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radial clearance can still be checked with the clay method, (that's what I do).
Actually I think that is the easiest way to check it. You can use a razor blade and cut the clay in a few spots and actually "see" how much room you have.
 

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Just because a piston has valve reliefs doesn't mean you're out of the woods.. As mentioned clay is your best friend.. Even when I know a build won't hit, I still use clay.. helps with future cam advancing, etc...

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Discussion Starter · #43 ·
The pistons should be fine but I would pull all 8 and have them fly cut to give you enough room, especially if you are going with a larger cam. You need to be VERY careful having this done because it is very easy to cut into the top ring groove on those pistons.
Bill,
the valve bite mark in the pistons is roughly .090"deep, the new Howard's roller im
Going with has .110" more lift. (.490 to.600")
Am I right to assume that I would need to fly cut the pockets .200+ the additional radial Clearance of .060"?
If so, do you think these speed pro pistons can support that kind of machine work or should I get new pistons with reliefs made for the 2.19 and 1.88 valves?
 

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Bill,
the valve bite mark in the pistons is roughly .090"deep, the new Howard's roller im
Going with has .110" more lift. (.490 to.600")
Am I right to assume that I would need to fly cut the pockets .200+ the additional radial Clearance of .060"?
If so, do you think these speed pro pistons can support that kind of machine work or should I get new pistons with reliefs made for the 2.19 and 1.88 valves?
Lift isnt all, degree the cam and check clearance. Piston to valve isnt closest at max lift.
The intake valve is closest to the piston in the vicinity of 10 degrees after top dead center (ATDC), while the exhaust valve rides closest roughly 10 degrees before top dead center (BTDC).
 

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Discussion Starter · #45 ·
Lift isnt all, degree the cam and check clearance. Piston to valve isnt closest at max lift.
The intake valve is closest to the piston in the vicinity of 10 degrees after top dead center (ATDC), while the exhaust valve rides closest roughly 10 degrees before top dead center (BTDC).
I guess what I'm trying to avoid is tearing it down to have the new cam bearings put in. Re assembling it to check clearances on the old pistons to then find out there is not enough "meat" on them to have them fly cut.
If theres a way to say there will or will not be enough to machine them before taking it into the machine shop so I can have it all done in one trip is my ultimate goal.
 

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I guess what I'm trying to avoid is tearing it down to have the new cam bearings put in. Re assembling it to check clearances on the old pistons to then find out there is not enough "meat" on them to have them fly cut.
If theres a way to say there will or will not be enough to machine them before taking it into the machine shop so I can have it all done in one trip is my ultimate goal.
Why not check it with the old bearings before you drop everything off? This is stuff you just cant guess.
Always mockup and check clearance etc before final assembly.
 

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Discussion Starter · #47 ·
Why not check it with the old bearings before you drop everything off? This is stuff you just cant guess.
Always mockup and check clearance etc before final assembly.
Great idea, Thank you for mentioning that!
how would one check to see how much more the valve will be in contact with the piston with the new cam if it is already hitting with a smaller lift cam? Would this have to be done mathematically with a dial indicator rather than a clay test?
 

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Great idea, Thank you for mentioning that!
how would one check to see how much more the valve will be in contact with the piston with the new cam if it is already hitting with a smaller lift cam? Would this have to be done mathematically with a dial indicator rather than a clay test?
Duration and ramp rate...is more important than lift...

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Great idea, Thank you for mentioning that!
how would one check to see how much more the valve will be in contact with the piston with the new cam if it is already hitting with a smaller lift cam? Would this have to be done mathematically with a dial indicator rather than a clay test?
I would start and see if you have clearance at all. I use feeler gauge to check piston to valve at closest point and clay to check radial clearance.
Your problem was intake valves? Thats little strange imo but maybe the piston reliefs arent for 2.19” valves?
 

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Discussion Starter · #50 ·
I would start and see if you have clearance at all. I use feeler gauge to check piston to valve at closest point and clay to check radial clearance.
Your problem was intake valves? Thats little strange imo but maybe the piston reliefs arent for 2.19” valves?
Yes it was the intake valves. Only on one head. Seems there is some machining differences on the heads that I did not catch.
yea I was told that these speed pro H118CP are for stock valves and not oversized like I'm running
 

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Yes it was the intake valves. Only on one head. Seems there is some machining differences on the heads that I did not catch.
yea I was told that these speed pro H118CP are for stock valves and not oversized like I'm running
Ok I would mockup and check clearance if same bank has problems I would flip heads and see what happens just for reference. Your problem only seems to be radial clearance with old camshaft? Ofset head dowels are avaible.
 

