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History Home made Hemi

Discussion in 'The Hokey Ass Message Board' started by Jalopy Journalist, Nov 13, 2011.

  1. Jalopy Journalist
    Joined: Nov 4, 2011
    Posts: 255

    Jalopy Journalist
    from Austin, TX


    I have been thinking alot about home made hemis for quite some time. I know that it would be hard, but people have always done hard stuff and will continue doing hard stuff because they want to.

    My question is, has any one ever home made a hemi. Just the heads? If so, please post up a picture or two, a story if you know it. Anything would be helpful.
    Last edited: Nov 16, 2011
  2. Chevy had a few but not home made
    Micky tompsom for pontiac.
    Ardun for the flat head but again
    And there a thread on here about a guy who has twin over head cam.hemi. been working on for over 40 years.

    Not to many folks have a foundry in there living room or a machine capable of carving a head in there garage.

    Gonna make your own engine to go along with the scratch built car.
  3. Deuces
    Joined: Nov 3, 2009
    Posts: 18,503

    from Michigan

    There's a company that has a kit to convert an RB 413-440 into a Hemi... I read an article about those kits a few years back....

  4. Jalopy Journalist
    Joined: Nov 4, 2011
    Posts: 255

    Jalopy Journalist
    from Austin, TX

    See this stuff is helpful. But I have been wondering, what all is required for a hemi change over? I mean, couldn't someone just get there heads modified to fit hemisphereical pistons and an overpiston spark tube or is there alot that I am missing from having a real hemi?
  5. Just combustion chamber design, valve location, rocker ARM geometry just the basic hemi stuff yea and the cool valve covers with spark plug tubes. The head is going to have to start from scratch to make a hemi change over. Hemi heads are huge because or the design. Picture a ball, half of that is the combustion chamber. Now suround that ball with vale stems like a porcupine, intake and exhaust manifold flanges, now cover all that stuff with a valve cover. The further out you go the bigger it gets.

    I did see someone mount hemi valve covers on top of Chevy valve covers. He did that after work at home in his garage.
    Last edited: Nov 14, 2011
  6. Jalopy Journalist
    Joined: Nov 4, 2011
    Posts: 255

    Jalopy Journalist
    from Austin, TX

    You say the valves have to be changed over but really they dont. I know if you wanted a REAL hemi but the issue is, you would be designing a whole new head if you did that. Might as well start producing it.

    Sure, you will be sacrificing power and gorgeous sound (which hemis are the only thing that sound like hemis) but you would still experience power gains and you would truthfully have a hemi right?

    The reason I am asking is becasue if I could just alter the head of a straight 6, I could have higher compression, a fancy valve cover, and I could even upgrade the valves and rockers, then why wouldn't I have a hemi 6?

    Can anyone post up a design drawing picture of the differences?
  7. Last edited: Nov 14, 2011
  8. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 8,178


    M/T also manufactured Hemi heads to suit 427 FE's. He built this 64 Ford Thunderbolt Fairlane, (#10). M/T was building motors, out of a 427 Ford Short block, and then using Chrysler 392 Hemi Heads, and converting them to fit the Ford 427, and put a Cross Ram intake on the car, with Dual Carburetors.
  9. What was the company in the early 90s that offered hemi head conversions for the small block chevy? I recall them being around 3,500 a pair. But havent even seen an ad for them since maybe '92.
  10. Paul
    Joined: Aug 29, 2002
    Posts: 14,958


    get a crayon and write HEMI on the valve cover

    check out youtube for the dual plug hemi heads Eddie Landers carved from billet for the '55 Olds 324

  11. rod1
    Joined: Jan 18, 2009
    Posts: 715


    What about Mooneyham and Sharp 554
  12. Jalopy Journalist
    Joined: Nov 4, 2011
    Posts: 255

    Jalopy Journalist
    from Austin, TX

    Thank you for this stuff. Just cause I am wondering, is there a company you know of that can machine custom heads? Specificly, I am thinking about a chevy 230 inline 6.
  13. 51 Hemi J
    Joined: Sep 27, 2006
    Posts: 394

    51 Hemi J

    Get a set of 392 Hemi heads and put them on a 70's Pontiac Block. Crank centerlines are nearly identical and Pontiac is 4 bolts per cyl, just like the 392. Thats the closest fit of these two makes that is possible. Do it and check back here and let us know how it works!
  14. Big Block Chevy + Arias heads = BBH.
  15. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,266

    Rusty O'Toole

    You may be confused about the meaning of hemi head. Hemi is short for hemishpere. A hemisphere is half a sphere.

    The defining characteristic of the hemi engine is the hemisperical combustion chamber. Yes, this does require a completely different head design. No, you can't change a Chev six to a hemi without designing and casting a whole new head.

    It would be easier to buy an old Jaguar six which is roughly the size of a Chev six but with hemi head. Or an old Mercedes, they used a hemi head six for years. Or BMW. Or even Nissan Maxima. A lot of Japanese cars used hemi head fours , and a few had hemi head sixes.
  16. Jalopy Journalist
    Joined: Nov 4, 2011
    Posts: 255

    Jalopy Journalist
    from Austin, TX

    No, I understand what a hemi is.
  17. HemiRambler
    Joined: Aug 26, 2005
    Posts: 4,157


    Yes I believe you're over simplifying this. Modifying a stock head wouldn't yield much for a couple reasons:

    First there is doubtfully enough material thickness there to allow you to get even close to a hemispherical chamber.

