Thread: Help to get off the line please!

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Originally Posted by gearGrinder

Not too sure it is a fuel issue, my problem happens when standing still and flooring the pedal, the truck just bogs and will stall if you stay on it. Anything you ask it to do over 1500 RPM happens without hesitation.

The really vexing part of this is 1 out of 20 times the truck WILL launch, I just haven't figured out what is different between when she does and when she doesn't - which is why I am looking at the carb first - of course 4.11 gears couldn't hurt but let's not go there

How much part could operating temperature play? My cooling system is apparently SUPER efficient with an electric fan and aluminum radiator, engine runs around 160 all the time unless I turn the fan off...

Thanks Mikej!
BTW that is a sweet ride you've got there

operating temp has a major role. You cant go off of anything if ts not at temp.

Originally Posted by BigTruckDriver

operating temp has a major role. You cant go off of anything if ts not at temp.

I just got an adjustable thermo fan relay in yesterday, will install tonight - the existing one was just on all the time.

The adjusto turns off the fan 10 degrees lower than it starts it so what temp range should I be looking at?

Thanks for this, I assumed cooler was better...

Thanks to all who responded to my post I am happy to report there is progress!

Installed new thermo fan relay, set ON temp around 180-190
Found a possible vacuum leak at vac can on trans, fixed that
Played with springs in dizzy, went with blue/yellow from my crane vac adv kit
-lighter combo than stock springs
Played with initial timing
-16 degrees advanced was good all around
-20 was better low end but killed top end
-18 is actually a good compromise of decent low and still fairly aggressive top end
-it is set now somewhere between 16 and 18 degrees adv
-did several runs including heavy load (1 mile steep hill) at partial and full throttle, no knock at all
I didn't check it after the last run (was 2 AM) but mechanical advance is all in by 2000 RPM or sooner
Total timing is around 37 degrees
Played with mixture at idle, went 3/4 turn richer
Truck launches OK now! It doesn't spin 'em every time but that's wasteful anyway right?
Did 100 MPH on the way home on a flat section of fwy with no problem (no ping, hesitation or starvation) backed off to 90 and at partial throttle noted the tach just under 4000 RPM with about 16" manifold vacuum
-didn't want to take my eyes off the road in power mode

So the good news is that was a successful evening, the bad news is it seems like my torque converter stall is around 1400, not as high as I previously had determined
Now I am on leak patrol, everything except the brakes and coolant is leaking, I am going to go through all the engine/trans bolts today (ALL of them) and re-torque. The trans is leaking out of both ends so I will consider swapping torque converters when I pull the trans to re-seal it.

I am getting an HEI adjustable vac can today so I can play with adding vacuum but the mechanical only curve I have right now feels pretty durn good...

I will try to find a place to dyno/sniff for further carb tuning

Again thanks for all the help/advice!

Another tip is to get a oxygen sensor wired in to the system. It will tell you if you are running rich or lean at idle or through out the rpm range. I think edlebrock sells one for about 100 dollars. Or you can buy one and wire it up to a volt meter and it will do the same. Should get you right on with your fuel mixture. You can also tune your idle mixture with the vacuum gauge.

What a difference a day makes, or in this case a weekend

Changed spark plugs over the weekend, WOW what an improvement! The plugs that were in there were not seating all the way in and there was fouling on the threads but not the electrodes, the spark was happening IN the plug hole rather than in the cylinder and leaking as well... Not sure how the obviously-wrong plugs got in there but I decided to try swapping plugs and I'm sure glad I did.

Now this thing launches and runs like a champ, and boy did I need to change my timing, now my initial timing is around 8-10 degrees advanced otherwise she pings under load - even with the vacuum disconnected which leads to another topic and thread...

Originally Posted by BigTruckDriver

Another tip is to get a oxygen sensor wired in to the system. It will tell you if you are running rich or lean at idle or through out the rpm range.

This is a good idea, looks like AutoMeter sells a kit with sensors, bungs and gauge for around $350 - ouch

Originally Posted by BigTruckDriver

You can also tune your idle mixture with the vacuum gauge.

This is something I need to learn how to do. One thing I did notice, the vacuum dips a bit during idle then returns, not sure why.

If I had to guess I'd say there were a valve timing problem allowing intake and exhaust valves to overlap too much? My cam does overlap the valves but only by 2 or 3 degrees if I remember correctly - next issue on the list to chase...

Thanks again to all who chimed in with advice and suggestions!

A sensor would cost 50 dollars new and the bung 5 dollars, digital volt meter 20 dollars. If your really on a budget you could get a sensor from the junk yard for free.
Also are you using a adjustable vacuum canister?

Originally Posted by BigTruckDriver

Also are you using a adjustable vacuum canister?

Yes and since installing it I cannot get the car to NOT ping under various conditions, even with the vac hose disconnected, must be those new spark plugs