Valves losing adjustment...and diagnosis questions

[Anonymous]

Hey all. You may have read my post a bit ago about a problem I was having with the #2 cylinder...ended up being SOMETHING along the lines of a stuck valve or mal-adjusted rocker arm assembly. I had VERY low (nearly 0) compression on #2. I pulled that rocker off, reset the adjustments from scratch and viola. Back to running great. It almost seemed like one of the pushrods was up to high or stuck up to high. What can cause this and how do I correct it?

Unfortunately, that wasn't the end of it. Not long after getting her back into shape, the same symptoms have now crept up again. Running like crap. SO, i went about the same solution. This time, I pulled every rocker assembly off, reset the adjustments, bolted it back together, and once again, viola. She was running right again...for a while.

Driving her last night, she started acting up again after driving it a bit..but slightly different symptoms. Now, the engine has a bad surge to it at idle...like the same effect you get when turning a rheostat on a light switch..up and down and up and down. Down to the point that it would stall if I didn't throttle it up a bit.

I got home last night and fiddled with the mixture a bit and I seem to have corrected it...for now.

So, with my novela above completed, here are my ?'s:

1. I've STILL got the headers tied into my crappy old exhaust system for lack of $ to complete it. Could that constriction be causing backup and buildup in the valves to cause them to stick? Beside changing the exhaust out (which is happnening in the next few days hopefully), what can I do to clean up the mess in there? I've heard drizzle a tiny bit of tranny fluid through the carb...thoughts?

2. what would cause the valves to lose adjustment seemingly so quickly?

3. the surging I'm (was) getting...does it sound like fuel delivery issues? Could it be something up with the fuel pump surging fuel? I plan to rejet the Holley very soon as I know I'm way to rich. Could it be the idler circuit clogged up or something? Maybe powervalve blown?

I know it's super hard to do these online diagnosises (?), but I appreciate the effort! Thanks all!

 

[Anonymous]

noone with an idea?

 

[Mustangaroo]

2. what would cause the valves to lose adjustment seemingly so quickly?

The first thing to check is for a collapsed lifter, when my son rebuilt his engine and installed new lifters one went bad shortly after putting it back on the road. When a lifter collapses it is loosing oil to the lifter and there for does not provide the lift to the valve. When adjusting the rocker arm adjustments should be about the same, once the adjustment is done run the engine a few minutes and recheck your rocker arm adjustments those that are now loose again probably have bad lifters. The fix will require removing the head and replacing the bad lifters.

 

[Anonymous]

Thanks, but I dont have a problem with the adjustments becoming too lose...it seems more like they get tighter, holding the valve(s) open, causing my loss of compression. that's why I thought maybe a lifter was sticking UP, keeping the spring compressed, and hence, the valve open.

A collapsed lifter would keep the valves from opening BUT I'd still show compression on that cylinder right?

My gut tells me that my #1 above is the root of the problem. Carbon buildup on the valves, guides, etc causing them to stick. Am I way off base?

 

[BIGREDRASA]

What valve springs are you running? Are you revving the p*** out of it? Are you floating the valves? Could the valves float and the pushrods jump out of the recess in the lifter?

 

[Anonymous]

i'm using stock valves from the OZ head, checked and shimmed. Yes, I occasionaly rev her up, but not rediculously How do I know if I'm flaoting a valve (what is that exactly)? Yes, that is a possibility I guess...elaborate please

 

[BIGREDRASA]

Just a shot in the dark. When you get one of these instances, can you compress the valve spring to take the load of the pushrod, and see if it will perhaps pop in and out of the lifter?

 

[Anonymous]

i can try if and when it happens next. What is valve float?

 

[BIGREDRASA]

Valve float is when the springs can't close the valves fast enough, so they hang open, and the engine runs out of power.

 

[Anonymous]

hmm...guess that's a pastability. How do you check for it? CAN you?

 

[Mustangaroo]

I just noticed in another post that you had your valve springs shimmed up? To what spec's and did they check to see if your roller rockers may be binding the springs when compressed?

 

[BIGREDRASA]

It's nothing I've seen or heard of, but worth a shot. Compress the valve spring to take the load of the pushrod, and see if it will pop in and out of the lifter.

 

[Anonymous]

What type adjuster does an OZ rocker use? Center stud like a v-8 or end of the rocker like a US 6 or 390? Solid or hydraulic lifters? If solid, what clearence are you using? Are you setting the valves hot? Are you adjusting them with the engine running?

Chuck

 

[Anonymous]

The full rollers I bought from Mike (Yella Terras):

http://cquesttechnologies.com/fspp/prod ... D200%2DFRR

End-style adjuster, hydraulic lifters, yes adjusting on a hot engine but not while running.

I had the springs shimmed per recommendation to .060 (if memory serves me). I did the reassembly so no, binding was not checked .

How do i compress the spring with it on the head? Is there a special tool?

The more I think about valve float, the less I think that's what it is. Isn't valve float a high-rpm runs-out-of power experience? This car's power band right now is AT high RPM's. She tugs well off the line, but get her up to 3KRPM and step on it and hold on. I've had it to 90MPH spinning north of 4KRPM and there seemed to be LOTS more to give, but I girlied out of trying. :roll: