[rednecks70]

Got a chance to test the ATI 8" this morning and that thing really needs some rpms to get going, just pulling out of the driveway the rpms shoot up to 3000 but I'm not going all that fast, I'm assuming this is normal? The car idles great in gear now but it feels like it has no power under 3000 rpms, anyone else have this problem? Keep in mind the car is way out of tune so maybe once I get my carb & ign. issues cleared up it could be alot better. The plugs take forever to clear up in this cold weather so everytime I try to hit it hard the engine backfires, I think it's time for a 6AL box. Once I get rid of the 2.25" exhaust I'll most likely pay someone else to tune this thing, I feel like I'm going in circles and making one bad decision after another. I know many of you said street driving with an 8" ATI wouldn't be any problem but I'm not too sure I can live with the lack of power under 3000 rpms. Any suggestions would be appreciated, here's my combo:

454 + .030
10:1 comp.
Brodix Ovals (110 cc)
Lunati solid flat tappett (25?/26? @ .050)
Edelbrock Performer RPM
Holley 850VS (I have 950HP that runs worse)
MSD Distributor (locked out at 38*)
TH400 with 8" ATI
12 Bolt Posi with 4.11s

 

[driver]

I had a B&M 3,000 stall in a street car one time and hated it.

 

[Bob West]

Its going to stall when taking off... the rpms catch up to the stall or vice versa, I can cruise mine just fine. I'm around 2800 or so at 60mph, I know its not locked up but I can drive it easily. Did you check fluid level?

 

[grovey]

hey *******, how do you like your cam ? i'm thinking of going to a solid , and would like to know if you have power brakes,and how they work with your cam? whats the specs on your cam ? did it feel lazy before the converter change ?

 

[rednecks70]

Its going to stall when taking off... the rpms catch up to the stall or vice versa, I can cruise mine just fine. I'm around 2800 or so at 60mph, I know its not locked up but I can drive it easily. Did you check fluid level?

I did notice that when cruising at 30 to 40 mph the rpms would settle back down. The fluid level maybe be slightly high, I have a drain plug so I might drain a little before I drive it again. I talked to a guy once at a cruise night who had a 4500 stall and he claimed that his car would pull away from a traffic light normal but at the track it would flash to 4500. I was hoping mine would act the same but I realize that everything has a trade off. Will making adjustments to the governor or vacuum modulator help any?

 

[rednecks70]

hey *******, how do you like your cam ? i'm thinking of going to a solid , and would like to know if you have power brakes,and how they work with your cam? whats the specs on your cam ? did it feel lazy before the converter change ?

It's 402A5LUN
Advertised Duration IN/EX: 285/295
Duration @.050 IN/EX: 252/261
Gross Valve Lift IN/EX: .595"/.595"
Lobe Sep Angle / Intake Ctr Line: 110/104
Valve Lash IN/EX: .025"/.025"
RPM Range: 3000-7200

It pulls about 5.5" of vacuum and it's not working well with my power brakes (another bad decision), I'm going to get a vacuum pump before spring. Even with all my problems the cam performed well, once the plugs cleared up I could light the tires from a dead stop, I would say it wasn't lazy under 3000 but if I had to do it again I would probably knock 10* of duration off both the I/E and maybe have it ground on a 112 lsa.

 

[Bob West]

Governor or modulator adjustments wont affect it. Just need to be easy on the throttle around town and driving normally, it wont accelerate as it did with a stock/lower stall pulling away from a light, but nail it on the track and hang on.

 

[driver]

If you don't like how lazy it is before 3,000 comes in chances are you'll never like it.It is what it is.. It will remain the same.I know the feeling because I had the same problem in a 70 chevelle with a 402.I HATED IT. The nova I have now has a 3,800 stall in it but it don't have the lazy feeling like the chevelle did.Why? I don't know?

 

[64malss468]

:sad: i just put a 10in 28 to 3200 rpm converter and mine does the same thing..................my rpms aint matching my speed!! until i stomp on it. this is in a 468 wth th350 and 373s also having a unkown cam! ........so what im doing is replacing my peanut ports for some 781s and running a cam that demands that high of stall ( comp magnum 286) and crossing my fingers cuz to me it is just annoying also :sad:

 

[rednecks70]

If you don't like how lazy it is before 3,000 comes in chances are you'll never like it.It is what it is.. It will remain the same.I know the feeling because I had the same problem in a 70 chevelle with a 402.I HATED IT. Now the nova I have now has a 3,800 stall in it but it don't have the lazy feeling like the chevelle did.Why? I don't know?

Well that's interesting...I was hoping since I spent more money on a good name converter I could have the best of both worlds. Maybe my combo has too much cam for the low rpm range and my torque is way down? Like I said earlier I might have an experienced shop start making decisions for me beacuse the more parts I throw at this car the worse it gets.

