Slant Six Forum
https://slantsix.org/forum/

hydraulic valves in late slant6s
https://slantsix.org/forum/viewtopic.php?t=21439		 Page 2 of 2
Author:  440_Magnum [ Tue Jan 16, 2007 7:13 am ]
Post subject: 
Quote:
This aside, the main reason I never liked Mopar hydraulic lifter engines is based on the non-adjustable stamped steel rocker arms they used. The hydraulic lifter needs a set amount of plunger preload and setting this on a Mopar can only be done by adjusting the length of each valve stem or pushrod. (when the rocker arms have no means of adjustment)
The factory had a way to set this (so we hope) but once you get a little wear or valve seat recession, you are in for poor preformance , lifter clatter or "pump-up" and no easy way to fix it.
For what its worth, in my rough million miles on Mopar v8s that's been a complete non-issue. In fact, my experience is that the valves on adjustable-valve Ford and Chebby v8s are far more offten out of adjustment than the non-adjustable Mopars. Maybe the Magnum LA engines are the best of both worlds- I've never heard them clattering along even though they're similar to Ford/Chevy ball-stud rocker engines Actually they're identical to the AMC valve setup- good way to use inherited engineering! :D

Now the one hydro-lifter slant-6 I had was another story altogether... but then that's such a bass-ackwards system that it should come as no surprise that it doesn't work that well.
Author:  Doc [ Tue Jan 16, 2007 8:24 am ]
Post subject: 
The key to success for any non-adjustable rocker arm - hyd. lifter engine is to set-up the head(s) correctly. All the valve stem heights need to be the same, or at least within .010 to .020 of each other.

This is something a good machinest will do during a valve job and it is easy to check by putting a straight edge across all the valve stem tips. (use a feeler gauge to size any gaps you see)

If all the valve stems are set to the same height, you can use rocker shaft shims or custom length push rods to fine tune the plunger positions.
Note: most hyd. lifter have appx .06 of plunger travel and I tend to set a high reving engine with about .020 of preload. (.020 down into the .060 available travel.) The factory sets them to the middle of the available plunger travel. You can see how having an adjustable rocker arm would make the preload setting process a lot easier and accurate.
DD
Author:  bob fisher [ Sat Jan 20, 2007 7:00 am ]
Post subject:  a reply and a question for the doctor on hydraulic valve sl6
hello doctor- thanks for the info on this sl6. again surprised that this engine was less than desirable. about to buy an 80 sl6 vehicle. does that year start the changeover to hydraulic valves or was it later sl6s that had the hydraulics? havea real difference of opinion here. never saw here or elsewhere negative reports on the hydraulic valves. should one expect the same legendary durability and longevity from the hydraulic engine as from the solids engine? my only experience with hydraulics was with 318s and small v8 chevrolets. none of them required any attention to the valves in over 150k miles. one 74 amc 232 inch 6 did punch a pushrod through a wear hole in a rocker, which i replaced but i dont think that had anything to do with the hydraulic lifter under the push rod. thanks again for you sage advice. regards bob f
Author:  volaredon [ Sat Jan 20, 2007 12:31 pm ]
Post subject: 
Actually 81 was the 1st year of hyd lifters... Ive have 2, 80 Volares and an 80 Aspen ALL were solid lifter engines.... I have HEARD that there were a few hydro setups out as early as 78, as "guinea pigs" to see how well they would work out in the real world. I personally have not seen any cars before the 81 model year with hydraulics, that hadnt had a story of an engine swap come with the car.
Now my dad had an 82 gran Fury that was a hyd /6, and when we had to pull the head for a valve job we found out its head was cracked, and I had a drool tube head here that was freshly redone, so to save $$$$ we used the drool tube head on the hydro short block w/o a problem. All I remember was something with 1 rocker shaft bolt.... having to drill out 1 hole in the shaft and use the bolt in that hole from the other setup. I dont remember exactly why as it has been a while. I remember the power and mileage was up with the drool head on there. Several years later the float stuck and gas overflowed onto the converter that mounted right under the manifold in the eng. compartment and the car caught fire. Before the ins co. took the car, I swapped heads back as I had another slant that needed a head.
Author:  SlantSixDan [ Sat Jan 20, 2007 11:16 pm ]
Post subject:  Re: a reply and a question for the doctor on hydraulic valve
Quote:
about to buy an 80 sl6 vehicle. does that year start the changeover to hydraulic valves
1981 was the first year for the hydraulic lifters in the slant-6 (though there was a production test in '78 ).
Quote:
real difference of opinion here
Not really...most of us don't like the hydraulic setup as much as we like the solid setup!
Quote:
never saw here or elsewhere negative reports on the hydraulic valves
There's been lots of negative opinion stated here and elsewhere over the years on the hydraulics. Not nearly as much camshaft selection, fiddly and nonadjustable rocker setup, lots more small oil passages to clog...
Quote:
should one expect the same legendary durability and longevity from the hydraulic engine
That's not as simple a question to answer as it might seem. The engines were cheapened and cheapened progressively starting in '75. As the years went on, the slant-6 was allowed to die of neglect. No, I would not expect the same durability out of an '87 slant-6 as out of a '77, nor would I expect the durability of a '67 out of a '77.

Quote:
my only experience with hydraulics was with 318s and small v8 chevrolets
Those are all side-feed setups with the lifters fed via a short internal passage off the main oil gallery...it doesn't have to travel through the cam, through the block, through the head, through the rocker shaft, through the rocker arms, and THEN through the pushrods to get to the lifters (which is how it works in the '81-up slant-6 setup)
Page 2 of 2 All times are UTC-07:00
Powered by phpBB® Forum Software © phpBB Limited
https://www.phpbb.com/