head recession and valve clearance


glen english LIST
 

To cut a long story short-
1) rear two cylinders of a late Gen3 3300 (roller, hydra) have about some head recession around the lower bolt. ~0.2mm
2) fully contracted hydra lifters have only approx 0 to 0.5 mm of cold clearance on the valves.
3) the clearance on the rear cylinders was negative , causing valves to not fully close and fail leakdown during initial reassembly.
4) the depth of the spherical socket in the rocker (that the push rod goes into) is found to vary ~ 0.2mm
5) high clearance rockers (deep push rod sockets) were swapped with low clearance rockers (shallow sockets) , and now the rear valves in the rear cylinders close. just. makes leakdown.
6) previous owner/maint lapped EX valve #6 30 hours ago, reducing material available.

Solutions ? (yes it is OK right now, but it is hairy edge)
1) increase depth of spherical sockets in shallow rockers
2) change push rod lengths
3) 0.25mm shim under head-cylinder interface
4) mill head interface flat and shim .(better)

-glen


Jay Scheevel
 

Have you measured the pushrod lengths ?

I would be inclined to shorten pushrods. Least invasive. If you shorten you will need to harden the new rounded and polished end. There is a groove in the lifter end of each rod. Need to make sure not to shorten that end so to allow the lifter to bleed off.

Jay

On Apr 25, 2021, at 5:59 PM, glen english LIST <glenlist@cortexrf.com.au> wrote:

To cut a long story short-
1) rear two cylinders of a late Gen3 3300 (roller, hydra) have about some head recession around the lower bolt. ~0.2mm
2) fully contracted hydra lifters have only approx 0 to 0.5 mm of cold clearance on the valves.
3) the clearance on the rear cylinders was negative , causing valves to not fully close and fail leakdown during initial reassembly.
4) the depth of the spherical socket in the rocker (that the push rod goes into) is found to vary ~ 0.2mm
5) high clearance rockers (deep push rod sockets) were swapped with low clearance rockers (shallow sockets) , and now the rear valves in the rear cylinders close. just. makes leakdown.
6) previous owner/maint lapped EX valve #6 30 hours ago, reducing material available.

Solutions ? (yes it is OK right now, but it is hairy edge)
1) increase depth of spherical sockets in shallow rockers
2) change push rod lengths
3) 0.25mm shim under head-cylinder interface
4) mill head interface flat and shim .(better)

-glen





glen english LIST
 

Hi Jay
thanks for the message .
pushrods are all identical. and apparently is problem is very common.

a couple of others have said the best fix is pushrod length change.

they cut the tube down and reattach the end ? I am getting details .

On 4/26/2021 11:24 AM, Jay Scheevel wrote:
Have you measured the pushrod lengths ?
I would be inclined to shorten pushrods. Least invasive. If you shorten you will need to harden the new rounded and polished end. There is a groove in the lifter end of each rod. Need to make sure not to shorten that end so to allow the lifter to bleed off.
Jay


glen english LIST
 

interesting, the book says for my engine
"Again, the 215mm long part is recommended."

mine are all 217.

On 4/26/2021 11:24 AM, Jay Scheevel wrote:
Have you measured the pushrod lengths ?
I would be inclined to shorten pushrods. Least invasive. If you shorten you will need to harden the new rounded and polished end. There is a groove in the lifter end of each rod. Need to make sure not to shorten that end so to allow the lifter to bleed off.


Jay Scheevel
 

This is correct. There was an unpublished change in solid pushrod length that only the dealers were aware of. I was made aware of it during a phone conversation about another topic with Pete K (now retired Jabiru USA dealer). I shortened my pushrods, but ended up replacing the hydraulic lifters with solid lifters instead. I think the new rod length was 2mm shorter but I cannot swear to that. I still have them and if you want me to measure them I can do that.

Jay

On Apr 25, 2021, at 8:24 PM, glen english LIST <glenlist@cortexrf.com.au> wrote:

interesting, the book says for my engine
"Again, the 215mm long part is recommended."

mine are all 217.

On 4/26/2021 11:24 AM, Jay Scheevel wrote:
Have you measured the pushrod lengths ?
I would be inclined to shorten pushrods. Least invasive. If you shorten you will need to harden the new rounded and polished end. There is a groove in the lifter end of each rod. Need to make sure not to shorten that end so to allow the lifter to bleed off.




wmax351@...
 

