Backfiring

carboy · 03-01-2002, 08:21 PM

Just rebuilt my engine and can get it to start but starts to pop and backfire a little after about 10 minutes of engine running. i just installed a rebuilt edelbrock. (i just removed the 750 holley). it seems to run better but the backfiring is still there after 10 minutes. idouble chkd the points gap, and its good. have new plugs wires and soforth.
anyone got any ideas on how to adjust these edelbrock carbs. when i adjust the 2 screws on the front of the carb it doesn't seem to do anything. it did seem to run better when i plugged both vacum lines on the carb and also plugged the vacum advance on the distributor.
anyone got any tips on what i can do????

73 Mustang Boy · 03-01-2002, 10:08 PM

I think I might could help but I need a little more info. Does the car "backfire" throught the carb or through the exhaust? Does it backfire all the time, just at idle, or while accelerating. What is the timing set at? Are you sure you dont have a vaccume leak? If you give me a little more info I will try and help but it might be tomorrow morning before I can post a reply.

carboy · 03-02-2002, 12:04 AM

it's backfiring through the carb. i run it for around 15 minutes then try to restart it and it's a real pain to try and restart. it backfires through the carb and exhaust. i haven't installed my mufflers yet and i'm running straight tri-y headers. i have a crane RV cam in it. edelbrock performer intake, 600cfm carb (edelbrock), i haven't got a timing light but when i put my vacuum gage on it reads 13lbs . i wonder if all my valves are too tight. it's really weird because it also did the same thing when i had the big holley installed. but it does run a bit better with the edelbrock carb.

73 Mustang Boy · 03-02-2002, 12:20 PM

Try turning the timing down it sounds like you might have the timing to far advanced that would make the car hard to start. How did you adjust the valve lash? Having the valves too tight could cause the condition you have also. Try the timing first though that will only about 5min. Let me know what you figure out.

Gearhead999 · 03-03-2002, 12:28 PM

Are you sure the firing order is right?? You know that 289, 302 and 351W parts interchange. You can install the cams in one another. This will change the firing order.

Next where is the intial timing?? If you're not sure. Pull #1 plug, turn the engine over till #1 is on compression stroke. Line up the timing marks and install dist. to fire on #1. Many, many are installed wrong. Very common problem.

How did you adjust valves?? If they are too tight you will get backfire. Easy enough to check.

Pull valve covers, turn engine over by hand and do each valve adjustment seperatly.

carboy · 03-04-2002, 07:46 AM

i have double chked the timing and it is firing correctly. i guess i'll double chk the valves. thanks for the info. i'll post the results.

carboy · 03-04-2002, 11:17 PM

I could kick myself in the you know where. a friend of mine came over and said it sounded like it wasn't firing on all cylinders. i told him i triple chkd the firing order,,,,well he looked up the engine numbers and come to find out i have a 302HO,,, not a regular 302, the difference is the 302HO has the same firing order as a 351,,,, boy does it sound cheeky now.
all i need is the body work(rear quarters) and a paint job and it's off to the races.
thanks for all the input guys!

03-01-2002, 10:08 PM	#2
73 Mustang Boy Registered Member Join Date: Aug 2001 Location: Georgia Posts: 84	I think I might could help but I need a little more info. Does the car "backfire" throught the carb or through the exhaust? Does it backfire all the time, just at idle, or while accelerating. What is the timing set at? Are you sure you dont have a vaccume leak? If you give me a little more info I will try and help but it might be tomorrow morning before I can post a reply. __________________ 73 coupe, 351W, GT-40 heads, edlebrock 750, offenhauser intake, .488 lift cam, 2.5 exhaust, 2 chamber flowmasters, blah, blah, blah...

03-02-2002, 12:04 AM	#3
carboy Registered Member Join Date: Jan 2000 Location: Corpus Christi, Texas Posts: 66	it's backfiring through the carb. i run it for around 15 minutes then try to restart it and it's a real pain to try and restart. it backfires through the carb and exhaust. i haven't installed my mufflers yet and i'm running straight tri-y headers. i have a crane RV cam in it. edelbrock performer intake, 600cfm carb (edelbrock), i haven't got a timing light but when i put my vacuum gage on it reads 13lbs . i wonder if all my valves are too tight. it's really weird because it also did the same thing when i had the big holley installed. but it does run a bit better with the edelbrock carb. __________________ 66 coupe, 306 balanced bluprinted, performer intake,725 Road Demon, Crane Cam, Tri-Y Headers, factory Shelby glass packs 2 1/4 with exit in front of rear wheels, 3:50 rear, 8 inch rear, mustang plus suspension, 41/2 mideye leafs, 620 springs on front, kyb gas shocks. tony branda shelby hood, r-model valance, rear side scoops(functional),stainless steel slotted front brake system,,13.39 1/4 mile with no slicks and no posi.

