Hey everyone, my friend just inherited a 67 camaro. Its a very nice car but unfortunately it sat for about 2 years. It ran great before it was parked. Its got a 454 in it, long tube headers, msd ignition, 4 speed manual, HEI dizzy of course. He could not get it to idle using some seafoam in the gas and carb, but was able to get it to run using the throttle, under about 1000 rpm it will just die if you let off the gas.
First thing we did was pull bowls and check the jets, blow out everything we could with carb cleaner. It didnt look too bad really after sitting for two years.
It has a holley 4150 doublepumper, 71 main jets, idle mixture screws set at 2 turns out on the driver side, and 1.75 turns out on the passenger side.
Since it sat so long and he couldnt get it to idle, I recommended a holley trick kit and a partial rebuild. He pulled the carb and brought it over, we took the bowls off, blew everything out, removed the metering blocks, dipped them in carb dip, blew them out, and blew out the rest of the carb. Everything looked clean when it went back together. I set the mixture screws at 2 turns out, and the idle screw so that the primary side butterflies were just barely open, maybe 1/16".
He took it home, primed the carb bowls by filling them from the sight holes, then tried to start it up. I told him to get it fired up and get it to idle around 8-900 rpm and then I can bring a vacuum guage and set the mixture screws correctly and idle where it works well.
He says when he cranks it it backfires really loudly through the exhaust when he gives it gas. It wont idle, and is backfiring enough that he is scared to crank it any more.
I'm not sure if it is too lean or too rich. Its not blowing smoke when he is trying to get it going. Plugs were pulled and cleaned, and he said the wires are all in the right spots.
Timing has not been messed with, and no visible issues with header leaks. We had it running before and drove it around the block before we stripped the carb off to clean it, but it had to be idling very high to stay running and dieseled pretty bad when he killed it due to the idle being so high.
I'm not sure where to start next, any ideas what the mixture screws should be? Why would it be backfiring so bad?
Any advice is appreciated.
-Nate
First thing we did was pull bowls and check the jets, blow out everything we could with carb cleaner. It didnt look too bad really after sitting for two years.
It has a holley 4150 doublepumper, 71 main jets, idle mixture screws set at 2 turns out on the driver side, and 1.75 turns out on the passenger side.
Since it sat so long and he couldnt get it to idle, I recommended a holley trick kit and a partial rebuild. He pulled the carb and brought it over, we took the bowls off, blew everything out, removed the metering blocks, dipped them in carb dip, blew them out, and blew out the rest of the carb. Everything looked clean when it went back together. I set the mixture screws at 2 turns out, and the idle screw so that the primary side butterflies were just barely open, maybe 1/16".
He took it home, primed the carb bowls by filling them from the sight holes, then tried to start it up. I told him to get it fired up and get it to idle around 8-900 rpm and then I can bring a vacuum guage and set the mixture screws correctly and idle where it works well.
He says when he cranks it it backfires really loudly through the exhaust when he gives it gas. It wont idle, and is backfiring enough that he is scared to crank it any more.
I'm not sure if it is too lean or too rich. Its not blowing smoke when he is trying to get it going. Plugs were pulled and cleaned, and he said the wires are all in the right spots.
Timing has not been messed with, and no visible issues with header leaks. We had it running before and drove it around the block before we stripped the carb off to clean it, but it had to be idling very high to stay running and dieseled pretty bad when he killed it due to the idle being so high.
I'm not sure where to start next, any ideas what the mixture screws should be? Why would it be backfiring so bad?
Any advice is appreciated.
-Nate
