Help anyone. I did all of the recommended mods to my engine while I had to replace the camshaft for worn lobes. Put in an H260 comp cams cam, 1:6 steel rockers, LS1 valve springs, locks and shims, older style rocker studs and manually adjusted valves, new timing chain and 22# fuel injectors. Car runs like crap. :icon_evil:Will idle smooth but anything above idle on acceleration and it makes a pop-pop-pop-pop noise like it is backfiring through the intake or out the exhaust. Spits and sputters horribly. I am out of options. :damnit1: Have not had the chip done yet because others have said you would be able to drive it and it run pretty smooth without changing the chip. I do not want to spend money for a chip if there is something else wrong. It seems as if it is spark knocking badly and the retarding the timing. To be quite honest, I am fed up with this car and see no good reason to not crush it! If nothing else for the joy of knowing my troubles are over. If any one has any suggestions as to what may be wrong, please let me know. I have spent over 3,000 dollars in parts trying to make this car run and it seems to be all for nought. Please help!!
Did you get the intake and exhaust pushrods mixed up?
Another thing to check is spark plug wires, you did get them on correct right? Any way of checking the O2 readings, is it way rich?
The cam/crank timing your positive is correct? Map sensor is alright and the vacuum lines plugged in. Iv herd if you accedently miss match the pushrods you get some very poor running like you describe. The car will idle alright if you put the plug wires on backwards, (like thier wasted side as primary on accedent) but under a load it wont spark well.
what injectors are you using?
Quote from: z284pwr on April 04, 2009, 05:17:08 PM
Another thing to check is spark plug wires, you did get them on correct right?
Agreed, check your wires first. If your wires are fine, be sure your pushrods are all in their correct positions.
Agreed, check spark plug wires to their locations. On the cam...you did point to point on the crank right. Also, when you installed the cam..did you use brake-in lube> ..just to be sure. What was the valve lash you came to? ONE more thing. On the push rod guides..you needed to grind them a little because the cam AND the rockers push up againts it and bind. Make the pocket deeper. You did do that right?
Or if he didn't grind them, he could have replaced his pushrod guides with the ones from the 1.6 car.
Is the engine hard to start? Have you tested the fuel pressure yet?
What rockers are you using? If you have the rockers too tight it can cause the valves to hang open which can lead to the popping. It isn't as noticeable as much just idling either but once it revs, you really notice it. We had this issue recently with ours when we adjusted the rockers, got one too tight and it did that exactly and was a lot harder to start.
Thanks for everyone's input! :icon_biggrin: Just to answer your questions, I did line timing gears up dot-to-dot. Took pushrods out and put them in cardboard I made to keep them in order. I checked wires and they are right, however they may not be on the exact tower on the coils. Changed plug gap to 28. However did use aftermarket coils and IM. but that was done 6 months ago and car seemed to run great up till the time the came failed. Upon initially completing the upgrades mentioned, I did not change the rocker studs and just bottomed out the nuts to spec as if it still had the 1:5 rockers. Someone suggested as you did that maybe the valves weren't closing all the way. Just put in the studs and adjusted valves starting at zero lash plus 1 1/2 turns. Still doing the same thing. Car ran pretty good before the teardown and upgrade, just a slight miss on #5. Very frustrated and have run out of Satudays and patience to work on it. Will hook up a scan tool and try to read the data and see what the computer/sensors are doing. Thanks again yall!!!