Weird thing-when I gave the valve the half-turn on the wrench, the engine sputtered initially then ran much better. Is that normal? I found it odd, though I suppose the ecm has to compensate for it?

 

You certainly threw Bfenty (and maybe others) a curve ball on that one! Why would you post stuff that you know is b.s.? Why should we have any credibility in your posts, if you don't even believe your own information is correct??

That's the advantage of hydraulic lifters. They always run at the equivalent of zero valve lash, regardless of engine temperature. I believe running solid lifters "a little bit loose" will reduce your valve opening lift and the valve open time, which will reduce your power. Or maybe you can explain how running your solid lifters "loose" will increase your power. What am I missing?

 

Yes, that's normal. The valve wasn't closing entirely, since the hydraulic lifter was a bit too long, until it self-adjusted to its correct height.

 

Engine masters did a test on it a few weeks back. They also couldn't really theorize how it worked either... but running the lash loose they picked up something like an average of 12 hp and about the same on the torque across the RPM band. Now granted that is on a ~800 hp engine but... A gain is a gain.

As far as hydraulic, about 5 machine shops, 3 pro racers and like literally any online forum has claimed improvements running looser on the lash on a hydraulic set up. Heck when I talked to one of the techs at howards they said I can run the preload a little looser if it's an all out type build. To me it makes no sense. I can't wrap my head around it. But people way more knowledgeable than me or heck, even the designers of the damn thing have said it.

Didn't mean to stir the pot or anything. I've run it both ways. It helps me to learn when I misspeak and I definitely did that here. Sorry.

 

I will say, that it’s running smoother than it was before I did anything. Not sure if it’s got more HP but it’s definitely feeling good. I’ll endorse running the valves a little bit loose, 1/2 turn past zero lash seems to be a really good place to be.

 

84 4+3 - nothing personal. but if Engine Masters claimed they picked up 12 HP on HYDRAULIC lifters by setting them a bit loose, well IMO, i'd have to throw out the on that one - unless it had something to do with allowing the engine to rev a bit higher. I VAGUELY remember why GM sets 1 full turn - had something to do with valve float occurring at a lower RPM - below the threshold of the engine's internal component failure. kind of like an insurance policy. I can't quote the source of that information, so take it FWIW. IMO, for the average street driven car, there is no performance advantage in setting them "loose." setting them loose may allow the engine to rev higher before a "pump up" condition is met, but since L98's are not high revving engines, and as long as the lash adjustment is in the normal operating window, there is no advantage. to filter through all the hearsay, this is an area where google is your friend. as far as my 85's L98 goes, personally, I don't want to put too much thought into it. set them cold to 3/4-1 turn, per the factory recommended procedure, and forget it.

 

My bad, the engine masters test was a solid lifter engine. I agree BS on hydraulic. The only reason I even began to question it was when the manufacturer of my lifters said I could run it loose if it were all out... but they also said for every day to set it by preload depth hot. As in use the thread pitch on the stud to determine how may turns are needed to set the preload in the range they reccomended. In my case about 1/2 to 3/4 turn max. On iron head and block it was different. On 7/16 studs it was different. I'm wondering if its more oem vs aftermarket parts than anything...

 

not to argue the point, but I have never seen a "factory" service manual that says, "adjust hot, or adjust on a running engine" think about this - GM builds tens of thousands of engines every day. these engines are assembled cold - including the valve adjustments. they come off the assembly line, shipped to the final assembly plant, and dropped into the car. nowhere do they fine tune these engines hot and after the fact. this is what is great about hydraulic lifters - there's so much latitude in the overall adjustment (1/4 - 1-1/4 turns). set them cold. I doubt there's .010" difference in adjustment due to heat soak. I have never seen so much controversy over such a simple task as adjusting a hydraulic lifter as on some of these forums. not sure why, but it seems folks are trying to out-smart the factory, and putting way too much thought into such a simple task. i'm surprised nobody has brought up the nonsense of finding the base circle of the cam lobe as part of the procedure - . I think i'm done here....

 

Question. What changes when it is hot? Dry, sure. Usually they tell you to soak them in oil before installing. AFAIK it's to fill the lifter but after that, maybe a few seconds of run. So unless it has all drained out, what is the point of hot? How much change is there?

