Author Topic: How do you check piston to valve clearance on hydraulic lifter engine (Read 9127 times)

Jako · **on:** March 07, 2019, 11:10:29 pm

I just pulled down my brothers CGT to fit Hitchcock's cams and valves , Dynojet PCV and shorten the barrel to correct the squish band (it was 2.28mm) . Very surprised to find the exhaust valve guide completely flogged out in only 4000 km ( 2400 miles ). Took head to engine shop for guide replacement, guy said it was the most worn guide he's ever seen. The bike was running a reverse cone silencer with no fuel correction , it was running well but the header pipe was blueish and the exhaust valve was greyish white . I guess the lean fuel condition caused the valve to overheat and wear the guide ? Now with the barrel 1.2mm shorter and high lift cams I need to check the valve to piston clearance, how do you do that with hydraulic lifters ? Wouldn't the lifters have bleed down some with the engine not started for a few weeks and give a false reading using modeling clay method ? How can I pump oil into lifters ?

gashousegorilla · **Reply #1 on:** March 08, 2019, 01:55:23 am

The lifters may or may not have bleed down from sitting. But... once you turn the motor over by hand a few times, with the rods and valve train installed, the oil in the lifters will be forced out. So yes.. your lifters will then be collapsed and useless for checking. Ideally you want to check your piston to valve clearance using a solid lifter , an adjustable push rod and lite weight checker springs. Then adjust to zero lash before you check clearance. But... It's not very easy to install solid lifters in these bikes. You would need to covert your Hydro's to solids with a machined slug , and either remove the lifters by removing the top end , remove the lifter retaining pins down inside the case , and then pull out the lifters . OR.. removing the internals of the Hydro lifters through the tappet inspection cover and installing a slug.

Short of doing that... you are going to have to calculate what the deck height change is, and what the valve lift change is and use an adjustable checker rod to get to your final rod length and lifter pre-load. You can bottom out the lifter with an adjustable rod and get to zero lash so you can check valve to piston clearance . And then figure out what your final rod length should be for pre-loading the lifter. Generally... you set your lifter pre-load to half the travel of the plunger inside the lifter. On the Bullets, there is .100" of travel inside a dry and fully collapsed lifter. You should also consider that these top end's GROW with heat , and that will reduce your pre-load when the motor is hot. And you should also consider what vale to piston clearance is, that you find in there when considering rod length and lifter pre-load. If you should float a valve... you don't want the valve smacking into the piston because your rod is too long and your pre-load too much.

gashousegorilla · **Reply #2 on:** March 08, 2019, 03:06:21 am

BTW Jako, to get yourself in the ball park as far as what your final push rod length should be . Subtract that 1.2 mm AND.. then likely add the difference in base circle size, between the stock cam's and the new cams. Those Hitchock cams likely have a smaller base circle I'm thinking , to gain the added lift. So you would have to lengthen your push rod to compensate for that. If that is the case with their cams....

Jako · **Reply #3 on:** March 08, 2019, 11:22:20 am

Thanks for the detailed explanation Dan . I have been trying to reply with a long detailed message all night but keep getting that Error has occurred message , its driving me nuts. I have talked with Bullet whisperer who did the same mods to a GT without any interference.

ace.cafe · **Reply #4 on:** March 08, 2019, 02:28:36 pm

Chances are you will be okay. I just don't have the necessary data for the H cams to say it with certainty.

If you measure your "free drop", by putting the head on the bench and measure how far the valve can go down to where it touches the benchtop, and then subtract .020"(half mm) and then you know how far you can lift at max around TDC with a 1mm thick head gasket setting the squish height with your piston at zero deck height at TDC.

As long as your lift around TDC is less than your free drop minus .020", then you are good to go with the recommended .060" p to v clearance safety margin.

Make sure that your lifter preload is about .020"(half mm), and then the valve won't hit the piston if it floats and the lifters pump up to take that up.

FWIW, we didn't have piston/valve contact issues until we went to very high ratio rockers AND .357" lobe lift on the cams, along with zero deck and 1mm head gasket.

Jako · **Reply #5 on:** March 09, 2019, 01:39:13 am

Thanks Ace, I have a spec sheet on these cams , I will post them here over the weekend .

Jako · **Reply #6 on:** March 10, 2019, 10:32:56 am

These are the only specs provided , will they help

Narada · **Reply #7 on:** March 10, 2019, 12:51:15 pm

Now this is an interesting method (from that Hitchcock attachment) for determining correct pushrod length, if like myself you have adjustable pushrods...

