Launch Problems

[Siciliano15]

went to the track last night and was still getting the crappy launches. 2.0 and 2.1 60ft times. this is with me using QTP dot slicks so there is no traction problem. Seems like the truck does not want to get out of the hole and its a regular cab with 4.56 gears and a 3000 stall and only weighs 3,800lbs with me in it so around 3,640 without me. It was actually getting a better launch with my old transmission and 2400 stall even though i was making about 15 rear wheel hp less on that trans. Is the 3000 stall too much? Should I get a 4bbl M1 which should help the engine rev up to 3000 quicker?

[uwntsumrtII]

4bbl will make it worse.

[Five9Dak]

A lot of guys in the NE have found out the hard way that it's hard to hit anything better than a 2.0 with 360ci, nearly 4k lbs and the m1.

How much torque does your combo make, and where?

[BTLFED R/T]

What RPM are you launching at? Most have found leaving at 1000-1500 rpms works about the best.

[Intense RT]

Not sure it'll help but see if you can try out a 52x55mm TB, I just switched from a ported stocker on a bolt on 360 and suffered no bottom end loss. 60ft was the same as my best. May want more air but I also think a 4bbl might be too much.

[Siciliano15]

i tired launching at idle, 1000, and 2000 rpm. at idle was the best. i just thought with 4.56 gears and a 3000 stall and only 3640lbs it should be like a 1.8 60fts. i did notice the engine isnt a free revver so i thought maybe a 4bb1 would bring the rpms up quicker but i dont know. i have eddy heads and i just hope the 2bbl m1 isnt choking the engine. the combo makes 322 ft-lbs..... i forget which rpm that is at... right now i have a f&b 52mm. maybe that is too small?

[bad360rt]

One more for where is your peak torque?

[Siciliano15]

im gonna look when i get home and let you know.....

[Adobedude]

I was stuck in the 2.02 60' syndrome.

So I made a few changes:
Replaced the 2800 stall with a 8" 4K PTC converter.
Added Monoleafs w/ Caltracks.
Swapped out the 46RE for 727

First run after the above mods I cut a 1.8 with 15 lbs of air in the slicks and hitting the rev limiter at 5800 rpm.
I think it's got a high 1.6 in it.

[ADakotaRTGuy]

What tune do you have?

[slvr03dakrt]

hmmm you should be doing a little better than a 2.0 my cc cuts 1.8s with a 2800stall and stock gears but then again I have a few more hp and tq on you but it also weighs 4275 with me in it.

[Adobedude]

What tune do you have?

SCT...

Sean sent me a new performance tune, everything set at 8000 rpm, and 36º total timing.

[Five9Dak]

The m1 2bbl port cfm is kinda low, but I'm not sure if out of box eddies will outflow it, port mismatch could be an issue though. Does anyone remember the number shady dell was quoting? 235?

A 360 at 100% VE and 6k rpm only needs 623cfm, does the 52mm TB supply that? I thought they were over 860, but I could be mistaken. Doesn't mean in practical experience bigger isn't better though.

At 322ftlbs, it really shouldn't be earth moving off the line, especially if it is at elevated rpm. you may very well be restricted by what I said above, but that doesn't mean addressing those concerns will help low end, it will most likely make it worse.

I say you just hit with a small shot of juice, that will give it a kick in the ass down low.

[Siciliano15]

looked last night at the dyno and the peak torque of 322 is at 4000 rpm and the peak hp of 292 is at around 5400 rpm. also i originally had a b&g m1 flash but then they didnt seem to want to work with me to custom tune things so i called tom fox and he adjusted my air/fuel and i actually picked up a small amount of power like around 5 or 6 ft-lbs

[Five9Dak]

I would say there is nothing "wrong" with the way your combo is 60 footing, it's just a 360ci truck with probably 300 or less foot lbs at converter stall. Physics sucks sometimes.

I have more torque lower in the power band and also 60 foot the same, so you're no doing bad.

[Siciliano15]

it just sucks cause i was pulling the same 60 foot times when i just had some minor bolt-ons and 3.92 gears and a stock converter. the 4.56s and stall are really not all that they are made out to be. and besides that, when i was near stock the truck was about 200lbs heavier but since then i got rid of the ac compressor, changed to eddy heads, ss rollpan, and a few other minor things so im sure u can see my disappointment with the truck right now.

[Five9Dak]

The converter helps every time you put your foot in it, not just launching. Drive your combo with a stock converter, I bet you wouldn't like it as much. I can understand your frustration though.

Arn't your ETs in the 12s? That IS impressive for an NA360 truck. What matters is how quick you react and get to the stripe, nothing else.