03-02-2002, 12:20 PM	#4
73 Mustang Boy Registered Member Join Date: Aug 2001 Location: Georgia Posts: 84	Try turning the timing down it sounds like you might have the timing to far advanced that would make the car hard to start. How did you adjust the valve lash? Having the valves too tight could cause the condition you have also. Try the timing first though that will only about 5min. Let me know what you figure out. __________________ 73 coupe, 351W, GT-40 heads, edlebrock 750, offenhauser intake, .488 lift cam, 2.5 exhaust, 2 chamber flowmasters, blah, blah, blah...

03-03-2002, 12:28 PM	#5
Gearhead999 Registered Member Join Date: Sep 1998 Location: Oviedo, FL Posts: 992	Are you sure the firing order is right?? You know that 289, 302 and 351W parts interchange. You can install the cams in one another. This will change the firing order. Next where is the intial timing?? If you're not sure. Pull #1 plug, turn the engine over till #1 is on compression stroke. Line up the timing marks and install dist. to fire on #1. Many, many are installed wrong. Very common problem. How did you adjust valves?? If they are too tight you will get backfire. Easy enough to check. Pull valve covers, turn engine over by hand and do each valve adjustment seperatly. __________________ "Support our Troops" Dave 1968 Cougar 2004 Thunderbird 2007 F150 Harley-Davidson, SuperCrew 1986 LTD 1997 Ranger 1992 Honda Civic

03-04-2002, 07:46 AM	#6
carboy Registered Member Join Date: Jan 2000 Location: Corpus Christi, Texas Posts: 66	backfiring i have double chked the timing and it is firing correctly. i guess i'll double chk the valves. thanks for the info. i'll post the results. __________________ 66 coupe, 306 balanced bluprinted, performer intake,725 Road Demon, Crane Cam, Tri-Y Headers, factory Shelby glass packs 2 1/4 with exit in front of rear wheels, 3:50 rear, 8 inch rear, mustang plus suspension, 41/2 mideye leafs, 620 springs on front, kyb gas shocks. tony branda shelby hood, r-model valance, rear side scoops(functional),stainless steel slotted front brake system,,13.39 1/4 mile with no slicks and no posi.

03-01-2002, 08:21 PM	#1
carboy Registered Member Join Date: Jan 2000 Location: Corpus Christi, Texas Posts: 66	Backfiring Just rebuilt my engine and can get it to start but starts to pop and backfire a little after about 10 minutes of engine running. i just installed a rebuilt edelbrock. (i just removed the 750 holley). it seems to run better but the backfiring is still there after 10 minutes. idouble chkd the points gap, and its good. have new plugs wires and soforth. anyone got any ideas on how to adjust these edelbrock carbs. when i adjust the 2 screws on the front of the carb it doesn't seem to do anything. it did seem to run better when i plugged both vacum lines on the carb and also plugged the vacum advance on the distributor. anyone got any tips on what i can do???? __________________ 66 coupe, 306 balanced bluprinted, performer intake,725 Road Demon, Crane Cam, Tri-Y Headers, factory Shelby glass packs 2 1/4 with exit in front of rear wheels, 3:50 rear, 8 inch rear, mustang plus suspension, 41/2 mideye leafs, 620 springs on front, kyb gas shocks. tony branda shelby hood, r-model valance, rear side scoops(functional),stainless steel slotted front brake system,,13.39 1/4 mile with no slicks and no posi.

03-04-2002, 11:17 PM	#7
carboy Registered Member Join Date: Jan 2000 Location: Corpus Christi, Texas Posts: 66	backfiring I could kick myself in the you know where. a friend of mine came over and said it sounded like it wasn't firing on all cylinders. i told him i triple chkd the firing order,,,,well he looked up the engine numbers and come to find out i have a 302HO,,, not a regular 302, the difference is the 302HO has the same firing order as a 351,,,, boy does it sound cheeky now. all i need is the body work(rear quarters) and a paint job and it's off to the races. thanks for all the input guys! __________________ 66 coupe, 306 balanced bluprinted, performer intake,725 Road Demon, Crane Cam, Tri-Y Headers, factory Shelby glass packs 2 1/4 with exit in front of rear wheels, 3:50 rear, 8 inch rear, mustang plus suspension, 41/2 mideye leafs, 620 springs on front, kyb gas shocks. tony branda shelby hood, r-model valance, rear side scoops(functional),stainless steel slotted front brake system,,13.39 1/4 mile with no slicks and no posi.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Help! Backfiring and loss of power	spuckie	Blue Oval Lounge	1	11-24-2003 01:08 AM
Help! Backfiring and loss of power	spuckie	Windsor Power	1	11-21-2003 07:40 PM
Backfiring Problems!	MITCHL	Windsor Power	5	11-21-2002 01:52 PM
Backfiring on deceleration fixed !!!!	70 Pony	Classic Mustangs	2	09-01-2000 08:37 AM
Backfiring on Deceleration...	Idhomustang	Classic Mustangs	12	08-31-2000 01:59 AM