[J & A waters]

I am having a backfire issue,when I accellorate at all, she back fires on me.Now its back fireing at an idiol,and I haven't done anything to it.Is a valve,timing or ? Please help,going nuts. Thank you so much & looking forward to any input & knowledge.

J & A.

[Rob Keller]

This will be better addressed if your "Q" is in the appropriate forum try this one


http://www.hotrodders.com/forum/general-rodding-tech/

This forum is for the introductions

[poncho62]

moving to engine forum.

[NXS]

--double post--

[NXS]

It sounds like a lobe may be down or a rocker popped off. not to scare you, just a quick shot in the dark. A compression test would be a good place to start if it progressivle got worse and no work was done.
Although a bad set of plug wires can do this among other things.

[57 Chevy]

Originally Posted by J & A waters

I am having a backfire issue,when I accellorate at all, she back fires on me.Now its back fireing at an idiol,and I haven't done anything to it.Is a valve,timing or ? Please help,going nuts. Thank you so much & looking forward to any input & knowledge.

J & A.

Need a little more info.
Year, stock, modified, miles on it?

[J & A waters]

Thanks for the 411,James says when he puts his finger over the plug hole,and roles the motor,theres barely any back pressure. But doesn't burn any oil? We're

[J & A waters]

Not sure what year... But have block #. Some mods,Edelbrock street preformer intake, Holly 650 cfm double pumper carb.Not sure about miles,been passed around the family,originally came out of a old dirt hauler.Uncle cuck was said to have possiblly rebuilt it at one time.Was running great when James's sister got .She let it set for about 2 yrs.Her kids used it as a jungle jim. It's in a 1972 Land cruiser.She gave it to him in 2004 and it has been a loving restore.Coming to the engine,when it does run it either backfires & run doggy or chirps through the exhaust & runs strong. Hope this helps...

[57 Chevy]

If it has a "point" type dist. I'd start there. That would be the easiest.

The worst it could be is a flat cam lobe. A compression check would be next place to go. Motors that have been setting can have strange problems.

[57 Chevy]

Originally Posted by J & A waters

Thanks for the 411,James says when he puts his finger over the plug hole,and roles the motor,theres barely any back pressure. But doesn't burn any oil? We're

Did he take out all of the plugs, disconnect the coil and prop the carb open?

[NXS]

Originally Posted by J & A waters

Thanks for the 411,James says when he puts his finger over the plug hole,and roles the motor,theres barely any back pressure. .........................when it does run it either backfires & run doggy or chirps through the exhaust & runs strong. Hope this helps...

You might get lucky and find there's an exhaust valve sticking. pill the valve covers and crank it over, watching all the rockers and springs for smooth operation.

[StevenC]

plugs 5 and 7 mixed up?

[docvette]

Doc here,

Well, If it ran good when you parked it..

And nothing has been done to it timing wise...

Do A compression Test, IF it's low all the way around, suspect a jumped timing chain. If you've been doing a lot of backfire on a high mile chain, it's a good candidate ...

If it's just low on some and not on others, Suspect STUCK valves (open ) pull the valve covers, spray the stems down with WD 40 or light penetrating oil, and massage them up and down by hand (Or rubber mallet)

If all that's good the fire order is 1 8 4 3 6 5 7 2..Pay attention to 5 and 7 , these are easy to reverse (even by pro's) because they are right next to each other on BOTH ends, cap and plug holes.

Pull the cap, inspect for condensation or wildlife living in there..and if HEI pull the access door and inspect the coil too..

If it's points, check to be sure they aren't too tight, about 17 thousands will get you running better..

Drain and replace the fuel, and fuel filters..If it sat longer than 6 months, it's weak..and may be full of water..

The static timing, #1 plug location (stock) is about 7 O'Clock. Rotation is right or Clockwise..At TDC, Compression, Timing marks aligned, Your rotor should be dead on tower #1 IF you can't coordinate all but the rotor position, you have mechanical issues..(timing chain jumped)

While inside the dizzy, inspect both the mechanical advance and the vacuum advance..for freedom of movement, and keep an eye out for anything that may be hitting the wires inside as the advance plate moves.

Next if all good , put a vacuum gauge on any handy manifold source, at warm idle, it should pull between 17 and 20 In Hg on the gauge, steady, no fluctuations..(unless you have a real lumpy cam) If you get a lot of needle excursions (bouncing) you have bad valves/Seals/guides..If you can't pull at least 17 In Hg, you got vacuum leaks..track them down and repair them.

Doc

[J & A waters]

Thanks for the info Doc Will put to good us right a way.Nice to meet you! J & A