backfire

Karl Muller · #1 (**permalink**) 11-24-2003, 07:16 AM

I started my 514 and moved it out of the garage but only let it run for about 1 min. When I did a re-start it blew smoke from the passenger side pipe...just a puff and it was gone...
I let it warm up...took it for a ride and it ran great...
What is this all about?
The next problem ,and it might be connected is that I have a small backfire on occasion when stoped at idol (at light or stop sign) also on the passenger pipe...
Are either of these problems a real concern...as I said the car seems to be running great
Thanks

Karl Muller · #2 (**permalink**) 11-24-2003, 07:17 AM

I bought it with 2200 mi...it now has 3200 mi
thanks

blykins · #3 (**permalink**) 11-24-2003, 07:20 AM

Sounds like you're running a little rich in that area. Sometimes the intake manifold doesn't do a good job of distributing the air/fuel on some cylinders due to the casting flaws or shape of the intake runners.

Karl Muller · #4 (**permalink**) 11-24-2003, 07:21 AM

should I worry about it?

blykins · #5 (**permalink**) 11-24-2003, 07:25 AM

Well I don't think it's gonna cause a lot of problems, but if it were me, I'd wanna get it fixed. Have you had it dyno'd? If so, did they put any temp sensors on the cylinders?

You could always try a carb spacer...or a turtle.

Karl Muller · #6 (**permalink**) 11-24-2003, 07:28 AM

It was dyno'd by the prev owner...I will ask him
What will a carb spacer or turtle do and what about the puff of oil?

blykins · #7 (**permalink**) 11-24-2003, 07:33 AM

The spacer or turtle will even out the mixture and help distribute it a little better.

I'd say it's not oil you're seeing, but gas....where it's rich. What color was it?

Karl Muller · #8 (**permalink**) 11-24-2003, 07:35 AM

I guess a light blue/grey

blykins · #9 (**permalink**) 11-24-2003, 07:46 AM

Hmmm...I can never remember which is which...maybe the other users can help out...but I always thought that blue was gas and white was oil...

I really don't think you have anything to worry about. I'm almost positive it's just a little rich. It's really not gonna hurt anything...just maybe pop and crack every now and then. A rich cylinder won't make as much horsepower as one towards the lean side....But of course you know, it's better to be rich than lean.

Now that I re-read your post, I see the part about doing it at idle...I'm gonna retract my statement about it being the intake manifold...hehehe....I'd say your carb is just a little off-tune.

What kind of carb is it? Most higher performance carbs have 4-corner idling circuits....you could probably lean it up a little bit with the mixture screw on that corner. Or....change out the idle air bleed on that corner. Let's see, you would want more air to that corner, so you would put in an idle air bleed with a bigger orifice...

I'll be the first one to tell you that carb'd engines are really finicky. It's not like a fuel-injected engine....everytime the weather changes, or it gets colder outside, you'll probably have to tweak something.

Karl Muller · #10 (**permalink**) 11-24-2003, 07:55 AM

It' a Holly 850...will the spark plugs reveal a problem with mixture and or an oil problem?

blykins · #11 (**permalink**) 11-24-2003, 08:11 AM

Yep they sure will....if it's blowing oil, they should be a little oily....if it's really rich, they will be sooty.

From your saying that it just does it basically on idle, I'd say your carb just needs adjusted.

Do you know what Holley it is? Does it have a choke?

Karl Muller · #12 (**permalink**) 11-24-2003, 08:21 AM

It has a manual choke...It' a Holley 850 (are there many different 850's?) also...could it be a bad plug or gap?

ERA 626 · #13 (**permalink**) 11-24-2003, 08:35 AM

Check for an exhaust leak!

blykins · #14 (**permalink**) 11-24-2003, 09:03 AM

Yeah, there are several Holleys that have 850cfm....some are race carbs....others are street carbs....some have chokes, some don't....I was just checking to see what all would be adjustable on yours.

All the things you're naming are pretty valid. However, I don't think plug gap would hurt you that bad. Also, if a plug was bad, the engine would be missing. It could be fouled however, and just needs a good dose of high-performance driving.

You can check the plugs on that side and see what they look like. That will give us a good starting point to see what's going on.

Karl Muller · #15 (**permalink**) 11-24-2003, 09:19 AM

I appreciate your help...
it got "a good dose" yesterday and ran great...I am just concerned
thanks

Tony Aprile · #16 (**permalink**) 11-24-2003, 11:19 AM

Karl
My problem might have been a little different ?? The car ran fine (460/486) but I noticed a little blue smoke at startup and the idle seemed ok but seem to pop a bit more then normal, then I noticed while above 3000 rpm's on deceleration I would get popping out of the left sidepipe. I was told to look for an exhaust or intake leak on the left side. While in the process I changed the plugs and found one plug on the right side that was oil fouled. I was also down a quart of oil.
It turns out the the 460's have a known problem with the intake manifold gaskets and the left side gasket moved enough to create an intake leak right at the gasket. I pulled the manifold and saw the disformed left side gasket.
I also found I had a crack in the right side gasket at #3 cyl so thats where the smoke was coming from as it was sucking oil. This Fel-Pro gasket was installed at the factory as mine is a crate engine and now has 2500 miles in a years time. I was told 1 out of 3 460's have this problem. Just something else to check
Tony

Karl Muller · #17 (**permalink**) 11-24-2003, 11:32 AM

I did see something about the manifold gasket on the 460...I also..by the way I now see some oil at the rear of the manifold around a hex nut...do you know what that is?

Tony Aprile · #18 (**permalink**) 11-24-2003, 11:39 AM

karl
Since your manifold (514) is a little different in design from mine im not sure which hex nut you mean. Is it one of the bolts that secures the intake down or just a 3/8 plug for a vaccume source ??
Tony

Tony Aprile · #19 (**permalink**) 11-24-2003, 11:47 AM

I just went out to look at the engine and you might mean oil is resting by the plug right behind the intake manifold not on the intake. If that's the case and oil is on the back of the engine behind the intake the rear gasket might be leaking causing a massive vaccume leak causing the engine to run lean.
Tony

Karl Muller · #20 (**permalink**) 11-24-2003, 12:10 PM

correct...it is behind the manifold...do you know what that plug is for. (I may sound a little novice but I have'nt owned a BB since 1967 and it was a 390 Cyclone)