piston to valve clearance Boss 429

I did a check using feeler gauges and used the stock balancer , 0 lash and no head gasket. Engine is original Boss 429 with the stock .506 solid flat tappet cam.

Exhaust - .216 + .013 valve lash + .005 gasket thickness = .234

Intake - .152 + .013 valve lash + .005 gasket thickness = .170

Going to set up the dial indicator for a maybe a more accurate measurement tomorrow. These numbers seem reasonable for the type of engine it is?

You actually have more than that as the clearance increases when checking with the "proper" lash instead of zero and adding the lash figure. Why? Because no lash picks up the cam the moment it moves off of the base circle which increases the duration the valve "sees" . When you add lash the lifter begins to move later as it has to "take up the lash" and piston to valve increases.

rmk57 wrote:I did a check using feeler gauges and used the stock balancer , 0 lash and no head gasket. Engine is original Boss 429 with the stock .506 solid flat tappet cam.

Exhaust - .216 + .013 valve lash + .005 gasket thickness =  .234

Intake -   .152 + .013 valve lash + .005 gasket thickness = .170

Going to set up the dial indicator for a maybe a more accurate measurement tomorrow. These numbers seem reasonable for the type of engine it is?  

.005" gasket?
The numbers are way more than reasonable but I agree with gt350...you need to check with lash, and you really should have a gasket.

A factory BOSS 429 has NO head gaskets; it only has "O" rings with required receivers between the block deck and heads.

Compressed gasket thickness is somewhere around .005- .010.

My valve spring installed height is 1.82. Would it be safe to run comp cams 924-16 springs with a cam in the upper 500's lift, 234-240 @ .050?
Seat pressure is 112 lbs @ 1.90 I/H and 355 lbs. @ 1.20. Im not sure how much the seat pressure would increase with shortening up the installed height that much.
If it's questionable +.050 locks could be used to give me 1.87.

Randy

rmcomprandy wrote:A factory BOSS 429 has NO head gaskets; it only has "O" rings with required receivers between the block deck and heads.

I remembered that after I posted.

Gasket thickness is a straight off change , valve lash is different as I explained. MANY guys cut pistons when it is not needed because of "different" ways of checking piston to valve. Checking as close as possible to ACTUAL running conditions is how it "should be done".

gt350hr wrote: Gasket thickness is a straight off change , valve lash is different as I explained. MANY guys cut pistons when it is not needed because of "different" ways of checking piston to valve. Checking as close as possible to ACTUAL running conditions is how it "should be done".

Most people think it will be more with running springs vs. checking springs because that's how it checks on the engine stand.

Scott Foxwell wrote:

gt350hr wrote: Gasket thickness is a straight off change , valve lash is different as I explained. MANY guys cut pistons when it is not needed because of "different" ways of checking piston to valve. Checking as close as possible to ACTUAL running conditions is how it "should be done".

Most people think it will be more with running springs vs. checking springs because that's how it checks on the engine stand.

So you're saying a checker spring gives the same figure as a "running" spring?

cool40 wrote:

Scott Foxwell wrote:

gt350hr wrote: Gasket thickness is a straight off change , valve lash is different as I explained. MANY guys cut pistons when it is not needed because of "different" ways of checking piston to valve. Checking as close as possible to ACTUAL running conditions is how it "should be done".

Most people think it will be more with running springs vs. checking springs because that's how it checks on the engine stand.

So you're saying a checker spring gives the same figure as a "running" spring?

No. Well, over the nose, yes, but that really doesn't play into v/p clearance. Truth is, in a running engine you'll see more load at lower lift (closer to where valve/piston can come in contact) than over the nose or at higher lift but IMO you want to account for as much lift as possible. (This applies to the intake valve) Don't "assume" you'll have more in a running engine at those critical areas because of running springs or any other "dynamic assumptions". The highest load the valve train sees is when the lifter starts accelerating up the lobe. At that point, the pushrod, cam, rocker, and everything else in the valve train start to flex. This is very early in the lift. At some point everything "unloads" acting like a secondary spring in the system. At this point there can be zero load on the lifter, all the way over the nose of the cam and can actually loft the lifter. You can just about guarantee that at some rpm, every lifter experiences a certain amount of loft. This is different than valve float. Point is, if you use checking springs, you will never "induce" a negative number into your calculations which may or may not be there in a running engine. These numbers are for safety, so stay safe. JMO.

