Lash Pad thickness

[naviathan]

I've read BRAAP's awesome write up on setting up a custom head. Now I'm in a quandary of sorts. I have the lash pads that came with my springs and performance cam (that is of course wiped out now). No I'm setting up a stock cam in the same head and trying not to make the same mistake twice. This head has had the valve seats ground which of course messed with the lash pad size. I'm getting my hands on a micrometer to figure the right size out, but I've got it nailed using small washers. According to BRAAP's thread for the DIYer it's not necessary to buy every lash pad size there is, but you can use snippets of feeler gauges to make them thicker with solid pads. My question, is this safe to do? Can I just adjust my valve lash with these little washers till it's right and leave them in instead of purchasing the large lash pads necessary?

[naviathan]

Ok just did the measurements and it seems I would need .200" thick pads just to get my stock cam right?!?!?!?! That seems a bit much too me, what do you all think?

[JMortensen]

If it's right, it's right. You should check on several different valves too, and intake and exhaust should be checked separately.

 

As to the feeler gauge thing, that's ONLY TO FIGURE OUT WHAT SIZE YOU NEED. One you figure that out, you still need to buy the correct size and install them. It saves you from having to buy a huge assortment of pads, but you do still need to buy the correct size.

[Careless]

that feeler guage trick is cool. they can be had for pretty cheap too, and it would save you from buying all sorts of lash pads

[aarang]

Wow, .200 for a stock cam. I have a delta regrind for a turbo which is 260 dur 460 lift and I'm using .180 pads. My head has also had the seats cut a little. Aren't the stockers .120? Also, is it advisable to use that thick of a pad with the stock retainers?

[naviathan]

Wow, .200 for a stock cam. I have a delta regrind for a turbo which is 260 dur 460 lift and I'm using .180 pads. My head has also had the seats cut a little. Aren't the stockers .120? Also, is it advisable to use that thick of a pad with the stock retainers?

I'm not using stock retainers fortunately. I have the schneider performance springs and retainers. I thought .200" was a bit much too, but I'm not real sure what else it could be.

[Dane]

I was just reading this and wanted to make sure I understand the feeler gauge trick correctly:

 

So the idea is that you stick a feeler gauge between the tip of the rocker arm and valve stem. Then you spin the cam and check the cam lobe wipe pattern on the rocker arm contact pad. If the wipe pattern is okay, then the thickness of the feeler gauge is the thickness of lashpad that needs to be used? Would you also need to subtract the valve lash (measured between cam base circle and rocker arm) * 1.5 (rocker ratio) from the feeler gauge thickness to get the true lashpad thickness, or could you just use the feeler gauge thickness as previously stated and then adjust the valve lash from there?

 

Am I on the right track here?

[naviathan]

You use the snippets of feeler guage under the lash pad to adjust it's height. Then you take the thickness of the lash pad and add the total thickness of the feeler guage snippets to it and you have your total size required for your new lash pads.

[Tony D]

What you can do is simply buy thicker lash pads, and then take them to a machine shop to be ground down to proper thicknesses. If I were in a remote portion of the world, that is exactly how I would do it.

 

Ingersoll/Rand Centrtifugal Compressors use a similar setup for setting up clearances in their machines, and I am constantly finding machines hops with magnetic/chucks and a surface grinder to make final clearance adjustments to our `bulk shim stock` which is supplied with each overhaul kit...in .375 thcknesses (even though normal finished thickness is around .120)

 

Check to see if you have an industrial machine shop with a surface grinder. If you do, use the feeler gauges to measure the thicknesses you need, and then have them finish grind them all to the thicknesses you need. They can do it in a day easily. I get 9 shims cut to at least three different thicknesses in less than 2 hours usually, 4 hours at the outside in a Union Shop. It´s an alternative that is viable, especially if the pads you have now are ´too thick´ for what you need now.-..saves buying new pads.

[naviathan]

My pads aren't too thick, they're too thin. I have .160" pads and it looks like I need .200".

[1 fast z]

If stocks are 3mm which they are, and your valves have been ground as well as the seats, that would make the gap SMALLER, requireing less then 3mm thickness. You say you need .200" I say you have something going wrong there.

