Milwaukee Midget

[grumm441]

See my post #3230 to this thread. I apologize for being repetitive, but there doesn't seem to be a very widespread understanding of traditional O-ring/copper/receiver-groove functionality.

Yep
even commented on it
Don't remember it
But you are entirely right, without the use of the O ring......
G

[Milwaukee Midget]

Well, some of this is going to be determined once I know how much pop-up I can get by with, how much I'll have to notch the pistons, and if I'm even going to be using this engine or head.

The issue I see with the copper gasket/O-ring setup is I don't know how consistently I can pull up to tolerance with respect to my valve-to-piston clearance.  The stainless steel gasket is pretty repeatable - I don't know about the copper O-ring set-up.

[Peter Jack]

It should be totally consistent Chris. The large copper area will be what determines what the head pulls down to and the o-rings will only help the seal. their area is so small that it shouldn't affect the overall way the head pulls down.

The only concern I have is how much thickness have you got left in the head to allow for the o-ring groove.

Pete

[Jack Gifford]

... The only concern I have is how much thickness have you got left in the head to allow for the o-ring groove...

As I said before- I can't believe his head won't live with a .020" deep receiver groove.

Unfortunately, the real drawback of O-ring/copper has yet to be mentioned here- sealing fluids (i.e. coolant) can be problematic. Various schemes have been used, including the printed elastomer sealing on SCE gaskets- which doesn't always perform perfectly. The ideal solution is to eliminate the fluid at the head/block juncture by dry-decking (closing passages in both block and head). But this requires re-thinking coolant flow path and adding additional exterior plumbing.

[Speed Limit 1000]

We have used copper gaskets with and without O rings. Had good luck with coating the gasket with copper coat, it is like paint, the spray was best to use.

[Peter Jack]

We used Copper Coat with complete success on the sprint car.

Pete

[fordboy628]

yaah - go bears dare, aina hey . . .

All possibilities are on the table.  I need to calculate the pop-up I can get by with and maintain the valve-to-piston clearance, and still allow enough variance so we can rock the cam a degree or two without crashing into things.

A friend of mine showed me how to do that! 

Midget,

Perhaps some play time with some clay on the tops of the pistons might prove useful.   At least it would establish what might be achieved, C/R wise, with the current build geometry and chamber shape . . . . .         Then, the clay can be carefully removed and its' volume measured to calculate the final C/R you can achieve . . . . .     Just sayin' . . . . . .

Low compression ratio . . . . .   Nevermore . . . . . !!!!

Go Ravens!  Go Bears!
Baltoboy

[jacksoni]

yaah - go bears dare, aina hey . . .

All possibilities are on the table.  I need to calculate the pop-up I can get by with and maintain the valve-to-piston clearance, and still allow enough variance so we can rock the cam a degree or two without crashing into things.

A friend of mine showed me how to do that! 

Midget,

Perhaps some play time with some clay on the tops of the pistons might prove useful.   At least it would establish what might be achieved, C/R wise, with the current build geometry and chamber shape . . . . .         Then, the clay can be carefully removed and its' volume measured to calculate the final C/R you can achieve . . . . .     Just sayin' . . . . . .

Low compression ratio . . . . .   Nevermore . . . . . !!!!

Go Ravens!  Go Bears!
Baltoboy

If you are going the custom piston route anyway, you can take a mold of the combustion chamber with one of the various products available for port molding etc and send to the mfg. They can then design the piston top to get what you want. I have used CP for that, through Nick Arias III (b'ville racer and 2 club member) who used to run Atomic speedware but now is working for Arias pistons. You have to be careful though as domes, though they help CR, may cause enough interference to flame travel that the process is negatively affected. Watch and see what you can do with squish/quench area also. May be some power there (area and piston to head clearance). All these things, as you have mentioned, can give P-V clearance problems and you get limited with what you can do cam wise. I currently run P-V and P-Head clearances that really raise eyebrows, so far without problems though I would be hard pressed to say this set up is better (am I making more power???). Watch sharp edges on the piston top/dome as well. They need to be well massaged smooth. A point of CR only makes a small percent more power under best of circumstances and other changes may need to be done to make use if it. Is it worth the trouble and money when you are already at 13:1. Of course, you are looking for every pony you can find, I understand.