Naturally, I've been using a more masochistic process.

14. Reassemble with the new pushrods following the reverse of the above sequence. It is important with the pushrod positioned on tip of the lifter with no cam lift, the rocker and rocker housing are then placed on the head with the fixing screws loosely attached with no pressure. At this stage it would be expected for there to be between 1mm and 2.5mm gap between the base of the rocker housing and cylinder head. (If the valves are being held open beyond this, there is too much preload which can be solved with a slightly shorter pushrod)

ace.cafe · **Reply #8 on:** March 10, 2019, 01:54:51 pm

Quote from: Jako on March 10, 2019, 10:32:56 am

These are the only specs provided , will they help

Well , it doesn't give lift figure at TDC but rough figuring would estimate about .100" - .120" lift around TDC. That would be at the valve, including the rocker ratio.

I don't have a head in front of me right now, but I feel pretty confident that it won't be hitting. I suspect H set up the cams to be a safe install on normal heads. It is the amount that you shorten the barrel that raises questions.

If you have the head off, try the free drop test to see what it has. The exhaust valve is not at risk.

As GHG mentioned above if you shorten the barrel, and have reduced base circle cams, then look at the sum of those changes, and contemplate if a different pushrod length is needed.

A half mm of preload is good for function and safety margin.

gashousegorilla · **Reply #9 on:** March 10, 2019, 05:35:27 pm

Quote from: Narada on March 10, 2019, 12:51:15 pm

Now this is an interesting method (from that Hitchcock attachment) for determining correct pushrod length, if like myself you have adjustable pushrods...

Naturally, I've been using a more masochistic process.

14. Reassemble with the new pushrods following the reverse of the above sequence. It is important with the pushrod positioned on tip of the lifter with no cam lift, the rocker and rocker housing are then placed on the head with the fixing screws loosely attached with no pressure. At this stage it would be expected for there to be between 1mm and 2.5mm gap between the base of the rocker housing and cylinder head. (If the valves are being held open beyond this, there is too much preload which can be solved with a slightly shorter pushrod)

Their method works... provided that the lifters were still pumped up and not collapsed when you check it that way. And also provided everything is stock with the bikes top end. Those measurements that they are giving, would preload the lifter between about half way and bottomed out inside the lifter. So it would be extremely important to make sure that there is NO down ward push on that lifter when you set them up in this fashion.... the lifter would have to be pumped and locked at the top. Or you could get a false measurement.

Narada · **Reply #10 on:** March 10, 2019, 07:36:42 pm

Oh well, back to the old fashioned way...self-flagellation by adjustable pushrod!

gashousegorilla · **Reply #11 on:** March 10, 2019, 08:47:05 pm

Quote from: Narada on March 10, 2019, 07:36:42 pm

Oh well, back to the old fashioned way...self-flagellation by adjustable pushrod!

A ball tipped screw adjuster on the STOCK style rockers, without reinventing the wheel , would make life sooo much easier ... for Hydraulics or solids for that matter .

gashousegorilla · **Reply #12 on:** March 10, 2019, 09:24:42 pm

JUST... as an example of what I am talking about with the base circle differences Jako . And if all things are the same, and to get you to the same preload on the lifter that you have now.... Base gasket the same , head gasket the same , the same valve height and etc. If you are getting valve work done... you should discuss this with your machinist. Things may change with head work...

Compare the width of the stock cams base circle , to the width of your new cams. In this example the stock cam is .2915 ".... the new cam measures .2245 " . The difference being .067 ". So in theory, to get the same preload on your lifter, you would need to have a rod that is .067 " LONGER to make up for that difference. If you shaved the barrel by 1.2 mm or .047" , you have to factor that .020 " height reduction in. So to maintain the same pre-load that you have now, and if all those other factors are the same as they were that I mentioned above, you would need a rod that is .020 longer then what you have now....