[naviathan]

If stocks are 3mm which they are, and your valves have been ground as well as the seats, that would make the gap SMALLER, requireing less then 3mm thickness. You say you need .200" I say you have something going wrong there.

I understand that, unfortunately I can't find anything wrong... Compression is good, all the valve springs are the same height, all the lash pad measurements from all the valves give me the same size, .200", and I don't get it. Aside from the performance springs from MSA, the valve grind and the head decked, every thing is stock.

[DHale_510]

Where do you have the "adjusting screw"? It needs to be set properly before you can measure the pad thickness. If you have it too far down you will get a false thick measurement and then have no adjustment range left. This very long range is there to be able to remove the rocker arms, not to extend the adjustment range. The wipe pattern will be off if you do this wrong, possibly enough to run off the hardened pad and destroy the engine with ground down cam. It has happened a lot.

I have managed to toss the pad a few times and would not trust a goofy shim adjuster to stay in place.

Shortcuts never are.

[naviathan]

Yes I know how to check my wipe pattern. I started with stock pads, set the clearance by the cold settings in the FSM, .007 int .009 exh, turn engine over one rotation pull the rocker and check wipe pattern. I used a sharpie marker to color the pad on the rocker. It came out really low with stock so I put in the performance pads that were .160" and they were really low on the pad so I added a small washer that measured .035 and it put the wipe a hair on the pivot side of the pad if that. So .160" + .035" = .195". Pads go in .010" measurements and .195" was just slightly low anyway (not low enough to make a difference though) so .200" is where it's at.

[BRAAP]

I've read BRAAP's awesome write up on setting up a custom head. Now I'm in a quandary of sorts. I have the lash pads that came with my springs and performance cam (that is of course wiped out now). No I'm setting up a stock cam in the same head and trying not to make the same mistake twice. This head has had the valve seats ground which of course messed with the lash pad size. I'm getting my hands on a micrometer to figure the right size out, but I've got it nailed using small washers. According to BRAAP's thread for the DIYer it's not necessary to buy every lash pad size there is, but you can use snippets of feeler gauges to make them thicker with solid pads. My question, is this safe to do? Can I just adjust my valve lash with these little washers till it's right and leave them in instead of purchasing the large lash pads necessary?

 

Naviathan,

Now keep in mind, that trick using the shim stock is only for “finding” the correct wipe pattern in an effort to determine the correct lash pad thickness so that you can order the correct lash pad. Whatever you do, do NOT run the engine using those snippets of shim stock under your lash pads.

 

 

 

 

 

Ok just did the measurements and it seems I would need .200" thick pads just to get my stock cam right?!?!?!?! That seems a bit much too me, what do you all think?

 

For a stock cam, .200” does seem a bit much and should be investigated further.

 

 

 

 

 

I was just reading this and wanted to make sure I understand the feeler gauge trick correctly:

 

So the idea is that you stick a feeler gauge between the tip of the rocker arm and valve stem. Then you spin the cam and check the cam lobe wipe pattern on the rocker arm contact pad. If the wipe pattern is okay, then the thickness of the feeler gauge is the thickness of lashpad that needs to be used? Would you also need to subtract the valve lash (measured between cam base circle and rocker arm) * 1.5 (rocker ratio) from the feeler gauge thickness to get the true lashpad thickness, or could you just use the feeler gauge thickness as previously stated and then adjust the valve lash from there?

 

Am I on the right track here?

 

Dane,

Post #18 in this link below talks about the process with pics, that Naviathan is referring to.

 

Click ME for valve train set up..

[naviathan]

I just thought about something. Is it possible to fit P90 valves in a N42 head? I know the P90 valves are shorter than the N series valves and my machinist had both my P90 and my N42 in his shop at the same time. I'm starting to wonder if he mixed the valves by mistake and that's why my lash pads seem to be measuring out thicker.