[Intense RT]

it just sucks cause i was pulling the same 60 foot times when i just had some minor bolt-ons and 3.92 gears and a stock converter. the 4.56s and stall are really not all that they are made out to be. and besides that, when i was near stock the truck was about 200lbs heavier but since then i got rid of the ac compressor, changed to eddy heads, ss rollpan, and a few other minor things so im sure u can see my disappointment with the truck right now. In cyl head class we are learning air flow behavior and I truly believe, if you haven't already, a larger tb will help. You have to open the plenum up to match and try to gradually taper the transition to the roof of the runner. That's going to help. Lastly gasket match the runner of the intake to the head. If the runners opening is smaller than the heads, that means there is a "step" that will cause separation of airflow and a swirl that that will come back around and "pinch" airflow coming from the intake runner. These suggestion may even help with your current setup, but it's very hard with fuel injection to have a tb that is too big as long as the tune is adjusted accordingly.

[Siciliano15]

my best et so far is a 13.3 at 105mph so with a good launch 12's are possible i think. if i upgrade to a 52x55mm f&b do i have to modify the entrance to the M1 manifold or is it big enough? If it comes down to it I might send my M1 to shady dell and see if they could max port it and port-match it to out of box eddy heads.

[Intense RT]

my best et so far is a 13.3 at 105mph so with a good launch 12's are possible i think. if i upgrade to a 52x55mm f&b do i have to modify the entrance to the M1 manifold or is it big enough? If it comes down to it I might send my M1 to shady dell and see if they could max port it and port-match it to out of box eddy heads.Yes, the entry has to be opened up because the blades are larger, front to back, than the plenum opening.

[Adobedude]

my best et so far is a 13.3 at 105mph so with a good launch 12's are possible i think. if i upgrade to a 52x55mm f&b do i have to modify the entrance to the M1 manifold or is it big enough? If it comes down to it I might send my M1 to shady dell and see if they could max port it and port-match it to out of box eddy heads.

Ditto on the opening up the M1 for the 52x55. It's easy with a die grinder...I have an electric one.

Gasket matching the M1 to the heads is easy, but time consuming...Mine was Waaaaaaaaay off on a couple runners. Also use gasket sealer on the bottoms of the intake gaskets (head side) lightly torque the M1, let the sealer dry, pull the intake and trim the gaskets...It's typical to have a few protruding into the runners 1/8", especially after you gasket match everything.


Your truck is modded about like mine, I just went out and cut a 1.8 60'....I think the difference is the 727.

Are you on the stock diff....I toasted my Auburn in 1 year so I went with a Detroit Locker.

[Siciliano15]

im on the auburn which hasnt been that great.... seems to put more power to the right rear than the left rear because i see more burnt rubber on the right rear wheel well than the left. also if i make a right turn and give it too much gas it spins the inner wheel but if i give too much gas on a left turn both wheels spin and the back end breaks loose.

[rattler360]

are you running caltracs?

[rattler360]

do caltracs and a tru trac or detroit locker

[Pete102580]

looked last night at the dyno and the peak torque of 322 is at 4000 rpm and the peak hp of 292 is at around 5400 rpm. also i originally had a b&g m1 flash but then they didnt seem to want to work with me to custom tune things so i called tom fox and he adjusted my air/fuel and i actually picked up a small amount of power like around 5 or 6 ft-lbs

try a higher stall? your truck and mine have almost identical mods.. i would even call yours a little more/better. we dyno VERY close.

in my ccab i average a 1.9/2.0 60' on a 3500 stall and hoosier DOT's. i can do 1.8's, but they're not regular. with the 3500 over the 2400 stall i removed- i picked up 2 tenths from 13.5 to 13.3. mph was the same of course- 102.
pete

[Siciliano15]

try a higher stall? your truck and mine have almost identical mods.. i would even call yours a little more/better. we dyno VERY close.

in my ccab i average a 1.9/2.0 60' on a 3500 stall and hoosier DOT's. i can do 1.8's, but they're not regular. with the 3500 over the 2400 stall i removed- i picked up 2 tenths from 13.5 to 13.3. mph was the same of course- 102.
pete

those are great 60 fts especially that u have the extended cab..... i really want to try to stay with the stall i have if i can because i just put it in there and id hate to have to go change it for the third time...... but i may end up doing that if nothing else works. only other thing i can think of is maybe the stall isnt fully broken in yet because i have only put about 1000 miles on the truck since i got it installed and it has a heavy duty lockup clutch on it because on my previous stall the lockup went out after a few months and i had horrible gas mileage and rpms on the highway.