Negative Deck Height ?'s

[SlingShot]

I'm assembling a 1776cc and was working on checking the deck height. I haven't checked all the cylinders yet but noticed that the no. 2  piston comes up just passed the cylinder on one side (towards the flywheel) It's roughly about .005 or so, it's about .0 on the opposite side (Towards Crank Pulley). The Heads have a .075 step that tapers lower towards the chamber. Heads are apparently 52cc's. Cam is a stock regrind transformed into an engle 100 grind. This engine is not going to be a hell raiser, just a stock carb 1776. What do you guys think?

[DKK Ted]

If it was me, I would split the case and check the deck that they are flat and at the same height. Then check the barrels that they are the same lenght. I would assume that the pistons from the pin holes to the top are the same, both sides of pistons. In the head, if the seating surface has a tapper, to me should have them recut FLAT. If ya need more deck use copper head gaskets. Stock or performance, everything to me has to be perfect. My two cents. You don't want problems after it's assembled.

[Shubee2 (DSK)]

could be the piston is on wrong the wrist pins are offset is the arrow facing the flywheel? Could be a Bent Rod,piston top has been machined incorrectly,you need to measure and Check pistons,rods,and barrels,

[SlingShot]

is the piston Arrow Facing the Flywheel? on that Cly? could be the piston is on wrong,Bent Rod,piston top has been machined incorrectly,you Do Have A Problem There you need to measure and Check pistons,rods,and barrels,

Yes arrows are facing the flywheel. I'm leaning towards the case deck not being true.

[Shubee2 (DSK)]

is the piston Arrow Facing the Flywheel? on that Cly? could be the piston is on wrong,Bent Rod,piston top has been machined incorrectly,you Do Have A Problem There you need to measure and Check pistons,rods,and barrels,

Yes arrows are facing the flywheel. I'm leaning towards the case deck not being true.

Try swapping Rods,another piston,and barrel and see what happens      is that Rod upside down? notch facing up? the Wrist pin is offset and that could also do it

[SlingShot]

is the piston Arrow Facing the Flywheel? on that Cly? could be the piston is on wrong,Bent Rod,piston top has been machined incorrectly,you Do Have A Problem There you need to measure and Check pistons,rods,and barrels,

Yes arrows are facing the flywheel. I'm leaning towards the case deck not being true.

Try swapping Rods,another piston,and barrel and see what happens      is that Rod upside down? notch facing up? the Wrist pi is offset and that could also do it

I swapped barrels, that didn't help. I didn't try a different piston yet. Rods are stock and right side up. I can't imagine a rod being bent towards the crank pulley dirrection or Flywheel. Let me reiteriate that the difference in measerment is coming from the Left to Right side of the piston.

I did notice that there is a fillet radius on the mating face of the barrels that is around .020, and the case bore opening had a sharp corner. I thought this could cause the barrel to not seat square. I took a deburr knife and knocked down the corner, but no success, it did seat the barrel better but that caused a little more negative deck.   

[Bruce]

  is that Rod upside down? notch facing up? the Wrist pi is offset and that could also do it

A flipped rod isn't going to contribute to this problem.  They're the same length installed both ways.

[SlingShot]

Is it going to hurt anything having .005 or so Negative Deck?

[DKK Ted]

I would say yes. Your head will not sit flat at even .005. Has that chance of head leaking. Seating surface has to be flat and the same to each other. I tend to think more on the case not being flat and equal to each other. Its better to have it re-done or checked by another machine shop to be safe. It would be cheaper in the long run.

[rick m]

Slingshot,

Definitely tear it down and make sure the case halves are the same distance from the centerline of the crank to the deck where the barrel sets.  You want all of them the same. It is not worth taking a chance. Remember that the performance and longevity are based upon the little things that make a big difference.

Rick M

[SlingShot]

So here is where I'm at. Cylinders measure within .001 from mating surface of the case to the top of the cylinder. I haven't checked the pistons, but from swapping them around they seem to be pretty close as well.
Cylinder 1 & 4 come to zero deck. 2 & 3 have .005 positive negative.  I used my calipers as a straight edge on the top of the cylinders and they are uneven, so I agree the heads wouldn't seal correctly. So If I put a .005 shim under 2 & 3 everything should be peachy. Do you agree?

[Shubee2 (DSK)]

Sounds like the Case Deck needs to be machined flat I would not use a shim on 2 & 3  that is like putting a Band aid on a Cut its not Right it is really up to you but everything should be machined flat before a build  When you are checking the deck do you have the barrel torqued down? when you are checking it?

[Ron Greiner]

it sounds like the decked the case more on the one side, your going to have to run shims to set your deck height anyway, you can use a .005" thicker cylinder on the one side or take the motor back apart and have them re machine the case.

[DKK Ted]

RE-MACHINE THE CASE, THIS IS THE ONLY FIX.

[Jon]

My new Mexico case (Rimco) has one side decked correctly and parallel to the crank, the other side is NOT parallel to the crank...! try to shim that out.... re-machining is the only choice.   

[DKK Ted]

Slingshot, were all just trying to help ya out here. The bottom line here is get the case re-machined. You save yourself alot of greif later. Continue to keep us posted on this journey. 

[SlingShot]

Slingshot, were all just trying to help ya out here. The bottom line here is get the case re-machined. You save yourself alot of greif later. Continue to keep us posted on this journey. 

I know, and appreciate the input. I'm building this one for someone else, and I do want it right. I'm just dreading pulling it all apart, again. I think I'm going to start dry assembling every engine wether it be a 1200cc or a 1915cc. I thought this one would go together like butter but no dice.

[DKK Ted]

It happens to all of us at one time or another, but that shows you care how an engine goes together, by doing it the right way.

[SlingShot]

OK I tore that mother down, and measured the 1,2 side deck. First of all the deck isn't flat, it has a .003-.004 negative draft that goes away from the bore (hope that makes sense). This is most likely caused by the flycutter bit. I would think you would want this flat for an optimum seal against the cylinder. Also #1 Seems consistant, still has the draft but is parallel with the case half within .001. #2 however measures off. I will try and make this easy, if you were looking directly thru the bore like a clock. 12 o clock = .0000, 3 o clock= -.0005, 6 o clock= -.002 9 o clock= -.002. That's makes sense why #2 deck would be about .005 on one side and .000 on the other.

[Zach Gomulka]

Dry assemble them all!


If Steve was a little more ambitious... I would get him to do all of your machine work.

[SlingShot]

If Steve was a little more ambitious...

[DKK Ted]

Hey Zack, who's Steve? Or is that an inside thing?

[SlingShot]

Hey Zack, who's Steve? Or is that an inside thing?

you have pm

[Zach Gomulka]

He does fantastic work. The only person I trust 100% to do work on my car.