 

Hey guys-let’s not get into this debate here. We are arguing a moot point now.

I think the main thing is-
don’t over tighten the nuts, you’ll end up misfiring.
Anything past a single turn is probably close to over tight.

Under 1/4 turn is too loose. Ideal is somewhere like 1/2-3/4. Because of the hydraulic lifter, it will self-adjust at that point.

Doing it cold works, there is some debate on the exact method. Pushrod twisting is the FSM recommendation.

doing it hot works, makes a mess but then it’s easy to hear/feel it running correctly (if I were to recommend something, this is how I’d do it).

Maybe I’m over-simplifying, but I’m trying to summarize for future googling to help the next guy learn from my mistakes. We can argue endlessly on minute details, but the fact is that for the average home mechanic, this is what you need to know to get the job done.

thanks all for the help!

 

Hello again Bfenty!

You DID IT! Congratulations on getting your Corvette back ready for action!
It sounds like a lot of us learned a bit here with you! Your doing this will encourage other Corvette Owners to try this job them selves.

The one thing I do that is different than a lot of folks is this: Take a old "useless" Valve Cover and cut out the center of it so you can have "some" oil control. This helps keep the oil where it belongs and not all over you and the shop. It is even harder to control on Big Block GM heads.

I made a "bad move" when I chose a pair of valve covers as I needed a pair for my 427 to keep me clean while adjusting the valves. I was at Corvettes@Carlisle and I saw a cheap set of big block valve covers so I bought them and then I went home and cut out the center section allowing me easy access to the valves while keeping the oil in my engine. When my Corvette Restoration folks saw the valve covers they immediately asked what idiot did this? I thought it was a smart idea myself, that is not what they were talking about. The Valve covers were original Chevy BB parts used on a 66 Corvette and I bought them for junk.

I am back working on my C3 and it's new EFI system. Today I need to teach the IAC how and when to work. Currently my idle is a bit wacky as it likes to slow down to 600-700 rpm and with my cam it sounds really funny. I wish the GM EFI system controls were as simple as the aftermarket is able to produce.

Thank You Bfenty for sharing this experience with us here on the Corvette Forum!

 

I am now confusing my marine service manual and Automotive service manual. I'm going to quit before I say something else stupid.

 

There are a couple of differences in marine but is this one of them?

 

One other lesson learned-cut a flap of cardboard to tuck into the bottom of the valve area while you're working. Believe me, the first time you drop one of the valve retainers, you will definitely be thankful that you did. I dropped one before doing this, and it luckily fell all the way through the engine and hit the ground below. Decided not to risk that again.

 

Merc is... uh... **** to say the least... let's just leave it there.

 

Only dealt on one Ford 302 in a boat I got to settle a bad debt. I had to put work into it, play for a bit and then sold it for a break even less my labor. They do say the happiest days of a boat owner' life is the day he buys it and the day he sells it. The day I sold it, the wife was ecstatic to see it go. After all the work I had to do and the time and involving her, if it had gone on any longer, she'd have probably put me in the boat and sunk it.

 

This is the source of endless confusion. Being "tight" means that all the clearance between the piston in the lifter, the pushrod, the rocker arm and the rocker arm / valve stem tip is taken up. If you gently move the push rod up and down you can feel when that clearance is taken up. Now rotate the pushrod; the pushrod should rotate with only the slightest amount of drag (compared to when it is loose). This is the starting point for 1/4, 1/2, 3/4, or 1 turn (your choice) adjustment. UNFORTUNATELY many people take "tight" literally, as in the pushrod is difficult to rotate between the finger tips; If you start at this point, the total preload may end up being WAY too high

 

nice

My only recent experience with motors of the F family was a 460 with a pedestal mounting system for the rocker arms; the only "adjustment" was adding shims under the pedestal till the piston in the lifter was down in the lifter body a set amount (0.080" if I recall). Adjusting that valve train was a not easy; Thankfully, a Chevy valve train is sooo much easier to adjust.

Then why does my LT4 also uses a non adjustable pedestal style valve train, can someone explain that to me?.

 

3/4 I heard

 

I mean, the definition of 'tight' in the FSM is when you can't ROTATE the pushrod, not when you can't lift it up and down. I'm not saying you're wrong, but I did follow the FSM procedure to the letter. I agree that doing exactly that led to it being overtightened.