im running open headers on a 305tbi, and i was having trouble with its drivability and a code 33. i found out the vacuum wasnt hooked up. that problem is fixed. BUT now, once the car warms up, it will occasionally throw a fit and backfire and cough and sputter. that **** gets loud and annoying. The tach will kinda jump around with it. it runs fine, with the exception of low torque at low rpms, and it runs out of steam pretty quick, but that doesnt affect drivability. this backfiring does. the tach will even start to dance at a light and shut off (if it throws one of those backfiring fits.

can it be timing...it hasnt been set in over two years. spark plugs are new, good msd wires, cap and rotor havent been changed in over 2 years also. (BUT THE CAR RAN FINE BEFORE HEADER INSTALL)
could it just be the lack of backpressure...and will cure itself when i put on the hi flow cat and catback?

thanks for any ideas guys

------------------
Rick
90 Camaro RS 305 TBI
Hooker 1 3/4 LTs, Random Tech Cat, Flowmaster 80 series
406 DFI on the way
MacEwen Motorsports White Gauge Overlays
14" K&N X-Stream Open Element
"Just because I've done it, doesn't mean I knew what I was doing!" - Me

 

The lack of back pressure has been know to cause exhuast valve problems. Basicly, if the valve isn't closing, when the spark plug fires, you get or "Backfire" from the motor, because the flame front will simply travel out of the header instead of being used to create power.

What long tubes are you using, and how did they fit, and are the plugs difficult to change?

BTW, why are you running open headers on a 170HP motor?

 

hooker long tubes 1 3/4 part number 2210 avail from musclemotors.com $360

they fit great, i guess....depends on what you mean.

did they slip right in? NO.
do they fit, YES.

you have to lift the motor, and the starter has to come out, and the knock sensor has to be moved to other side of block, but they fit great.

my car is stock height and i have lil ground clearance now. i dont scrape the collectors or anything but my shocks are shot, and if i really get some down force, im sure i could scrape em....havent tried speed bumps yet....none in SF....we'll see when i go to LA.

im runnin open headers...well y pipe (mufflex one) because i dont have a clamp for the 4" outlet on the mufflex Y. i need to weld it and am goin to my friends on sunday to weld the reducer and cat etc.

thanks for the info...

so some back pressure should fix it eh.
my friend was tellin me to stuff rags in teh collector(s) so that cold air wont crack the valves.

btw, it basically feels like the governor is kicking in, the car kinda refuses to do go, and then it will backfire.

 

LOL, car kinda rufuses to go eh? Kinda like if the exhuast valve wasn't shutting all the way, and the intake charge just went right through the cylander, and then by the time enough gas accumulates over a few revolutions, there is enough to ignite, but since the valve isn't shut...BOOM, backfire. I really think this is a back pressure issue.

 

ya, itll kinda repeatedly try to go but have nothing there, like if you squeeze the trigger and a revolver and there is no bullet, and try again and again, till finally boom!

the car keeps tryin and tryin to go, then backfires, FROM UNDER THE CAR...i payed attention this time, and then it will go.

otherwise it runs like a dream.

 

Well, now that you have varified that the "Boom" is coming from under the car, what you have is a case of a lack of backpressure. Not a big deal, hell, just some 3 foot sections of pipe will normally solve it. Some *******'s at the track run open headers, but put higher tension springs on the exhaust valves just for this. They don't give a crap about lifter life, or the cam lobes, so that's fine for them.