TheSamba.com :: View topic - Align bored and Thrust cut any good for mild motor

Sat Jan 06, 2007 8:04 pm

Ok case is an as41 freshly checked out from the machine shop, cylinder mating surfaces leveled and resurfaced .040 thrust cut and .020 line bore. Would this be OK for a mild 1776-1835??

Sat Jan 06, 2007 8:33 pm

Properly done, align bored case is fine for that purpose. I used a case that was .5mm on the o.d./1mm on the thrust for a turbo application and it is holding up fine. As long as the machine work is good, you won't have any issues.

Sat Jan 06, 2007 9:51 pm

If properly done a line bored case is good for all applications.

Mon Jan 08, 2007 7:45 pm

AMEN!!! :D

Thank goodness. Finally. Some sense of direction.

Mon Jan 08, 2007 7:52 pm

:shock: They have only been align boring cases for ......what 40 years?

Tue Jan 09, 2007 6:28 am

I do not see a problem with what has been done with your case...while you are at it make it full flow.

Tue Jan 09, 2007 7:06 pm

in 1993 I thought I would freshen up a running 1776.

It turned out to be 4th over on main and thrust.
I bought a cheap welded counterweighted crank that was .020 over.

I threw some .100 shims under the barrels which brought the compression down below 7 to 1.

I put that engine in service in a manx buggy, then a sandrail and then on the street. I gave it to my son to run the beegeezus out of it in a bus. That POS is still screaming today and leaks from every seam.

I think the trick was to keep the compression down.

You don't have anything to worry about.

Sat Jan 20, 2007 6:21 pm

Ok bringing back up this post, i received my bearings from the guy i bough the case from today and they are mahle ext- .50 int- std. are these the correct bearings??? I put the rear in to see how it fits i think thust is correct bearing isnt loose but snug if i push it in.

Please help are these correct bearings?? I have the specs in my first post.

Sat Jan 20, 2007 8:40 pm

1432 wrote: If properly done a line bored case is good for all applications.

What about heat and stress. An align bore doesn't do anything to correct this.

Sat Jan 20, 2007 10:03 pm

Ace wrote: 1432 wrote: If properly done a line bored case is good for all applications.

What about heat and stress. An align bore doesn't do anything to correct this.

Actually, yes it does. It returns the main saddles to a straighter line, therefor relieving the stress if a twisty crank or cocked gear and the resultant heat and HP loss from that internal friction.

Sat Jan 20, 2007 10:51 pm

[quote="cal63look"]Ok bringing back up this post, i received my bearings from the guy i bough the case from today and they are mahle ext- .50 int- std. are these the correct bearings??? I put the rear in to see how it fits i think thust is correct bearing isnt loose but snug if i push it in.

Please help are these correct bearings?? I have the specs in my first post.[/quote]

With your case +.020" and your crank at standard size your bearings should be +.05mm, std, + 1mm (os .040" thrust). be certain thrust bearing is a 'snug' fit in it's saddle, with the thrust bearing in position in the 1/2 case you should not detect any movement when wiggiling the exposed half of the bearing.
Tip, when final installing your crank in one case half, use the opposite 1/2 shell of the center main to straddle the crank (center main journal) when the two halves contact each other (or very close to contact) you can be confident that all bearings are aligned properly with their corresponding dowel pins. During pre assembly (always a good idea) when the case is torqued, with crank only, it should spin easily with no more than finger tip pressure as well as move freely front to back.

Sat Jan 20, 2007 10:56 pm

What about heat and stress. An align bore doesn't do anything to correct this.[/quote]

Any problems related to heat or stress should be evaluated and addressed prior to any machine work being done on the case.

Sun Jan 21, 2007 1:43 pm

propflux01 wrote: Ace wrote: 1432 wrote: If properly done a line bored case is good for all applications.

What about heat and stress. An align bore doesn't do anything to correct this.

Actually, yes it does. It returns the main saddles to a straighter line, therefor relieving the stress if a twisty crank or cocked gear and the resultant heat and HP loss from that internal friction.

You tell my old center main support that.

Sun Jan 21, 2007 4:47 pm

A properly done align bore should be good for any application, but one must make a reasonable judgement as to if the case is fit to be reused, and having it done by a reputable company with proper tools such as rimco, will ensure that the tolerances will be perfect and problems such as low oil pressures will not be a problem.

Sun Jan 21, 2007 6:30 pm

Ace wrote:
You tell my old center main support that.

Perhaps it wasn't the case or line-bore to begin with....

Tue Feb 13, 2007 2:29 pm

Ace wrote: 1432 wrote: If properly done a line bored case is good for all applications.

What about heat and stress. An align bore doesn't do anything to correct this.
about stress, it's easy to correst this.
the only way i find is to let the block in the garage during at least 3 months and it will be stabilized, and after, align it.
the same process is used on milling machine or other made with cast iron, but it need 6 months at least.

Tue Feb 13, 2007 5:32 pm

Ace wrote:

You tell my old center main support that.

Sounds like you center main was warped. A good shop would have checked that before alignboring and told you to trash that case. I clean and torque every case to check for warpage BEFORE I alignbore them.

It's the "little" things like this that make for a good build.

Wed Feb 14, 2007 1:41 pm

I'm curious to know exactly how you check for warpage and where?

I am assuming that you are not just talking about ovality in the housing...

Wed Feb 14, 2007 1:44 pm

GregZA wrote: I'm curious to know exactly how you check for warpage and where?

I am assuming that you are not just talking about ovality in the housing...

Bolt the case halves together with the six main studs/nuts and shine a flashlight down the case... if it is warped you will see light on the center main #3 bearing where the case halves touch on either side of the bearing saddle.

Wed Feb 14, 2007 1:51 pm

Okay so we're talking about warpage of the mating surface of the case halves?

Back in the day they used to standardize casings by facing both halves and align boring the main housings and reaming the cam housings, then you still had to remachine the oil pump housing.

Not really worth all the effort, especially considering the trauma that a case needing all this done would have been through but it was once common practice here. (South Africa)