Didn't get any replies in the Transmissions and Drivetrain forum...

I blew up my 700r4 right away and am now putting in a th350. Just curious as to what different opinions are on stall speed for a new converter.

388 cid
AFR 195
Comp XE274 (230/236 .523"/.523" 110*)
RPM Air-Gap
Demon 750 DP
Crane Gold 1.6 RR
Hooker Super Comp 1 3/4' LT
10.5:1 compression
26" tires
3.23s (building it for the 3.73 going in this winter this winter)
3700 lbs race weight

 

Have you run it enough to know where the power "comes on"?

If so, get a stall at or above that RPM level. I'd guess with that cam you'd want at least 3000. Of course, where a converter stalls will vary from engine to engine.

 

I have maybe a little over 100 miles on it so far. I had a 2500 converter in the 700r4 and it was a complete dog down low. The Demon 750 DP was pouring way more fuel than the engine could handle at low RPMs. It seemed like a different engine above 3000 or so. I also think that my mechanical advance was coming in too early too, causing more grief.

 

I say 4000-4500.

 

www.edgeracingconverters.com . tell them what you have, and they'll build you a TC that will compliment all your mods

 

3000 stall would work fine.

 

I agree. Couldnt be happier with mine, 9.5" custom (with lockup) for less than $600.

 

I think double pumpers aren't really meant for automatic equipped cars. It is mechanical secondaries, isn't it?

 

I bought a carb with mechanical secondaries to go faster at the track. Lots of guys use them with automatic trannies - you just need enough stall to make it run properly.

 

Get a B&M 10' Super Holeshot. I think they call it the Holeshot 3600 now. #20425

I picked up .4 sec from my old th700r4 and corvette (2200) stall.

Seems to have a good compromise of easy street manors, performance and $price$.

A good match with the 3.73's.
get some sticky tires.

Try running more initial timing, but a slower smoother advance curve that totals out at about 3000-3200rpm.
Then get an adjustable vacuum advance (Crane)
Limit the advance travel in the distributor to allow about 11degrees travel and set the initial at idle to 25degrees.
use a medium spring pair that max out at 3000-3200rpm.

 

That's general advice assuming inadequate stall. I listened to it too long.

A DP works fine with an automatic as long as you follow the displacement/minimum-RPMs-at-WOT chart recommendations.

 

I am running 10.5" ET Streets. For the very little bit that I actually drove the car, it seemed like almost a shake/knock?/ping? at instant load at low rpms. At instand load at high rpms, it seemed to run fine.

I thought maybe with my new setup (going from 8.3 to 10.5 compression), I saw detonation due to too much timing at low rpms from my mechanical advance. The engine seemed to love tons of initial timing at idle but would 25* initial cause a similar problem to what I am describing?

Are you talking about limiting the mechanical advance to 11 degrees (or the vaccuum)?

 

Only way to get it right is to put it on a dyno and find out where you are making your peaks at. Then you can determine what stall speed is best for your combo. Anything else is a guessing game. For only $70 for multiple pulls, it's well worth it.

 

Limit the mechanical advance. The vacuum advance rate and amount is a totally diffferent issue. It will need to be dialed in too.
Work on the mechanical first. 25 initial is not too much.
A cracked flywheel will make that noise too. They crack right between the crank bolts. the flywheel ring gear welds crack too. check it out.

the carb is not feeding "too much fuel" the problem is more likely a accelerator pump delivery problem. (not enough fuel, fast enough)
Also the throttle blades are too far open at idle ( from not enough initial timing at idle) this will create a flat spot when you try to launch from a low rpm. More initial will allow you to close the throttle more at idle and get better response.

Get the converter, (a stock converter is not going to cut it) and work on the advance curve. then the carb's accelerator pump shooters and cams.

I would get a 3000 stall at the minimum with a cam @ 230deg@.050"

The 10" 3600stall is "just right" .....trust me...

whats the highest octane pump gas that available in your area?

 

Thanks for the reply F-Bird'88.

For right now, I just have unhooked the vaccum advance. I sure hope nothing is cracked or broken but I guess I'll check it out this weekend when I pull the 700r4.

I'll also get some different size shooters and cams. The most me have around here is 91 octane.