Sorry , I had pictures. But for some reason I can't post them ? $:-\$

gashousegorilla · **Reply #13 on:** March 10, 2019, 10:17:26 pm

This is a good Video I think , demonstrating push rod length. It's a Harley motor and not the same as our's. It has double the travel inside the lifter as ours for one.... But the theory is the same.

https://www.youtube.com/watch?v=ujeU7QXB_Yk

Jako · **Reply #14 on:** March 12, 2019, 03:44:44 pm

Thanks for all the advice guys but I dont think this project will work. I measured a few things as accurately as I could with only a dial indicator and micrometer. Final squish 1.1mm (.044") measured with soft solder on piston. Inlet valve free drop 1.7mm (.068") these 2 figures should be accurate . Then measured inlet cam lift at TDC as 2.56mm ( .102") this figure may not be accurate but should be in the ball park. This was measured by placing dial indicator with extension rod down the pushrod hole of barrel onto the outside of the lifter (head was off at this time) then rotating the engine several times noting the distance lifter moves from base circle to TDC position. Factoring in a rocker ratio of 1.28 there will be interference. I hope I'm working this out wrongly.

ace.cafe · **Reply #15 on:** March 12, 2019, 09:22:37 pm

I suggest re-checking the free drop of the intake valve. I don't think that I have ever seen a head with as little free drop as .068".

And truthfully, I can't imagine the intake valve in that package is actually going to be more than .280" open at TDC, when the full lift is only .448" at 110 degrees later.

Something is not sounding right. A re-check is suggested.

The squish gap sounds like you have that nailed just right.

gashousegorilla · **Reply #16 on:** March 12, 2019, 10:05:15 pm

Quote from: Jako on March 12, 2019, 03:44:44 pm

Thanks for all the advice guys but I dont think this project will work. I measured a few things as accurately as I could with only a dial indicator and micrometer. Final squish 1.1mm (.044") measured with soft solder on piston. Inlet valve free drop 1.7mm (.068") these 2 figures should be accurate . Then measured inlet cam lift at TDC as 2.56mm ( .102") this figure may not be accurate but should be in the ball park. This was measured by placing dial indicator with extension rod down the pushrod hole of barrel onto the outside of the lifter (head was off at this time) then rotating the engine several times noting the distance lifter moves from base circle to TDC position. Factoring in a rocker ratio of 1.28 there will be interference. I hope I'm working this out wrongly.

Free drop on a Bullet valve is 5mm... it should be slightly less I imagine with a GT valve, because they are a little larger. I'm assuming you are factoring in your head and base gasket here ? Also.. If you measured from the outer rim of the lifter ? There is a mile of difference between the outer rim of the lifter and down to the cup where the ball end of the rod sits. I measure 1.6 mm there. Also... if you have a stock dished piston, when your intake valve opens, it should move in towards the dish, if it is like the Bullets. If you want be 100 % sure ? .... I'd Clay that motor.

Jako · **Reply #17 on:** March 12, 2019, 11:15:24 pm

Yes obviously I'm doing something wrong. GHG when I'm indicating from the outside of lifter I'm just measuring the cam lift from bottom to TDC to determine valve lift not pushrod length, so shouldn't make any difference should it ?

gashousegorilla · **Reply #18 on:** March 12, 2019, 11:25:24 pm

Quote from: Jako on March 12, 2019, 11:15:24 pm

Yes obviously I'm doing something wrong. GHG when I'm indicating from the outside of lifter I'm just measuring the cam lift from bottom to TDC to determine valve lift not pushrod length, so shouldn't make any difference should it ?

Lemme think about it ? Hahaha ! This is unconventional way of doing things !

Yes... lift is lift in this case. So it shouldn't make a difference.

I do think you are close Jako... And if I'm following your math correctly and in round numbers. Your piston is down in the hole at TDC .044"... measured around the outer edge of the piston. Your total valve lift at TDC is .131 "....so you need .087 " or there or about more room. If you look at the spec's on that Hitchcock sheet, they are checking the cam timing with 1 mm or .039" clearance. That's almost half the height of your .102 " cam at TDC . With Hydraulics pumped up or on that outer edge of the lifter , your going to see more lift at TDC then they show in that sheet. There is no clearance or lash with Hydraulics... I think they include that 1 mm as a fudge factor on the cam timing.Your cam timing is going to vary a little bit with Hydraulics, depending on when the lifter locks as it is going up the ramp. It would be MUCH more helpful if they gave their timing in both advertised and at .050 lift.

The dish depth on a Bullet piston at least, is...071 " Not sure if it is that same on the GT now ! So that's .016 " . I think it is going to depend on the valve angle and the dish in the piston. Whether or not the bottom of that valve clears that inner edge of the flat area around the piston and as it enters the dish. Again, clay is the way I think..

ace.cafe · **Reply #19 on:** March 13, 2019, 11:51:26 am

Okay, I did the multiplication wrong for the lift in my last post, and GHG gave the correct lift figure at TDC of .131" including the rocker ratio.