What solid lifters did you use? Were they just the standard chevy small block ones? 


Jay Scheevel
 

I used the Camit conversion kit, which is no longer available. I believe that kit used a chevy solid lifter (as well as Camit rockers and hollow pushrods). I could not tell you this was a chevy lifter for certain, nor what the dimensions are. I can only say that one jabiru owner in the past used an off the shelf chevy lifter and it turned out to be slightly oversized which apparently led to premature spaulling of the cam lobe, so if you do make the change, you will need to purchase adjustable rockers and make sure the OD of the solid lifter you use is consistent with the OD of the hydraulic lifter you are replacing.

 

Jay

 

From: main@JabCamit.groups.io <main@JabCamit.groups.io> On Behalf Of wmax351@...
Sent: Monday, April 26, 2021 12:42 PM
To: main@JabCamit.groups.io
Subject: Re: [JabCamit] head recession and valve clearance

 

What solid lifters did you use? Were they just the standard chevy small block ones? 


David Amsler
 

Some time back in the dark ages, recall reading an article by someone in France who used a stock hydraulic lifter converted to solid, vaguely recall that it was from a Toyota, but not sure.  My CAMit drop-in retrofit lifters looked like that may have once been hydraulic lifters.

David A.

On Mon, Apr 26, 2021 at 4:35 PM Jay Scheevel <jay@...> wrote:

I used the Camit conversion kit, which is no longer available. I believe that kit used a chevy solid lifter (as well as Camit rockers and hollow pushrods). I could not tell you this was a chevy lifter for certain, nor what the dimensions are. I can only say that one jabiru owner in the past used an off the shelf chevy lifter and it turned out to be slightly oversized which apparently led to premature spaulling of the cam lobe, so if you do make the change, you will need to purchase adjustable rockers and make sure the OD of the solid lifter you use is consistent with the OD of the hydraulic lifter you are replacing.

 

Jay

 

From: main@JabCamit.groups.io <main@JabCamit.groups.io> On Behalf Of wmax351@...
Sent: Monday, April 26, 2021 12:42 PM
To: main@JabCamit.groups.io
Subject: Re: [JabCamit] head recession and valve clearance

 

What solid lifters did you use? Were they just the standard chevy small block ones? 


glen english LIST
 

why do people hate hydraulic lifters so much ?

if the rocker clearances are adjusted about 0.5mm from end stop (rocker fully bled and compressed) , even if the spring breaks the ball wont fall out of the socket at the rocker end.

On 27/04/2021 6:43 am, David Amsler wrote:
Some time back in the dark ages, recall reading an article by someone in France who used a stock hydraulic lifter converted to solid, vaguely recall that it was from a Toyota, but not sure.  My CAMit drop-in retrofit lifters looked like that may have once been hydraulic lifters.


Jay Scheevel
 

Hi David,

 

We had the same conversion unit. I thought that they looked that way too, but then when I researched online source of solid lifters, I found that those have the same appearance. The fooler was that the conduit for the oil to reach the hollow push rod looks identical. Here is a link to a source of solid GM lifters. https://www.summitracing.com/parts/cro-66900-12

 

Here is a photo of what we installed (from Camit), which is very similar

 

Dark ages…that’s funny, I must still be living in the dark ages.

 

Cheers,

Jay

 

From: main@JabCamit.groups.io <main@JabCamit.groups.io> On Behalf Of David Amsler
Sent: Monday, April 26, 2021 2:44 PM
To: main@jabcamit.groups.io
Subject: Re: [JabCamit] head recession and valve clearance

 

Some time back in the dark ages, recall reading an article by someone in France who used a stock hydraulic lifter converted to solid, vaguely recall that it was from a Toyota, but not sure.  My CAMit drop-in retrofit lifters looked like that may have once been hydraulic lifters.

 

David A.

 

On Mon, Apr 26, 2021 at 4:35 PM Jay Scheevel <jay@...> wrote:

I used the Camit conversion kit, which is no longer available. I believe that kit used a chevy solid lifter (as well as Camit rockers and hollow pushrods). I could not tell you this was a chevy lifter for certain, nor what the dimensions are. I can only say that one jabiru owner in the past used an off the shelf chevy lifter and it turned out to be slightly oversized which apparently led to premature spaulling of the cam lobe, so if you do make the change, you will need to purchase adjustable rockers and make sure the OD of the solid lifter you use is consistent with the OD of the hydraulic lifter you are replacing.