 

The 91 octane is really pushing it with a true 10.5:1 cr. Even with aluminum heads.
Its always going to be right on the edge because of this.
Should have built with a little less cr.
Could spike it with some tolene or some 110 octane race gas to bring it up. Watch the total advance and the amount of vacuum advance. Start at say 30degrees total with a good bit of initial.
You're going to want a little slower advance curve than what most would recommend for max performance because of the lack of octane. keep the jetting fat. have to work within the limits of what you got.

 

My recomendation:
http://www.turboaction.com/frame.html
These guys are the best I've ever seen.
Click on the "how to buy" section.

 

personally when it comes to a converter, there isn't much that can top a precision industries version.

 

I agree 100%

 

With a cam in the 230/236 actual duration his peak torque should be in the 34-3600 range. At a minimum I would get a 9 or 9.5" convertor to utilize this power. Nothing wrong with a 10" other than too big and need extra fin angle to get the same stall speed as a 9 or 9.5" would provide with less slippage. Brand is up to you, ask 10 guys you get 10 different answers about what's best.

As far as following the "carb chart" on the DP issue....sure Guess I ought to get a 650DP for my stuff huh? Just as it took you awhile to see the light and quit running a VS, sooner or later you'll see the light and throw that formula out the window as it's waay to conservative for max effort. I too listened to that chit and actually bought a 750VS, soo as I threw on the 830DP for a trail pass, I seen the light with .3 pick up right away. Too many people have heard "dont over carb it" and have no idea wtf they are talking about. Unless you've done the A-B-A testing at the track as I have, leave the hear say to yourself. You cant just throw a 1050 dominator on a 305, but give me a 750DP and time to tune it in, she'll run harder than a 600 VS or DP for that reason. The hardest thing is you have to tune for the track or for the street, you'll be lean one way and fat the other so it has to follow what the car will be used for most of the time.

10.5:1 compression with aluminum heads should be fine on 92 octane so long as the motor is running cool and it's jetted correctly. Until you get it tuned it's better to err on the conservative side. Will it run at optimium with mostly 110 octane, probably not, but will it keep the pistons from swiss cheesing until you figure out your timing/tune etc... yes. I was driving mine last week with 5 gallons of 110 octane to a full tank 92 octane, once I get it tuned a wee bit better a full tank of 92 octane will be run.

 

when considering a converter though, it's also important to look at the vehicles use and what tires he's planning to run. if he's driving it on the street alot and running just a sticky street tire, he's going to want a bit less stall than what he'd want to race i with. for racing a 3500-3800 would be great, but for street it may not be the best route to go.

 

Thanks for all of the help so far guys. It turns out the guy building my Th350 is going to give me a converter as part of the deal. He said it went 3200 behind a mild small block and he took it to the converter shop in town to get taken apart, cleaned, and a to have a little more stall put in it. Its likely not a high end piece, but he convinced me to give it a shot and see what the motor really wants for a stall speed.

I understand your point about keeping the timing conservative and the carb on the fat side for now - especially until I get everything figured out. I do have forged pistons so I am playing with a little smaller fire.

As for the use of the car, I built it to race every weekend but I will likely drive it some on the street. I do however want it to run fast on the track first, and then have some street manners.

Also, the guy building the tranny suggested that there is the possibility that the noise I am hearing is a thrust bearing. I sure hope not.

It sounds like the tranny should be done tonight and my torque arm mount kit should be here tomorrow.

 

I'm sure by the motor specs he did'nt plan this to be a daily driver/cross country cruiser. Even at that a 9-10" convertor is perfect for street use even with a higher stall rating. Mine is a 4600 stall and after reading his latest post my car and his car are built for the same purpose, mostly strip but no way afraid to street drive the heck out of it.

So many misinformed people believe a higher stall wont budge the car until you reach that advertised stall speed which is so far from the truth it makes one look stupid for thinking it, but cant really call them stupid because they did'nt know! I've had a 2800, 3500 and now this 4600 and all were/are used on the street with zero problems, and guess what I could idle away from a stop light with everyone of them just like a car with a factory convertor. The biggest thing the aftermarket stall provides is flash point. When I'm at a dead stop and mash it, it flashes and holds to 4600 until the torque multiplication catches up with itself and then the rpms will start to rise.

Think it's too much for a street convertor because of heat build up with the slippage, think again. This convertor as well as the others all hold about 150*-160* max temp when stop and gop traffic in town and 30minutes to an hour of interstate driving.

Alot of things change when you step upto a 8" convertor which offer alot of low rpm slippage and notice I did'nt recommend one as I would personally leave that for 99% strip and a few street miles a year cars.

