backfiring through the intake...
 

Ok, so I installed LE3 heads and cam last week and it has been backfiring through the intake ever since. I know for sure that the rockers were way too tight to begin with, but now they should be pretty damn good. We did somehow break a pushrod into two pieces when the rockers were too tight. But other than the rockers being too tight I am at a loss. We checked all the wires for continuity and they were fine. I double checked the wires to make sure they were all in the correct spot. Anyone have any guesses as to my problem.

Oh yeah, we double checked the timing chain as well. Rotated it a couple times and the dots always lined up perfectly.

Re: backfiring through the intake...
 

I would have quessed the timing gears, dot to dot. It almost has to be, tuning wouldn't do that. Double-tripple check the wires, If thats not it recheck the timing gears.

does it run at all, or just sit there and backfire threw the intake???

Sorry to hear that with a new set up, good luck

Re: backfiring through the intake...
 

If the dots are lined up......and the wires are good. double...triple....quadruple check the Lash adjustment. Sounds like your holding a valve open.

Re: backfiring through the intake...
 

For fire to come out the intake, you mot likely either have a plug firing at the wrong time (cross wired or cam out of time) or an intake valve staying open (valved too tight).

If you are using a timing chain that has adjustable timing marks (advance, retard, zero), make sure that you are aligning the correct dots. When using a cranbk gear set on something other than 0 "zero", you need to align that dot with the correct upper dot, square, triangle or whatever your chain has. Being out of tim will cause it.

Maybe do a compression check and see what all of the cylinders are at. A leak down test will show a bent valve (if out of time) or valve hanging open. Just listen and see if the air is exiting through intake, exhaust or crank case pressure (heard in valve cover area).

I am hoping that the bent pushrod was not caused by the rocker being way too tight and P/V contact or cam out of time resulting in bent valve.

Lloyd Elliott
972-617-5671
Eportworks.com

Re: backfiring through the intake...
 

Yeah as Lloyd said i think it's a Plug wire. The right and left sides of the Opti are timed different. It took me about an hour to figure that out when i was new wires. If you are going by the drive side of the opti to line up the wires (since it's easier to see), you will cross thw two middle wires on the passenger side.

Re: backfiring through the intake...
 

My brother informs me that it wont even start right now, it just backfires through the intake when trying to start. When I was there this weekend it seemed like it was only one backfiring through one cylinder, but my brother tried again last night and thought it was backfiring on more than just one.

Re: backfiring through the intake...
 

How do you perform a compression and or leakdown test? We had the timing cover off for the second time and those damn dots line up perfectly at 6 and 12 (its a stock chain). I am leaning towards a bent valve or something of this nature, because we have triple checked the wires being in the correct spot. I personally did not adjust the rockers, but I had my brother read the message you sent to me before he re-adjusted them. Is it possible that the cam is in wrong? I dont see how it could be since the cam dowel only has one place to go.

Re: backfiring through the intake...
 

Its getting to the point where I just want to push it off a cliff.... Just makes me want to get a mustang.

Re: backfiring through the intake...
 

Sounds like you have an intake valve staying open. What method did you guys use to adjust the valves? The most consistent method for adjusting the valves, and the method I use everytime I adjust valves is...

Adjusting intake valve:

Rotate crankshaft until the pushrod on the exhaust valve (of the same cylinder) just STARTS to move up. Stop rotating engine. Set intake valve to zero lash (easiest way to find zero lash is to tighten the rocker nut while rotating the intake pushrod...once you feel resistance on the pushrod while rotating it, stop tightening the nut). This is zero lash. For most lifters, give another 1/4 - 3/4 turn. For Comp R lifters, you will want to set them at zero lash or 1/10 turn at the most. Repeat.

Adjusting exhaust valve:

Rotate crankshaft until the pushrod on the intake valve (of the same cylinder) has gone up and back down. Just as the intake pushrod reaches the bottom, stop rotating the engine. Set exhaust valve to zero lash (easiest way to find zero lash is to tighten the rocker nut while rotating the exhaust pushrod...once you feel resistance on the pushrod while rotating it, stop tightening the nut). This is zero lash. For most lifters, give another 1/4 - 3/4 turn. For Comp R lifters, you will want to set them at zero lash or 1/10 turn at the most. Repeat.


If it's not the valve adjustment, as others have stated, sounds like you may have crossed a couple plug wires. Good luck. :)

Re: backfiring through the intake...
 

zero lash is not when the pushrod has resistence on it while spinning it. That is actually past zero lash. You have to wiggle the pushrod up and down and when it won't move either way that is zero lash. You have to remember that if you go past zero lash, the lifter is compressed. If you loosen the rocker back up, the lifter takes a few minutes to pump back up. So don't readjust it right away

Re: backfiring through the intake...
 

Once there is ANY resistance on the pushrod, you are at zero lash. If you stop right when you feel resistance, the pushrod won't move up and down and you have found zero lash. I have adjusted a ton of valves this way with zero problems.

Re: backfiring through the intake...
 

The more I think about it the more I am leaning towards a bent valve. The reason being, that when we started the car up for the very first time I dont think it ever back fired through the intake. It ran real rough, but no intake backfires. My guess is that shortly after this is when the pushrod broke in two as a result of being way too tight which also bent a valve. Any one think this hypothesis could hold up?

Re: backfiring through the intake...
 

try unplugging your PCM for about 20 minutes and then plugging it back in and starting it up. See if it makes any difference.

Re: backfiring through the intake...
 

Just out of curiousity what does it do when you disconnect the PCM for a while?

Re: backfiring through the intake...
 

Opti fell off the slot, I gaurantee it. Went through this two months ago.

http://shbox.com/ci/opti_mounting.jpg

Your dowel pin fell into '4'. That little cavity between the place where its supposed to be. The opti will fit snug and seem like it is on correct. Mine also backfired through the intake during my first cam swap. I gaurantee this is the problem.