440 build need help again :)

[TheGodfather]

Backfiring engine

i use heady heads with kb 237 pistons on an 73 engine stock cam used(anybody here runs this setup????)....and about the vac advace its not connected from the distributorr??should i hook it up??
i put in a new set of msd street wires...but me mech had bend 2 sparkplug ports so it wounldt touch the headers...could this cause it?

YES......connect the Vac advance. This small rubber tube runs from the distributor to the carb. It will automatically advance the timing as you increase RPM. Set your initial timing at 25 degrees at 2000 rpm. I'm not certain that will fix your backfiring issue tho... The new MSD wires are a great choice and should eliminate bad wires as an issue as long as you've got the right firing order in place. Bending the plug wire boots going to the plugs shouldn't afftect anything. You certainly don't want them touching the headers. If the old plug wires were burning on the headers; that could've caused the problems you have described. Let us know what's going on after these things are completed.

 

[yannick47]

connected the vacum advance....still no luck....backfired about 2twice(porper ones like heavy)ather times small pop from the exhausts(about 30 mins of driving)...could this be cam problem???

 

[TheGodfather]

Time for another approach!!

connected the vacum advance....still no luck....backfired about 2twice(porper ones like heavy)ather times small pop from the exhausts(about 30 mins of driving)...could this be cam problem???

YANNICK47

If you and your mechanic have checked all the electonics + ignition wiring + distributor cap + timing curve + firing order and all is good then there's not much else to check electronically; however something mechanical may be wrong. A bent exhaust valve maybe? Or when the the cam was aligned and degree'd with the crank timing chain someone missed lining up the timing marks perfectly. I've seen this before with folks that don't know these engines. May I suggest you get a Longacre Leakdown Tester from Summit Racing. That will tell you if any of your valves are bent and not holding compression when they're suppose to. Click on the LINK below. Good Luck with getting this figured out.

http://www.summitracing.com/parts/LNG-73010/

 

[yannick47]

still cant solve the problem even though if the mechanic messes around with the carb AND TIMING IT WILL RUN FINE THE WHOLE DAY EXPECT THE NEXT DAY IT STARTS BACKFIRING ..................

 

[70rr-brian]

still cant solve the problem even though if the mechanic messes around with the carb AND TIMING IT WILL RUN FINE THE WHOLE DAY EXPECT THE NEXT DAY IT STARTS BACKFIRING ..................

Is the distributor not being tightened down and wandering causing this issue? Have you marked the distributor and the block after it is running fine and when it starts again comparing the line to make sure it hasnt moved?

 

[yannick47]

Is the distributor not being tightened down and wandering causing this issue? Have you marked the distributor and the block after it is running fine and when it starts again comparing the line to make sure it hasnt moved?

i i dont think thats causing it but will check either ways...what i noticed today is tha it only backfire/cutsout/stubles in the morning ..if i drive for about 15 20 minutes its smooth again no problems at all...

 

[HEMI-ITIS]

Sounds like a carb problem.Either the choke or floats,inlet sticking.
What ignition system is in use?

 

[67 B-body]

Does it have an electric choke??????
I wonder if it's running to rich when cold??? Then it warms up, choke opens, and everyones happy.....

 

[yannick47]

Sounds like a carb problem.Either the choke or floats,inlet sticking.
What ignition system is in use?

the floats seem to be in the right place if im not wronge....half way fr both sides and what d you mean by inlet sicking??

Does it have an electric choke??????
I wonder if it's running to rich when cold??? Then it warms up, choke opens, and everyones happy.....

yes it deshave an electric choke.....should i lean out the carb???

 

[HEMI-ITIS]

I was thinking needle & seat could be hangin up somehow:read:

 

[67 B-body]

the floats seem to be in the right place if im not wronge....half way fr both sides and what d you mean by inlet sicking??


yes it deshave an electric choke.....should i lean out the carb???

I would check that...... just mark its current position and lean it down untill it begins to start hard when cold, then richen back up a small amount.
I wouldn't get to carried away with getting it set correctly right off the bat though. Just lean it way down and see if your symptoms go away, then get it set to the correct "just rich enough" setting..... :VB toast:

 

[yannick47]

tried leanng the carb out still no improvement......the ather thing is the dual fan setup comes on as soon as i switch the car on(takes about 25 to 30 mins of driving to get the tem up to ideal temperature(on the dash stock gauge between the first 2 lines of C )could this be causing it just a cold engine?

 

[yannick47]

???

 

[mopar367]

If you have another carb lying around, I would put it on and see what happens. I dont think a cold engine would cause the intermittent problems you described. Sounds like a bent valve or a carb issue. Like someone else mentioned use a leak-down tester. And swap carbs.

 

[yannick47]

jut to clear things if a value is bent(hopefully not just got them new eddy heads)will the car run smooth when temp comes up?(as once the engne is warm i runs perfectly and idles smooth)and yah think ill just buy another carb and try it out

If you have another carb lying around, I would put it on and see what happens. I dont think a cold engine would cause the intermittent problems you described. Sounds like a bent valve or a carb issue. Like someone else mentioned use a leak-down tester. And swap carbs.

 

[mopar367]

If its a bent valve temp of the engine won't cure it.

 

[yannick47]

and when the engines cold the oil pressure is all the way up..about 80 to 90 while cruising and about 75 80 while at idle..once it warms upp goes to about 55 to 60 at idle and 75 top while cruising

 

[yannick47]

man im hoping its not :eusa_boohoo:

If its a bent valve temp of the engine won't cure it.