Hi Everyone,

I wanted to know if the Valve Timing remains the same with the following;

A new rebuilt old style TBI 5.7L block stock except, a Edelbrock performer cam and Vortec heads, Edelbrock EPS intake, flowmaster headers, and brand new Holley oem style TBI

I adjusted the rocker arms to 1/2 turn after 0 lash...

I'm having a bad problem with the engine backfiring when you go to WOT and whats weird is that at first I had adjust the Rockers to 1 turn after 0 lash and it ran better but back fired out the intake BUT someone recomended setting them to 1/2 a turn, NOW it runs worse but back fires worse out the exhaust.

I have NEVER had a problem with a engine like this before, there so simplistic.....

- If the New Cam & Lifters WAS NOT broke in properly would that cause the exsisting problem?

Weak Valve springs???

Thanks in advance!
David

 

loosen them up half a turn- all of them

with the motor running and a good glove move the tip of the rocker across the top of the valve

you should not be able to move it without a little force

adjust them all like that and take a ride

repost and tell me I am wrong

 

The best way to adjust valves is to remove both valve covers. Turn engine the same way it runs clockwise looking at it. When the exhaust valve begins to open adjust intake valve. spin the push rod with your fingers and you will feel when there is zero lash then go a half turn. turn engine till intake valve starts to close adjust exhaust. that will put the cam on base circle and will work with all cams.

 

Hydraulic lifters are tricky. Some people don't realize that it's easy to over tighten the rocker.

With the piston at TDC or both valves closed, back off the rockers and wait about 30 seconds for the lifter to reset. I could never do the spin test so I always wiggle the pushrod while tightening the rocker until it just starts to get tight. This will be close enough to zero lash. Turn rocker nut 1/2 turn more. If you wait then recheck the pushrod, it will spin again. Don't tighten more thinking it's still loose.

If you can't find TDC on each cylinder, use the open and closed method. When one valve is fully open adjust the other.

Recheck you plug wires. Did you have them off when you adjusted the valves? Recheck 5 and 7 since those are common to switch around.

 

in my haynes manual it says to take off the valve covers, turn the car on, and first start by loosening the rocker until you here a loud clicking noise, then tighten just until it stops, then from there give it another half turn

 

What messed with my mind is the fact then when I adjusted them 1 complete turn after 0 lash, it ran 1000 times better then adjusting then just 1/2 turn.

When the engine is cold you can floor it or wahat ever and it goes like a Bat out of Hell, Tons of power, No Back Fire, and as soon as it warms up, it back fire bad out the intake JUST if you try to floor it, WOT, IF you slowly step in to so far to gradually accelarate then your fine, and at a cruise it doesn't change.

When I had adjusted the valves to 1/2 turn the its not driveable at all. It will barely run and back fire bad out the exhaust and intake, cold or hot.

I have NEVER run it this before, WHY would it back fire LESS at 1 turn?????????

 

Collapsed lifters?

 

Maybe you should run them loose to make sure they are pumped up first. If they are collasped and you try to adjust them they will pump up and be to tight.

 

If something is screwing up the oil pressure to the lifters or if the engine builder possiblely installed used lifters with the new cam that are not pressuring up right, I wonder if that could cause it.....

like I said Its when the engine warms up......

I should maybe pull the intake and check the lifters and the cam.
Does anyone know if the stock 5.7, 5.7 TBI & 5.7 Vortec heads have the same Valve springs? That could maybe be the problem, This engine was a rebuilt Long block that was bought from a engine shop.



I appreciate all the help everyone is giving!
Thank you very much!

 

did you adjust them when the car was already warmed up? you could try that, and then adjust them with the car on

 

Colapsed lifters is something that I was thinking could be my problem.



So if this engine is lossing to much oil pressure at opperating tempature, that would be the cause of my lifters to colapse and thus cause my engine back fire...

Is that right????

 

I think I'm going to put a direct oil pressure gauge on it and see what it really is...

 

Here is the latest...

Yesterday, I installed a new Melling High Volume Pump in the engine, and was able to start it up before I had to leave and it ran 1000 times better!
NO BACK FIRING AT IDLE!!!!!
The "new pump" that was put in there by a engine shop here was not in good shape, It was binding even! You could see the clearance inside was off too, on one side the pump gear was scraping the pump wall bad like the gear shaft (NOT THE ONE TO THE DIS.) was slightly off, or bent.

I'll soon know more this morning but I wanted to tell everyone the progress so that IF someone else runs into the same trouble then we can help that person!

I post more later....