    Second it sounds like you intend to keep the valve locations stock - that gives away a huge advantage to the hemi design. Hemis can run very large diameter valve because the chamber is spherical. As an example a standard wedge motor with a 4" bore gets pretty hairy with a 2.06 intake and a 1.65 exhaust - but lets not argue numbers and instead go pure theoretical - it would be limited to 4" of combined valve diameter - be it a 2.25 intake and a 1.75 exhaust or whatever -the total diameter is 4" - can't go bigger and in reality they are smaller because you have to put a spark plug in there somewhere. Compare that to a 4" bore hemi. You can easily exceed 4" of combined diameter, but WAIT there's more! It's not just the size of the valve - it's the DIRECTION. Hard running wedge motors will shift valve locations in an effort to redirect the flow as well as get bigger valve in there - these modifications are unnecessary on a hemi because they already exist. Think about the flow entering and exiting the chamber - you lose a little with the valve right next to the cylinder wall - not much of a problem with a hemi since the vlave is tilted.

    So with your "straight" valves and little if any chamber shape all you have left is the piston shape - which at this point is gonna yield very low compression ratio since you don't have the combustion chamber to balance it out. But even if you did - the piston shape is NOT where you're getting the advantages of a hemi - that is merely a result of the combustion chamber shape. Keep in mind many a record setting hemi had flat top pistons.

    Can it be done - sure it can. Anyone with a shit load of determination can achieve wonders!! Look at "Twin Can Tommy" a real dedicated genius!!!!!

  18. silent rick
    Joined: Nov 7, 2002
    Posts: 4,017

    silent rick

    another benifit of the hemispherical combustion chamber and angled valves are the runner design. ever look into the intake or exhaust port on a hemi head? it's a straight shot to the valve and chamber, no turns.
    how are you going to create that without starting from scratch and redesigning the head.
  19. Jalopy Journalist
    Joined: Nov 4, 2011
    Posts: 255

    Jalopy Journalist
    from Austin, TX

    Alright. So it is all in the valves.

    I have seen hemi valves and I know what you mean, they are practically hallways. So it does come down to making a new head. This is a little issue as no one seems to know of a company that could do this, and I could design the head myself if I knew the parameters around which it was designed (cooling, bolts setup, ect.) but then where could I get it 3D printed to send to a place where they could replicate it in metal? Issues, issues, issues. It seems that I need some help..

    Hambers assemble?..
  20. blackprimer
    Joined: Jul 7, 2011
    Posts: 20

    from Reality

    Joined: Jan 31, 2009
    Posts: 25
    from H.B., CA

    You don't need to get it printed, you need someone to make a solid model for you in a 3-D CAD software like Solidworks. Then, once you are happy with the design, you send it off to a CNC shop along with your bank account number, title to your car and possibly your first born. They would then put this on a 5-axis machine and whittle a couple of blocks of aluminum into a pair of heads.
    It will be expensive.

    Alternatively, there are many companies that make castings from your solid models and many can have them done in just a couple of weeks; they use temporary patterns. This may be a little less costly, but you will still need all the standard head machining done, but this may be cheaper than full 5-axis custom job shop machining.

    I would guess that you would be looking upwards of 10K for machined heads.

    Ambitious, but totally do-able if you know how to design heads.

    I know solidworks if you need a starting point. (shameless plug).

    Good luck.

  22. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 5,106


    Could you give us a little background as to your education and experience? I've been doing engine building, transmission repair, frame work, body work, complete rewiring, and general automotive and motorcycle "stuff" for more than four decades.

    After all that time and experience, I still don't believe I have the skills to tackle the design of a new head. However, I can draw a damn fine picture of a chicken, and I can write a hell of a story.

    Attached Files:

  23. Jalopy Journalist
    Joined: Nov 4, 2011
    Posts: 255

    Jalopy Journalist
    from Austin, TX

    Lot of engine study, blah, blah, blah... Mostly, I am very effiecient with auto desk inventor and I wouldn't build one from scratch per say, I would build a 6 long hemi head and then change up the bolt scheme for the 230.

    Nice shameless plug, I actually might need your help though. The issue is, I no longer have updated autodesk (2009).

    Also, I thought it would be cheaper to get it printed in 3D first. Would it not. I really don't want to have to give up my first car, I mean born to do that... :eek:
  24. RichFox
    Joined: Dec 3, 2006
    Posts: 9,948


    I understand Don Ferguson get's $14,000 for a pair of his new Ardun heads with valve covers and rocker assembly. $10,000 for a new design seems a little low.
  25. derbydad276
    Joined: May 29, 2011
    Posts: 1,313


    I wonder what a set of M/T heads are worth today?
  26. belair
    Joined: Jul 10, 2006
    Posts: 8,497


    A perfect storm of arrogance and ignorance. Get that car you were going to design and build from scratch before you attempt to turn the engine world on its ear. Great stuff on the Pontiac hemi and stuff guys. I hate myself for reading this thread.
  27. Contact HAMBer Dzuari. He's the one building the custom 6/71 blower. He does 3D patterning for a living. Warning: be SERIOUS about it... the guy is a pro, don't waste his time.

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