Machine Shop Questions

[lennyjay]

I too am going to bring in a '64 409 block for some cleaning, checking bore and the like. I am in southern AZ also, and wondered if Jeffery found a shop that did work on the w-motors. I don't want to go on an 8hr (Phoenix) drive to find a shop that maybe in question on these motors. I questioned one shop and the response was "it's a chevy there'r all the same"...no they are not.

Let me know if you found a shop....lennyjay

 

[heddrik]

Gee, what a stupid, know it all response. Yeah, I would run from that one. Good luck finding a good shop.

 

[fourzeronine]

I too am going to bring in a '64 409 block for some cleaning, checking bore and the like...

...I questioned one shop and the response was "it's a chevy there'r all the same"...no they are not.

If all you want them to do is clean it, check it, and machine it, none of that is rocket science. The only atypical thing for a Chevy is the non-90 degree deck angle, which their equipment should be able to accommodate.

Do you want them to assemble the engine, too?

 

[lennyjay]

Agreed, but the over-bore is where the concern is. I am almost sure the cylinders just need a hone to bring them back. I took measurements down each and taper is minimal. I have yet to hear from the shops on how they would do the hone. Do they run it out completely from the cylinders or stop at the over-bore line? The shop would do the clean, crank, cam bearing, chase the bolts, install the freeze plugs.
I planned on the assembly my self.

If someone can explain the honing process, that would help.

 

[fourzeronine]

...Do they run it out completely from the cylinders or stop at the over-bore line?

What do you mean by "overbore line"? Are you referring to the relief at the top of the cylinder that forms part of the compression chamber?

This area would only be touched if going with a large overbore that removes that step. In which case, that area of new overbore would be honed as part of the honing process due to the way the hone tooling works. For a typical .030" overbore, the relief remains and wouldn't be touched.

 

[lennyjay]

Yes, it is the part of the combustion chamber. That relief has a totally different finish than the cylinder walls. So you are saying that if it is a straight hone that part of the relief maybe gone, and would it be added back by a machining process. I have the 348/409 book and does not go into that process very well. There are more shops near me and I will check them out. I don't want to over think this just would like to find a shop that has done a couple of these blocks.

thanks.....

 

[Skip FIx]

Koerner Racing Engines
You killed it, We build it!
520-294-5758

Check with Paul Carter there. He does some awesome detailed machining on Pontiac motors. I bet we could teach him 348-409s. He also can cryo engine parts for you too.

 

[Don Jacks]

If I remember the old Jahns piston adds correctly,that counter bore is removed at about .060 over bore and it''s not desired or needed to be put back into the engine.Cuts compression by as much as .5 .The only reason that it's there in the first place is to facilitate the tools used by the factory for quick piston/ring assembly.No need to hone that part because the rings don't go that far up into the bores.

 

[buildit]

The odd thing about the counterbore is that they were not even machined on the same setup as the actual cylinder bore. In other words, they are not very concentric to the bore. As I recall, a .060" overbore usually would clean up on one side and not the other. On the blocks that I bored larger, and the counterbore was completely gone, I would bore the counterbore .010" larger on the diameter. This is only a .005" radial counterbore depth. If you do not do this, and the counterbore is the same diameter as the cylinder, the hone gets pushed to the low side of the cylinder on the top "overstroke" of the hone. This results in a slight ovality of the bore at the top of the cylinder, and the more you leave to finish with the hone, the more it is noticeable. The .005" counterbore has a very minimal compression loss. Of course I realize that engine can still work without this step.
'
'