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Old 08-03-2019, 08:57 AM   #1
L-head
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Default tappets

Recently there was a discussion about adj tappets (lifters). It has been suggested that it is not wise to use 91A-6500 hollow and slotted non-adj lifters with a performance cam or a stock cam while using a 8BA type valve train. Is this the current thought on this subject?
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Old 08-03-2019, 10:23 AM   #2
Ole Don
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Default Re: tappets

Yes. The original valves for the hollow tappets had a foot that was as broad as the face of the tappet. The 8BA has a small stem, like most modern motors. Higher than stock valve spring pressure could force a valve stem through a hollow lifter face.
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Old 08-03-2019, 10:51 AM   #3
JSeery
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Default Re: tappets

Check out the other lifter thread currently on the Barn.
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Old 08-03-2019, 10:53 AM   #4
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Default Re: tappets

Quote:
Originally Posted by Ole Don View Post
Yes. The original valves for the hollow tappets had a foot that was as broad as the face of the tappet. The 8BA has a small stem, like most modern motors. Higher than stock valve spring pressure could force a valve stem through a hollow lifter face.
Can anyone reading this confirm this, or is it an old wives tale?
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Old 08-03-2019, 04:45 PM   #5
oldford2
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Default Re: tappets

Quote:
Originally Posted by Ole Don View Post
Yes. The original valves for the hollow tappets had a foot that was as broad as the face of the tappet. The 8BA has a small stem, like most modern motors. Higher than stock valve spring pressure could force a valve stem through a hollow lifter face.
Never heard of a stem breaking thru ANY lifter face. Where are you getting this info from?? Please explain
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Old 08-03-2019, 04:52 PM   #6
Brian
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Default Re: tappets

I've certainly pulled down engines running 8BA style valves on early, broad headed tappets, and seen indentations in the top face of the tappet, caused by this combination.
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Old 08-03-2019, 04:57 PM   #7
JSeery
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Default Re: tappets

You would think Ford used the mushroom tipped valves for a reason. Know idea if it is an issue, but can sure see how it could be at higher valve spring pressure.
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Old 08-03-2019, 08:01 PM   #8
Pete
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Default Re: tappets

A properly set up valve train will never poke through the top of an original STEEL lifter.

The cast iron ones with slots, maybe. These have no place in a performance engine.

The steel ones will stay put with 120 lb. on the seat and turning 7200 twice a lap for 40 laps, for 10 race programs.

The indents in old stock lifter tops are caused by either running too loose, valve float or stuck valves.
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Old 08-04-2019, 12:09 AM   #9
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Default Re: tappets

Good info Pete.
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Old 08-04-2019, 09:01 AM   #10
deuce_roadster
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Default Re: tappets

I have only seen valves punch through lifters when a gas tank that was treated with a sealant developed long before alcohol was put into the gas was installed in a Dearborn 34 phaeton long after alcohol was introduced. Some part of the sealant was dissolved into the gas and it stayed liquid and didn't bother the fuel pump and atomized fine through the carb but when it hit the hot intake valve stems it turned into a substance that LOCKED the stems in the guides like it was welded! Punched through several lifters and the car barely made it home before it wouldn't run.
The car ran and drove FINE before swapping out the tank for cosmetic reasons. I would estimate it ran about 20 miles after. The problem tank had been boiled out, painted and sloshed with sealing compound and sat on the shelf for future use.
All valves were removed and the ones not stuck had deposits building on them that came off with lacquer thinner and a 3M scuff pad. Replaced 3 or 4, valves and lifters, REPLACED THE TANK, flushed the fuel lines, pump and carb and my friend's car is running great today, 15 or so years after this fiasco.
The lesson was that the old sloshing sealant that existed prior to alcohol gas, if sitting in a spare tank needs to be removed and replaced. IF you don't, it gets ugly.
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Old 08-04-2019, 09:54 AM   #11
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Default Re: tappets

My experience was similar. An old farmer used his tractor to try and drag start an old F5 truck with stuck valves. The valves were stuck hard enough that a hole was punched in one of the followers and the cam broke into 3 pieces. That was one fun son of a gun to get apart but I got it after a lot of expletives.
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