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Discussion Starter · #1 ·
What's up guys? I'm new here. I've posted on several other forums about this problem, but people seem to lose patience with me. Everytime I think I have it fixed, it comes right back. I've been working on the same problem for over a year now. This truck has had 2 different motors, 6 or 7 carbs, and over 20 sets of fouled spark plugs. It's got a 6.0(Gen III) with a small cam and bolt ons. It's backed by a TH350 with a 3500 stall and 4.56 gears and 28X10.5 slicks.
The problem I've been having is getting it to take WOT from a stop. Here's how the carb is set up.
Holley 750 Doublepumper
Primaries: 70 Jets, 31 squirter, 50cc pump, float set to bottom of sight hole, 6.5 Power Valve, transfer slot is squared.
Secondaries: 76 Jets, 31[tube type]squirter, hollow screw, 30cc pump, jet extensions, float set to bottom of sight hole, No Power Valve.
Idle set to 900-1000rpm.
Fuel pressure is set to 6-7psi(it's been bouncing lately) with Mallory Comp 110 electric pump and Mallory 4309 regulator.
1" 4 hole spacer on a Victor Jr. intake.
14X3" drop base air cleaner

Timing is: 12*@0rpm, 20*@500rpm, 28*@1700rpm, 29*@4300, 36*@6000+rpm. No vacuum advance.

I've been told that I needed to let the truck warm up longer, but I usually let it warm up about 5 minutes before running it hard. Could that cause it to just go dead when I give it WOT? Maybe the motor is just too cold? It has a stock T-stat though.
I've also been told that it's the routing of my fuel lines. I have the regulator mounted on the firewall. From there, I have a line feeding the fuel log from the rear of the carb(with a filter and pressure gauge after that). But wouldn't the pump shot make up for any brief lack of pressure on the launch?
My wife seems to think it's water in the gas. The station where I get gas from has been suspected of watering down their gas before. Not only that, but it's been raining a lot and I may have got a little in my fuel cell through the little vent on top. I'm gonna drain the tank tommarrow and fill up at a different station to rule out this one.
What else should I be looking at? My filters shouldn't be clogged, they are pretty new...maybe 50miles or less on the whole truck/setup(except motor - 30,000mi).
Here's a better description of the problem. I'm at a stop, I'm idling at 1000rpms, then I smash the gas. The truck doesn't move, instead it sputters and dies. Sometimes it will recover if I let off the gas and continue to let it idle. A few other times, I've been at a slow roll(5mph) and try to go WOT and it will die or try to. I haven't tried lately, but when I had the 850DP on there, it was impossible to do a [stationary]burnout. It's very embarrassing. The truck would die if I stomped it while holding the brakes. If I went slowly, it would barely move the tires or just start walking forward slowly(but the motor would be singing). The best 60ft I could cut was a 2.15(not spinning)...and that's sad since heavier/less powerful trucks cut 1.8-1.9's with street tires.
 

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More initial timing will solve it. You are running 36 degrees total, so if you can run 18-20 degrees initial I am sure you will have it fixed.

Dave
 

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Discussion Starter · #3 ·
I will give that a try this afternoon.
 

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If your gas does have any water in it, the engine will run like crap all the time.
 

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Discussion Starter · #5 ·
I'm about to go dump the gas out right now.
 

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A few things from what you've wrote:

1) It shouldn't be fuel, since you're saying the same problem has been happening for over a year with two different engines, and different carburetors.

2) If the engine is that mild you may have too much carburetor on it. A smaller carburetor is going to have better air velocity which is going to respond better.

3) Increasing the timing should help usually 18° at idle, and about 36° total is a good starting point.

4) What is your converter actually stalling at, it sounds like it's not loose enough.

5) What happens when you change your squirter nozzle size?
 

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Discussion Starter · #10 ·
A few things from what you've wrote:

1) It shouldn't be fuel, since you're saying the same problem has been happening for over a year with two different engines, and different carburetors.

