High Rev Lean out 81' FB
 

Hey all, I've got an 81' FB that seems to be leaning out something fierce at high RPM!!! I can drive around under 5,000prm but when I go over for any period of time I blow white smoke like cheech and chong, the car then smells like it's leaned out horribly!!! I don't seem to be loseing much coolant so, I don't THINK it's a coolant seal!! I've rebuilt my OMP cause' when I got the car it was seized open, (it now appears to be to be working) I've tried to adjust the mixture but that doesn't seem to help either!!!!
Thew car is basically stock I've just got a header on and I've removed the rats nest (Leaned out before the rats nest was removed)
What should I be looking for??? Any help our input would be appreciated!!!


Apex

when was the last time you changed the fuel filter?

how old is you fuel pump and what type is it? output rating? (in that vein, how strong is your electrical system?)

where is your timing?

personally, i think you may be jumping the gun if your only criteria are smoke and a smell. could be oil at the higher RPM causing the smoke. (how many miles on the seals?) any bucking? power loss? backfiring? etc.

if you're worried about mixtures, i'd suggest investing in an EGT good gauge and track it that way.

Thanx for the reply!!
Fuel filter has about 4k on it, fuel pump I really don't know could still be stock for all I know!! The timing is set to timing marks!! Doesn't seem to be any really lose in power, occasional buck but not all that noticable!! When I bought the car a few months ago I was told that the motor had 40-45k on a rebuild, So assumeing seals "should" be good!
Thanx again


Apex

list your setup so we can help diagnose what is going on. It could be a number of things.

My setup consists of:

Stock carb
As far as I know stock fuel pump!!
Rats nest as well as all emmisions removed!!
Header with straight pipe to stock mazda muffler!!
I just replaced my intake manifold gasket!!
I cleaned the carb, was a bunch of crap in the float bowls!!
I've unseized my OMP so it now appears to be working!!
The spring against the diaphram for my secondary vaccumm acuation has been removed in an atempt to see if secondary's weren't working right!!!
I have reletively new plugs in the car, and after running at high RPM the I pulled the plugs and checked them, they look like it was leaning out!!

Thanx again

Apex

can you clarify? sounds like more than a chance that the secondaries are not opening. are they functional now?

The secondary diaphram assembly!!! that's what I took the spring out of!!
The secondaries "seem" to be functioning, however as to the accuracy I'm not to sure!!! I just piccked up an '82 so when I get the time I'm gonna try the fuel pump to see if it helps!!! If it doesn't could it be that maybe the floats are out??

Apex

I finally managed to have time to change out the fuel pump!!! It didn't seem to hlp at all, I also try'd changing out the carb, with no beneficial change, noticed that coolant level was acually down a little!! I guess I should start saving for a rebuild!!!
Also when I got the car the trailing plugs weren't firing, so I replaced the igniter and they're working as they should be!!! The guy I got it from said the engine was rebuilt about 40,000km ago, could the trailing plugs not working for that period of time leed to blowing a coolant seal??

Thanx all

Apex