Team Camaro Tech banner

1 - 7 of 7 Posts

·
Registered
Joined
·
49 Posts
Discussion Starter #1
As you know from a previous post, I was having an issue with fouling plugs. It apparently was caused from the PCV sucking oil. I was given the advice of course not to just do away with the PCV. So from what I understand, the short valve covers had no baffles, but the stud girdles were supposedly supposed to act as baffles but apparently not. So I bought tall valve covers with baffles and put the PCV system back on. I hope this will solve that issue. So far I think it has. Now I installed brand new plugs, wires, and even replaced the Carb with a new Quick Fuel SL-750 as there was speculation that the carb was bad. I set the total timing at 36* at about 3600rpms. This makes the initial about 12*. The car seems to run fine but will not idle worth a damn. The best vacuum I get is 8-9 at idle. Turning the idle mixture screws in or out doesn't change much at all. The vacuum pretty much stays between 8-9. The only change in vacuum seems to be if you turn the screws to where they are almost at seat, then the idle will drop. Back them out 2-3 turns and it don't change the idle much at all. Vacuum pretty much just stays between 8-9. I set the curb idle at 1000. Put the car in drive, the idle drops to a steady 900 for about 30 seconds or so, then fluctuates back and fourth between 500-900 and acts like its going to stall. Put it back to park and it goes back to 1000. But wait, that's not all. Hit the throttle a few times and now it stays at idle at about 2000 and won't come back down even hitting the throttle a few more times. Put it back into drive and it will drop it to 1000 and seem fine. Put it back in park and its back to a normal 1000 again. Put it back into gear, and its back to 500-900 and wanting to stall. This will then just keep going back and fourth, 2000, then back to 1000, etc. I might get lucky where it stays at 1000 in park, and a steady 900 in drive, but that might be 1 out of 5-6 tries. I can't just keep a steady 1000 and a steady idle in drive. But drive down the road cruising around, it runs like a champ. What is wrong with this thing? Is the Quick Fuel carb junk? I never had problems with the Edelbrock on my other car or the other engine before I put this new crate in. Please, Does anybody have any knowledge on what this seems to be. Help!!!!!!

Engine is a new crate motor, 383 stroker, less then 400 miles on it, Petronix Flamethrower II Distributer, mechanical advance, Howard Cam, 530/545, Quick Fuel SL-750 Carb.
 

·
Premium Member
Joined
·
3,570 Posts
too big cam for the stall?
 

·
Registered
Joined
·
614 Posts
1- Check your timing at idle with the vacuum advance disconnected. See if it stays the same when you slow the motor down. (Like putting it in gear.) You don't want the mechanical advance starting until you raise the RPM 2-300 above your (in neutral) idle speed. If you're idling on the advance curve you get a very unstable motor when you drop it in gear.
2- The mixture screws not responding means the throttle blades are open too far, exposing the transfer slots. These slots supply the fuel for part throttle cruising, which is so much more than the motor needs at idle that it overpowers the idle mixture screw supply and they lose authority over the idle mixture. This could be caused by the timing situation in point 1 above so make sure that's ok before you play with the carb.
If it is the carb you can open the secondary blades slightly and close the primaries to get the transfer slot exposure correct. The opening should look like a square when it's right. That will get the mixture screws working again.
 

·
Registered
Joined
·
1,424 Posts
I thought I explain this to you in another post a few days ago. With a big camshaft like your almost 240 duration your initial has to be 14*-16* and you will have to set your mechanical advance up in your distributor. Here is an wiki article that explains everything you need to do. http://www.crankshaftcoalition.com/wiki/Hot_rodding_the_HEI_distributor If you raise the initial timing it will increase your idle and vacuum to where you can close the primary throttle plates. But you have to reset the mechanical advance in the distributor to have 34*-36* total timing. The wiki article explains how to do this also. It also explains how to set up your vacuum advance. You may need an adjustable can and use a ported vacuum source.
 

·
Registered
Joined
·
13,337 Posts
As mark mentions of secondaries are too far open then u have a vaccuum leak and cant set the mixtures, close them up so the primary idle screw is 1 1/2 turns +/_ 1/2 turn , and juggle with adjusting mixture same time..
But if have a big street cam u will need an Idle advance (initial +VA) around 16/ 18 degs

so set you initial No VA , and blocked off ,at this while doing secondary butterflies...
Once set note the idle vacuum ....will be between 7 and 12" most prob around 10"

Now u have a 36 deg total (initial+ cent) with 12 deg initial that gives u a cent of 36-12=24 in the cent.
ideally on modern fuels u will find dropping the total back to about 32/ 34 better, say 33....which now gives an initial of 9....
Chances are u will have between 7 and 10 degs in the VA
u NEED the VA to be full in at the idle spec when u set the secondary butterflies above and noted the vaccuum....say 10" ..now connect the Va to manifold vacuum
With the initial now at 9 degs , the VA adds another say 10 degs giving an idle at 19 degs... a shade on the high side but ok with a big cam...
U now have a total of around 33 , and with big cam need that in a little earlier around the 3000/ 3200...replacing one of the springs on the cent counterweight with a lighter one will fix that...
All up 9 deg initial + cent 24 VA say 10 deg gives 43 degs
40/ 42 max is best to er on the safe side to prevent cruise detonation/ knock (inaudable) 1 deg over not really enough to get real worried about....
But dropping initial back 1 more , dropping total and idle back 1 deg to...would bring that back into a definite safe zone anyway...

u are very lucky to have a dizzie already pretty well set up with good basic specs

just make sure the VA vaccuum spec is all in at idle
 
1 - 7 of 7 Posts
Top