So, since the GT and UCE heads being the same, and GHG says 5mm(.198") free drop on a Bullet, that means .067" clearance around TDC.

Now, let's look at the valve being about .050" larger than a 500 valve, and figure a worst case of half that in your situation. Take .025" off your clearance margin, for a new figure of . .042" clearance around TDC.

And let's figure in another .020" lift in case piston dwell allows a little more lift on the valve before it starts going down. So, that takes clearance down to .022".

But, we have .040" crushed head gasket clearance with the head on, so we can add that back to the clearance margin, and get .062" which is the correct suggested clearance safety margin for an intake valve.

Remove .039"(1mm) for the 1mm clearance regimen that they use for timing specification, and get .023" for clearance. This is too small, but it won't hit the piston.

BTW , the reason Hitchcocks specified the cam timing at 1mm clearance is to simulate the timing figures at .040"(mm) which is the metric standard that is used in place of the US standard of valve timing specs at .050". Just a convention of measurement.

So, I concur with GHG to run a clay test to see actual clearance. What I would do first is put all the new parts in and do a very slow and careful rotation of the engine over TDC, and if you feel any resistance happen, like a valve touching, then back it off to relieve the touching. Then you know it touches. If it doesn't touch, the you have at least some amount of clearance.

You could put a clay disc that is .060" thick on the piston in the location where the intake valve will be closest. Put the head back on and turn the engine over TDC on the intake stroke. If there is no mark in the clay, you are good to go. If there is a mark, you need to measure how deep in the clay that the mark is.

In reality, rocker ratio is rarely as advertised. It is probably less.

If you run into a problem, just carefully grind a clearance relief into the piston where the valve would touch. Make it just deep enough to give .060" clearance, which is the accepted clearance safety margin for intake valves.

Always make pushrods preload less than the safety clearance margin, so if the lifters pump up from valve float, they cannot be pushed up enough to make the valve hit the piston.

Jako · **Reply #20 on:** March 13, 2019, 03:21:24 pm

Data base errors are killing me

Jako · **Reply #21 on:** March 13, 2019, 03:33:10 pm

Gaskets are included in all those calculations
Just redid the measurements .Valve drop is .068" I'm confident in that . Cam lift is difficult for me but again I placed dial indicator down onto lifter and rotated engine , lift started around 30 deg BTDC and reached .80" at TDC then increased to .100" before downward piston movement could be detected, this was repeated multiple times with consistent results.

Jako · **Reply #22 on:** March 13, 2019, 03:42:59 pm

With rocker ratio this will give between .102" and .128" valve lift at TDC
With gaskets in place squish is .044" and free valve drop of .068 for a total of .112" Ace is it safe to dremel a relief in the cast piston ? it shouldn't need much as it will run into the dished section . Also thinking of the Wossner forged piston with valve reliefs.
GHG the valve will catch the flat section of piston before it reaches the dish

ace.cafe · **Reply #23 on:** March 13, 2019, 03:57:44 pm

Yes, it is safe.
Just don't go deeper than you need to just get .060" clearance. The relief also needs to be wider than the actual valve because the valve does vibrate and flex some during operation. I would put about .020" extra side clearance in the relief to account for that.

The valve angle is about 26.5 degrees, so try to approximate that in the little half-moon shaped relief cut that you make in the piston crown. Soften all cut edges to prevent hot spots from forming.

Otto did it on his GT piston when he installed our head, and it came out fine with no drama. I don't think that you will have any trouble.

Jako · **Reply #24 on:** March 13, 2019, 04:09:00 pm

My calculation on valve lift wasn't to far off the money, I just got these figures from Allan at Hitchcock's

Jako · **Reply #25 on:** March 13, 2019, 04:54:42 pm

Thanks Ace , a relief seems to be the answer . So no need to check the exhaust clearance. ?

ace.cafe · **Reply #26 on:** March 13, 2019, 08:37:35 pm

Quote from: Jako on March 13, 2019, 04:54:42 pm

Thanks Ace , a relief seems to be the answer . So no need to check the exhaust clearance. ?

Might as well check, as long as you are doing all this anyway.
I haven't seen the need to worry about the exhaust, but our billet heads are so different that I can't tell you to not check. It probably won't need it, though.

If you find it closer than .100" for the exhaust, then make a relief for it that will give the .100" clearance. The recommended safety margin for exhaust valves is .100".

