Engine is a 350, with performer rpm intake, msd pro billet distributor, roller rockers, holley 650 DP (4777-4, 3205), and a larger than stock camshaft. When I bought the car, I knew that the cam was not stock, but the previous owner didn't know the specs. I'd guess around .520 lift maybe a little more. Anyway, when I got the car, it idled high, but idled nonetheless. The only thing that I did to it was rebuild the carburetor, nothing else was touched or changed. Now it starts but wont idle on its own; it only stays running if I give it gas or keep the throttle blades open with the accelerator pedal. Earlier today I had a hard time starting it, sometimes it only starts when I keep the choke and throttle blades open and after a while it made a loud popping sound from the exhaust so I shut it off. I would really appreciate any help that you guys can offer me. Thanks.
Car wont idle on is own
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Floats set?
Vacuum Leak?
Mixture screws adjusted correctly?
Vacuum Leak?
Mixture screws adjusted correctly?
The floats have been adjusted so that fuel only trickles out of the sight holes when the car is rocked, couldn't find any vacuum leak, and the mixture screws are turned out 1.5 full turns. The idle transfer slots have also been set to .030" each. Would the large cam have anything to do with idle problems? It's not like its an outrageous cam or anything so it should idle under 1000 rpm.Floats set?
Vacuum Leak?
Mixture screws adjusted correctly?
If it was fine but idled high before the carb rebuild, then it's in the carb. Could be a float problem, vac leak, or you have some trash stuck in a passage.
This is what gets me. I figured it would be one of these things, but it isn't. I've double checked vac. leak, floats, transition slots, and I made sure that I blew carb cleaner through all the passages. I may just tear it apart again and start from scratch if it comes down to it.If it was fine but idled high before the carb rebuild, then it's in the carb. Could be a float problem, vac leak, or you have some trash stuck in a passage.
Did you line up the old gaskets to the new to ensure a match?
When you pull it back down, inspect the gaskets carefully along their imprints, see if anything fell out of place.
When you pull it back down, inspect the gaskets carefully along their imprints, see if anything fell out of place.
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did you bump the distributor and retard the timing when you had it apart?
vacuum advance hooked back up?
vacuum advance hooked back up?
Thank you for the replies. The Distributor hasn't been touched, and nothing electrical has been changed. I made sure that the gaskets lined up and they matched. Today I was able to get the car to idle for a bit (~10 seconds) by itself by turning the primary throttle blade screw in 1.5 turns, which seems a little high. But after that it still cut out on me. I was reluctant to hook up the vacuum advance, because 1) I didn't know what the initial timing was and 2) the previous owner had been using ported advance so both advance locations are now plugged.
EDIT: I gave it another try today, and things were a little better. I turned the secondary throttle screw so that .040" of transition slot was showing, and then left the primary transition slot at about .025". Results were only slightly better, but when I hooked up the vacuum advance to manifold vacuum (there was none before) it idled high (~1500) but kept going for a while. The only problem I had was a slight knocking, so I disconnected it. My next thought is to open the secondary blades just a tad more, and then see where that goes. Am I opening the secondary throttles too much? When I got the carb before it was rebuilt, the secondary was open quite a bit and the primary was closed, maybe for a reason?
EDIT: I gave it another try today, and things were a little better. I turned the secondary throttle screw so that .040" of transition slot was showing, and then left the primary transition slot at about .025". Results were only slightly better, but when I hooked up the vacuum advance to manifold vacuum (there was none before) it idled high (~1500) but kept going for a while. The only problem I had was a slight knocking, so I disconnected it. My next thought is to open the secondary blades just a tad more, and then see where that goes. Am I opening the secondary throttles too much? When I got the carb before it was rebuilt, the secondary was open quite a bit and the primary was closed, maybe for a reason?
Stick or auto?
What is the base timing? My 350 with similar equipment, and a stock torque converter would not idle below 1100 in neutral, to get 800 in drive. Edelbrock Performer intake, Eddy 1604 carb, and 18 deg base timing on the HEI.
Put a smaller cam in and its much happier. Still needs 116-18 deg base timing.
Not familiar with that carb, does it have four corner idle? My Holleys idle on the primaries, with the secondaries closed for the most part. Irrc, the idle transfer slot should be above the butterfly at curb idle.
What is the base timing? My 350 with similar equipment, and a stock torque converter would not idle below 1100 in neutral, to get 800 in drive. Edelbrock Performer intake, Eddy 1604 carb, and 18 deg base timing on the HEI.
Put a smaller cam in and its much happier. Still needs 116-18 deg base timing.
Not familiar with that carb, does it have four corner idle? My Holleys idle on the primaries, with the secondaries closed for the most part. Irrc, the idle transfer slot should be above the butterfly at curb idle.
Auto. I hadn't thought to check the idle speed in drive, however, I was able to get it back to idling high again. It seems that the engine needed a higher fuel to air ratio, and on top of that, advancing the timing by a small amount seemed to help.Stick or auto?
What is the base timing? My 350 with similar equipment, and a stock torque converter would not idle below 1100 in neutral, to get 800 in drive. Edelbrock Performer intake, Eddy 1604 carb, and 18 deg base timing on the HEI.
Put a smaller cam in and its much happier. Still needs 116-18 deg base timing.
I'm running the majority of the idle on the secondary transfer slot, which most likely is the cause of the lean condition and the high idle. Once I lower the secondary throttle it should be close to where I want it.
As for the timing, there is no timing tab/plate on the block, and I'm not even sure if the balancer is set at TDC so I may have to do some work before I can get a full tune in.
dont know a lot about your motor,i'm gonna go with timing,adjust dizzy so it'll run,you mentioned popping,verify firing order then check it again!!!!!!! once you get it running fine do acceleration runs and adjust for no ping,once you have it running fine hook a vacuum guage up to it,find idle vac,check u have the proper vacuum can on dizzy with a vacuum pump and guage,run 18-20 initial,and limit your mech advance,get the proper va can from napa try part #vc1838
Alright... don't laugh at me too hard lol...
It was an ignition problem like some suggested. It turns out that the spark plug wires were in the right firing order, but they were one off causing a massively retarded combustion. It took a while to figure out because the balancer also happens to be out of order.
I'm actually very surprised that the engine was able to even idle very high like it did, and to produce a seemingly good amount of throttle response for having less than 0* of timing. Once I reset and advance the distributor properly it should be a pretty wild motor.
Thank you for your assistance.
It was an ignition problem like some suggested. It turns out that the spark plug wires were in the right firing order, but they were one off causing a massively retarded combustion. It took a while to figure out because the balancer also happens to be out of order.
I'm actually very surprised that the engine was able to even idle very high like it did, and to produce a seemingly good amount of throttle response for having less than 0* of timing. Once I reset and advance the distributor properly it should be a pretty wild motor.
Thank you for your assistance.
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18,121 Posts
how do you know that the timing was "less than 0" if you don't have a timing tab to use as a reference?
get a timing tab... make sure it's correct... then you can actually start tuning it..
get a timing tab... make sure it's correct... then you can actually start tuning it..
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