Check My Cam Degreeing

[nm9stheham]

I am certainly capable of using an exhaust by mistake. lol

And so are we all! LOL Juuuust checkin'....

Good deal on the open chamber area depth... .070" deep jives with the chamber volumes that you reported on those 915's, and both numbers are consistent with the notion that the heads have been milled about .040". With that new head gasket and all the other dimensions, I am thinking your gap from dome to open head area will be around .040" and that would be great. You'll have a good quench/squish gap to help reduce tendencies towards detonation with that higher CR and iron heads. Plus it helps combustion overall and efficiency, etc.

IMHO, do that clay test at all 4 corner cylinders of the engine to try to catch any spot that might be tighter than the others; the decks can slope front to back and so on. And, then check the dome height out of the block on each and every cylinder, as well as the open chamber depths. You don't want a longer-than-average rod or an offset crank throw to close that gap up too much. You're getting that piston-to-head gap snugged up nice and tight but you don't want to get too tight anywhere.

Your piston-to-valve clearance will change a bit if the cam timing is changed, so yes, be thorough and re-check.. But with what you had before, and the cam profile, it is very probably gonna still be fine.

 

[yellow rose]

Lemme see if I can clarify...

Definitely number 1 intake. I am certainly capable of using an exhaust by mistake. lol

The first readings I got (1st post), were about 98*. The crank gear was installed on the "0". Also, the crank gear was installed on "0" when I disassembled it. (To check what was inside an unknown-to-me engine.)

I moved the crank gear to the "A"dvanced position hoping to retard it to somewhere close to 108*.
That's when I started getting the 113* readings.
I stopped and rechecked everything and reset my indicator.

Moved the crank gear back to "0". Now I have gotten 108* twice, and I'm going to check it a couple more times.

Of course, that's the reading I should've gotten the first time. Maybe my TDC wasn't right, and I think my indicator may have been dragging on the side of the lifter bore.

The head gasket that was on it when I got it was .051 compressed. I'm using the MP P4120094, which is .038 new.

I'll check PV. It had a minimum of .180 I and E with the .051 gasket (at "0", of course).
I measured the open area on 1 cylinder. It is .070. I'll clay that with the thinner gasket and see what it is between piston and head.
Yes, a good time to check! I even have a set of the thicker gaskets in case.

Are you checking your P/V with clay and the springs you are going to use? If not, you should be. You'll find the valves are closest at about 10 degrees ATDC. With clay you will also see radial clearance.

Running soft springs will show much less clearance than you actually have.

 

[nm9stheham]

Are you checking your P/V with clay and the springs you are going to use? If not, you should be. You'll find the valves are closest at about 10 degrees ATDC. With clay you will also see radial clearance.

Running soft springs will show much less clearance than you actually have.

If you have hydraulic lifters, if the lifters are not pumped up properly to take up all slack and to STAY pumped up, if you use even stock pressure springs then you will get larger P-V clearance readings than you will actually have once the lifters pump up in operation. In my mind, that is the worst of the 2 outcomes. So I would rather get a lower P-V clearance with light checking springs, and then if the number is satisfactory, then I would know that I will have at least that much. If I got too little with that method, then it is time to use another approach.

But hydrualic lifter behavior is a problem if it is not filled with oil first.....while in the engine, with the valve train assembled and the lifter on the base circle. (Man, what a PITB! If the P-V clearance is too little then there is oil all over the place!)

Regardless, with those pistons' valve pockets and the cam type with slower ramp, I would not expect an issue.

 

[SpeedThrills]

IMHO, do that clay test at all 4 corner cylinders of the engine to try to catch any spot that might be tighter than the others; the decks can slope front to back and so on. And, then check the dome height out of the block on each and every cylinder, as well as the open chamber depths. You don't want a longer-than-average rod or an offset crank throw to close that gap up too much. You're getting that piston-to-head gap snugged up nice and tight but you don't want to get too tight anywhere.

I just did cyls 1 and 7. They both have about 1/8 at the top and 1/16 at the bottom between the head and piston. I used the .038 gasket, tightened by hand with the socket.

Are you checking your P/V with clay and the springs you are going to use? If not, you should be. You'll find the valves are closest at about 10 degrees ATDC. With clay you will also see radial clearance.

Running soft springs will show much less clearance than you actually have.

I get that theory. The running springs don't allow the valve to lift as far as a checking spring would, because of the spring pressure. I checked them with the running springs when I disassembled it.

