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  1. #1
    Join Date
    Mar 2019
    Location
    Sevenoaks
    Posts
    64

    Dial in Bellhousing HELP!

    Evening.

    Right, i have now after much effort and frustration and heated discussion with my dad (assistant) shimmed the bellhousing to parallel. 0.032 and 0.006 at opposite bottom corners pushed it out to parallel.

    Now i have followed the instruction of finding the closest point of the crank to the aperture on the bellhouse. Marking a "C" on the bellhousing, then moving the dial to the diametrically opposite position and taking a reading. This reading was 4.45mm. Divide this by 2, equals 2.225mm off set. This equates to 0.087 of an inch.........you can only get up to 0.021 off set dowels......HELP....what happens next?

    The engine came from the builder with (i assume) straight dowel pins in it already. The bellhousing does fit very snugly over these pins.

    Any help or ideas gratefully received.

    It is a Roadcraft new CNC machined bellhousing
    A re-engineer SBC 350 stroked 383 block which has been dyno'ed.

    I will give Brian a call tomorrow to see if he can impart any knowledge onto me.

    Regards

    Jules
    https://photos.google.com/photo/AF1Q...z4Jb330m_WrMRg
    https://photos.google.com/share/AF1Q...dKM3VDWlRORTJ3
    AK Cobra started 06/19
    Chevy 383 Stroker, TKO 600
    See my build on instagram: Julesdm14

  2. #2
    Join Date
    Aug 2004
    Location
    Christchurch, NZ
    Age
    59
    Posts
    2,311
    0.087" runout seems an awful lot, something else is going on here? What bellhousing is it?
    Cheers

    Myles D-W

  3. #3
    Join Date
    Sep 2010
    Location
    Nova Scotia
    Posts
    827
    Those shims to get things parallel are huge. It would also affect the bore run-out. Tilt the housing and the bore hole changes too.

    I think you ought to remove the shims and check the bore concentricity again. If it's in spec, or close enough offset dowel pins will correct it, then it's the bell-housing side that faces the transmission that is out, not the side that faces the block.

    It can be corrected by having it ground. I suppose you could trying shimming the transmission, but besides not liking that idea, I've never heard of it being done before.
    John

    “A prudent person profits from personal experience, a wise one from the experience of others.”

  4. #4
    Join Date
    Mar 2019
    Location
    Sevenoaks
    Posts
    64
    Quote Originally Posted by mylesdw View Post
    0.087" runout seems an awful lot, something else is going on here? What bellhousing is it?
    it is a brand new Roadcraft cnc aluminium bellhousing.

  5. #5
    Join Date
    Mar 2019
    Location
    Sevenoaks
    Posts
    64
    Quote Originally Posted by Eggbert View Post
    Those shims to get things parallel are huge. It would also affect the bore run-out. Tilt the housing and the bore hole changes too.

    I think you ought to remove the shims and check the bore concentricity again. If it's in spec, or close enough offset dowel pins will correct it, then it's the bell-housing side that faces the transmission that is out, not the side that faces the block.

    It can be corrected by having it ground. I suppose you could trying shimming the transmission, but besides not liking that idea, I've never heard of it being done before.
    Confusingly, whenbwe did the run out before parallel, at the weekend. The runout was 2.1mm.....so pretty much the same.....

  6. #6
    Join Date
    Sep 2010
    Location
    Nova Scotia
    Posts
    827
    That's too bad it doesn't change much. Unless something is going wrong when you measure, it looks about time to return the bell-housing and choose something else.

    One thing that can happen, is the magnetic base for your dial indicator may rock dependent on where it's mounted. I really had to play around with mine to find a spot where it was secure. The flywheel depression and/or the crankshaft bolt heads can cause problems.

    Seeing how you've measured things a number of times, presumably with repeatability, I doubt that's your issue. Might be time to return it. I would.
    John

    “A prudent person profits from personal experience, a wise one from the experience of others.”

  7. #7
    Join Date
    Sep 2004
    Location
    Bressingham
    Posts
    1,331
    i would be considering sending that back if it is new. or consult them for advice.

    A
    A S motorsport Ltd. 01379 688356 mob; 07909531816 web; asmotorsport.co.uk email \"andrewsoar@yahoo.com\"

  8. #8
    Join Date
    Dec 2008
    Location
    Newcastle upon Tyne
    Posts
    1,860
    Jules,

    Just a thought that might be relevant. I was dialing in the bell housing, upgrading from an LT77 to a T5 gearbox, when I had similar inexplicable errors. Turned out to be a gravity effect! I had to use a complex linkage between the magnetic base, attached to the flywheel, and the dial indicator. By a process of elimination I realised that the "error" was in fact the movement of the linkage, due to its weight, as it revolved to make the readings. When I beefed up the linkage the "error" disappeared.

    Hope this helps.

    Regards,
    Ian
    Pilgrim Sumo Mk3; IVA Apr. 2014; RV8 3.9 EFi ; Cosworth T5; Granada Donor
    Phase Two underway - Conversion to Japanese

  9. #9
    Join Date
    Aug 2004
    Location
    Christchurch, NZ
    Age
    59
    Posts
    2,311
    Good point, is your short measurement at the bottom by any chance?

    Rather agree with Eggbert, this isn't 'alignment', it is 'does not fit' at the moment. Do you have the old bellhousing to check against?
    Last edited by mylesdw; 13-11-19 at 06:37 PM.
    Cheers

    Myles D-W

  10. #10
    Join Date
    Mar 2019
    Location
    Sevenoaks
    Posts
    64
    Quote Originally Posted by Eggbert View Post
    That's too bad it doesn't change much. Unless something is going wrong when you measure, it looks about time to return the bell-housing and choose something else.

    One thing that can happen, is the magnetic base for your dial indicator may rock dependent on where it's mounted. I really had to play around with mine to find a spot where it was secure. The flywheel depression and/or the crankshaft bolt heads can cause problems.

    Seeing how you've measured things a number of times, presumably with repeatability, I doubt that's your issue. Might be time to return it. I would.
    Brian from Roadcraft has emailed me as he is on holiday and reckons it could be the Line Boring of the block has caused the crank to move. He is willing to check the bellhousing but is sure his CNC milling will be true. Brian doesnt get back for 2 weeks and so my build again goes into a stall!!!

    I reckon the solution is going to end up being, to have custom dowels fabricated and then enlarge the bolt holes in the bellhousing. I cant currently envisage any other solution.

    I have again tonight had the bellhousing off, cleaned all surfaces and reattached. i even knocked the straight dowels out and tried again.....still 2.2mm off!!!!!!!!!!!!!!!!!!!!!!! no magic pill here yet.
    AK Cobra started 06/19
    Chevy 383 Stroker, TKO 600
    See my build on instagram: Julesdm14

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