs but I have tortured a few 8 1/4"s without breaking them. I had a '95 4.0 Cherokee that I swapped a Klune-V 2.7 under drive and a 3.8 Atlas transfer case into before swapping to front HP Dana 60 and a rear 14 bolt with 5.13 gears. It had an automatic with a 91 to 1 first gear ratio in compound low with the stock axles. That's over 22,000ft/lbs of torque to the wheels. I welded that 8 1/4" too and had 35"x12.50" tires. I was amazed it held up. In 2wd compound low it would overpower the rear brakes at idle and slowly hop the rear tires. Top speed in 1st gear was about 6mph too or 20ft per minute at idle in first gear. Top speed in compound low and OD was 17mph on the rev limiter. It was ridiculous.... After the diff swap compound low was 132 to 1. Talk about some wild torque multiplication.

 

[73Swinger18]

Well guys...I got it running. I am very surprised how well it turned out. I did a compression check and it was 135 PSI all around. I set my initial timing at 18 BTDC and it idles nice there and no pinging under heavy acceleration uphill. I still need to re-curve my distributor. I have a miss at RPM above 3500, but it goes away when I retard the timing, so I hope the re-curve will fix that. I am going to get the carb tuned by a carb shop here. I'll have them put in the correct power valve and jets. I'll leave that to the pros since my experience with carbs is limited. The plugs are a bit too white for my liking. I changed the diff fluid and found out my gears are 2.76, not 2.71 after cleaning all the crud off the ratio tag. Watch out...break neck launch hahaha. But really, it drives great and was a big step up from before. Thanks everyone for all your help. I might just keep the rear end I got. Cruises the freeway under 3K.

 

[AJ/FormS]

Just wait a couple of weeks, we'll see,lol

 

[Killer6]

All of the above is sound advice,that being said, here is my 1st hand experience FWIW. I purchased a '72 318 swinger from a fellow tech school student in late '83, for the purpose
of swapping my '69 dart custom to said SB. That engine was bone stock untouched except for a new t-chain and a crane blazerII cam, which was not a small cam by any stretch, and
that thing would smoke the sh*t out of any stock size tires. The 7.25 in my car lasted about 3 mos., with about 40 nice burnouts under its belt before it spit the spider gears, any V-8
with any kind of traction will eventually break that. Even w/posi which is stronger w/twice the spiders, the next weakness just takes their place. One member had modded his for
more strength till he simply began twisting the pinion end right off. On the other hand, I tried to break an 8.25 on 275/60 street tires(not cheater slick type),w/a 4 spd. in an FMJ
bodied car before swapping an 8.75 rear in. I mean 5500 dump-powershift 2nd as soon as it stopped spinning-slam on the brakes& repeat over and over---and over.... w/a heavy
passenger, I gave up and left before someone would call the popo,......over 30 dump/powershift cycles w/a 383 in a car at more or less 3800#---one will serve your little SB a-body
just fine.

 

[AJ/FormS]

383s are under appreciated I think.They can be built to do some damage all right.

 

[Tuesday]

Piggy backing in this thread and looking for some PRACTICAL ADVIVE - as don’t want to change many things for a couple of reasons outlined below. Nearly finished the build of my 360 Magnum - very nice build (I think, at least on paper - after lots of advice from FAO members) - will post specs below this…..

Here’s my challenge - firstly, I need to establish what stall converter I have in my stock 904 transmission (car is a 1973 Plymouth Scamp running a 318) and if I need to change anything TEMPORARILY’ - making attention to temporarily as am getting a Tremec 5-speed in a few months and a new rear end (currently the shitty 7.25) - so I’m not looking for switch that etc. advice/comments just yet (but I will be). I’m just wondering what it will be like driving it for a few months and if I can get by with the stock/current set-up - are there any cheap mods I can do for the time being without having to go crazy on the cash? Or are there things I MUST do and are unavoidable?

 

[Tuesday]

Incase useful, following message above - here’s the main build specs…..

• 5.9 block Magnum 360 block from a 2001 Dodge Dakota
o Bore and Stroke: 4.030 in. and 3.580 in.
• Stock OE crankshaft externally balanced
• Stock Rods with ARP Bolts
• Speed-Pro Hypereutectic Pistons
o H11CP bored .030 over
o Compression ratio: TBD
• COMP Cams Custom Grind Camshaft
o Hydraulic Roller Tappet
o Duration: 275/279
o Lift .533/.536
• Morel 5321 Hydraulic Roller Lifters
• Liberty Performance pushrods - 6.8” by 0.080” wall
• Scorpion Racing SCP3302 Rocker Arms
o 1.6 Small Block Chrysler
o 5/16 Adjustable Pedestal Endurance Rocker
• PIE SuperTune EngineQuest Magnum Cylinder Heads - level-1 porting.
o 2.02" stainless intake and 1.625" stainless exhaust valves
o valve spring 125# seat 315# open @ .575 lift max
o 8mm valve stems
o 172 cc intake runners and 72 cc exhaust runner
o 62cc combustion chamber
• Edelbrock Pro-Flo 4 EFI including intake

 

[AJ/FormS]

Just drive then.

 

[Tuesday]

Thanks. In your opinion, is there anything I really need to do or can I get by for a few months with the current set-up?