exhaust and carb backfire

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     I will try to make this short and feel as tho I am loosing my mind, which is most likely the case! I am working on a 78 360 in my 74 javelin. A little over a year ago I stripped a distributor gear. I had just bought the car and was told it was a rebuilt engine. I had no specks on what was in the engine. I decided to upgrade the cam and intake while it was apart.  I dont have all the specks handy but I went with a thumper cam kit. Changed lifters, double roller gears, new HEI distributer and matching cam gear. I also added an edelbrock air gap intake and holly 600. It ran fine up until a week ago. I heard a loud ticking noise from the #8 cyl. and found that two of my comp lifters collapse on me. I bought a set of crane lifters and I believe 8.010 long pushrods. I put it back together after soaking the lifters in oil over night. I put that Indian schalk stuff on both sides of the valley Pan around the intake ports and silicone around the water ports and front and rear of the intake. I put the intake on and snuggled the bolts. I did not see any silicone squeezed out of the front or back so I put some on my finger and redid the front and back without loosening the intake. The next day I torqued the intake bolts. 
    I tried to start it. It started but was intermittently  backfiring through the exhaust and the carb. I checked the timing 3 times thinking it maybe 180 off but that did not seem to be the issue. 
What could it be???

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iwantmyx Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Jun/14/2018 Location: texas Status: Offline Points: 45	Post Options Post Reply Quote iwantmyx Report Post Thanks(0) Quote Reply Topic: exhaust and carb backfire Posted: Apr/13/2021 at 1:15pm
	I will try to make this short and feel as tho I am loosing my mind, which is most likely the case! I am working on a 78 360 in my 74 javelin. A little over a year ago I stripped a distributor gear. I had just bought the car and was told it was a rebuilt engine. I had no specks on what was in the engine. I decided to upgrade the cam and intake while it was apart. I dont have all the specks handy but I went with a thumper cam kit. Changed lifters, double roller gears, new HEI distributer and matching cam gear. I also added an edelbrock air gap intake and holly 600. It ran fine up until a week ago. I heard a loud ticking noise from the #8 cyl. and found that two of my comp lifters collapse on me. I bought a set of crane lifters and I believe 8.010 long pushrods. I put it back together after soaking the lifters in oil over night. I put that Indian schalk stuff on both sides of the valley Pan around the intake ports and silicone around the water ports and front and rear of the intake. I put the intake on and snuggled the bolts. I did not see any silicone squeezed out of the front or back so I put some on my finger and redid the front and back without loosening the intake. The next day I torqued the intake bolts. I tried to start it. It started but was intermittently backfiring through the exhaust and the carb. I checked the timing 3 times thinking it maybe 180 off but that did not seem to be the issue. What could it be???
	71401amcamx

Heavy 488 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Apr/27/2019 Location: In the Status: Offline Points: 3553	Post Options Post Reply Quote Heavy 488 Report Post Thanks(0) Quote Reply Posted: Apr/13/2021 at 1:50pm
	Sounds like a valve partially open or a rounded off lobe. Pull the valve covers and. Crank it around and watch each rocker. Or just do a compression test.

White70JavelinSST Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Joined: Aug/08/2012 Location: Minnesota Status: Offline Points: 4866	Post Options Post Reply Quote White70JavelinSST Report Post Thanks(0) Quote Reply Posted: Apr/13/2021 at 1:52pm
	It could be a rounded off lobe, if it is there will be metal in the oil and oil filter. If not, Recheck the timing, remember cylinder number 1 must be at top dead center compression stroke (both valves closed) when the timing marks on the pointer match up with the line on the vibration damper, then the distributor has to be placed such that the rotor points to number 1 boss on the distributor cap. I bet you are one or two teeth off. and your plug wires are not correct anymore because of it. Edited by White70JavelinSST - Apr/13/2021 at 1:55pm
	70 Javelin SST, second owner, purchased 1972

75Cj5 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Apr/05/2021 Location: Decatur, Tx. Status: Offline Points: 60	Post Options Post Reply Quote 75Cj5 Report Post Thanks(0) Quote Reply Posted: Apr/13/2021 at 2:57pm
	Very similar to my issue... I'm taking mine apart this weekend to check the cam.... really stinks...

iwantmyx Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Jun/14/2018 Location: texas Status: Offline Points: 45	Post Options Post Reply Quote iwantmyx Report Post Thanks(0) Quote Reply Posted: Apr/13/2021 at 6:24pm
	all the old lifters looked really good! only about 500 miles on this cam.
	71401amcamx

iwantmyx Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Jun/14/2018 Location: texas Status: Offline Points: 45	Post Options Post Reply Quote iwantmyx Report Post Thanks(0) Quote Reply Posted: Apr/13/2021 at 6:31pm
	cam only has about 500 miles on it and the bottom side of all lifters looked like new. going to thoroughly check the timing this weekend, kinda funny tho that when it was running the rotor was pointing towards the starter relay and the book has it pointing to the front of the car.
	71401amcamx

iwantmyx Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Jun/14/2018 Location: texas Status: Offline Points: 45	Post Options Post Reply Quote iwantmyx Report Post Thanks(0) Quote Reply Posted: Apr/13/2021 at 6:33pm
	did you change anything on yours before this started happening?
	71401amcamx

Buzzman72 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Sep/15/2009 Location: Southern IN Status: Offline Points: 2725	Post Options Post Reply Quote Buzzman72 Report Post Thanks(0) Quote Reply Posted: Apr/14/2021 at 5:35am
	Doesn't matter what the rotor points at under the hood, as long as it points at #1 cylinder when #1 cylinder is at TDC on the compression stroke.
	Buzzman72...void where prohibited, your mileage may vary, objects in mirror may be closer than they appear, and alcohol may intensify any side effects.

75Cj5 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Apr/05/2021 Location: Decatur, Tx. Status: Offline Points: 60	Post Options Post Reply Quote 75Cj5 Report Post Thanks(0) Quote Reply Posted: Apr/14/2021 at 8:16am
	Mine was a fresh build. Broke in cam ran it on and off for a couple weeks just short runs to tune. Had it starting and idling almost perfect but had some lag on acceleration. Tried adjusting timing and fuel mixture and it all went South. Here is my Thread these guys have been helping me out with for your reference. https://theamcforum.com/forum/timing-fuel-delivery-vacuum-leak_topic110134.html