Jump to content


Photo
- - - - -

Engine Building: Huge Crank Resistance With Only 2 Pistons

engine

Best Answer Moshtaraq , 08 April 2021 - 12:20 PM

To answer this thread: I took it to the machine shop for a linebore and now it runs like a clock!

Go to the full post


  • Please log in to reply
41 replies to this topic

#31 DeadSquare

DeadSquare

    Up Into Fourth

  • Members
  • PipPipPipPipPipPipPipPipPip
  • 2,853 posts
  • Location: Herefordshire
  • Local Club: Unipower GT Owners Club

Posted 12 March 2020 - 05:32 PM

When dissasmbling a couple of months ago I removed the dowels. Are they specific for every cap cause I just placed them randomly? I'll do a trail fit again tonight with all the advice you guys gave me. Crank is completely fine though, already checked that.

 

The Dowels are not specific.

 

Forgive me if I am telling you what you already know.

 

Common sense shows you which way to fit the front main bearing cap.  Look at it carefully;  the little tang on the shell leaves a tell-tale mark on the opposing surface.

 

If you didn't mark the center cap, use this tell-tale mark as a guide when fitting it.

 

The same marks will be on the big-ends, so you will know which way to fit them..........BUT........The big end caps are specific.

 

Did you mark which cap was on which rod, ?



#32 Moshtaraq

Moshtaraq

    Stage One Kit Fitted

  • Noobies
  • PipPipPip
  • 86 posts
  • Location: Antwerp

Posted 12 March 2020 - 06:10 PM

The main caps are indeed pretty hard tonget wrong, the big ends were marked but the machineshop who pressed the piston pins gave them back without the markings. How can I determine which is from which now?

#33 DeadSquare

DeadSquare

    Up Into Fourth

  • Members
  • PipPipPipPipPipPipPipPipPip
  • 2,853 posts
  • Location: Herefordshire
  • Local Club: Unipower GT Owners Club

Posted 12 March 2020 - 06:34 PM

Difficult !

 

Examine the caps and look for any machining marks that might line up, such as on either side of the rods.

 

If this fails, fit a cap on a rod without fitting the shells and run your finger nail across the join to feel if it is smooth.

 

Keep trying ....................................

 

You seem to have the ability to measure the journals accurately, so it might be worth measuring the width of the rods at the journal, and if there are differences, matching one or two with their caps like that.


Edited by DeadSquare, 12 March 2020 - 10:18 PM.


#34 Cooperman

Cooperman

    Uncle Cooperman, Voted Mr TMF 2011

  • TMF+ Member
  • PipPipPipPipPipPipPipPipPipPipPip
  • 23,079 posts
  • Location: Cambs.
  • Local Club: MCR, HAMOC, Chelmsford M.C.

Posted 12 March 2020 - 09:45 PM

It looks like you have identified the problem. The big-end caps have got mixed up.

As 'DeadSquare' says, you may have difficulty matching them now. The 'fingernail' test can work, but not necessarily will. Just a slight mis-match will cause the problem you have.

If you can't match them, take them back to the machine shop, point out their mistake (because it was their error) and ask them to skim a small amount off of each cap, and then line bore/hone each rods/cap sub-assembly until the required size is achieved. Then to mark each rod/cap to specifically identify them. They should thi for free since it was their error. However, they may say that it was your responsibility to have put identity marks on each rod/cap to prevent this happening. Most people do this before taking the road to have the pistons fitted. 



#35 Tupers

Tupers

    Up Into Fourth

  • Members
  • PipPipPipPipPipPipPipPipPip
  • 4,108 posts
  • Location: Devon

Posted 12 March 2020 - 09:59 PM

The main caps are indeed pretty hard tonget wrong, the big ends were marked but the machineshop who pressed the piston pins gave them back without the markings. How can I determine which is from which now?

Do you mean you had the connecting rods marked up with which cylinder they’re from or had to marked each big end cap to its connecting rod?

I’m a little confused as I can’t see a reason to remove the big end caps when fitting pistons and any machine shop should know not to mix up the caps.

Edited by Tupers, 12 March 2020 - 10:00 PM.


#36 Moshtaraq

Moshtaraq

    Stage One Kit Fitted

  • Noobies
  • PipPipPip
  • 86 posts
  • Location: Antwerp

Posted 12 March 2020 - 10:20 PM

I'm taking the block to the machineshop for the line bore tomorrow. The rods I can match I think. The problem now is that I cant turn the crank even with 1 bearing so I think something is really wrong.


Edited by Moshtaraq, 08 April 2021 - 12:19 PM.


#37 Hunter2

Hunter2

    Mini Mad

  • Members
  • PipPipPipPip
  • 211 posts
  • Location: Vancouver
  • Local Club: Vancouver Mini Club

Posted 14 March 2020 - 02:34 AM

Do you have a centre main strap?  If so, was it lapped to the cap?  If not you could some of the issues I've seen described.



#38 Moshtaraq

Moshtaraq

    Stage One Kit Fitted

  • Noobies
  • PipPipPip
  • 86 posts
  • Location: Antwerp

Posted 14 March 2020 - 07:34 AM

I don't have a centre main strap.

#39 Moshtaraq

Moshtaraq

    Stage One Kit Fitted

  • Noobies
  • PipPipPip
  • 86 posts
  • Location: Antwerp

Posted 08 April 2021 - 12:20 PM   Best Answer

To answer this thread: I took it to the machine shop for a linebore and now it runs like a clock!



#40 spi

spi

    Just On Tickover

  • Just Joined
  • Pip
  • 6 posts
  • Location: WINSFORD

Posted 08 April 2021 - 04:02 PM

I did an engine rebuild with the crank hard to turn,It just needed a light tap on each of the mains to seat the brgs and it turned ok?.



#41 PoolGuy

PoolGuy

    One Carb Or Two?

  • TMF+ Member
  • PipPipPipPipPipPipPip
  • 759 posts
  • Location: Bucks

Posted 08 April 2021 - 04:10 PM

I did an engine rebuild with the crank hard to turn,It just needed a light tap on each of the mains to seat the brgs and it turned ok?.

That would concern me to be honest. 



#42 Cooperman

Cooperman

    Uncle Cooperman, Voted Mr TMF 2011

  • TMF+ Member
  • PipPipPipPipPipPipPipPipPipPipPip
  • 23,079 posts
  • Location: Cambs.
  • Local Club: MCR, HAMOC, Chelmsford M.C.

Posted 08 April 2021 - 04:36 PM

[quote name="PoolGuy" post="3689949" timestamp="1617898221"]

[quote name="spi" post="3689948" timestamp="1617897726"]

I did an engine rebuild with the crank hard to turn,It just needed a light tap on each of the mains to seat the brgs and it turned ok?.[/quote]
That would concern me to be honest. [/quote

That would indeed seem most unusual.





Also tagged with one or more of these keywords: engine

1 user(s) are reading this topic

0 members, 1 guests, 0 anonymous users