stall converter and gear ratio question for blown sbc

I have a 355 dart block , iron eagle 64cc 215 heads ported to 222 , compression 7.84, scat crank 3.5 stroke 6 inch rods , cam is a hydralic roller erson 548 lift 234 int 248 exh at .050 duration 112 lsa. Running about 7psi of boost . Timing locked at 28 total . 2 edelbrock 750 air fuel with wide band between 12 and 13 . Trans is a th350 stock with shift kit 3 k stall converter . Rear is a 10 bolt with 2.73 .
The car is really light guess is around 2900 lbs . Question I have motor doesnt seem as responsive as I hoped shifts are kinda soft wondering if I need to change stall or rear gears . Car is street driven maybe a trip to the track every once and a while . I figured with such a light car and skinny tires that 2.73 wouldnt be a problem but lost so much torque . I didnt want to have the car screaming on highway at 70 - 80 mph .
Seems like because of the 2.73 may be blowing through the torque converter . I dont want to change the converter . From what I have read if I drop 3.73 or 3.42 in it I will gain a ton more torque back and also tighten converter back up by changing gears . Does any one have any experience with this ? The other question is do higher stall converters generally shift softer than lower stall ?

 

B.S. isn't it? 85 people looked, but nobody has a single thing to say about it. Hopefully bringing it back ttt will get a response for you

 

I looked this morning - one of the 85 but I didn't know where to start.
It's a wired combo and there's things I would change for the street.
It's set up more for running WFO on the salt

But nothing seems be giving.

Rpms gotta come up to match the cam and converter. Way up is where the torque is hiding. Do that with the gears for the street.

 

Daddy o thanks for the bump. How did you make out with your motor ? I know I have to change the gears is where I was heading just not sure 3.42 or 3.73 . and how much it will tighten up the converter . Shooting for 70 mph at around 3k rpms . may go to 3.73 with 28 inch tire after I burn off the 26 inch tire I currently have .

 

I would change the gears first and see how it works before changing anything else.

if you want 70 mph at 3000 rpm ...

- with 26 inch tyres, you would need a 3.32 gear
- with 28 inch tyres, you would need a 3.57 gear

This is the calculator I used for that, http://www.richmondgear.com/101032.html

 

needs more gear

 

Checked with my buddy and his 31 has 3:50 gears, 29" tall rear tire and he has 2800rpm at 60mph. Mine is getting better, I'll PM you the details so not to derail your thread. I think your going to have to step up to the 3:73's I'm afraid, or maybe swap out converters. I'm pretty happy with my 2400 Holeshot.

 

Still up in the air rear gear torque multiplication chart shows going from 2.73 which -12% to 3.42 which +25 % for total increase of 37 % If I go 3.73 increase is 37 % for a total of 49%
Do I sacrifice the torque for for 300 rpm on the high way ?

 

How much highway driving are you doing? If it is only occasional, I would try something in the 3.5:1 - 3.7:1 range. If all you do is highway, I would leave it alone.

 

Ok , define a goal for us.

Your 273 gear and low rpm wish requires low rpm torque and lots of it.

Your cam choice will not provide any low end torque.

Your converter will hide the fact that there's no low rpm torque by sliding right past the low Rpms weak zone allowing the engine to reach high Rpms without much load. The cam won't wake up till 3000 Rpms, the driveline won't wake up until 3000 Rpms . Coupled with those gears the car won't do anything worth while until you are going over 100mph -- hang on at that point because it will probably scare the shit out of you.

This set up you currently have will be a complete pig off of a stop light and probably won't pull a sick whore off a piss pot on the street.

Now you to need either :
A . drive this at 3000 Rpms
Which requires a numerically higher rear gear to slow the MPH per rpm.

B. make gobs of Low rpm torque
Which requires a cam and matching converter change. Then probably a blower drive ratio change.

Pick your comprise and make everything match

Your chasing the converter from the wrong end, it needs to match the input end . You really can't manipulate the converter action from the rear end

 

Match the convertor to your cam.

 

I think that they are matched, it's just that they are set up to come in at a higher rpm than the OP wants.

 

I was thinking the same thing!!

 

Speaking the truth daddy-O.
I'd like to see what it runs at elmirage, southern Ohio, or bonneville.

