Thread: 350 running issues

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Hi guys, got a few problems I'd like to run by you. I've got a 1970 350 block in a 63 nova. The bottom end and pistons are quite tame, 9:1, 2 bolt etc.

I have a set of 1.94 camel humps I had redone, a Holley dual plane intake, 650 edelbrock thunder elec choke, a motha thumper cam ( specs not on hand, msd billet distributor w/vac advance, tied to 350 auto with a 2600 stall.

I'm not happy with how it runs. Starts fine from cold and choke seems to be working nicely. When it's hot it wants to idle in park at around 1100 to 1400....too high. It seems to pull this idle even if I've got the idle screw all the way out. Then it seems to wanna die as the carb resets itself and had no idle at all. When I'm cruising its like I have cruise control, 2000 rpm with my foot off the gas. When I apply breaks it dies back down.

I'm thinking bad timing, or the carb/ intake don't get along. There is the proper 4 holed base in between the carb and intake. Vac line from distributor is on the passenger side port of the carb...as per the instructions for vac assisted timing. All other vac for tranny and brakes are off a manifold tree.

I timed the engine dropping the distributor in at 8 btdc, adjusted accordingly to fire the motor.

Any thoughts? Is

Have you taken any vacuum readings? Have you checked the operation of the throttle by hand? Is it smooth and free? Take off the return springs and run the throttle by hand, make sure it's not hitting a burr or something. And get back to us with those vacuum readings.

I had the gauge on earlier this summer and if I remember its around 12" right now. That cam doesn't help. I even tried a different power valve in a Holley street avenger to help. I ended up going to to new, smaller edelbrock, which seemed to help a bit.

Both those carbs had the idle issue. I'm set up right now with a lokkar pedal and cable for the throttle. It seems loose enough, so does the linkage on the carb it self.

I though you were talking about an Eldobrock carb so I deleted my post

Did you set the carb by using the vacuum gauge?

Also, connect the vacuum gauge so you can see it in the car and ride around. Make mental note(s) of what the readings are while motoring down the road. And pay special attention to the reading when it's idling weird....

I'm not a fan of the thumper cam but I can't say it's causing all your issues... But you need to identify what's changing when the idle goes wrong.. If the vacuum goes way up when the idle goes up then we can probably eliminate any air leakage.. If the vacuum falls off and the rpm's go up when it gets hot then maybe we do have an air leak being created.

Did you set timing by a light? what was the rpm when setting it? vacuum hose disconnected when timing?

Cam is 235/249 @0.050" tappet lift, needs more ignition advance.
1. Verify TDC on the damper inertia ring via this procedure.....
http://www.crankshaftcoalition.com/w...op_dead_center
2. Set initial timing at the crank at 16 degrees BTDC
3. Curve centrifugal advance for additional 20 degrees, 36 total, all in by 2800 rpm.
4. Install adjustable vacuum advance cannister. One listed here is for HEI, not MSD.
Crane Cams 99600-1 - Crane Vacuum Advance Kits - Overview - SummitRacing.com
5. Install timing limiter plate
Crane Cams 99619-1 - Crane Vacuum Timing Limiter Plates - Overview - SummitRacing.com
Connect vacuum line to manifold vacuum, see how it runs
Connect vacuum line to ported vacuum at carb, see how it runs
Choose one.
Do you see any oil on the plugs that might indicate an internal air leak at the intake manifold gasket? (oily vapors being pulled from the crankcase with the intake valve open?)