Weird Head: This Yenko/Weslake Four-Valve Small Block Chevy Head Is Insane and A Unicorn


Weird Head: This Yenko/Weslake Four-Valve Small Block Chevy Head Is Insane and A Unicorn

So we have managed to find some interesting and rare parts on eBay over the years but this one really takes the cake. You are looking at one of 20 ever made Yenko/Weslake four-valve small block Chevy heads from the 1970s. Supposedly of the 20 heads ever made, only about six were ever actually assembled and placed on engines to be run. Up until this minute, we had no idea that such a beast existed at all, let alone how many were made.

These were insanely exotic at the time of their making and had to have been expensive as hell. These are not overhead camshaft heads but rather pushrods activate the valves when the car is running. They have a pent roof combustion chamber and we’re wishing we could see what the piston design was on the engines that were actually completed to show these suckers off.

Originally 100 heads were ordered to be made but production stopped at 20 and as mentioned above only a fraction of those were actually assembled and installed on engines.

Why did this project fail? Who knows. How did these guys end up with one head and nothing else? Will anyone spend nearly $8,000 just to have some wall art? These questions and more will be answered on the next episode of Batman!

eBay: This Yenko/Weslake 4-valve small block Chevy head is insane 


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15 thoughts on “Weird Head: This Yenko/Weslake Four-Valve Small Block Chevy Head Is Insane and A Unicorn

  1. Mark Gillespie

    Part of Don Yenko’s ” Special Engines ” program. Refer to my book ” The Yenko Era..continued ” for more info.

    1. Jim copeland

      never seen such an animal for a small block. i am a true chevy man & worked for chevrolet for 30 yrs as a tech. Built many small blocks for racing. This is a werid set up. wish i could find a set for my 55 chevrolet drag car. Thanks for the info. will tell my friends about these one of a kind heads. thanks.

  2. barry

    found some photos on the net assembled. I had guessed the intake would be very skinny.. and it is. looks like they attempted hillborn type stacks on the runners.

  3. Mark Gillespie

    As can read in my book ,it was not a matter bolting the heads onto a Chevy block..it required dedicated cam and internal components…limited benefits for the cost , not to mention not meeting the rules for most racing organizations. I have original documents on the program.

  4. Pizzandoughnuts

    I do remember somebody doing a hemi head way back in the late 60’s or 70’s, but never a 4V head, amazing stuff.

  5. Billy

    Boy, I wish there were someone out there with more info on these heads! I\’d pay just about anything for a book that explains where this head came from.

    1. Mark Gillespie

      Billy..go to Amazon books and order ” The Yenko Era…continued ” You can read about this engine ,who helped design it , as well as Yenko’s involvement in the Chevy ZL 1 aluminumblock…I am a former Yenko employee from 1967 -1972

      1. Roger

        Mark, I have a 1974 Red Vette which I\’ve owned since \’76. Was told it was one of Don\’s cars back in the day. It has a LT1, 370 HP motor. Have not been able to verify this. I understand this was after you left but any chance you can verify if this could be true?

  6. Brendan M

    Check out the Triumph Bonneville’s from the early 80’s.
    There were two models I believe that sported an 8 valve head made by Weslake, the TSS and TSX. The principal was the same, a singular push rod would actuate a splayed rocker to open two valves. Super rare stuff!!!

  7. Zadok Nelson

    It seems odd that the author of this article, nor anyone that I\’m seeing make comments have heard of Arao cylinder heads. They were designed and manufactured by Russ Arao. Seems like it was down in Chatsworth, Ca. He had four valve heads for traditional first gen small block Chevy\’s. They were compatible with standard intake and exhaust manifolds and headers. A solid roller cam was recommended because the pressure generated from controlling two valvesprings gets excessive. I describe everything in the past tense, because I\’m not sure if he\’s still manufacturing his products. He ripped several people off, and tore another guy\’s C6 apart. Never heard of what became of it. He made heads for LS motors as well. Not to mention BBC, SBF, and Ford 385 series. He even made 4-valve heads for air-cooled VW\’s. I don\’t know how Arao double crossed do many people, but I personally think he was losing the battle to addiction. Heroin, pills, who knows?

    1. Fred

      Seems odd to me that you make assumptions about a mans personal life while you yourself dont know….
      But i digress

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