6000 Rpms with a 31" rear tire will be 203 mph if the motor can pull it.

 

I goal would be able to keep up on the parkway keeping up means 70 to 80 and not kill my motor . But with that being said I would say 60 to 70 % around town the rest probably 40 to 60 minute ride on the park way . The gears in the car are what was in it when I got it . Torque converter and trans are staying till I kill it then going to th400 . Cam was said to be good 2500 to 6500 rpm . I am 100 % changing gears Just cant decide 3.42 or 3.73 I know once these tires are destroyed I can drop the rpm a little with bigger tire. But really in the end regardless of tire size , Do you guys think dropping 300rpm between the 2 gears set is worth the loss of torque .

 

since 70% around town,i would go with the 3.73's,2800-3000 stall

 

Ok, you aren't loosing torque, the torque curve of the engine will remain the same. What you are doing is picking a MPH cruise speed and corresponding rpm v ia rear gears that keeps you on the torque curve. Your cam and converter say that it's around 3000 Rpms. If you think 3000 rpm is going to kill your engine then you are looking at a cam change and converter change.

What's your tire OD ?

 

If it was only occasional I'd be looking at 4.10s or 4.30s, but then I'm a maniac. You have been reading all this 3.08/2.73 bullshit on the HAMB, now the reality of that compromise is setting in. Bottom line is, do you want a street rod or a hot rod?

 

question all, with wanting to cruise@ 3 k wouldn't it be better to go to the 373 rear with the 28"tires, and a converter with a lower stall than the wanted cruise rpm? (2500 ish stall) seems like you cant have 3k in both places, lotta lost energy there. or am I wrong? I'm with George, I chose 4.10 28" tires built 350 2200 stall still building.....

 

The reality is,it's gonna live on the street for the most part,but the engine,size of cam,a blower,etc... dictates that it needs to move serious air to be liveable,a 3000 stall,3.73's,i also would personally would put a shift kit in it also, would mean it's gonna live in the upper RPM ranges at a lower rate of speed.It's also gonna see some 1/4 mile action time to time also,you want respectable times.4.10's aren't really out of the question either it's NOT gonna be an "Econo cruiser"any engine made to run with a blower already determines alot of factors right off the bat!JMO

 

Measuring exactly 26.5 with car on the ground . I Dont think 3k rpm will kill it . Just dont want to be cringing when I do it for a long cruise . Probably just more in my head due to newer cars turning such low rpm . I had a 57 chevy with 4.11 they are out .

 

Not worried about gas mileage just rpm at high way speed . I do have a shift kit it was in the car when I got it .

 

That's just it FG, a compromise.
You can pull off 2.73 gears but you need a engine that makes GOBS of torque down low. For example a 401 nailhead with 450 ft lbs at 2800 Rpms or any of the other monsters. The trade off is - its usually done pulling well before 5000 Rpms. I know you know this so it's for the others who might be reading this.

I ran with a bunch of guys who loved their 456 gears. They were a hell of a lot of fun on a freeway on ramp. The rest of the free way as in couple miles was torture for them. 10 mile drive was almost not spoken of. I ran a 308 behind my Pontiac and could go across country. They always beat me down the ramp ... That was their compromise and my compromise.

Now if an engine is cammed so that it doesn't even wake up until 3000 Rpms you are going to have to wing the Rpms up there and the rest of it should be built to handle it. It's all got to match.

 

So what way would you go ? 3.42 or 3.73

 

FWIW, I run a 3500 stall, 3.50's and 29" tires. I love my combo, it works good everywhere. Notice I didn't say great. Like everybody else said you have to compromise somewhere.

That is until I buy a gear vendors overdrive.

I think 3000 RPM for me is around 70. I'm not exactly sure but I can keep up with traffic and even pass some people.

 

4.25 gear will get your Rpms up on the cam and converter at highway speed.

http://www.richmondgear.com/01calculators.html


If you don't want the high rpm,
You have only 2 choices.
1 Re cam and converter to match
2 sell the blower engine and get something else and take your honey out to dinner on the extra cash.

 

Would love gear venders over drive but boy are they pricey but money aside I dont have the room under the car for it . Iam running saddle tanks .

 

gotcha

ever think about an TH700R? brutal low end gear,and an OD to boot!and it's not computer controlled

it would give you what you're lookin for..

Or a Gear Vendors unit? pricey but you'd also get what you're after.

 

Love to but heard even built up they dont hold up to the horse power I have .

 

Hello ! Is this thing on ? Boom boom boom.

You aren't making any horsepower , not until you get the Rpms up on your current combo

456 gears and OD should do it though.