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Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
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| | | | Joined: Nov 2008 Posts: 57 'Bolter | | 'Bolter Joined: Nov 2008 Posts: 57 | Apologize if this is spam to you all, but I searched several times through all 700+ pages of old topics....
I have a '58-'62 235 according to the block casting #. How do I tell if it already has a "high pressure head" or needs the modification described by a couple of members? It did come out of a truck. Thanks from a "newbie" (my last project Chevy was before Al Gore invented the internet) | | | | | Joined: Nov 2008 Posts: 57 'Bolter | | 'Bolter Joined: Nov 2008 Posts: 57 | | | | | | Joined: Mar 2005 Posts: 1,513 'Bolter | | 'Bolter Joined: Mar 2005 Posts: 1,513 | Welcome,
3836848 is the casting number of the highest compression head produced by Chevrolet for that engine. Frank McGurk claimed milling .030" off this head would result in the same gain as milling .125" off a 261 head.
1952 1300 Canadian 1/2 ton restomod You Tube | | | | | Joined: Nov 2008 Posts: 57 'Bolter | | 'Bolter Joined: Nov 2008 Posts: 57 | Curt, thanks. That is the casting # I have, and that sounds like good news, HP-wise. The "high pressure head" question I'm asking has something to do with oiling. Does that ring a bell? | | | | | Joined: Sep 2003 Posts: 1,820 Shop Shark | | Shop Shark Joined: Sep 2003 Posts: 1,820 | You're talking about a "full pressure" engine when referring to the oiling system. The head most used on the 235 "full pressure" engine was the "848" head. Joe 
"Truckin' Around .......... Since 1937!" My name is Joe and I am addicted to Classic Country Music. I just can't hep myself.Operators are standing by to take your calls! Now cruising in the Passing Lane | | | | | Joined: Jun 2005 Posts: 388 Shop Shark | | Shop Shark Joined: Jun 2005 Posts: 388 | In 1959 the method for getting oil to the rocker arms was changed on the 235-261 engines. Is this what "high pressure" head means? link to shop manual Hoyt | | | | | Joined: May 2006 Posts: 8,351 'Bolter | | 'Bolter Joined: May 2006 Posts: 8,351 | The head would be the same. The oiling change was in the block, with a drilled passage (which was enlarged in '59) instead of the little steel line that snaked around the pushrods.
Bill Burmeister
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