Tom

gashousegorilla · **Reply #27 on:** March 13, 2019, 10:12:04 pm

You can use lite weight checker springs installed temporarily and some clay at the same time for those valve reliefs Jako. You will see contact with the piston , and then measure the deflection on the valve stem... then add your .060 to that number . And in the clay, it will leave a starting pattern , so you know where to grind in . Mark the center of that pattern, then take your valve and center it on that mark.... line up the stem, then trace it out. You will find that the valve is not centered over the piston , the valves favor the right side of the motor.

Jako · **Reply #28 on:** March 17, 2019, 01:16:21 pm

Thanks Dan and Ace your knowledge is appreciated. Cut the valve relief in piston and engine is running , just waiting for a break in the heavy rain so we can road test . Hopefully the PCV map provided by Hitchcock's for these cams and mods will run OK .
On another topic do you have theories on why the exhaust valve guide would be totally worn out in only 4000 km ,I assumed it was from lean fueling but the engine shop guy thinks the piston would have been damaged if that was the case .He thinks it may have been faulty from the factory.

ace.cafe · **Reply #29 on:** March 17, 2019, 03:30:25 pm

Glad it worked out well for you.

Regarding the exhaust valve, the typical causes could be lack of oiling, bad geometry, or bad clearance set up during manufacture. Or any combination of those.

Overheating the valve would cause lack of oil(burnt off), so that may have been a contributor. Very often, the geometry of the rockers is pretty bad. We saw a lot of bad geometry in the Iron Barrel engine rockers with similar block system.

It was good to get that exhaust valve out of the engine before it failed. A lot of them fail.

gashousegorilla · **Reply #30 on:** March 17, 2019, 06:36:25 pm

Good deal and sweet bike Jako !

I'm thinking that PC-V Map you have for the Cams , may now be on the bit too rich side of things . Or at least in certain area's. With your now higher compression ratio, you are burning more efficiently and wont need quite as much fuel... a little less volume around TDC, valve maybe a little more shrouded and etc.

Yeah, the contact patch where the rocker pad rides on the valve tip may have been or still off. At full lift it may have been favoring one side or the other on the tip of the valve. Riding off the edge of it even. $:-\$ I would check that with your new valve job, or your guy may have already. He may have had to grind the tip of the valves, or work on those rocker pads a bit. I would also check the oil squirters on the rocker blocks and make sure they are clear. There are two on each ... one pointing at the valve stem and the other at the push rod tip. You can take a can or crab cleaner or WD 40 or Brake cleaner or some such.... and with the straw attached, blow in from the bottom oil passage of the rocker , and make sure they are clear . You can also see the spay pattern blowing out , to make sure it is directed to where it should be. WATCH your eye's !

Jako · **Reply #31 on:** March 20, 2019, 04:08:55 am

Got a short test ride in today, very impressed so far , seems to still have good torque throughout the range even though its running the bigger diameter header pipe . Hitting the rev limiter in 4th with ease . Haven't had a chance to open it out in top gear yet but it feels like it wants to get up and go. Fueling feels good everywhere except idle ,might need a little playing around there. Around town it still rides like a stock bike which is good . See supplied maps below, I was surprised to see so much fuel removed at the 100% throttle positions but it seems to really work well. Will be going on Dyno soon but the nearest dyno is a few hours from home.

gashousegorilla · **Reply #32 on:** March 21, 2019, 12:51:03 am

Yeah , interesting. The stock GT fueling is different then the Bullet, I'm sure. But I see similarity's there when Cams are installed. At 100% throttle up there in the top end, I usually find that fuel is added.. but not much more. Cam profile and how your intake is flowing... and the how stock fueling is will play a roll. A Vacuum gauge hooked up to the intake manifold would tell you though, at wide open throttle and at red line. Down low at idle and start up, in the smaller throttle openings and RPM's... yeah , similar to the Bullet's. You likely don't need as much fuel down there now with the bigger Cams. That's effecting your idle a bit I think. There is likely LESS manifold vacuum now... particularly at lower RPM"s and at idle. So less air flow down low ... less fuel. For your idle, I think you might need to pull a some fuel out between 500 and 1500 rpm's. When they create a canned map, they generally don't tune that 0 throttle position at idle. And depending on what your shooting for as far as air fuel ratio on a Dyno or with an auto tuner ?.... I would venture a guess , that a little more fuel would be taken out and it would perform a little better with your higher compression ratio. Anyway, I think it will be interesting to see after you get it on that Dyno.