# Hydraulic tappet or known as hydraulic lifters **URL:** \ **Category:** General Discussion\ **Created:** [April 1, 2009, 8:20pm UTC](https://community.cartalk.com/t/hydraulic-tappet-or-known-as-hydraulic-lifters/28618 "2009-04-01T20:20:43Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![felix\_the\_cat](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/felix_the_cat/32/1229_2.png) [@felix\_the\_cat](https://community.cartalk.com/u/felix_the_cat)\ **Post date:** [April 1, 2009, 8:20pm UTC](https://community.cartalk.com/t/hydraulic-tappet-or-known-as-hydraulic-lifters/28618/1 "2009-04-01T20:20:43Z")
Does an engine with hydraulic lifters have valve springs? ---
**Author:** ![Docnick](https://avatars.discourse-cdn.com/v4/letter/d/ecae2f/32.png) [@Docnick](https://community.cartalk.com/u/Docnick)\ **Post date:** [April 1, 2009, 8:24pm UTC](https://community.cartalk.com/t/hydraulic-tappet-or-known-as-hydraulic-lifters/28618/2 "2009-04-01T20:24:09Z")
Yes it has, the hydraulic pressure is there only to keep the gap between the tappet and the valve guide closed so there is no clatter. As things wear down, the hydraulic pressure prevents a gap from forming. ---
**Author:** ![texases](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/texases/32/862_2.png) [@texases](https://community.cartalk.com/u/texases)\ **Post date:** [April 1, 2009, 8:27pm UTC](https://community.cartalk.com/t/hydraulic-tappet-or-known-as-hydraulic-lifters/28618/3 "2009-04-01T20:27:44Z")
You mean pushrod or follower, not valve guide, right? And yes, all engines with valves have valve springs, be they metal or air (some Formula 1 engines), except for those very few (some Ducati motorcycles) that have a desmodromic mechanism that controls the opening and closing of the valves. ---
**Author:** ![Docnick](https://avatars.discourse-cdn.com/v4/letter/d/ecae2f/32.png) [@Docnick](https://community.cartalk.com/u/Docnick)\ **Post date:** [April 1, 2009, 8:31pm UTC](https://community.cartalk.com/t/hydraulic-tappet-or-known-as-hydraulic-lifters/28618/4 "2009-04-01T20:31:20Z")
Right you are; I’m referring to pushrod or the follower, i.e. the part that transmits the force. Yes, the Mercedes racing car engines from the 50s had desmodromic valves gear (no springs) that allowed them to rev up to 10,000 rpm without valve float. ---
**Author:** ![felix\_the\_cat](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/felix_the_cat/32/1229_2.png) [@felix\_the\_cat](https://community.cartalk.com/u/felix_the_cat)\ **Post date:** [April 1, 2009, 8:43pm UTC](https://community.cartalk.com/t/hydraulic-tappet-or-known-as-hydraulic-lifters/28618/5 "2009-04-01T20:43:09Z")
I don’t have pushrods but a rocker arms not that it matters but the desmodromic mechanism what is that exactly? ---
**Author:** ![texases](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/texases/32/862_2.png) [@texases](https://community.cartalk.com/u/texases)\ **Post date:** [April 1, 2009, 8:52pm UTC](https://community.cartalk.com/t/hydraulic-tappet-or-known-as-hydraulic-lifters/28618/6 "2009-04-01T20:52:26Z")
Here you go > **[Desmodromic valve](https://en.wikipedia.org/wiki/Desmodromic_valve)** > > A desmodromic valve is a reciprocating engine poppet valve that is positively closed by a cam and leverage system, rather than by a more conventional spring. The valves in a typical four-stroke engine allow the air/fuel mixture into the cylinder at the beginning of the cycle and exhaust gases to be expelled at the end of the cycle. In a conventional four-stroke engine valves are opened by a cam and closed by return spring. An engine using desmodromic valves has two cams and two actuators, each fo... ---
**Author:** ![felix\_the\_cat](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/felix_the_cat/32/1229_2.png) [@felix\_the\_cat](https://community.cartalk.com/u/felix_the_cat)\ **Post date:** [April 1, 2009, 9:03pm UTC](https://community.cartalk.com/t/hydraulic-tappet-or-known-as-hydraulic-lifters/28618/7 "2009-04-01T21:03:22Z")
cool thanks ---
**Author:** ![felix\_the\_cat](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/felix_the_cat/32/1229_2.png) [@felix\_the\_cat](https://community.cartalk.com/u/felix_the_cat)\ **Post date:** [April 1, 2009, 9:56pm UTC](https://community.cartalk.com/t/hydraulic-tappet-or-known-as-hydraulic-lifters/28618/8 "2009-04-01T21:56:44Z")
yeah rocker arms, no valve guide ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [April 1, 2009, 11:51pm UTC](https://community.cartalk.com/t/hydraulic-tappet-or-known-as-hydraulic-lifters/28618/9 "2009-04-01T23:51:54Z")
One additional point: while tappets and lifters are technically different, both fill the gap in the mechanical connection between the cam lobe and the valve stem, be they mechanical or hydraulic. And many folks, myself included, are sloppy enough with our liguistic disciplines to use the terms interchangably. ---
**Author:** ![B.L.E](https://avatars.discourse-cdn.com/v4/letter/b/848f3c/32.png) [@B.L.E](https://community.cartalk.com/u/B.L.E)\ **Post date:** [April 2, 2009, 12:02am UTC](https://community.cartalk.com/t/hydraulic-tappet-or-known-as-hydraulic-lifters/28618/10 "2009-04-02T00:02:57Z")
The Ducati for sure and most likely the Mercedes Desmodromic engines actually did have light hairpin style valve springs to hold the valves completetly shut after the cam closed them. The closing cam needs some clearance and without a closing spring to keep the valves sealed, intake vacuum on an idling engine will suck the exhaust valves open just enough to make it idle like an engine with a burned exhaust valve. I learned this from a Ducati forum, it was long supposed that the springs were there so the engine would have enough compression to start easily but someone who left the springs out found out that it started and ran at full throttle OK, it just wouldn’t idle. ---
**Author:** ![JoeMario](https://avatars.discourse-cdn.com/v4/letter/j/3bc359/32.png) [@JoeMario](https://community.cartalk.com/u/JoeMario)\ **Post date:** [April 2, 2009, 12:53am UTC](https://community.cartalk.com/t/hydraulic-tappet-or-known-as-hydraulic-lifters/28618/11 "2009-04-02T00:53:45Z")
My first motorcycle, back in 1971, was a Ducati 250cc with the Desmo head. That engine would keep pulling right up through 12,000 rpm. I sold it to my brother a few years later. He once brought it into a Ducati dealer to be serviced. When he got it back, the Desmo head was gone - they swapped it out with a regular head. Apparently the Desmo heads were in demand.