Powered by Team Mondor
Page 1 of 15 1234511 ... LastLast
Results 1 to 10 of 146

Thread: High compression high RPM 7M-GE build

  1. #1
    Junior Member

    Join Date
    Mar 2008
    Location
    Melbourne
    Posts
    79

    Default High compression high RPM 7M-GE build

    Hi guys, thought i should start a thread about the new engine i'm building for my Cressida (yeah yeah, its not a supra, but close enough!)
    For those that dont know, 7m's are kinda my thing, GE's in particular. I'm not really into turbos.
    What i do like is a nice responsive high rpm NA screamer, which built properly the 7m-ge is quite good at.
    The motor will be run on dedicated LPG (Propane) which is great as the 110RON out of the bowser means you can run silly compression and it loves ignition timing. Not to mention it is cheap as chips here in Australia and allows a lot of the EFI crap to be deleted from the engine.

    Let's start with the head. Last year i bought a big new milling machine which i converted to CNC, and i wanted to CNC port a 7m head. There was so much f'ing work in coding this up, and a lot of machine time for the actual porting!
    Being only a 3 axis CNC i cant get absolutely everywhere in the ports, but i was able to work on the important bits, being the valve bowls and combustion chambers. Still, being CNC it has one very distinct advantage in that each port/bowl/chamber is exactly the same as the next. Also it beats the hell out of spending 40 hours with your die grinder....
    All the machining work was done concentric to each valve seat (or port)



    The intake ports were left alone past the bowls as they are already too big, however the exhausts were opened up by 1mm at the port exit to maintain a reversion dam, and this bigger diameter was carried back to where the 2 valves join into 1 port which according to my cross sectioning was the most restricted part of the exhaust port.



    you can sort of see here how much meat was taken out of the mid-port area


    end result without valves


    with valves



    While we're on the exhaust side, remember that pesky EGR hole in the #6 exhaust port, normally blanked off by a plate on the rear of the head in ADM cars... well that's gone now.


    as in completely gone, i press fit a plug in the hole before milling out the port and the extra bits of plug were cut away with the rest of the port....




    The chambers were actually left with the standard cloverleaf shape to maintain squish, but the shrouding around the valves was heavily cut back. I did a 3 angle valve job and the 3rd angle then leads into a large radius into the chamber. The radius is in fact the same as the valve radius so in theory maximising the flow without removing more meat than necessary (cant loose to much comression!)

    So here is the original chamber, complete with valve shrouding. at low lift in particular they are quite restricted, with max lift not a lot better TBH



    New chambers and bowls. The seats were bored out 2mm and again there are some funky radii going on in the bowl. The valve guides were also milled with an aerofoil shape on the inlet to split air around the valve stem, and create a low pressure point behind it which is otherwise a dead area of the port. a simple chamfer is enough on the exhaust.






    An idea of the various curves and arcs involved in the valve bowl toolpath. No CAM, the code was all written in MS Excel

  2. #2
    Junior Member

    Join Date
    Mar 2008
    Location
    Melbourne
    Posts
    79

    Default Re: High compression high RPM 7M-GE build

    I did some other work while the head was up on the CNC as well.

    Firstly the water galleries -usual missing #6 coolant drain was added, but i have also tried to address the airlocks inside the head by milling out the pockets so that the air cannot get trapped in this area.




    Originally those passages come out around 3mm off the roof of the pocket, meaning air bubbles can get trapped in that remaining area and there is no path for them to escape upwards and be burped out at the radiator filler. Now they are basically just at the roof of the pockets so there is no stagnant areas.


    I have also added ARP insert washers to go under the head studs. These press fit into the head and the idea is to stop the head bolt hole caving in around the stud and allowing the head to lift. More an issue on soft heads but still good insurance even on a rock hard head like this one.

    Milling out the press fit


    Washers installed




    I had a lot of time staring at the head while it was on the CNC so i got bored and chased every thread in the damn thing (except spark plugs, still need to buy a tap) which is really nice when assembling stuff, all bolts go in by hand then just need half a turn with a spanner and they are tight.


    Head all machined and ready to assemble





    Installing valves, and heavy duty springs. Took this all apart again as i have changed over from OEM 2jz valves to Ferrea stainless 7m ones in 1mm OS





    Still need to reassemble with the new valves and set lash, but the head is mostly complete. Ive got some 280* x 8.5mm cams to go in it, adjustable gears, shim under bucket conversion and some other goodies.