 

[rednecks70]

:sad: i just put a 10in 28 to 3200 rpm converter and mine does the same thing..................my rpms aint matching my speed!! until i stomp on it. this is in a 468 wth th350 and 373s also having a unkown cam! ........so what im doing is replacing my peanut ports for some 781s and running a cam that demands that high of stall ( comp magnum 286) and crossing my fingers cuz to me it is just annoying also :sad:

Wow, that converter doesn't sound all that radical. The converter I replaced was an 11" TCI breakaway. With the idle set at 1100 rpms I had alot of trouble keeping it running when I put it in gear. Be careful with you cam choice, you may end up with other problems.

 

[GRUMPYVETTE]

redneck70

http://www.crower.com/misc/valve_timing_chart.html

http://www.kb-silvolite.com/calc.php?action=comp

your cam specs, deck height, piston compression height, quench,gasket thickness, etc were not clear but its reasonable to assume you might be well below 10:1 true static compression and closer to 7- 6.5:1 dynamic compression with flat top or a small dome pistons and those heads, which would easily explain the loss of potential low rpm tq to make the converter work effectively, take some exact measurements and Id bet youll find your true cpr is lower than you might expect and the cams got far more durration than would be ideal, if thats true. seems like some domed pistons matching your heads that get you in the 10.6-11:1 STATIC cpr would help

 

[rednecks70]

redneck70

http://www.crower.com/misc/valve_timing_chart.html

http://www.kb-silvolite.com/calc.php?action=comp

your cam specs, deck height, piston compression height, quench,gasket thickness, etc were not clear but its reasonable to assume you might be well below 10:1 true static compression and closer to 7- 6.5:1 dynamic compression with flat top or a small dome pistons and those heads, which would easily explain the loss of potential low rpm tq to make the converter work effectively, take some exact measurements and Id bet youll find your true cpr is lower than you might expect and the cams got far more durration than would be ideal, if thats true. seems like some domed pistons matching your heads that get you in the 10.6-11:1 STATIC cpr would help

I didn't build the engine but a reputable "one employee" performance engine shop did, I'm not sure if he doubled check the combustion chamber cc from Brodix, deck height, quench, etc. but the pistons are 25.7cc (TRW-L2465). Even before the converter change I often wondered if the compression came out high enough because I think this builder relies on what the piston manufacturer lists in their catalog for compression ratios. And we all know that things like deck height and gasket thickness can drastically reduce static compression if your not carefull.

Here's another one of my "lets throw money away" ideas...would stroking this engine to a 496 help the 3000 below rpm range? Or would it make the converter stall more because of the added torque? I ask because the oil pan has a small leak and if I have to pull the engine to fix the leak I could have a 4.25" crank installed which would hopefully elminate the need for a vacuum pump. If it would kill two birds with one stone I'd consider it but in reality I know I should get a more street friendly cam and converter.

 

[GRUMPYVETTE]

before you go spending your money sit down, have a few beers and THINK ABOUT what your goal is here! YES a 496 stroker kit will help but that costs a good deal more than a set of pistons and a lower durration cam, and a good engine tune. and a good engine tune. and measureing & correctly adjusting what you currently have , and knowing EXACTLY what your dealing with is the first step, before spending a dime, on new components!
once your sure what your dealing with you can make valid choices based on FACTS
throwing money and parts in a random manor is foolish

 

[sschevellefan]

the cam you have probably doesn`t start making power untill around 3000-3500. you could cam it down some but i don`t know how it would effect your converter. I had a 10" 3200 stall with 3.08`s for a while and I could drive it normal just fine but when I nailed the gas it would flash to about 4000rpms. It sounds like either they made the converter on the loose side or your just not use to driving a car with a high stall converter. Going to a 496 just to get some power below 3000 is expencive considering the gains you`ll see might not be worth the extra money. Not only that but since you`ll be making more torque, your converter will stall even more.

 

[gnicholson]

Before you can accurately evaluate your combo. you must properly tune the car. Things like adv. curve ign.. timing and. fuel mixture are critical.Whats your actual stall? Check after dialing in.Is this the converter ATI recomended? Good points about dyn. compression earlier.

 

[Tom Mobley]

so when you drive away normally does the engine have to rev up to 3500 or whatever the stall speed is before the car will move?

or is it more like the converter hooked up but the engine doesn't have enough power to move the car like you'd expect?

what happens if you power brake it? what RPM does it get up to before it starts creeping against the brake?

 

[hoffbug]

Im assuming that you are after low ET's at the track?? Most guys wouldnt run a high stall converter on the street unless it was a street strip car.. or something really light.

Before you make any more changes.. Id consider..
Running the valves...... take it to a chassis dyno and get the jetting and timing ballparked.. and take it to the strip and make some runs.
You might surprise yourself.

 

[gnicholson]

I agree with Bill.

 

[kirkwoodken]

What Hoffbug and others say: Get to a chassis dyno guy with a good reputation. Give him a few hundred dollars for his time and experience. That will be much cheaper than jumping into another unknown. Your engine should make 450 ft. lbs. at some RPM range. From your question, it sounds like it's not doing that. First, make it do what it is capable of, then see if that is enough. I know you can do it. It is only a machine.