If you have hydraulic lifters, if the lifters are not pumped up properly to take up all slack and to STAY pumped up, if you use even stock pressure springs then you will get larger P-V clearance readings than you will actually have once the lifters pump up in operation. In my mind, that is the worst of the 2 outcomes. So I would rather get a lower P-V clearance with light checking springs, and then if the number is satisfactory, then I would know that I will have at least that much. If I got too little with that method, then it is time to use another approach.

But hydrualic lifter behavior is a problem if it is not filled with oil first.....while in the engine, with the valve train assembled and the lifter on the base circle. (Man, what a PITB! If the P-V clearance is too little then there is oil all over the place!)

Regardless, with those pistons' valve pockets and the cam type with slower ramp, I would not expect an issue.

I have checking springs. The lifters are soft now. It hasn't run in years.

I have one mech lifter. I could check them with the running springs and the solid lifter. That would be a lot of work.
I could use the checking springs. That would be a lot of work, too!

I had plenty of PV when I disassembled it (Min .180). I didn't move the cam, the only change I made is a gasket that's about .016 thinner.

 

[yellow rose]

I just did cyls 1 and 7. They both have about 1/8 at the top and 1/16 at the bottom between the head and piston. I used the .038 gasket, tightened by hand with the socket.

I get that theory. The running springs don't allow the valve to lift as far as a checking spring would, because of the spring pressure. I checked them with the running springs when I disassembled it.

I have checking springs. The lifters are soft now. It hasn't run in years.

I have one mech lifter. I could check them with the running springs and the solid lifter. That would be a lot of work.
I could use the checking springs. That would be a lot of work, too!

I had plenty of PV when I disassembled it (Min .180). I didn't move the cam, the only change I made is a gasket that's about .016 thinner.

Actually, all rockers (good rockers...not stock junk) are built (or should be built) with a higher than nominal ratio. And it depends on the rocker manufacturer. So a 1.5 rocker could actually be 1.55 or more.

That's why you need to load the rocker. I refuse to notch Pistons that were checked with light springs or valve drop.

 

[mtolley]

Sometimes folks will set the cam 2-4 degrees retarded to bleed off some cylinder pressure, especially when using high static compression pistons with an iron head, in an effort to be able to use pump high test fuel(91-93octane)

 

[nm9stheham]

I have one mech lifter. I could check them with the running springs and the solid lifter. That would be a lot of work.
I could use the checking springs. That would be a lot of work, too!

Yes, how to do to exact measurements with hydraulics.... With very light checking springs, the hydrualic lifter inner springs will not compress and you'll get tighter clearance than actual. You could shim up the rocker shaft until the lash is just barely taken up with light checking springs and then do the check; that should give you very close numbers.

Your thinner head gasket should close up the PV clearance by that same amount.

 

[SpeedThrills]

I just checked piston to head clearance on cyls 2 and 8. About the same as 1 and 3. (1/8 at the top, 1/16 at the bottom.)

Heads are torqued and I'm just waiting for rocker shaft hold downs from Angelucci, and spacer washers from Mancini.

After that, I'll check rocker geometry. So, I could be back again!

Thanks to everyone for the help.

 

[PRH]

If you have the degree wheel/pointer properly zeroed out already...... post the results for:
Readings taken at .050 lifter rise from the lowest point....... on both an intake and ex lobe for the same cylinder-
(Or take a pic of the degree wheel & pointer at those 4 positions)

Intake opening...... BTDC=
Intake closing ...... ABDC=

Exhaust opening .. BBDC=
Exhaust closing ... ATDC=

That will provide everything you need to determine lsa and intake c/l

I thought the SB 508 cam was only offered with a 108lsa........ but I wouldn’t swear to it.
I know it was offered as a 108 or 114 in a BB.

The SB 484 was offered as both a 108 or 114.

 

[SpeedThrills]

Thanks PRH, it's in at 108*.

I won't have the compression that I was going to have. I realized that I didn't clean the oil passages to the rocker shaft very well when I had it apart. I pulled the heads to do that. I had a pair of FelPro's that mic new at .057. So I used them. The ones on it when I took it apart were .051.

 

[nm9stheham]

They oughta crush down about that much...

 

[SpeedThrills]

They oughta crush down about that much...

Sorry, I meant that the gaskets that were on it when I first tore it down were .051 compressed. On reassembly, I used .038's. Now, after pulling the heads, I'm back to .057. I agree they will compress to .051. I are confusing...