Ace100 leak down test

[mac]

Fail !! Really bummed,but I am glad that I checked. I don,t know if I would have had it not been from the urging of others on here in various post. It,s hard to tell if it,s the top of the cases or the base gasket,but I,m leaning towards the center case right at the top.
I have a couple of questions: Do you think it would be okay to re-use aluminum head gasket ? The base gasket was greased on both sides so I,m hoping it can be re-used if it,s not damaged and causing the leak.
This is what I used for sealing the center cases,was it the right sealer ?

[mac]

Small update. I was able to re- break away from the kitchen remodeling job. I think my wife felt bad or maybe could just tell that my mind was else where.
I pulled the top end back off to see how every thing looked. Only thing that I could see was a very small offset in the front of the cases where they meet. I gingerly filed it level,wiped the gasket down,flipped it over and put everything back together.
It did rule out a center case leak as now there is no leak in the front like before. There is a tiny tiny leak at the back of the base gasket and a pretty good leak at the cylinder head gasket. I do have a copper gasket that was new when I did just the top end rebuild that I,m going to try next. It had about 5 minutes of run time and still looks good so we shall see. I,m guessing the aluminum one can,t be re- used or maybe I have a problem there.

[thrownchain]

If you have a head gasket leak, make sure the head gasket surface is flat, on the head and the cylinder. Make sure the head nuts screw down far enough to fully tighten on the studs. When looking for the leak, spray soapy water on the seams and look for bubbles.

[mac]

Thanks thrownchain. I did chase the cylinder studs and nuts and made sure the nuts threaded all the way down easily. I am using soapy water and I just came in from trying the copper head gasket. It still looked like new,but I still have a leak there. I,m now thinking that your call on the mating surfaces might be right. What’s the best way to lap them ?
Also,the book said 105 inch lbs for torque on the cylinder head and that’s what I went to. Is that still a used/correct torque ?

[thrownchain]

Yes 105 inch lbs. Don't overdo it. Take the gasket out. Put the head on, see if you can rock the head side to side or front to back. If you can do either you'll need more than lapping to flatten it.

[taber hodaka]

I hand lap heads on a piece of glass with fine sandpaper, until I have one unified tone. --------Clarence

[mac]

You were right thrown,it did not pass the rock test and checking it with a machinist straight edge shows it,s not too flat. For grins I also snugged back on the cylinder and put a bore flash light in the spark plug hole which also revealed not a very flat surface.
Pretty disheartened at this point with all the money I,ve spent thinking the end of the project was close. I will try to lap it but I,m guessing a new head is what will be needed.

[mac]

Thank you Clarence, I was typing while you posted. I will try that first.

[thrownchain]

Lotsa spare heads out there.....

[Bullfrog]

I use a standard blue Sharpie as "Machinist's Blue" on the sealing surface of the head. Just scribble blue over all of the sealing surface and let it dry a bit before starting the lapping operation. When all the blue is gone, the head sealing surface is flat.
Ed

[Bruce Young]

Mac, I would suspect that even a brand new never used NOS head should if one wants perfection of a sealing surface should be lapped in as well, I would bet that even a new head has some issues. I hope my thoughts are correct, if not, I am sure we will hear about it, I like Ed,s way of lapping, its darn near a perfect way to do it, you will need a pretty solid surface to work on. Good Luck and great build project. Bruce Young

[MTrat]

Tape a sheet of #600 wet-or-dry paper to a piece of glass for your lapping surface...

[mac]

Thanks for all the help and advice. I,m heading out to the garage now armed with a sharpie,600 wet/dry and a piece of glass to see what I can do.

[mac]

Just a quick update. I haven,t had much time to work on it due to other duties,but I was able to lap the head and do one leak down test which it passed.
No more leaking at the head gasket so a big thank you to all for the help.