Can't do a burn out.

[Mertz]

I have my 72 Chevy truck 350 set up with the Qjet all dialed in and get great accelleration. I tried powerbraking it and doing a full throttle takeoff and it launches rather slow and then once it gets going it goes great. At one point I had it standing on its wheels but I haven't been able to reproduce that since. I don't have the 350 trans kick down installed and I have a stall converter set up for towing. 2500 if I remember correctly. I can do a nice burnout if I am turning when I take off with or without the power brake. It just seems like it doesn't have much power as I hit full throttle but as I get going I hear the secondaries working. 50 to 70 takes just a few seconds without the secondaries. The truck does not have a posi. I am not sure what my rearend is but think it is a 3:08 or 3:28. I have a 1" 4 hole spacer on it to try to help with torque but it soesn't seem to help. Intake is a Edelbrock 2101 with ceramic headers and flow through exhaust.

[prostreetC-10]

No fun when you can't do a burnout. Time for a BBC.

What is your initial timing set at? That can make a big difference.

[Mertz]

Inital is at 12 with total around 50 mechanical and vacuum all in at 3000. Around 34 with mechanical no vacuum. MSD Ready to Run distributor.

[Fitz]

Originally Posted by Mertz

Inital is at 12 with total around 50 mechanical and vacuum all in at 3000. Around 34 with mechanical no vacuum. MSD Ready to Run distributor.

50 degrees total? seems like a bit much. GM says mine should be 36 total.

[Fitz]

Originally Posted by prostreetC-10

No fun when you can't do a burnout. Time for a BBC.

What is your initial timing set at? That can make a big difference.

The Doctor at GMPP has the cure for your problem! If your truck won't do a burnout with one of these your problem is the loose nut behind the wheel.

[mclairmo]

How tall are your tires?

[Mertz]

They are fairly tall 16" Uniroyal LTs

[usmcchevy]

Probably not your problem, but these trucks do have pretty good rear brakes (at slow speeds). When I was driving my '70 the rears would lock long before the front.

[cdowns]

if you go on a slight uphill incline and let the truck roll slowly back and rev the crap out the engine then just drop it in lo you might b able to burnout of course you might also pop the ujoints or crack the tranny case too

['72customdeluxe]

I have a new goodwrench 350 with a 2101 manifold, richened 1978 q-jet, and flowtech ceramic coated headers. I know my eBay hei has a VERY lazy mechanical advance curves, as did many factory smogger hei setups. A new advance spring and weight kit might help and is cheap. Your gears and tires aren't helping for sure. If your carb is lean you're not getting full power either

[tim21391]

are u running points? if so they might be shot i had a problem with this before i went to hei

['72customdeluxe]

Says an msd hei. I guess my theory about his mech advance was wrong too, all in by 3000 sounds fine

[scott's69]

Your stall convertor might be one reason. Too much convertor not enough motor would cause your problem.

[tim21391]

oh snap my bad i mustve missed that part.. maybe the coil went bad in it?

[Mertz]

The ignition is working perfectly. I read some techniques for doing burnouts on line, like rolling backward and then hitting it or rolling forward slightly and then stomp on the gas and brake at the same time.

[BarryB]

I had this problem once before, my advance inside the dist. was stuck, wasn't letting the timing to advance properly. double check it, even though its new.

[jholley]

Originally Posted by Mertz

but think it is a 3:08 or 3:28.

I doubt it's a 3:28. Someone here can correct me if I'm wrong but I don't think they ever came with that gear and I've looked around I don't think you can even buy that gear for a Truck 12 bolt. 3:08, 3:42, 3:73, 4:11 are the most common. I had 3:73 gears in mine and could turn the tires just stomping on the go pedal. I mistakenly put 3:08 gears in it hoping for some mileage and it just killed the fun factor. My motor isn't anything special, 290hp 350 and TH350 tranny. I could power brake it with the 3:08 gears but that sucks. Ultimately I put the 3:73 gears back in. Is the diff open or a posi? If it's an open and you can't even turn one tire that sucks!

[Mertz]

Its open. The mechanical advance is working fine. I tried rolling backwards a little yesterday and stomping it and I got it to let go for a short distance. I think the gears are probably 3:08 but I couldn't find anything on the build sheet. Is there a number somewhere to tell me what the gears are?

[tasian]

Originally Posted by Mertz

I think the gears are probably 3:08 but I couldn't find anything on the build sheet. Is there a number somewhere to tell me what the gears are?

check for a tag on the diff cover if theres nothing there you can always run the other numbers stamped on the rear end

what kind of top speed are you getting from it? 3:08's are pretty tall that may not be all of your problem but i doubt its helping much for your low end

[handsomerob]

Whats the stall on your converter? if your stall speed isn't matched with the torque curve of your engine your truck will be a dog.

[breeh]

Originally Posted by handsomerob

Whats the stall on your converter? if your stall speed isn't matched with the torque curve of your engine your truck will be a dog.

It sounds like a converter stall and rear gear ratio mismatch to me. If you bought a converter without considering the rear gears then you are learning a lesson that many of us have had to learn. Cam, stall, rear gears; all must work together.

[Oklahoma]

I had a old tired 350 with 2:73's, that's right 2:73's with a one wheel wonder and I could smoke that tire like no body's business. I think it is the stall, not an expert on then, because I have never had one, but was told by lots of people who like good daily drivers not to put one in mine. I just rebuilt every part of the power train, rebuilt 350, 7000r4, 3:73 posi rear end, electric fan to help the power, and now I can barley spin the tires, a little depressing, but not a big deal to me, but like you said you want to pull a trailer, as do I, so I will be building a stroker motor my self so I know what I have and I guarantee when I'm done it will smoke the tires.
Note: I you just want to smoke the tires for the fun of it, just put a little oil on the tires before you start the power brake and watch the tires light up.

[BIGBLU 72]

i doubt that having a 3.08 gear is the problem cause mine will lay about 10 foot of one wheel wonder rubber with no power break. Secondaries not kicking in a possiblity or not getting full throttle from accel linkage?

[Mertz]

I have been removing and replacing the carb to get the jets and rods right so I haven't verified that the linkage is allowing for full throttle but the secondaries are definitely kicking in once I get going. You can hear them a few feet down the road when it starts to take off. I also don't have the kickdown cable connected.

[prostreetC-10]

It's a pretty funny post really. A guy begging for burnout help. It's not unheard of for a truck with hwy gears, tall tires and a tired motor not be able to do a burnout. Do you know for a fact it's a 350? 305 and 307's are dogs. Can you have someone lift up on the right rear part of the bumper??