si_camaro

Hi all,

Quick rundown of the car - 1985 Camaro Z28, LG4 with Comp Cams XE265, Edelbrock Performer (non-RPM) manifold and Hedman Hedders. Lightly polished and gasket-matched heads, non-cc Quadrajet and distributor (from a '78 Trans Am, complete with vacuum advance). I have fitted a spring/weight kit on the lightest springs.

If the engine revs drop below 1000, the idle is quite choppy and erratic, and more often than not it'll drop out completely. As it's an auto, this means I have to have the idle set at over 1500RPM in Park so it's above 1000 in Drive. My brakes are not liking this at all!

I've checked for vacuum leaks. Until I can check the timing at the weekend, I am looking for some expert opinions on my two theories, and any other suggestions also.

1: With the mechanical advance on the lightest spring settings, is it possible that the timing is advancing at idle, and would this cause the idle rate to be "artificially" increased, thus when the idle is reduced the weights are pulling in and the timing is too retarded to stay running? Or is that flawed somewhere?

2: Would the Comp Cams XE265 camshaft be too wild for a 305, and the lopey idle is just a fact of life?

Any suggestions would be great! Many thanks,

Simon

Tobias05

lighter springs are gonna allow the mechanical advance weights to swing out sooner, they may be flopping all over the place under 1000 rpm if your distributor is worn.

i personally run the crane hei kit, heaviest springs for a 800-3200 curve, and a vacuum advance can limited to 16*, with the rate at 8 turns clockwise.

was this an off the shelf hei kit? most of those are complete crap.

any info on your ignition setup? recent tune up?

si_camaro

Thank You for the reply, Tobias.

The kit was an off-the-shelf unit. I think I will try the heavy springs at the weekend to see if it makes a difference. I can always experiment with the medium ones later if things change.

The distributor is an HEI unit with the standard coil. As far as tune-up goes, I put a new cap and rotor arm on when I did the springs and weights. This was during the complete engine build a few months back, so the car has only been running a matter of weeks.

Tobias05

how do all the plugs look?

when you get that timing light, go around the engine and clip it to each individual wire, making sure all the plugs are firing. might find a fouled plug if you get an erratic timing light.

yeah swap out those springs, with at least two medium tension. wouldn't put too much faith in that spring kit. if you can afford it, go with the crane setup. myself and a few others have had great luck with it.

Genhero

iTrader: (3)

What degree does the intake valve close on the cam? Yeah I would have to agree about the springs, some nice high quality ones may help.

90gtpony

Sorry to butt in but I have the same problem but i have a stock 305 tpi. My Rpm's in park are around 1600 and in drive its 1200. I have changed the plugs, wires, rotor, and cap and still nothing. I adjusted the idle set screw inwards to the point that the TB blade doesnt come in contact with the set screw and still nothing. What are you guys talking about as far as the springs? Is it the piece that sits inside of the cap?

tiek101

I had this problem with a 350, non CC HEI and Edelbrock performer carb. After looking for vacuum leaks, changing the timing, changing the mechanical advance, come to find out it was the carb. There was some crap in the idle circuit. Cleaned, rebuilt runs great. I suspect the quadrajunk could have the same problem.