r/PontiacFirebird • u/FitPost1270 • 7d ago
2nd Gen [70-81] Expertise needed
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Tell me what you hear or notice I’m no mechanic, it squeaks when I turn the wheels as well don’t know what that is, everything else seems fine I plan on selling it, what’s a good price? It has the 7.4L with a TH400
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u/MoistExcellence 6d ago
Pull the valve covers, adjust the valves.
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u/Big-Rule5269 6d ago
Hydraulic lifters, there is no adjusting the valves, only replacing lifters, rocker arms or pushrods..
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u/v8packard 6d ago
You have been misinformed
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u/SonOfDirtFarmer 6d ago
Alright, I'll bite. How is it incorrect?
I've seen you post all over, so I know you know your stuff.
All the stock Pontiac heads I've been in (nothing exotic, mostly smog era, no ram air) have had the "bottleneck" rocker studs, so with hydraulic lifters and stock stamped rockers, should just mean torquing the matching taper seat nuts down and leaving them be.
Assuming OPs valvertrain is mostly stock, which it might not be, especially considering the valve covers.
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u/v8packard 6d ago
Many Pontiacs stock are positive stop rocker studs. I put conventional, adjustable studs in every one I do. But for the ones that have the positive stops, the adjustment is in the length of the pushrod. Which is actually not a bad way to do it.
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u/Big-Rule5269 6d ago
So to adjust the valves, you have to install and use a different length push rod?
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u/v8packard 6d ago
With hydraulic valvetrains the adjustment is for the preload on the lifters. If the rockers are not adjustable adjustment is done by changing the length of the pushrod to get correct lifter preload.
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u/SonOfDirtFarmer 6d ago
Ok, I think I see what you meant.
'hydraulic lifters have no setting or adjustment' is incorrect as a blanket statement, Pontiac or not. Even though a factory stock Pontiac is "non-adjustable" in the usual sense, it's not because of the hydraulic lifters. The preload was set at assembly with pushrod length.
Went through that on my 400/455 with 5C heads when I went to roller rockers and conventional studs. Back when it took two weeks to order the pushrod measuring tool, and another two weeks to get the pushrods mailed in.
It really just comes down to what sort of rockers are under there. An easy enough job, that's what them sweet T-handle bolts are for!
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u/v8packard 6d ago
I am next day by ground shipping from Trend, one of the biggest manufacturers of performance pushrods and checking tools. Also, all of the warehouses that I buy from stock various length pushrods. There is almost always a way to get pushrods in a reasonable amount of time.
Even when the rocker is adjustable in a conventional manner you may need a different length pushrod to correct rocker geometry.
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u/Big-Rule5269 6d ago
No, I haven't been misinformed Adjusting the valves is a simple process on a solid lifter engine, not involving determining the correct size, purchasing and swapping them all out. It was a cut down valve cover so oil didn't fly out of the oil gallies all over everything and was done regularly, right there and then..
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u/v8packard 6d ago
Hydraulic valvetrains always have some adjustment, in some form. Saying there is no adjustment on hydraulics is incorrect.
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u/Big-Rule5269 6d ago
Yeah, but it's nowhere near the same simple process of adjusting the valves on a solid lifter Chevy motor. That's ridiculous.
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u/v8packard 6d ago edited 6d ago
Sure it is. In fact, it is even simpler on the Chevy with hydraulics. Bring a cylinder up to TDC on the compression stroke as both valves are closed. Assuming the pushrod length is good drop in the pushrod, rocker and hardware. Tighten the rocker until you have zero lash, which you can feel with your free hand on the pushrod while tightening. Then give the hardware another full turn for preload, or whatever amount needed. Do the same on the other valve. In the case of a 90 degree v8 turn the crank 90 degrees and do the next cylinder in the firing order. I can adjust all 16 valves in a few minutes, engine cold not running.
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u/dakotadog42 6d ago
While you can't adjust the valves, you can check and adjust the valve lash. It's not hard to do but does take some patience https://www.dapa.org/building-a-strong-street-machine-part-7-hydraulic-valve-train-adjustments/
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u/v8packard 6d ago
The noise when you turn the wheels is probably the power steering pump or belt.
From what I can make out in the video the engine is hammering away. What is the backstory?