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Discussion Starter · #1 ·
Picked up a pair of ported 336x heads for a pretty cheap price. They have 1.94/1.50 valves, but are seated for 2.02/1.60. Since it's already started, going to buy the bigger valves. But do I need hardened seats for these? Or is what I have fine?
 

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Mekanicus Automotive Group
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Valves

The only reason you need hardened seats is for running on unleaded gasoline, and since that's all we can get at the pump nowadays, they more than likely have hardened seats in them, since they've been milled for the larger valves. Have a look at the valve seats. If the exhaust valve seat has been replaced, it should be a hardened one already.
 

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Discussion Starter · #3 ·
That's what I thought, about the unleaded fuel. But it doesn't look to have the hardened seats. Don't know why the guy got them milled but not seated. Must've aborted it halfway, or so I would guess since the old valves were put back on.
Thanks for the help.
 

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Mekanicus Automotive Group
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Pricing guide

Well, this may not be accurate, but when I had my Pontiac No. 16's redone it ran me a little over 600. This included new valves, guides, springs, retainers, locks, 3 angle valve job, (Always recommended.) and hardened seats. Just a seat job alone should run under 300.
 

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I won't quote you a price, but Speedshift_Sam is pretty close.

The cost will depend on the condition of the valve guides and if the last seat work was done correctly. The heads you have gain very little if any horsepower by just installing 2.02/1.60 valves. This is due to the restriction of the port/lower seat area and shrouding of the intake valve at the chamber sides.

When I install larger valves in sbc heads I use a profile cutter that GM used on the original 2.02 heads ( back in the seventies, it evidently walked the four miles from the Flint engine plant to this shop!!). This cutter does the seat areas and cuts the chambers to the correct size. Cerdi cutter finishes the seat/bowl area. Handy item.

The other problem to watch for is. If the shop you use is not into high perf work. They may use the incorrect exh-seat. This will intrude into the intake seat area and can cause problems later down the line.
 
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