Mr Fordboy- where in Baltimore? I live in Annapolis but school and work was downtown, Hon. Go Ravens.

[Stainless1]

Chris, PM or call John Noonan as well, he is a racer, frequents this site and will work with you on pistons.  You may need Pork Pie to read some of the blue prints, but the quality is beyond compare.  I assembled head on block with gasket, sprayed on some penetrating oil, poured in mixed resin, sent the resulting chunk to John with cam specs, compression height and said we needed the max compression they could get. 

[jacksoni]

Chris, PM or call John Noonan as well, he is a racer, frequents this site and will work with you on pistons.  You may need Pork Pie to read some of the blue prints, but the quality is beyond compare.  I assembled head on block with gasket, sprayed on some penetrating oil, poured in mixed resin, sent the resulting chunk to John with cam specs, compression height and said we needed the max compression they could get. 

Second this also. I don't know John but he was the motorcycle piston guy at JE Pistons. Have heard him talk  and certainly would also be good resource.

[Queeziryder]

Chris,

I'll third the recomendation for John and the team at Wossner.

My dad's bike ate the CP piston in his Vincent. We sent the dead pidton to Alex at Wossner and he and John came up with the goods 

New piston, minimal running in, and many thousand of miles later and one happy biker 

Neil

[Dean Los Angeles]

When you get the pistons from Noonan, there is a dropped cell phone in every box. 

[wisdonm]

I wouldn't use resin. I'd use silicone mold rubber. It won't stick to anything, but itself and is flexible when cured, so it will pull away from undercuts, spark plugs, valves, and ports.

[Stainless1]

Flexibility is not your friend when measuring 

[Milwaukee Midget]

Well, a little progress -

I dropped the head off by Fordboy - he's back from his Absinth swilling week with the inlaws in Baltimore.  He's going to do a bench flow on it - it's already been done at C&S, but there have been modifications to it since then.  He's recently flowed about a half dozen BMC heads by Swifttune, Longman and PHP (Pommy Head Preparation?  Potentially Hideous Performance?  Poopy Head Porting? - I digress) and he's putting together a database for his consulting practice.

Here's what we're investigating -

I'm going to stick with the Cometic gasket, and if I have to, have one custom punched at a thickness that I know will provide me with the maximum CR with this combination.  The standard sizes are .027, .030 and .036.  The last time I talked to them, they didn't have a .030 available, so that's a new option.  Given I was seeing - this is from memory - .003 crush on the .027, it's my hope a .030 will take me to where I originally wanted to be.  The head itself is 17.3 cc's, the gasket would pull .6 cc out of the combustion chamber.  The engine is small enough that .6 would be a worthwhile get. 

We're going to flow the head with the existing valves , and with a pair of Paul Ivey anti-reversion valves.  The Iveys give better low lift and mid lift flow, and help minimize charge robbing between the shared intake ports.  The downsize is that they are a bit thicker faced than the dimes and quarters-on-a-stick valves I currently have -  and a touch heavier.  But because they have thicker heads, they take up more space in the combustion chamber - a plus and a caution.  More occupancy gets me more compression, but cam timing will be critical if they can be made to fit without colliding with the pistons.  I'll need to take some measurements on those.

Once I have the valves in place and on the block, I'll see how much room I have to rock the cam without clearance issues.  Then, back to the dyno to determine where peak cam performance is between the extremes.

A thought I had is that if we can get better flow at low and mid lift with the Ivey valves, I might be able to re-bush the rockers back to about a 1.45:1 ratio, which might let me go with a pop-up piston without the pistons and valves getting too friendly.  High lift flow is not a problem - if I can compensate low and mid lift flow with valves, I think I can sacrifice a touch on the high end and still fill the cylinders.

One thing we didn't push was timing.  According to Dick Luening, he's had success with his MGB by pulling the timing back a bit in the higher revs.  Once it's on the dyno, it's an easy reprogram to do, so that's on the agenda.

The low hanging fruit has been picked and canned for the winter.  These last few nibbles are going to be the tough ones to reach, and one wrong move could upset the whole apple cart.