backfire throgh carb and no power under load
06-23-2012, 10:17 PM
#1
Thread Starter
Join Date: Jun 2012
Location: washington
Posts: 9
backfire throgh carb and no power under load
I jsut picked up a 67 mustang that hase been nearly restored. I understand the 302 engine is rebuilt Thee car will start but has little to no power in gear and backfires through the carb quite a bit. With the vacume line attached to the distributor will backfire occasionaly throught the carb at idle.
Here is what I know abouit the engine
302 High output - not original and not sure of vintage
Eldabrock 1406 4bbl carb
Spped pro CD1217 cam
Engine is very clean, all new hoses lines, fuel filter etc...
I have the timing set at 8 degrees BTDC
vacume is pretty consistantly low at 12-15 - lower with vacume line on distirbutor connected
The timming seems to be in the sweet spot at idle. Adjsuting the carb does not seem to effect the vacume. nothing ive done thsut far resolve the problem of lack of powet and backfire under load. I am by no means an expert and would welcome suggestions.
Here is what I know abouit the engine
302 High output - not original and not sure of vintage
Eldabrock 1406 4bbl carb
Spped pro CD1217 cam
Engine is very clean, all new hoses lines, fuel filter etc...
I have the timing set at 8 degrees BTDC
vacume is pretty consistantly low at 12-15 - lower with vacume line on distirbutor connected
The timming seems to be in the sweet spot at idle. Adjsuting the carb does not seem to effect the vacume. nothing ive done thsut far resolve the problem of lack of powet and backfire under load. I am by no means an expert and would welcome suggestions.
06-25-2012, 09:22 AM
#2
2nd Gear Member
Join Date: Sep 2007
Location:
Posts: 248
There are a bunch of reasons but check the firing order. Some new cam grinds have a different firing order than stock, sounds like there is a vacuum leak in the distributor advance and your timing may be low depending on the cam grind.
06-25-2012, 10:04 AM
#4
4th Gear Member
Join Date: Aug 2008
Location: Goodyear, AZ
Posts: 1,674
according to what i found online, it uses the 302 order. So, double check the firing order as stated above.
http://www.northernautoparts.com/Pro...tModelId=18681
other than that you could have a valve hanging open.
http://www.northernautoparts.com/Pro...tModelId=18681
other than that you could have a valve hanging open.
06-25-2012, 02:02 PM
#5
2nd Gear Member
Join Date: Jan 2010
Location: U.S.
Posts: 216
It can be a lot of things. However, one simple thing that it could be is the carb to intake gasket worn. Tightening the carb will not always solve this, you may need a new gasket. I had the same issue and went through the timing etc. and it ended up being the carb gasket.
06-26-2012, 11:50 AM
#7
Thread Starter
Join Date: Jun 2012
Location: washington
Posts: 9
I picked up a new Edaborck 1406 carb and installed it. The new carb fixed the problem I was having wiht the advance from teh distributor. THere is now no advance whne at idle. THe car runs decent cold, but when warmed up same old backfire through the carb and barley runs at all under load........ I'm not sure where to go from here... Any suggestions?
06-26-2012, 03:10 PM
#8
4th Gear Member
Join Date: Jun 2006
Location: Fontana, California
Posts: 1,483
Most back fires are electrical related so check the condition of the plugs and wires. Wires can look good at idle but go to crap when under load. still have points? check the dwell and or the point gap and look for excessive arched mat'l on the contacts.
What is the compression of the engine. I suspect your timing chain may have slipped or was put in a tooth off. The CD1217 R cam specs say its a 302 firing order so this may indicate your problem.
What is the compression of the engine. I suspect your timing chain may have slipped or was put in a tooth off. The CD1217 R cam specs say its a 302 firing order so this may indicate your problem.