Converter Or Carb/Fuel Problem ?

I have a friend that has a 408 sbf running nos...When he tested on just motor, it bogs bad off the line through about the 60-80 mark, then runs fine...On nos it leaves like a bullet...In these links its a motor pass , then a nos pass...Track is not prepped good , so he would hook and then break loose...

Motor Pass
https://www.youtube.com/watch?v=xW3dBPGvT84

Nos Pass
https://www.youtube.com/watch?v=l5duIMzOeTk

jet extensions on carb, as well as a bigger squirter/squiter volume. Lean bog.

kim wrote:jet extensions on carb, as well as a bigger squirter/squiter volume.  Lean bog.

Onlything he has done so far is patrick got him to change airbleeds...He changed jets on his own and made no differance..

try a different carb

richter69 wrote:try a different carb

I think some one don't like Pat? lol

Ace

If the problem is a lack of jet EXTENSIONS (as Kim suggested), simply changing jets won't be much help.  Do you know if it actually has extensions in the rear bowl or not?

powerstrokeace wrote:

richter69 wrote:try a different carb

I think some one don't like Pat? lol

Ace

seems legit.

richter69 wrote:

powerstrokeace wrote:

richter69 wrote:try a different carb

I think some one don't like Pat? lol

Ace

seems legit.

Yes he checked it and it has jet ext's in the back..... Patrick has been trying real hard , getting him to change everything he can think of, just no luck yet...We are trying to find another good carb to try on it....If its dry enough her sat im gona let him put my 1150 on if we dont find a smaller one...

It just never comes into power without the N20.


What converter is in the car? What gear? It might be in the carb, but it could simply be the thing is trying to launch outside the engines power band, and takes that long to come on. The instant 150 hit sure wakes it up, but its going to really spike the torque curve, and that's why its so responsive. Also why it blows the tires off.....

Is there an air cleaner on the carb? If so how tall from top of carb?

TO check if its vent tube slosh, simply connect front and rear vent tubes with some rubber tubeing, put a T in the middle so they can suck air.

kim wrote:It just never comes into power without the N20.


What converter is in the car? What gear?  It might be in the carb, but it could simply be the thing is trying to launch outside the engines power band, and takes that long to come on.  The instant 150 hit sure wakes it up, but its going to really spike the torque curve, and that's why its so responsive.  Also why it blows the tires off.....

Is there an air cleaner on the carb?  If so how tall from top of carb?  

TO check if its vent tube slosh, simply connect front and rear vent tubes with some rubber tubeing, put a T in the middle so they can suck air.

Never thought about vent tube slosh!!!! I will get him to try that sat at the track....No air cleaner....Stall is suppose to be a 5000 PTC......410 Gear

colormebad wrote:

kim wrote:It just never comes into power without the N20.


What converter is in the car? What gear?  It might be in the carb, but it could simply be the thing is trying to launch outside the engines power band, and takes that long to come on.  The instant 150 hit sure wakes it up, but its going to really spike the torque curve, and that's why its so responsive.  Also why it blows the tires off.....

Is there an air cleaner on the carb?  If so how tall from top of carb?  

TO check if its vent tube slosh, simply connect front and rear vent tubes with some rubber tubeing, put a T in the middle so they can suck air.

Never thought about vent tube slosh!!!! I will get him to try that sat at the track....No air cleaner....Stall is suppose to be a 5000 PTC......410 Gear

Have you stood behind the car and checked the exhaust to see if it is running rich or watched it launch and see what the tires and suspension are doing ?
I think the stall is too tight on motor and on the nos. the converter works because it is making more torque
.

whitefield wrote:

colormebad wrote:

kim wrote:It just never comes into power without the N20.


What converter is in the car? What gear?  It might be in the carb, but it could simply be the thing is trying to launch outside the engines power band, and takes that long to come on.  The instant 150 hit sure wakes it up, but its going to really spike the torque curve, and that's why its so responsive.  Also why it blows the tires off.....

Is there an air cleaner on the carb?  If so how tall from top of carb?  

TO check if its vent tube slosh, simply connect front and rear vent tubes with some rubber tubeing, put a T in the middle so they can suck air.

Never thought about vent tube slosh!!!! I will get him to try that sat at the track....No air cleaner....Stall is suppose to be a 5000 PTC......410 Gear

Have you stood behind the car and checked the exhaust to see if it is running rich or watched it launch and see what the tires and suspension are doing ?
I think the stall is too tight on motor and on the nos. the converter works because it is making more torque
.

He didnt have anyone to help him..We gona take a few parts and carbs and try out some new things sat...We talked to Kenny earlier and PTC and found out he only has a 3500 street/street converter...Kenny said he needed a 4500 they make which alot of people run..We gona test this other stuff everyone has mentioned before he changes converters

colormebad wrote:

whitefield wrote:

colormebad wrote:

kim wrote:It just never comes into power without the N20.


What converter is in the car? What gear?  It might be in the carb, but it could simply be the thing is trying to launch outside the engines power band, and takes that long to come on.  The instant 150 hit sure wakes it up, but its going to really spike the torque curve, and that's why its so responsive.  Also why it blows the tires off.....

Is there an air cleaner on the carb?  If so how tall from top of carb?  

TO check if its vent tube slosh, simply connect front and rear vent tubes with some rubber tubeing, put a T in the middle so they can suck air.

Never thought about vent tube slosh!!!! I will get him to try that sat at the track....No air cleaner....Stall is suppose to be a 5000 PTC......410 Gear

Have you stood behind the car and checked the exhaust to see if it is running rich or watched it launch and see what the tires and suspension are doing ?
I think the stall is too tight on motor and on the nos. the converter works because it is making more torque
.

He didnt have anyone to help him..We gona take a few parts and carbs and try out some new things sat...We talked to Kenny earlier and PTC and found out he only has a 3500 street/street converter...Kenny said he needed a 4500 they make which alot of people run..We gona test this other stuff everyone has mentioned before he changes converters

Is the 4500 a 9.5 or 8 ? I ran a 9.5 4800 and then change converters several more times and wound up with a 8 5000 . What is the engine build ?

whitefield wrote:

colormebad wrote:

whitefield wrote:

colormebad wrote:

kim wrote:It just never comes into power without the N20.


What converter is in the car? What gear?  It might be in the carb, but it could simply be the thing is trying to launch outside the engines power band, and takes that long to come on.  The instant 150 hit sure wakes it up, but its going to really spike the torque curve, and that's why its so responsive.  Also why it blows the tires off.....

Is there an air cleaner on the carb?  If so how tall from top of carb?  

TO check if its vent tube slosh, simply connect front and rear vent tubes with some rubber tubeing, put a T in the middle so they can suck air.

Never thought about vent tube slosh!!!! I will get him to try that sat at the track....No air cleaner....Stall is suppose to be a 5000 PTC......410 Gear

Have you stood behind the car and checked the exhaust to see if it is running rich or watched it launch and see what the tires and suspension are doing ?
I think the stall is too tight on motor and on the nos. the converter works because it is making more torque
.

He didnt have anyone to help him..We gona take a few parts and carbs and try out some new things sat...We talked to Kenny earlier and PTC and found out he only has a 3500 street/street converter...Kenny said he needed a 4500 they make which alot of people run..We gona test this other stuff everyone has mentioned before he changes converters

Is the 4500 a 9.5 or 8 ? I ran a 9.5 4800 and then change converters several more times and wound up with a 8 5000 . What is the engine build ?

He was wrong about the converter...He called kenny at PTC and found out its a 3500 strit/strip 3500.. 10"
sbf 408 stroker
13:1 compression
C4
410 Gear
Nos