Andreas_91GTA

First - I have searched the forum!

I swapped heads on my 91 GTA, from cast iron to Corvette 128 aluminum, and by doing that I also changed rockers from self aligning to guide plates.
And now the car has an annoying tick, and I can't understand why?! It comes from the head/rocker area. It's extra audible when going from park to D, when the RPM drops for a second.

Of course I fired the parts cannon!

Header gasket - nope. Changed a perfectly fine remflex to a new one. Torqued to spec.
Injectors - nope. Tried the screwdriver listen trick.
Rockers - nope. Tried two different sets. Both set 3/4 turn after zero lash
Vacuum - nope. It has a steady 700 rpm idle pulling 18 in/hg

So, I am now thinking the pushrod slightly kiss the guide plate (but it looks like there's enough clearance). I run 1.6 ratio. I can of course try the old stamped steel and see if it goes away.
Any other tips for me to dive in to?

BigBlock73

iTrader: (1)

I just pulled my TPI intake to address a rear oil leak.
Everything went well until I started it...Tap,Tap,tap.
Pulled the valve cover and inspected the rockers.
Looked under the intake and found I mixed up the intake bolts and installed a longer one in the center position, It was slightly touching the push rod.

Andreas_91GTA

Interesting, I will have to check that out since I changed intake from stock GM to Edelbrock 3860 to match my SuperRam. But how can any center intake bolt even reach the pushrod? Aren't the intake bolt holes just dead holes in the head?

BigBlock73

iTrader: (1)

On the ZZ3 aluminum heads I have only the outer most holes aren't open .
Using the factory bolts, 4 are longer than the rest.

Andreas_91GTA

Didn't notice that (about length) but I also didn't reuse the old torx head intake bolts. I changed to regular bolts of appropriate length. The car din't tick with ordinary bolts on the stock intake base but the Edelbrock might have a thinner casting in the bolt area. I hope bolt length isn't the problem. Removing a SuperRam to get to the intake bolts is hours after hours of work (not to mention waiting for a new gasket set if they rip apart). Shouldn't I feel the pushrod hitting a bolt if I remove the rocker and see how much clearance I get?

BigBlock73

iTrader: (1)

You can look down the push rod hole to see if there is any interference.
I have Accel intake and runners and had to replace gaskets which aren't easy to find and are expensive.
Like you said, it took hours to fix and that lesson wont be forgotten !!!!

Andreas_91GTA

Maybe it's just a combination of noisier valvetrain, compared to the old self aligning setup. And in combination with 5w-40 synthetic oil. Maybe the lifters can't hold pressure with that light, free flowing stuff? But, it was qiueter with the iron heads and self aligning rockers, with the same Mobil1.
I might try to go 1 full turn after zero lash on the rockers to see if it gets quiter. The noisy area is the back half of the engine.

I can't concentrate on my day job until this is solved!!

BigBlock73

iTrader: (1)

A pic from ebay with vette aluminum heads.
You can see the intake mounting is open

Andreas_91GTA

God d*mmit you're a champ. Fingers crossed it isn't my problem

BigBlock73

iTrader: (1)

If it is
The lower intake doesn't need to be removed.
Change bolts one at a time

Andreas_91GTA

Absolutely. Just did the one-bolt-at-a-time on my leaky head studs.
If it is - then another washer or two should do the trick. As you and I know, the SuperRam hell is the runners

EDGE

I have the ticking as well but it goes away about a minute after starting a cold engine. I'm running flo-tek heads and scorpion 1.6 rockers with Johnson lifters. I'm thinking maybe 1 lifter isn't holding pressure on long shutdowns. Not really sure if that's a problem. Car runs pretty good. Just annoying

sofakingdom

iTrader: (1)

Use the Permatex/Loctite "high temp automotive thread sealer w PTFE" (or equivalent available in your location) on the threads of the intake bolts. Otherwise, you'll end up with the infamous pools of oil on top of the intake around each bolt. The same kind of sealer - NOT silicone or the like - should have been used on the head bolt threads.

The correct bolt length is 1¼". Some may be longer, where there are brackets or whatever, mounted under them. The factory may also have used studs for some, that had a hex head that is tightened exactly like the bolts, then had a part slipped over them and nuts on top.

Andreas_91GTA

Good news and bad news.

Good: The intake bolts are nowhere near the pushrods. Can't even see them sticking out at all.
Bad: Still ticking.

Could it be oil pressure related, making a lifter collapse? Since the tick really ticks when going from park to drive and the rpm (and oil pump) slows down for a moment? Pressure is, according to my 33 year old dash, really good. Upper third of the meter, always.

EDGE

I run and have for years, Mobil 15W40. Why don't you try that and see if it changes anything?

Andreas_91GTA

Yep, I might just do that. I changed oil after changing the heads, then I changed again after the head studs leaked some coolant in my engine. The motor is rebuilt and has 1000 miles on it. It runs real good and crispy.
What really bugs me out is that it was quiet before i changed heads and intake, so Im blaming myself for doing something wrong, if only I knew what it was??

EDGE

Oh I know. The ticking drives me up the wall but mine does go away once it's running for about a minute. Maybe I have to much lifter preload on one of them, I don't know. But I think by the book it's up to 1 1/4 turns. I know I didn't crank them that much.

NoEmissions84TA

iTrader: (1)

Step #1 - find the source of your tick. Use a length of vacuum / windshield washer size tubing to locate.
Put one end in your ear and use the other end to probe around. You are just guessing until you definitely find the tick.

EDGE

In my case the sound doesn't last long enough to track it down.

BigBlock73

iTrader: (1)

Not sure it is "Good" that it wasn't a bolt touching the push rod... at least you would know what the issue is.

What I enjoy less than R&R the runners and plenum might be your next step.
Running the engine without the valve covers on.

Andreas_91GTA

No, thats why still ticking was filed under "bad"

Im gonna try with a little bit thicker oil and set rockers 1 turn after zero lash. My suspicion right now is that a lifter isn't pumping up correctly..

Switched oil to semi synthetic 10w40 and set rockers yesterday night, so it's just a matter of getting some me-time and start cranking.

Running with the valve covers off is my everyday life for the past two weeks..

Andreas_91GTA

Changed to 10w-40 and set the rockers for the 10th time. Still ticking under load. Judging by the frequency it sounds like it's one cylinders intake or exhaust pulse. Quiet when cruising. I'm completely out of ideas. Worn valve seal?? (since it came after the head swap)

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