I think there is a thread on here from the recent past where Dan was saying the harden seats weren't needed because the gas formulation had changed for the better from the '70s.

For what it is worth. I am not running harden seats and the engine builder valves. So far no problems and I drive my Dart daily using standard cheapo ARCO gas.

OK, I'll grant you there is a risk of hitting water...but that's why machining for hard seats is the first step. If you hit water, start with another head. Enough hard seats have been put in enough Slant-6 heads that if it were really anything as bad as 50/50 odds, we'd know it. We know of other high-odds-of-a-dammit aspects of the Slant-6: the "Bermuda Triangle" right front corner of the oil pan gasket...the manifold studs...the hotbox gasket. Hard seats don't have anything like that rate of dammitry. I stand by my view that not putting in hard seats is silly.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

The post you're thinking of is this one. It doesn't quite say what you have in mind. It explains why in light-duty passenger car service, there is no reason to waste money on lead "substitutes" or to do a valve job that's not yet necessary, because the valves will keep working fine for quite awhile. That post also advises putting in hard seats when a valve job does come due, and what we're talking about in this thread is not light-duty service and does not involve the small, easily-cooled stock valves.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

No offense Dan, but I know some pretty well respected head porters who will not put seats in a Slant head, especially if bigger valves are to be installed, simply because of the high chances the seat will drop. By the time you cut the chamber out for the seats there is very little metal left between the seats to hold them in. I had a very lengthy discussion with Blaine Mueller before we did my first head, and it came back with no seats installed.

I have run some higher spring pressures than most, made hundreds of passes, drove thousands of miles, sprayed a couple hundred pounds of nitrous, and never so much as nicked a seat.

Now pistons is another story........

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Official Cookie and Mater Tormentor.

I agree with Dennis. I have seen seats come out on other people's motors, but luckily not mine.

Always be careful how surely you state things you "know". It is often the things we assume are right that bite us the hardest later when it turns out they are wrong...

Lou

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Home of Slant6-powered fun machines since 1988

So, I may just buy the normal valve springs and put them on - using the stock cam for a while, don't want to run the risk of wiping out a lobe with increased spring pressure or keeping one of the hydraulic lifters collapsed. Anybody know the difference in spring force between the 340 and the regular slant six springs? Stock springs good to 4500 rpm?

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Tom
'86 Alfa Romeo Spider, red "Dinsdale"
'10 Corvette, red "" (no name yet)
'95 Ferrari 348, red "Zoom"
'04 Maserati, black "Evil"
'05 Aston Martin DB9, green "Bond, Treasury bond."
'82 Dodge W150 Power Ram, yellow "E. Valdez"

If its a stock cam the stock springs and lifters are the safe way to go.

There are ways to get a better spring pack that dont involve radically increasing pressure.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Them thar newfangled beehive critters?

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Tom
'86 Alfa Romeo Spider, red "Dinsdale"
'10 Corvette, red "" (no name yet)
'95 Ferrari 348, red "Zoom"
'04 Maserati, black "Evil"
'05 Aston Martin DB9, green "Bond, Treasury bond."
'82 Dodge W150 Power Ram, yellow "E. Valdez"

Yup. The 318 springs will control the valve motion to well above the speed the engine will make power.

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Joshua

On a hydraulic lifter engine the important thing is to make sure the tips of the valvestems are even, and make sure to check lifter preload. You might have to get longer or shorter pushrods since there is no adjustment.

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Official Cookie and Mater Tormentor.

%^$%#!$@!!!. #2 intake and #4 exhaust are high. I've completely forgotten this stuff - haven't played with a hydraulic lifter motor in 20+ years. &%^%*&#@#!!. Those valves are about 0.030" higher than the rest - the rest are 0.00X close together. Grrrr. Thanks for mentioning this - I had planned to do the cam (got a mechanical tourquer cam, mech lifters and mech rocker assy) and head at the same time, but then thought about doing just the head for now.

Oh well, luckily my cheapie Maserati Biturbo blew up before I had to do any valve anything on it. Mechanical cams. three valves per cylinder, V6, and one rocker arm and three shims - no adjustments, shims - as in the cam has to come off the engine to replace a shim.

So, what do I do with the two that protrude the 0.030?

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Tom
'86 Alfa Romeo Spider, red "Dinsdale"
'10 Corvette, red "" (no name yet)
'95 Ferrari 348, red "Zoom"
'04 Maserati, black "Evil"
'05 Aston Martin DB9, green "Bond, Treasury bond."
'82 Dodge W150 Power Ram, yellow "E. Valdez"

chainsaw raker file

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Yeah....Im the one who destroyed this rare, vintage automobile.....

The replacement hydraulic lifters I checked had a LOT of plunger travel.

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Joshua

Thanks. And ugh, lifter preload. Time to track down some pushrods, or, (Nomex suit ON) is it possible to put sheet brass shims between the rocker assy shaft and the block? I know that's 0.060's impossible - radius of mating face gets smaller - worn't work - ehh - no matter what I do the pushrods have to be shortened as .065 got milled off the head - I'm NOT trying to play with the valve stem height as eventually this head will be used with a solid lifter cam.

Is there any way to modify a solid lifter rocker arm assy to work with a hydraulic cam? That would give me adjustability . . . .

I'm just thinking out loud.

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Tom
'86 Alfa Romeo Spider, red "Dinsdale"
'10 Corvette, red "" (no name yet)
'95 Ferrari 348, red "Zoom"
'04 Maserati, black "Evil"
'05 Aston Martin DB9, green "Bond, Treasury bond."
'82 Dodge W150 Power Ram, yellow "E. Valdez"

Head is cut 0.065"

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Tom
'86 Alfa Romeo Spider, red "Dinsdale"
'10 Corvette, red "" (no name yet)
'95 Ferrari 348, red "Zoom"
'04 Maserati, black "Evil"
'05 Aston Martin DB9, green "Bond, Treasury bond."
'82 Dodge W150 Power Ram, yellow "E. Valdez"