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Thread: Formula Atlantic 4A-GE turbo conversion

  1. #16
    Junior Member 1st year Apprentice
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    Default Re: Formula Atlantic 4A-GE turbo conversion

    I gapped the rings tonight using my new powered ring grinder. I have always gapped rings by hand in a small vice with soft jaws, and on a V8, V10 or V12 it takes forever. This new gizmo should be a lot faster, plus it's VERY accurate. Wish I'd found these years ago.... I have also double checked the rod bearing clearances with Plastigauge.

    In the photos you can see the difference in piston crown volume between the Formula Atlantic N/A pistons (12.75 to 1 CR) and the new turbo pistons at 8.75 to 1 with a 1mm head gasket. Not so clear is the 1 mm bigger piston pins in the turbo pistons, the slightly thicker rings for better heat transfer to the block, and the fact they are a bit meatier around the pin boss area. The Carrillo rods have their own CARR bolts in them, I haven't used them before, but at the price they should be damned good The bolts are 3/8 inch as opposed the 5/16 inch bolts in the Atlantic rods, again, a bit of extra strength, although it won't be revved as hard in the new turbo format.

    I need to make an oil feed restrictor for the block to head oilway, and then I can get on with the head.

    Photos at http://www.chriswilson.tv/4ageblock/4ageblock.html

  2. #17
    Junior Member 1st year Apprentice
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    Default Re: Formula Atlantic 4A-GE turbo conversion

    And that brings it up to date as of tonight. About 6 months in 15 minutes

  3. #18
    Junior Member Backyard Mechanic toyo-al's Avatar
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    Default Re: Formula Atlantic 4A-GE turbo conversion

    This is very interesting! Nice read. Needs more pics though...
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  4. #19
    Building Corollas Chief Engine Builder Cuzzo's Avatar
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    Default Re: Formula Atlantic 4A-GE turbo conversion

    yes needs moah pics but it looks like near 300kw for you
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  5. #20
    Forum Member 1st year Apprentice
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    Default Re: Formula Atlantic 4A-GE turbo conversion

    Interesting. I like your pistons.
    As I will be going through something similar over the next 6 months I have a few questions.

    Why the custom pistons, rather than some off the shelf ones? Just so you can control the CR better?
    What are the ridges above the 1st ring land for?
    Do you know why the main caps move? I assume it is a combination of high cylinder pressures and high engine speed.

    I can't wait to see the build finished.

  6. #21
    Junior Member 1st year Apprentice
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    Default Re: Formula Atlantic 4A-GE turbo conversion

    Quote Originally Posted by Dangerous Beans View Post
    Interesting. I like your pistons.
    As I will be going through something similar over the next 6 months I have a few questions.

    Why the custom pistons, rather than some off the shelf ones? Just so you can control the CR better?
    What are the ridges above the 1st ring land for?
    Do you know why the main caps move? I assume it is a combination of high cylinder pressures and high engine speed.

    I can't wait to see the build finished.

    The build has been on hold for some months as I have a Mugen F3000 race engine that needed urgent attention, and from starting as a simple refresh it progressed into a VERY expensive rebuild with parts having to be sourced from Hungary to Switzerland, Japan and the UK, plus having customs pistons made. It's now finally done, and funnily enough I took the cover off the engine stand (OK< bin liner to be honest.... ) to have a reminder what else needs doing.

    I needed custom pistons as I went with a custom Carillo rod with a bigger than Atlantic size piston pin diameter and bigger rod bolts. The Atlantic engines were all about low reciprocating weight and inertia, and a lot of RPM. I wanted some reliability and strength going back in. The piston grooves may be for det suppression or oil retention, not sure, quite a lot of US sourced small bore pistons seem to have them.

    As for the main caps the stock cast iron caps were known to crack in half in Atlantic engines. Maybe harmonics, may be the revs, may be just old age and fatigue. When I stripped the engine it had one cap come off in 2 pieces, yet oil pressure was fine and no outward signs of it were apparent. It had obviously been cracked and moving for some time as there were witness marks on the back of the cap half of the bearing shell.

    I hope to get on with this build again very soon, and will try and get more photos.

  7. #22
    Senior ****** Carport Converter Sam_Q's Avatar
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    Default Re: Formula Atlantic 4A-GE turbo conversion

    amazing build, thanks for sharing

    why not a water over air intercooler?

  8. #23
    Junior Member 1st year Apprentice
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    Default Re: Formula Atlantic 4A-GE turbo conversion

    Weight, space, packaging, cost and complexity, plus it's a circuit race car and water to air heat exchangers can heat soak without a fairly large (and heavy...) water volume. I like to keep things as simple, light and cheap as I can, but realise cheap and race engines rarely make happy bedfellows

  9. #24
    Senior ****** Carport Converter Sam_Q's Avatar
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    Default Re: Formula Atlantic 4A-GE turbo conversion

    well that makes sense, please keep us updated

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