With the lifters in, you have to check the Cam Toe, lifter Foot clearance.
Not all blocks have to be done, this one is a 1921.
Finished Clearance is a snug .020,at it's tightest, and a snug .025. for cam toe and lifter foot, at its biggest.
Even if it just clears, it may be not enough.
Block as it was.
Butting (refacing) both ends of lifters.
showing a partly done lifter foot.
Nice job Herm, but when one hasn't got all that nice machining tooling, the one and only block I had to do for some clearance took me a little less time to set up, I just used a valve guide pilot and a 90' seat cutter on a slow speed cordless drill.
Yup, that would work Kerry, should be true.
Herm, is that my block?
Herm,thanks for the post.I learned some stuff from it. I have given some thought to using a 280 in the next motor and did not know this could be a problem Why did you leave crank in while doing machine work?
No Tom, your blocks are still at Verns, and he went on a two week vacation. Last I heard, still waiting for a crank, as I guess the other is cracked.
Vern should be back Friday, or Monday.
Why did you leave crank in while doing machine work? "END QUOTE"
Jack, I had the crank in, and then I put in the lifters,and slide in the cam, and that is when I seen there was a problem. I didn't take out the crank because it was not in the way, and the milling cutter only rotates at 50 R.P.M's, and I keep a Big Shop Vac. on the milling bit at all times, and you never see smallest of a shaving.
First of all, I don't know if every block would have to be milled, just what I found. I did talk to another machine today and he said they had to do one also, but I don't know the year.
I have used 3 280's, and two of my friends have put some in, and they fit OK, but they were 26-27 blocks. This one is a 1921.
Milling the bosses is no big deal, the 280 cams are worth it.
Herm, I am interested in how you made the measurements. I think you said that you measured from the pan rail to the bosses. This must have been a rough measurement in that the bosses are cast. Then with the cam installed you measured between the top of the cam toe to the bosses? And subtracted and found there was interference of about 0.016"? You removed 0.025" from each boss and that should give 0.009" clearance. Obviously you need this clearance so the parts do not jam together. How much clearance is really needed, is it because the metal will expand when the engine is hot? I'm an arm chair machinist and would like to know, thanks
Could it be the lifters are too thick? I've got 280 cams in three of my T's and haven't had that problem. I'm using the currently available self locking lifters.
Mike what I had on that sheet of paper was .025, but when I had finished I decided to take another .011 thousandths as not all the Bosses were the same height, but they are now.
I used a depth Mic. to get the measurements from the pan rail to the top of the lifter Bosses.
I have a 1926 motor here which has a reground stock cam and the same lifters and it has about a 1/4 inch of foot clearance.
I do not know how much clearance it needs, but the 20 to 25 thousandths should be plenty of room.
Larry, that is the first thing I checked, the ones I took out were also lock nut type, and both sets measured with in .002 thousandths of each other on the thickness of the feet.
Mike, I don't think I answered your measurement Question very good.
I measured from the pan rails of a 1926, and the 1921 block to the lifter bosses of both.
The 1926 Bosses were .016 thousandths more room then the 1921 Block.
There have been past posts here and other forums where some says the cams of what ever they use, or the lifters are no good because in just a very few miles they were all chewed up.
Anyway, I ended up with .020 to .025 thousandths.
Maybe this could be one of the reasons?
You would think that if there was no or negative clearance between the cam lobe and the lifter, wear would be a problem. The more I read about things like this on the forum, the more I try on my own engines when I have them apart. I suppose that for us the do not have a depth gauge, a feeler gauge should work OK. Then the machinist could mill down the boss if needed.
Should Work Mike.
Thanks for posting this. I have a 17 torn apart right now and have ordered a stipe 280 cam and adjustable lifters. The valves and lifter guides will need to be reamed to fit. I will check the fit of the cam and if it needs it mill the bottom for clearance if necessary.
Keep us posted Norm, it will be interesting to see how yours turns out.
I have found the same issue with the 280 cam and as Herm points out you need to have some clearance. Also agree with his .025" clearance.
Out of a dozen or so installs only three required milling, one was a 26/27 and the other two were generator blocks, one a 1920 and I don't recall the other. No big deal.
I've never installed a 280 cam but it would make sense to just relive .030 from the casting and be done with it. That's the difference between the stock cam and the 280 cam. Right? I don't see the need for all the complicated measuring unless you're building a 5-6000rpm engine.
Ops. That's relieve not relive.
If you don't relieve, you will relive the rebuild!
Try to say that one fast five times!!
NYUCK NYUCK NYUCK!
Oh, a Wise Guy, Eh?
(No wonder my wife thinks I spend too much time on the 'puter!)
Because that's what a good machinist does. He doesn't guess.
LOL... You mean they can't understand math?
All I said was the 280 cam is .030 over stock so cut the bosses down .030". The existing clearance is still there. What's guessing about that?
Just trying to make it easy to understand. Apparently that doesn't work for everybody.
LOL... You mean they can't understand math? "END QUOTE"
Ken, you can't do it that way, it won't work.
Jerry is right, they all have to be measured, and I think he knows his math.
They are ruff casting, not machined, and all different heights.
The first thing you have to do is find the one with the least amount of interference, so if the least amount on the one cam toe to lifter foot is .010 and it clears good at that, you have to take off .040 to get .030 thousandths clearance.
If you just cut the bosses off .030 thousandths, the extra height of the other bosses will be shorted clearance.
Are you not a machinist Ken?
Does the 250 ever need the end of the bosses chopped off also?
It doesn't matter for a 2000rpm engine. You won't see floating valves. If there's clearance for the stock cam, cutting each boss .030" will give the same clearance for the new cam. Each boss is cut .030 from an index of 0. They don't all have to be same or Ford would have milled that area to begin with. The real engine builders know the difference.
I'm surprised you let Kerry get by with his manual method. Don't make a suggestion into a challenge. Go with it or not, it makes no difference to me. You would be better off spending the time gauging threaded holes to H2 or H3 and repairing those.
Here's picture. (Not to scale) Maybe this will help.
Larry Smith asked if the lifters might be too thick. I recently rebuilt an early open valve motor and had similar problems. In this case the lifters fouled on the T head of the brass valve guides. I do not know if the flanges of the guides were thicker than they should be. The problem was compounded by the fact that the underside of the lifter head was tapered towards the stem. I solved the clearance issues by removing the guides and machining the flange down somewhat. 5 of 8 needed attention. The motor was fine with the standard cam.
For further interest.
Allan from down under.
Some of the new tappets were or are thicker than the originals so it is a good idea to check the clearance no matter what cam is used.
Ok. I see that as a different problem but agree with that.
Does the 250 ever need the end of the bosses chopped off also? "END QUOTE"
I don't know Dave, but I have never had trouble with one.
Ken, you haven't grasped the problem yet.
What you are missing is the cam did not turn as the toes were hitting the lifters to just pass one would have needed .005 , another .010, and so on.
If you would just take .030, they would all be different gaps, not .030 on every one.
1.--The cam bearings are centered.
2.--- The cam lobes are centered.
3.---The toes all lift the same.
The lifter Bosses are all different heights.
How do you Ken, take take .030 thousandths off each Boss, and put the cam back in and get a .030 thousandths gap clearance between each toe, and lifter food.
Answer, You Can"t!!!!!!!!!
Ken, you are not getting it.
"I see that as a different problem..."
So does Herm, which is why he takes careful measurements, "does the math", and goes forward with an educated plan, like a good machinist would.