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Yes it was the intake valves. Only on one head. Seems there is some machining differences on the heads that I did not catch.
yea I was told that these speed pro H118CP are for stock valves and not oversized like I'm running
You already know what the problem is, tear is down, the machine shop will fly cut the pistons, pistons are already marked (the hard way unfortunately) it's an easy deal.
 

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Bill,
the valve bite mark in the pistons is roughly .090"deep, the new Howard's roller im
Going with has .110" more lift. (.490 to.600")
Am I right to assume that I would need to fly cut the pockets .200+ the additional radial Clearance of .060"?
If so, do you think these speed pro pistons can support that kind of machine work or should I get new pistons with reliefs made for the 2.19 and 1.88 valves?
This is completely more dependent on amount of duration change rather than peak lift.
At peak lift, the piston is far down the bore and moving away at that point. no chance for collision there.

Valve-to-piston issues are during the overlap period, the time when the piston is coming to TDC pushing exhaust out and getting ready to start pulling fresh air/fuel charge in and both valves are just slightly open.
The closing exhaust valve is being chased shut by the rising piston but the intake valve is starting to open and moving towards the rising piston.
The area of crank rotation between 15° before to 15° after TDC Overlap is where piston to valve clearance is closest and where it needs to be checked.

The .110" increase in peak lift might only result in .010" decrease in V-to-P clearance.
A 20° increase in .050" duration might result in a .075" decrease in valve-to-piston clearance.
 

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Valve timing which is ground into the camshaft is the biggest factor which dictates piston to valve clearance as far as comparing one camshaft to the next is concerned. For instance, with all else equal, camshafts with tighter LSA's are going to have the valves coming closer to the pistons than ones with wider LSA's will. It's the cams with lots of valve overlap that will reduce piston to valve clearances the most. This is something that I learned from the cam designer, the late Harold Brookshire, (AKA "UDHarold").

I can also assure you that you're not going to be able to have .200" removed from the piston crowns, nor will you need to anyway. A tech guy from the piston manufacture Mahle told me over the phone that the rule of thumb is that the maximum amount of material you can safely remove from most pistons is about .040" and I've heard of some professional engine builders removing as much as .050" but that's about it.
 

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Discussion Starter · #55 ·
Billy and Eric, thank you for those reply's. That was very useful information and helps me understand valvetrains a little better.
if .040 is the max i can fly cut, I think I will look at some new pistions with larger valve reliefs.
The valves already self clearanced 4,8 pistons .090"
The cams are more Similar than I thought. I'm only adding ~.050 lift, little more exhaust duration, and a little less intake. Increasing LSA from 110 to 112.
 

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Well those cams aren't anything radical. Talk to the pro engine builder of your choice and get his advice on your options, including what aftermarket pistons have generous sized valve reliefs. And be sure to explain to him what pistons you have now, and that there wasn't enough radial valve clearance. I haven't followed this whole thread, so I have to ask: did you figure out why the valve clearances were adequate on one cylinder bank but inadequate on the other bank? That would be my first concern if I were you.
 

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Discussion Starter · #57 ·
Well those cams aren't anything radical. Talk to the pro engine builder of your choice and get his advice on your options, including what aftermarket pistons have generous sized valve reliefs. And be sure to explain to him what pistons you have now, and that there wasn't enough radial valve clearance. I haven't followed this whole thread, so I have to ask: did you figure out why the valve clearances were adequate on one cylinder bank but inadequate on the other bank? That would be my first concern if I were you.
I agree and it is my first priority. No I have not figured out why it's only one bank yet
 

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I agree and it is my first priority. No I have not figured out why it's only one bank yet
I know I'm stating the obvious here, but just in case you haven't already concluded this: it sounds to me like you need to get that engine block to a machine shop and have the two decks measured. Something isn't right.
 

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I agree on why one side hit and the other didn't. What is different? Are the dowels the same? Is one side of the block missing dowels? Could there be offset dowels on one side and not the other (very doubtful) but possible? Did both sides of the intake have the same thickness intake gasket?
 
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