Scott Foxwell wrote:

cool40 wrote:

Scott Foxwell wrote:

gt350hr wrote: Gasket thickness is a straight off change , valve lash is different as I explained. MANY guys cut pistons when it is not needed because of "different" ways of checking piston to valve. Checking as close as possible to ACTUAL running conditions is how it "should be done".

Most people think it will be more with running springs vs. checking springs because that's how it checks on the engine stand.

So you're saying a checker spring gives the same figure as a "running" spring?

No. Well, over the nose, yes, but that really doesn't play into v/p clearance. Truth is, in a running engine you'll see more load at lower lift (closer to where valve/piston can come in contact) than over the nose or at higher lift but IMO you want to account for as much lift as possible. (This applies to the intake valve) Don't "assume" you'll have less in a running engine at those critical areas because of running springs or any other "dynamic assumptions". The highest load the valve train sees is when the lifter starts accelerating up the lobe. At that point, the pushrod, cam, rocker, and everything else in the valve train start to flex. This is very early in the lift. At some point everything "unloads" acting like a secondary spring in the system. At this point there can be zero load on the lifter, all the way over the nose of the cam and can actually loft the lifter. You can just about guarantee that at some rpm, every lifter experiences a certain amount of loft. This is different than valve float. Point is, if you use checking springs, you will never "induce" a negative number into your calculations which may or may not be there in a running engine. These numbers are for safety, so stay safe. JMO.

my safe zone is to use checker springs and figure on having another.025 with the real thing. All that "dynamic assumption " and " lofting" I would think greatly depends on the application,not arguing with you or doubt what you believe,just saying.

cool40 wrote:
my safe zone is to use checker springs and figure on having another.025 with the real thing. All that "dynamic assumption " and " lofting" I would think greatly depends on the application,not arguing with you or doubt what you believe,just saying.

Of course it does. If we knew exactly what it was going to be, we wouldn't need so much clearance. That's why you can't assume you have another .025 with the "real thing". Use a correct thickness head gasket, lash the valves, and check your clearance.

I went back and edited my statement...I had written don't assume you'll have less (clearance) in a running engine. Should have said don't assume you'll have more...

Scott Foxwell wrote:

cool40 wrote:
my safe zone is to use checker springs and figure on having another.025 with the real thing. All that "dynamic assumption " and " lofting" I would think greatly depends on the application,not arguing with you or doubt what you believe,just saying.

Of course it does. If we knew exactly what it was going to be, we wouldn't need so much clearance. That's why you can't assume you have another .025 with the "real thing". Use a correct thickness head gasket, lash the valves, and check your clearance.

I went back and edited my statement...I had written don't assume you'll have less (clearance) in a running engine. Should have said don't assume you'll have more...

I always check clearances with the " real thing" if it's remotely close. One can't assume things dealing with close tolerance and high rpm.

May not apply to the op - or be the best way to do it, but I use silly putty.... this has helped me to also check radial clearance which I have had an issue with in the past. also need to put a little extra in to allow for piston rock imo.

Kurt.

I used a checker spring with a dial indicator and feeler gauges. Came up with .010 or a bit more difference between the two depending how tight you want
the feeler gauges. Close enough for the small cam I'm going to run. Radial clearance wont figure into it either, using stock valves and pistons.

With the cam installed and lash set on the actual springs , I begin checking the exhaust closing ( with an indicator on the retainer) at 16*BTDC and check every two degrees to find the tight spot ( usually 10*s) . Then I put the indicator on the intake and start checking at 6*s ATDC for the tight spot ( 8-12 ATDC usually) . I use my Moroso spring tester to move the rocker and watch the indicator for the clearance or "drop" on the retainer until it contacts the piston.

Use the real springs to check it,and set it to .000 lash, install the o-rings,and tq the head to about 50lbs, this is the best way to check for ptv .


and no 1.82 is not a good installed hight for these, try to get 1.90, , then you can use a better spring,or even shim down.

make sure since your making changes you check full lift,and rocker travel in case you need to shim up rockers


and just because you have a lot of thread in the adjuster doesnt mean that just screwing them in is ok, should see 2 threads or so above the nut when lash is set . this should get you very close.