Hi everyone, this is my first post on the forum.

I have a 1988 Firebird formula 5.7, it blew a head gasket and I have since taken it apart and rebuilt it, I swapped the stock heads with Trickflows 23 degree'ers, and upgraded to Elgin 1.6 rocker arms, high flow\ported intake & runners etc.All the other engine parts are stock, stock lifters, cam, pushrods are hardened, but stock length.

Here is my problem, everything is completely reassembled, I followed the manufacturer's instructions ( and the haynes manual)to the letter. When I crank the engine with the starter, I get very excessive noise coming from the valvetrain, and I mean 'very' excessive, klunk klunk klunk kind of sound, not a simple loud tick. The engine turns over, but it will not start.

Also, when I attempt to turn the crank manually it spins fairly easily, then freezes at a certain point at about
3\4 of a turn after TDC; at which point it becomes almost impossible to turn manually(spark plugs are out). I proplerly oiled the valvetrain before attempting to start the engine, and I am fairly certain I properly adjusted the rockers to spec.



I am completely stumped at this point and any help would be greatly appreciated.

 

Is the engine in the car? What's the oil pressure?

 

Yes the engine and everything else is assembled in the car. I'm not planning on cranking the engine again until I figure out the valve noise issue to avoid damaging anything, I'm concerned that it may be serious; so an oil pressure reading may be tough to get.

 

are you sure and I mean are you sure that you adjusted the the valves right. I made this mistake as a rookie and bent 3 pushrods.

dont shoot the messenger. I did not want to hear it when it happened to me

 

I believe I adjusted the valves properly, I followed the instructions (tighten to zero lash, defined as the point when you meet resitance whilst turning the pushrod, then 3\4 additional turn). However This is my first time doing it so I may have done it wrong somehow. I'll try adjusting the valves again.

 

Post your definition of zero lash and resistance.

Edit -since you're gonna redo the valve lash anyway, back off all the valves wayyyy off and see if you still have resistance in the one spot when spinning the engine manually.

 

Hi lo-tec, that is definitely part of the problem...the definitions seem very vague to me...I have read the textbook definition of zero lash as being the point when you first meet any resistance against spinning the pushrod with your fingers whilst tightening the rocker arm adjusting nut. When you can feel resistance...that is zero lash. I have hydraulic lifters so I am then instructed to tighten an additional 3\4 turn past zero lash.

The crank spins freely by hand when all the valves are loosened up. The car has been sitting for several months without being turned over, prior to today, if that information helps any.

If there is a 100% foolproof way to more precisely determine zero lash that would definitely help me out. This is my first rebuild attempt so all my information is simply textbook.

 

I had a problem making sure that I was at number one TDC

both valves should be closed for a long time as the marker comes up to 0

 

Before "zero lash" you can pull the rocker off of the pushrod. As you get closer, you can move it less and less. The "resistance" increase at zero lash is minimal, but the rocker will no longer be able to be pulled off of the pushrod (big clue here). Play around with it, and you will find the slight increase in resistance once you hit zero lash. I would only go 1/2 turn past that for valve adjustment. Also, here is how I adjust my engine:

Adjust Rocking
1--------6
8--------5
4--------7
3--------2
6--------1
5--------8
7--------4
2--------3

Adjust both valves in the left column when the valves in the right column are rocking (ex. closing intake opening). This puts the cyl. you are adjusting at TDC firing where both valves are closed. Good luck and post your results!!

 

Thanks for the quick replies fellas, I'll give that adjustment method a shot tommorrow.

 

Adjust each cylinder at a time. Rotate the crank by hand till a intake valve opens and then just closes (on seat).Lifter is down. Adjust the exhaust valve for that cylinder. Then rotate the crank by hand till that exhaust valve just starts to open (first motion) adjust that intake valve. Now repeat for the rest of the cylinders. Intake closes set the exhaust, exhaust opens (first motion) set the intake. You may find it helpfull to mark the push rod near the top and watch it as you adjust the valve. "0 lash is a slight increase in rotating resistance felt just before the push rod starts to compress. Or the valve starts to open. If either the push rod moves or the valve opens, you've gone past "0 lash"
Using my method of positioning the crank to adjust each of the valves ensures that you are on the back side of the base circle of the cam and not partally into the open or closing ramp. This is the only and best way to setup the valves *accurately* on any 4 cycle motor. The lifter must be on the back side of the lobe oposite of full lift to adjust that valve.
When the intake valve just closes, The exhaust for that cylinder is ready to be adjusted. When the exhaust just starts to open, the intake lobe is properly positioned for adjustment.

 

OK, makes sense - but when you re-check your valve lash as stated above, and go for a "start", pay particular attention to your oil pressure and temps. Nothing will kill a newly rebuilt engine quicker than lack of oil pressure and overheating.