On your timing, unless your running vortec heads which are notorious for liking lower timing, almost every sbc in the world built for power will be darn close starting at 36* total and try to have it all in with your advance kit by 3500rpm. If your running street tires you can go down to 30* so you have no bottom end at all and wont spin, but with your combination I'm guessing if you have everything in order you will be anywhere from 36-40* total timing. Some say higher compression engines need less timing....and dyno with our 383 in the truck says....BS not with that combination-41* total was optimum. Have'nt had a chance to make an all out pass with mine, but I did take out 2* down to 36* total to help slow down my lights and it also dropped me .2 and kept mph the same. Supposed to have excellent air this weekend so if time permits after the races I'll go up to 40* and see what happens. Know it's just my opinion, but 30* total is nowhere to even start with timing on any mild sbc or bbc for that matter.

Now as far as taking anything to the track, if you go out with regular radial tires you got at tires plus or walmart that's your own fault when you have no traction regardless of hp, tq, stall speed whatever. kinda like taking a knife to a gun fight. There are plenty of drag radials as well as dot slicks that can be had for a fair price considering the money put into to some these cars it's a drop in the bucket. So to all these supertunas that install a 200 shot of nitrious then say they cant get any traction, that's their own fault and just solidified the fact there's a reason they have wings and fart cans on their cars and people think they're gopof *****. That's why I've been rolling on DOT slicks for 3 years since none of my motors will let regular tires stick at the track and sure as helll not on the street, ask me about jerking the tires on the street now with the new stuff and ask yourself what's neater, seeing somebody blazing tire smoke like they're in high school with daddy car or jerking the tires on the street?

Let's not forget the goof ball mistake of trying to go mach 1 and not upgrading the stopping power, but I'll save that for later. For now, do a search on convertors and read what some of us already know, then offer adivse. My car has been baised to straight lining since day 1 as well as street driving whenever time allows and I've tried just about everything in this past 3 years so I have first hand knowledge of what works and what does'nt. Dont know it all by anymeans, but I've bought numerious parts and tries different things so there is actually background behind my recomendations and not stuff read in a magazine or heard from a buddy which usually gets alot of these guys in trouble.

 

i've driven cars with 4000 stall and higher on the street. other than watching the temperature which isn't usually too big a deal if you're just cruising around and have a good cooler, they put too much shock on the tires for street racing. i've personally ran bfg drag radials on the street myself and a few of my buddies run et streets on the street. street racing is done on an unprepped dirty surface and to challenge how high of a stall you can go with and not make smoke shows is touchy. if you're just planning to race it only then set it up for the track. i'm a street guy that goes to the track when i get around to it and i set my stuff up to be able to do both.

 

Not intentionally ******* you or your buddies set-up, but I'll just leave it at this, if your blowing off your tires on the street-normal radials I can understand-but if your rolling on drag radials and et streets and still have this problem; my advise save some of your go fast money and use it to tune your suspension and make the power you have now work.

Case in point, my old small motor only ran 13.00's and high 12's, but I continueally smoked guys in our group BBC powered 11 second rides on the street casue 1 I did'nt have much, and 2. I could stick all my power and walk away, by the time they were done frying the hids I was slowing down for the next light. Not a great example, but I did'nt meet a vette that could give me a run for my money either N/A.

Another case, while I have'nt done much to my suspension it's working. I can feel a small amount of slippage when going off the trans brake on the street, but then it hooks and the front end comes off the ground and I'm gone. So I beileve when your building something powerful it's because you want to go faster, and there's a whole list of other items that must be addressed besides dropping in a big stroker or adding a super charger and calling it a day.

 

there are more than a few of my friends running that kind of stall. one has a 72 chevelle with a 3800 stall and a 430 small block that has been dyno'd with somewhere around 570rwhp (i forget the exact number) back when he was running the smaller hydraulic cam. he's went back to the solid and was expecting it to run just over 600 with the new set up. on nitto drag radials it can lift the left front on the street, but that doesn't mean it'll do it on all of the surfaces. there is a big difference between a prepped track and a very unclean road to run on. running a lower stall allows less shock on the tires and no where near as big of a tire needed. driving around on drag type suspension gets old real quick. even adjustable drag shocks on the tightest setting are terrible for anything other than going straight and launching. i've got plenty of slips with 60' times considerably better than others with a similar set up at the track and they'll do just as well on the street as at the track.

 

Nuff said!