Ignition-Fuel mixture tuning....please step in
Thread Starter
Burning Brakes
Joined: Nov 2000
Posts: 810
Likes: 4
From: Austria
Ignition-Fuel mixture tuning....please step in
hi all
corresponding to this thread
http://forums.corvetteforum.com/c4-t...ny-needed.html
first, please let me give some specs on the engine
AFR 180cc heads, Airgap-Intake and a 224/230 110LSA comp cam (08-423-8), 750cfm speed demon carb..
the problem we have now is the following:
we adjusted the ignition to 10° at idle, with vacuum hose pulled.
the vacuum hose is connected to manifold vacuum (not to ported vacuum), the car seems to like it much more!
idle is very stable, car runs strong...
but..when cruising under light load at about 1800 rpm and get very slowly on the gas, some hesitation and bogging occur..we put a wideband O2 in, in this moment it jumps to about 20:1 AFR
after this hiccup the car is running normal
when stepping on the gas heavier at 1800 rpm, theres a small spike in AFR 20:1, but not enough to be noticed without Lambda Equipment.
the distributor, thats now in the car, is the stock dist. from a 350HO engine
can you give us some info how to cure the problem?
thank you very much
corresponding to this thread
http://forums.corvetteforum.com/c4-t...ny-needed.html
first, please let me give some specs on the engine
AFR 180cc heads, Airgap-Intake and a 224/230 110LSA comp cam (08-423-8), 750cfm speed demon carb..
the problem we have now is the following:
we adjusted the ignition to 10° at idle, with vacuum hose pulled.
the vacuum hose is connected to manifold vacuum (not to ported vacuum), the car seems to like it much more!
idle is very stable, car runs strong...
but..when cruising under light load at about 1800 rpm and get very slowly on the gas, some hesitation and bogging occur..we put a wideband O2 in, in this moment it jumps to about 20:1 AFR
after this hiccup the car is running normal
when stepping on the gas heavier at 1800 rpm, theres a small spike in AFR 20:1, but not enough to be noticed without Lambda Equipment.
the distributor, thats now in the car, is the stock dist. from a 350HO engine
can you give us some info how to cure the problem?
thank you very much
Burning Brakes
Joined: Jan 2007
Posts: 1,057
Likes: 4
From: Concord Calif
hi all
corresponding to this thread
http://forums.corvetteforum.com/c4-t...ny-needed.html
first, please let me give some specs on the engine
AFR 180cc heads, Airgap-Intake and a 224/230 110LSA comp cam (08-423-8), 750cfm speed demon carb..
the problem we have now is the following:
we adjusted the ignition to 10° at idle, with vacuum hose pulled.
the vacuum hose is connected to manifold vacuum (not to ported vacuum), the car seems to like it much more!
idle is very stable, car runs strong...
but..when cruising under light load at about 1800 rpm and get very slowly on the gas, some hesitation and bogging occur..we put a wideband O2 in, in this moment it jumps to about 20:1 AFR
after this hiccup the car is running normal
when stepping on the gas heavier at 1800 rpm, theres a small spike in AFR 20:1, but not enough to be noticed without Lambda Equipment.
the distributor, thats now in the car, is the stock dist. from a 350HO engine
can you give us some info how to cure the problem?
thank you very much
corresponding to this thread
http://forums.corvetteforum.com/c4-t...ny-needed.html
first, please let me give some specs on the engine
AFR 180cc heads, Airgap-Intake and a 224/230 110LSA comp cam (08-423-8), 750cfm speed demon carb..
the problem we have now is the following:
we adjusted the ignition to 10° at idle, with vacuum hose pulled.
the vacuum hose is connected to manifold vacuum (not to ported vacuum), the car seems to like it much more!
idle is very stable, car runs strong...
but..when cruising under light load at about 1800 rpm and get very slowly on the gas, some hesitation and bogging occur..we put a wideband O2 in, in this moment it jumps to about 20:1 AFR
after this hiccup the car is running normal
when stepping on the gas heavier at 1800 rpm, theres a small spike in AFR 20:1, but not enough to be noticed without Lambda Equipment.
the distributor, thats now in the car, is the stock dist. from a 350HO engine
can you give us some info how to cure the problem?
thank you very much
Sounds like you don't have a pump shot at frist movement of the butterflies.
Thread Starter
Burning Brakes
Joined: Nov 2000
Posts: 810
Likes: 4
From: Austria
hi and thank you!
we thought about that, and we observed the moving of the pump arm very closely...it has no play in it, and starts to move with the very first movement of the throttle lever...
another thing..when the throttle is tipped in very slowly, so the pump shot is added very slowly, and maybe "not seen" by the engine, because, in comparison, the added fuel is not enrichening the incoming air enough..?
should we try different pump cams?
thanks
we thought about that, and we observed the moving of the pump arm very closely...it has no play in it, and starts to move with the very first movement of the throttle lever...
another thing..when the throttle is tipped in very slowly, so the pump shot is added very slowly, and maybe "not seen" by the engine, because, in comparison, the added fuel is not enrichening the incoming air enough..?
should we try different pump cams?
thanks
Burning Brakes
Joined: Jan 2007
Posts: 1,057
Likes: 4
From: Concord Calif
hi and thank you!
we thought about that, and we observed the moving of the pump arm very closely...it has no play in it, and starts to move with the very first movement of the throttle lever...
another thing..when the throttle is tipped in very slowly, so the pump shot is added very slowly, and maybe "not seen" by the engine, because, in comparison, the added fuel is not enrichening the incoming air enough..?
should we try different pump cams?
thanks
we thought about that, and we observed the moving of the pump arm very closely...it has no play in it, and starts to move with the very first movement of the throttle lever...
another thing..when the throttle is tipped in very slowly, so the pump shot is added very slowly, and maybe "not seen" by the engine, because, in comparison, the added fuel is not enrichening the incoming air enough..?
should we try different pump cams?
thanks
Without the engine running you should see fuel at frist movement, if not fix the linkage so it does. Now if you have fuel after checking that then yes look for a cam that is more aggresive at frist movement.
