really need some help guys pulling my hair out on this one

1st of all just done a bottom end rebuild all back together and now this

(from the 1st time on fire up) car runs but very poorly like its on 6 cylinders, had 2 sets of plugs in one old set and new set, the ht lead have all got a spark, injectors have all got a pules, good fuel psi, i pulled the front end of the make sure the timing is right, set the dizzy up again and again.

running out of ideas must of cheeked every thing 3,4,5.

plain for tomorrow is another set of plugs and to pule the fuel rail of and see if there fuel in all out

any ideas would be great really any ideas!!!!!!!!!

thanks

 

If you're sure it's missing, the best way to find which cylinders is to run it for a minute, then feel each header tube, right near the head. Be careful you don't get burnt. But whichever cylinders aren't firing won't get hot.
How does it sound? If you over-tightened some rocker nuts, then you may have some valves not closing. If so, then no power from those cylinders.

 

Swap the wires on the dist cap that you think are 5 & 7.

If that's not it, back all the rockers off by ½ turn.

 

If those 2 were swapped, then it would be backfiring.

 

thanks guys. some really good ideas to try out

i am getting a lot of back fire.

 

See my signature for some help with logic.

 

That wasn't in your original post. But since you're getting backfiring, then Sofa is probably on the right track. You may have some wires swapped. If not, then it's back to the rocker nuts.

 

i have done the valve nuts for the 2nd time but a 3rd time wont hurt if the wire cross over dont work

 

right done a little more digging.

its 100% not to do with fuel. had the injectors on the fuel rail out of the car tested them all, all fine. so can cross that of.

the valve covers are of but dint have time to play with them befor we had our english summer i,e rain. so will have a look at them tomorrow.

played around with 7 and 5 on the dizzy cap with no luck.

any more ideas????

 

It may not be 5 and 7, it may be any 2 wires. If one plug is firing 90 crank degrees to soon, you get a backfire.
Alternately, if one of the intake valves isn't fully closing, you get a backfire.

 

i think its more likey to be the valves. iv done the wires some many times, unless the gta has a funny firing order from any other small block chevy?

how much turn do you guys put on your valves the book says 1 full turn but iv always know it as 3/4 of a turn?????

 

I just go 90 degrees.

 

really as little as that?

 

It's supposed to be a performance setting. It has always worked fine for me.

 

hummm been haveing a hunt on the net for how much of a turn and iv seen from 1/4 to a full turn and a 1/4 lol

if 1/4 turn works for you then ill give it a go

 

Spin the push rod with ur fingers until u feel resistance while tightening and that should be sufficient.

 

today was a good day!!!! put the fuel rail and intake tubes back on after cleaning them up.

re did the valves this time only 1/4 f a turn and wow of she wents fired up with no probs and sounds sweet as.

crazy iv always done 3/4 of a turn and the book says 12 full turn. a week of **** to get there in the end but so happy.

thank you so much for all your help guys

bad

 

No, that's not when you stop, that's when you give it a final 90 degrees. Without that last 90 degrees, it'll end up too loose.