    Oh, i also milled a good chunk (ie >2mm) off the head chasing moar compression, probably unnecessary now with the pistons im going to use, but oh well at least it will run on diesel if need be

  3. #3
    Junior Member

    Join Date
    Mar 2008
    Location
    Melbourne
    Posts
    79

    Default Re: High compression high RPM 7M-GE build

    My new cam covers are still a long way from finished, but you get the idea. I only just test fitted it on the head properly for the first time today! They were designed to be as slim as possible and also NO LEAKS. No rubber gaskets to get squished "just right", no juggling the torque on bolts ~300mm apart to not bow the covers but still get a seal, these are studded through each cam cap and when it all bottoms out there will be a .5mm gap off the head for FIPG. Do the nuts up, wait for the FIPG to dry and never worry about it again

    They are basically only just tall enough to clear the front cam cap/cam seal and are relieved underneath to clear the cam lobes.
    Why lumpy cam covers? Because lumpy cams!

    I need to get some shorter studs as they look a bit funny atm, but they are noticeably slimmer than stock










  4. #4
    Junior Member

    Join Date
    Mar 2008
    Location
    Melbourne
    Posts
    79

    Default Re: High compression high RPM 7M-GE build

    Today was a nice day to be working out in the sun so i final washed the block, gave it a quick lick of paint and dragged it inside into the engine building room. Also drilled/plugged it for front sump and plugged the main oil gallery between the pump and filter which i wont be using anymore.
    block was bored & honed to 1mm OS while "stressed" with torque plate, main caps etc and surfaced with the minimum amount off to get a good seal around the bores (0.011")








  5. #5
    PACNW
    jdmfreak's Avatar
    Join Date
    Oct 2010
    Location
    north clark co. WA.
    Posts
    2,241

    Default Re: High compression high RPM 7M-GE build

    Hmmm interesting...... Subscribed

    Quote Originally Posted by Faye View Post
    that was my 69th post lol
    Quote Originally Posted by Bird87 View Post
    Du king Shawn got my drunk loll
    http://s561.photobucket.com/albums/s...ayer/jdmfreak/

    Running on MS3X

  6. #6
    Regular Member

    Join Date
    Sep 2010
    Location
    Omaha, NE
    Posts
    283

    Default Re: High compression high RPM 7M-GE build

    Interested to see how ot comes out.

  7. #7
    Supramania Regular
    7M4EVR's Avatar
    Join Date
    Oct 2012
    Location
    fah, fah away
    Posts
    695

    Default Re: High compression high RPM 7M-GE build

    After going to a turbo I've never understood why the average guy would spend a bunch of money to build up a NA. However, clearly you are not the average guy haha. Nice work. It will be cool to see how this all comes out for sure. Good luck!

  8. #8

  9. #9
    Supramania Regular
    supraguy@aol's Avatar
    Join Date
    Dec 2005
    Location
    Atlanta
    Posts
    4,172

    Default Re: High compression high RPM 7M-GE build

    Very cool cam covers. I like.
    My Over-budget, Over-deadline build: http://www.supramania.com/forums/sho...-come!-Stage-1... It now runs!
    Project: Lexx- 1988 Targa 5spd.
    NA-GTE swap, Megan EZ Street coilovers, ST swaybars, custom endlinks, Energy Suspension bushings, 18x9/18x10 FR500's, ECU masters DET3, Denso direct-fit 680cc injectors on a brand new oem harness, Aeromotive Stealth pump, Driftmotion IC/ hardpipe setup, Kamainari whaletail, 3in. Magnaflow/Borla exhaust, chromoly flywheel, Spec 2+ clutch, aluminum driveshaft, Wiseco pistons, Cunningham rods, full flow oil cooling setup, Cometic 2mm HG, ATI super damper, ARP head, rod, main and flywheel fasteners, HKS style exhaust manifold, Precision 6266 CEA turbo, DG500 COP setup, Fluidyne radiator, GTmat sound deadening, new carpet. Coming soon: New leather, new sound, new paint.


    My under budget, clean & slow build: http://www.supramania.com/forums/sho...RY-short-build
    Daily: Dora- 1989 Targa 5spd.
    7MGTE, mhg and ARP's, aluminum radiator freeflow DP, Apex'i intake, HKS Super Drager exhaust, 18" FR500's, Tanabe GF210 springs, ST swaybars, Illumina 2 TEMS shocks.
    Lexus afm, 560 injectors, Apexi Neo, wideband. Two-tone black/grey tweed interior, Pioneer Bluetooth/ Pandora/ Sirius/XM stereo. So much for keeping it stock.

  10. #10
    Keep Laughing.You're Next
    akito's Avatar
    Join Date
    Jul 2006
    Location
    Springfield/Va
    Posts
    1,568

    Default Re: High compression high RPM 7M-GE build

    I want to hear this thing when it's done. More pics!

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •