Greg, you said that this would be a learning process and you were right.

This is the stall converter issue that we discussed in some length a little while ago. Just to back up some, this is the 71 Sport Custom that I'm trying desperately to turn into a real hot rod truck, but so far I ain't hit the right combination yet! Main points to note are: Edel heads, RPM intake, Dove roller rockers, Comp 292h cam... full list of specs are HERE

Had a Dacco stall converter in it, with way too much stall, was slipping all of the time and would never even come close to locking up and acting right. It was so loose that it let the motor run free and would allow it to rev to the moon at any given time, but that power just wasn't making it through the drivetrain. It was pretty much stopping at the converter. On taking off from a dead stop, because it would let the motor rev so high, it would bake the tires for a good while, but that was about all it could do. At any time during driving it, at a WOT hit, the motor would get up and scream, but the truck wouldn't move accordingly. Way too much slippage in the converter. Wrong converter for the application.

So, upon several recommendations and checking the charts, I purchased and installed a TCI StreetFighter. Just got it back together and I do think that this is the right converter for this engine, so that's ONE step forward. Unfortunately, it also took one step BACKWARDS!

There's no slipping anymore. Mash the gas and the truck responds. Doesn't let the motor go crazy anymore. The power the the motor is making is actually making it through the drivetrain for the first time. That's a good thing.

The downside is that the bottom end is GONE. And I mean completely gone. This thing is a real dog from takeoff. Now, once it gets going, it's pretty responsive, but it's got to get up there first. It used to smoke the tires, not it won't even turn them over and that's no exaggeration. The first thing my 9 year old son said was "daddy, why ain't it spinning?" It will NOT spin the tires anymore. Try explaining that to a kid!

A couple of reasons I reckon...

1) Not enough gear. It's had a 3.25:1 from the start and that's not enough for a cam this big (292 adv dur / 244@.50, .560" lift@.50). A little large... all of my "expert" friends say it's too big, but it is what it is.

2) Overcarburated. Started out with a Holley 750 dual feed/vacuum secondaries, but it needs a little work, so we swapped it out for a friend's Pro-Form modified Holley, 830cfm. Obviously too much carb for this 390, but since that old converter was letting the motor rev so high, it actually liked all of that gas being dumped into it. Sort of woke it up a little and made it more responsive. Anything was a help, since probably not even half of the power was getting to the rear end. Worked ok with the old converter, but now since this TCI is actually putting a load on the motor, it doesn't want all that gas at once. Bogs real bad from the start and it's easy to flood. Too much gas going in.

Now, to find the solution. I have another rear carrier that's fitted with a 3.89:1 gear that's ready to go in. Maybe sometime this week. Then, fix the Holley 750 and get it back on there.

I'll update later, but in the meantime, maybe someone has suggestions?

Thanks,
Mark

p.s. - sorry to add to an already long post, but HERE is the thread where we all discussed the converter issue, FWIW.

 

Well one thing right off..to much cam for the Gear.... I'am putting one together now 232/237 dur.@ .050 .567" lift..but I also have 3:73's in the rear..that will be changed to 4.10's.... And I'll be running probably a 29 or 30" tire on the back..instead of the 33x12.50's on there now..

Russ

 

Yeah, the 3.89 is going in this week, if I can stay out of the doghouse long enough, but it may take going to a 4.10 or so.

 

I was going to say something about too big of a cam. It sounds like you went from too high stall to too low stall on the TC for that cam. I'd change the cam out for something smaller. The Crane 343941 comes to mind. Or alternatively, you could change out the TC to the next size larger.

I definately agree with the gearing statement. I'm running a similar 390 with the aforementioned Crane cam. Gears are 3.50's, and tires are now 255/70R15. I'm also running the stock TC. Everything works good together.

So here's what I would do, in order:
1. Change the gears.
2. Change the cam if not satisfied with #1.

 

Forget the carb. You have way too much gear. Get that other gear put in and then take it for a ride. You will be amazed at the difference.

My 511 has 38.5 tires and 4.11s. That is roughly equivalent to your tires with 3.25s. I could not spin the tires from a roll until it hit about 4500rpm. She's getting 5.38s now.