2) If the engine is that mild you may have too much carburetor on it. A smaller carburetor is going to have better air velocity which is going to respond better.

3) Increasing the timing should help usually 18° at idle, and about 36° total is a good starting point.

4) What is your converter actually stalling at, it sounds like it's not loose enough.

5) What happens when you change your squirter nozzle size?
1) That's exactly why I have to post on forums like this. My common sense went right out the window after my accident last year. Memory is shot too, I had to leave notes of every thought and every purchase just to build this truck. Glad you pointed that out.

2) The engine is mild, but it put down 380HP to the rear wheels when it was EFI in my wife's daily driver. It should have a little bit more now with a better intake, bigger headers and a much better exhaust. There should also be slightly less drivetrain loss.

3)So should I set it to 18*@0-1000rpm, then full timing from 1100rpm up.

4)I'm not sure exactly what it stalls to because it used to just fly through the rpms so fast that I'd be on the rev limiter before I could get the pedal to the floor. I'll check it when I take it out next time. I know I sometimes footbrake it to 3000.

5)There was no change with the squirter nozzles. I tried a 35 in there and just settled on 31's front and back instead of 28/31(stock).


Jeff McCK - I'm running the stock heatrange plugs(whatever walmarts book says) I think they are projected tip. I've also tried NGK TR55's and they didn't last 1 day.
 

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Did I read your parts list correctly? You said that you have a 50cc pump on the front? I would think that is a little overkill, especially on a somewhat mild motor. Have you tried a 30cc pump on the front? If not, you may want to.
I do agree with everyone else on the timing. Get as much initial timing as the starter will stand and limit your total to around 36 or so to start with.
 

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Discussion Starter · #12 ·
Yeah, I have a 50cc pump on the front. A few other LS1 guys told me they used one, so I figured I'd try it. We got rained out yesterday and today, so I'll have to do my testing over the weekend on the backroads.
 

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Discussion Starter · #13 ·
I set the timing to be normal from 0 to 1100rpms. I locked it to 24* after 1100rpm. The truck feels a lot more responsive and doesn't have that crazy heavy feel to it(or atleast not as much). I also decided to play with my 2step since I never had one before and I didn't really know what to expect. At first, I thought my trans was slipping real bad because I didn't seem to move much after getting off the 2step. My brother told me that I was just sitting there spinning, but the tires didn't smoke or make any noise. Then after that, we went back to look at the marks I left on the road, and it was spinning pretty good. I'm glad. I can finally do a burnout in this truck. Thanks guys for all your help. I really appreciate it. I'm gonna take it to the dyno and then to the track soon. I'm trying real hard to hit high 11's and lots of people are telling me I can't do it with what I have. We'll see.
 

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24 total isnt enough.
 

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Agree.
 

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Discussion Starter · #16 ·
The guy who tuned this motor when it was EFI told me that's what this motor needs. Atleast I think that's what he said[my memory sucks]. Anyway, over on LS1tech there were a few guys who said these motors don't like more than 28-29* but 24 was a good starting place. I planned to increase it a little at a time once I get it on the track to see what runs best.
 

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It should make more power with more timing.
 

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A few things from what you've wrote:

2) If the engine is that mild you may have too much carburetor on it. A smaller carburetor is going to have better air velocity which is going to respond better.

X2, CarbGuy has given you the answer to all of your problems but you seem to have over looked his responce.
 

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If that were the case then you couldn't make a 750 cfm carb work correctly on a mild 350 cubic inch Chevy.

The Gen III 6.0 at 364 cid and making gobs more power stock than any mild old school SBC ever has.

Some guys are running 950HP carbs on them.
 

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Discussion Starter · #20 ·
I didn't overlook his response, I'm just kinda limited on options. I have a 670 Avenger, but I'm not to familiar with it + I feel it's a bit small for my future plans(more compression + bigger cam). A lot of other guys seem to be running pretty big carbs on their GenIII's like Billyman said. But I guess it wouldn't hurt to try it. I'll take the 670 with me when I go to the dyno/track.
 
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