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Yates "D" Head Spring Loads Etc
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Author:  DaveMcLain [ Fri Feb 08, 2019 12:40 pm ]
Post subject:  Yates "D" Head Spring Loads Etc

A friend of mine has a Ford engine with a set of the Yates D heads. It is 12:1 compression with a roller cam and it makes 820 horsepower at 8200RPM with a 950HP carburetor. This engine came from a Camping World truck team that was selling off their Ford engines. Anyway I was doing some repair work on one of the heads and while I had it apart I checked the mass of the valve, the retainer, locks, lash cap and spring along with the spring loads:

Valve = 85 grams
Locks = 4
Lash Cap = 1
Retainer = 15
Spring = 142

The spring loads are 213lbs at 2.040 installed heigh and 601lbs at 1.204 which is .042 away from coil bind .800 lift. The rate is 464lbs/inch. I don't know the specs of the cam so I would assume that the lift is around .780 or so which puts the open load at 570lbs.

On the exhaust side the spring was the same with a valve that weighs 68 grams and has no lash cap.

I thought it was interesting stuff.

Author:  coupe3w [ Fri Feb 08, 2019 1:16 pm ]
Post subject:  Re: Yates "D" Head Spring Loads Etc

Dave what size are the valves?

Author:  booyah45828 [ Fri Feb 08, 2019 3:06 pm ]
Post subject:  Re: Yates "D" Head Spring Loads Etc

I assume he's using ti on the intakes, but what was he using on the exhaust?

Author:  blykins [ Fri Feb 08, 2019 3:32 pm ]
Post subject:  Re: Yates "D" Head Spring Loads Etc

For 68g, has to be titanium.

Goes to show how far lightweight valvetrain goes to make it easier on spring pressures.

Saw a Cup engine being used as a dirt track engine at my buddy's shop. It was a solid roller, but had titanium valves and non-adjustable rocker arms. It was under 500 lbs open pressure and turned over 9000 rpm.

Author:  DaveMcLain [ Fri Feb 08, 2019 7:16 pm ]
Post subject:  Re: Yates "D" Head Spring Loads Etc

I did't measure the sizes of the valves but I'd say that they were probably 2.100 intake and 1.780 exhaust or so in titanium. This engine when run in the truck used an open 390 carburetor with a tapered restrictor plate and I think in that configuration it would make about 700 horsepower at 8200rpm. With the larger carburetor and no restrictor the RPM is very similar but the torque numbers are a lot higher. I think that in the truck they would turn it about 8800rpm depending on the track.

I believe that the rocker arms are about a 1.9-2.0 ratio so that also allows the valvetrain to get by with a little less spring.

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