Your cam is definately a big 'un. Only you can decide if it's too big. If your intent is to make a hot rod, then you already know that your bottom end is going to be soft, so you just build the rest of the truck to keep your rpms up above the soft spot. Changing gears will help.

-Scouder

 

Like everyone said, the rear change will be a significant improvement. I went from 3.23's in my '65 Coronet to 3.91's and it was a big difference in launch. Though it kicked it up 500 RPMS at 60mph.

With that cam you might even want to run something like 4.10 or 4.38 so you can get out fast and keep the motor wound up in its high RPM band. A limited slip is going to be a MUST.

Money money money..... I don't think it ever ends.

 

Never thought I'd hear that from YOU, Scouder!! He he...

That's the hard part. Getting the right combination. People say it's up to me, but how do you decide between a big cam and something smaller? I just want a hot street truck. Something that will run as fast as it can from a dead stop, for no longer than a quarter mile at the time, and still be able to drive it on the road. Big cam, small cam... I just want what works!

One thing I forgot to mention in the beginning of this thread - I can now get a fairly accurate foot brake stall since I've swapped converters. Never could do that with the old one. Truck sitting on grass, holding the brakes in drive, the engine will rev to about 2800 and that's as far as it'll go. Whenever I tried that with the other TC, it would go on up above 3500, but would be baking the tires by that point, and that was on pavement.

Dacco's website says that the foot brake stall is supposed to be about 80 percent of the actual stall of the converter, so that would put it right about 3500. For whatever that's worth!

 

The cam that is in my 511 right now is a 295 advertised. Your 292 is a BIG street cam by anybodys standards. Even mine!

And you are right. Getting the right combination is a time consuming endeavor, not to mention expensive. That's why you see old timers tweaking combos that they have had for years. I am in the same boat you are. I have FAR less than 100 miles on the 511 and I'm changing the cam, lifters, timing set, and ring and pinions in both ends. I am also having new advance bushings made for my MSD, so I can nail the exact timing curve I want. Right now I'm thinking of a 28 degree initial and a 38 degree total.

My point is that "perfect" is dang tough to attain. We make changes, evaluate them, then make more changes. It's the game we play. Fun game, innit?

-Scouder

 

Got the rear carrier out last night and verified that it was indeed a 3.25:1 gear. 39 ring gear teeth / 12 pinion gear teeth. It actually matches the factory tag! Anyway, the 3.89 is already in another carrier and ready to go in. Hopefully this will wake things up a bit. May not be enough, but it's a start. And it's free! More later...

 

FREE.............is GOOD!!! LOL!

Yup, you need some gear. My 428 has a 240-250 @ .05 camshaft(probably around 290 advertised duration). With the 4 spd and 4.56 gears it goes anytime you want!! I run 29 x 12 tires so it helps tame the gear a bit. It runs around 3300 @ 65 mph(give or take). Right in the sweet spot of cam..no downshifting is needed to pass someone.

You'll be pleasantly surprised how the gear wakes it back up.
Keep up posted!

 

It's nice to see some other suckers out there, dumping wads of cash and time into the learning process :-)

I agree, the gear change will be a big help and should be first. It sounds like you have plenty of stall speed, if it's in the 3000-3500 range. you may still have some tuning to do regarding the timing that can help the bottom end. As Scouder is trying for, you may want a lot of initial, but don't let the max advance go off the chart.

I'm off until the 6th, so I hope to get my POS running again.

 

Greg, I ain't been through nearly as much trouble with mine so far as you have with yours, and I'm still ready to blow it up! Jesse James style... BOOM!

 

I always thought it would be good to get a big ignitor, like the ones they use in the Looney Tunes cartoons, with the big box and big T shaped handle on top, and rig that up to some TNT under the truck. Stand back, push down the handle, and KABOOM!

 

Yeah, I may be in the market for one of those soon... I'm sure I have the number for ACME around here somewhere...

 

kurt, you're definitely going to beat me to 5000......

I should have expected some of the troubles I've had. I'm trying to build something complicated, very custom and without much experience on my part. Let's face it, trying to run 13s in a 4600lb 3/4 ton truck, that can still work like a truck, is asking a lot from the truck. Oh well, I gotta be me.