[naviathan]

Ok it all makes sense now. Still not sure "how" but I'm convinced now that I have P90 valves in my N42 head. I found the numbers on how much shorter the P90 valves are from the N42 valves, 2mm. As we all know (I'm sure) 2mm is roughly .080". I have a stock cam in my engine now and the stock .120" lash pads are about .080" too short...I wonder...What kind of problems could I be looking at here?

 

Increased seat pressure causing the valves to beat the hell out of the brass seats?

[naviathan]

Anyone? Will the shorter valves effect my engine? Will it damage it at all?

[naviathan]

OK, I am at my wits end here trying to figure this one out. I dug through the garage and found the P90 valves. I verified it by setting one of them next to my N series stainless valves and it was notably shorter. So, if the P90 valves are out in the garage that means the valves in the N42 are the ones that are suppose to be in there. Which makes sense as I sent the head to the machinist with the valves springs and valves in it and he says he kept the valves with the head the whole time he was working on it and that I never sent any valves with the P90, which obviously is true as the valves are sitting in the garage right now. What now? I'm at a loss here, I have no clue what the problem could be now. I measured the height of the valve springs tonight and compared them with a N47 and the N42 spring height is lower by about .080". So that proves it, the valves are sitting lower in the head. The machinist didn't put new seats in, he just lapped the valves and ground the seats to match. HELP!!!!

[BRAAP]

Naviathan,

Hmm… Dang bouy.. Your cylinder head woes just keep coming don’t they? I truly feel your pain. Ouch..

 

Here is the scenario as I see it;

 

Valves are shorter and as such means your spring installed height is now that much shorter; you are now that much closer to crashing the retainer into the valve guides and/or stem seals; you are that much closer to coil bind; spring “seat pressure” and “over the nose pressure”, (if the cam will open the valve at full lift before coil bind), is considerably higher. “If” all is clear, so to speak, spring life will also be considerably shortened as they are now being asked to work MUCH harder than they were designed to and with aftermarket springs on a stock cam, is a total waste with all that seat and over the nose pressure. Stock cams with beefy springs is OK especially with highly boosted engines, but not to this extreme.

 

Options;

 

1) Install the proper length valves, (these appear to be too short).

 

2) Possibly locate spring retainers that allow for higher spring installed height.

 

3) Disassemble the head and using stock springs and retainers, (stock springs now will be stiffer at this much shorter installed height, but most likely be at coil bind which wont work any how), verify spring installed heights, retainer to stem seal/guide clearance, verify coil bind doesn’t happen to long after max lift, at least .080”. "If" they will work, spring life will be considerably shortened as they are now being asked to work out of their designed element.

 

My best professional advice is to verify without doubt that those valves are indeed too short, (remove them and measure them), and install the correct valves.

 

 

Here is a snippet from this thread…

 

A look into custom cylinder head building and set up..

 

 

 

......

During the initial seat cutting on cylinder heads such as this' date=' which are utilizing a big lift cam, we will cut only one intake and one exhaust seat. Then we install an intake and exhaust valve using our “soft” springs with the retainers and keepers that are to be ran in this head. Then we measure spring installed height, retainer-to-valve stem seal clearance, etc, and make note of anything that needs adjusting. Then we go back and cut the valve seats to the depth that offers the least compromise without having to sink the valve too deep into the head. This allows adequate retainer-to-stem seal clearance and installed spring height. We also use spring shims of varying thickness to help adjust spring-installed height in order to maintain correct seat pressure. There are also a couple other techniques we will use to achieve more retainer-to-seal clearance such as machining down the under side of the retainers, but only up to within .010” of the keepers, no further, just as we did on this set up (see pics below). FWIW, the Fel-Pro Ford V-6 stem seals allow for considerably more retainer-to-seal clearance [i'](the valve spring retainer “WILL” crash into the valve stem seal with big lift cams)[/i], and the Viton rubber is much more resistant to degradation over time vs. the OE style polycarbonate seals.

 

 

These pics show the retainers as originally sent to us, and then modified by removing .050” material from the bottoms allowing for another .050” clearance between the retainer and the valve stem seal. This also lightens the retainers just a smidge. Note, the shorter Viton Ford V-6 stem seal next to an OE style polycarbonate seal, height mic, various spring shims, etc.