DragStuff

hi guys, i recently ran my car for the first time this year and on the 3 passes i made, the car stopped making power at the top of second and third gear. it feels like fuel starvation but i have a bg400, -10 line to a magnafuel log with a mallory fuel regulator to a pro-systems 950. however,i do not have a visible fuel pressure guage i can monitor during the run.
the car weighs 3500 lbs with me in it,406 chevy with track 1 heads approx 11.1 compression 630 roller cam with 260 @.050 th400 with 4800 stall and 12 bolt with 4:10 and 40 degrees of timing
anything else i should be looking at? possible fuel pump issue??
any ideas would be greatly appreciated
thanks in advance

Sounds to me like you have too much timming in it. I would back it off to about 32 , and make a pass and then advance in 1 deg. increments till the mph doesnt get any better then back off a deg. JMO

i move the timing around from 36-42 with no change

If it's fuel it ought to really lay over, pretty noticeable.

Sometimes weak valve springs will do this too, noticed any other signs like a small miss at the top of gear changes, maybe a pop here or there?

Clutches in the transmission fried? They'll start to lay over and loose ET before you smoke them sometimes.

Just some other things to worry about hehe

X2 on the tranny possibility. I'd look at the converter pretty close also.

I'm not too afraid of the timeing your running but the jetting has to be there also. Might try backing it off to 35° or so. But I'd bet if the jetting is correct then you might even like a few degrees higher. Is the distributor locked out? If not then what the initial? When is the timing all in by?

Is this a MSD system? If so....is the are you running a charging system and is it operating properly? Is the battery properly charged? Are you sure the pickup wires going from the distributor to the MSD box have the correct polerity? Are you running a 2 or 3 step? If so,...have you tried to change the chips around a bit?

Fuel system could be the culprit,...but it could be a low float level, kinked line, or some other kind of restriction in the fuel line. What kind of scoop are you running? Is it set up correctly? This could be speed related which could be air delivery....

Just some things to think about.

Don

How about the vent in the fuel tank?

no miss and the trans is tight and fresh; it feels like fuel to me because it just goes flat. has anyone seen this kind of condition from a fuel system like this. i used a mallory 140 pump for years with a number 8 line and never had any issues; i upgraded to this fuel system and its been a headache ever since. my fuel pressure does bounce around at the bypass fluctuating from 25 psi to 29psi. any ideas?

fuel cell is vented
i dont run an air cleaner and i have a 5 inch cowl hood
could this be a problem???

Sounds like a little too much timing. Whats your plugs look like?

IMO 40* of timing on a 406 at 11-1 comp is too high. May still be a fuel issue too though.

i am going to install a bypass regulator on my fuel distribution block, go through the carburetor and make a few more passes;i will post my results
thanks

after changing a bunch of fuel parts,carb,regulators,etc. i have concluded that my fuel system is not at fault. i find that this condition occurs during hot days ; when it is cooler ambient air temps the problem doesnt normally occur. during one pass, it started to lay down hard and all of a sudden it started to make power again which takes valve springs out of the equation. now i am leaning toward ignition. i have a mallory unilite dist. running to a msd 6al box which feeds an accel super coil it also has msd wires(new) and ngk 5671-8. any ideas would be helpful as this is draining my wallet of a lot of greenbacks!
thanks in advance

If the engine is fat (too much fuel) it will run worse on a hot (bad air) day, and pick up on a cool day. What do the plugs look like?

they are a gray color at the electrode and show some tan at the porcelain

Tan = lots of passes and idle time usually. The gray is fuel and if you're seeing plenty of it, chances are it's fat. Start taking some fuel out of it (jets) and see if it picks up MPH. It will help read the plug if you put some new ones in it.

If it's still at 40 degrees, that amount of timing may be making up for it being fat. I'd suggest putting some new plugs in it, back the timing off some, to say 36 and make a pass. It might be slower but that's ok, use that MPH for your baseline. Now start taking out fuel by dropping your jets and see if your MPH picks back up. Try and do this all on the same test so weather isn't as much of an issue. Keep going till it slows down MPH. Look at the plugs or at least a couple of them as your doing this, they should start cleaning up. Once you find your top mph, try adding or taking away some timing and see what it wants. You're getting a lot closer at this point and just make some adjustments from there.

Anyway, something to try to see if it's a AFR issue.

this problem i am having happens withought any warning and it wont rev or make power my jets are currently 74/84 which is very close to where i should be at. you can feel the car slow down in 2nd and 3rd. in first gear it pulls hard right up to 7500( i normally shift at 6800) timing is back to 38*