 

Jay

 

From: main@JabCamit.groups.io <main@JabCamit.groups.io> On Behalf Of wmax351@...
Sent: Monday, April 26, 2021 12:42 PM
To: main@JabCamit.groups.io
Subject: Re: [JabCamit] head recession and valve clearance

 

What solid lifters did you use? Were they just the standard chevy small block ones? 


Jay Scheevel
 

I don't think anyone said anything about hating hydraulic lifters. The problem is that Jabiru did a poor job engineering their hydraulic lifter system, at least in the Gen 3, non-roller version, so a fix was needed.

Jay

-----Original Message-----
From: main@JabCamit.groups.io <main@JabCamit.groups.io> On Behalf Of glen english LIST
Sent: Monday, April 26, 2021 2:57 PM
To: main@JabCamit.groups.io
Subject: Re: [JabCamit] head recession and valve clearance

why do people hate hydraulic lifters so much ?

if the rocker clearances are adjusted about 0.5mm from end stop (rocker fully bled and compressed) , even if the spring breaks the ball wont fall out of the socket at the rocker end.

On 27/04/2021 6:43 am, David Amsler wrote:
Some time back in the dark ages, recall reading an article by someone
in France who used a stock hydraulic lifter converted to solid,
vaguely recall that it was from a Toyota, but not sure. My CAMit
drop-in retrofit lifters looked like that may have once been hydraulic
lifters.


glen english LIST
 

ahhh OK. I have roller hydras.

So I am told that engines of my gen, the push rod ends are press fit on and can be removed and the rod shortened.

I need about 0.5 to 1mm.

On 27/04/2021 7:03 am, Jay Scheevel wrote:
I don't think anyone said anything about hating hydraulic lifters. The problem is that Jabiru did a poor job engineering their hydraulic lifter system, at least in the Gen 3, non-roller version, so a fix was needed.


Ron Milan
 

Glen:  I can tell you that the cam shaft lobe profile for a hydraulic lifter characteristically is an accelerated ramp where by the solid lifter uses a constant velocity lobe profile.  Back "in the day" one could get a bit more power from the solid lifter engine.  Many of the folks on this list have commented that they feel that they experienced an engine performance gain with the switch to the solid lifters keeping all other engine related parameters the same.

In our application I am not convinced that we are as concerned with the last morsel of power as much as we are with reliability (hence Jay's comments in the previous post).   There is definitely more regularly required maintenance with the solid lifter valve train---ONE MUST ADJUST THE VALVES!   This is even more prominent in our horizontally opposed air cooled engine design. There is also a potentially accompanied gain achieved by a warning that if the valve clearance has changed a great deal one should be alarmed (THIS WOULD BE INDICATIVE OF AN INTERNAL ENGINE PROBLEM).  This potential wear clearance is often masked by the somewhat generous lash adjustment of the hydraulic lifter valve-train and ONLY shows up after a significant amount of wear has occurred which has exceeded the lash adjustment capability.  

Today's hydraulic roller valve trains offer a tremendous amount of power gain.  The camshaft lobe profile can be VERY accelerated, thus allowing a longer duration of valve opening and potential power gain without sacrificing longevity of the valve-train components involved.  This phenomenon was touted by Pete Krotje during an  interview with Dan Johnson.  Pete touted better climb performance, smoother engine idle and other positives with the "NEW" hydraulic roller tappet gen-3 engines.   I know that back in the day we could gain the most performance with the use of roller tappet/roller valve train components.  Today's automobile manufacturers have mostly, if not exclusively, employed the use of roller valve-train components---for what this is worth.  Many of these automobile engine manufacturers have used a fully roller valve train with not only roller tappets but also roller rocker arms that use not only a roller at the valve stem; but, also use needle bearings where they articulate on their respective rocker arm shaft.  I believe that Jabiru still uses a bronze bushing on the rocker arm shaft and no roller at the valve stem end?  Someone update me if I am behind the times here!

Anyway, I did get a bit of air time today social distancing at 4500' MSL.  I had blue skies and <5 mph wind so the flight behind my 3300 Jabiru was a success.  My oil level was exactly on full during my post flight check and I have little to complain about with my hydraulic flat tappet 3300A engine so far.  I am however starting to notice an occasional oil drop forming about the right distributor area (shaft seal?) I will have to do further investigation at some point in the not too distant future.

All stay safe,  and hopefully have calm air or only a tail wind with blue skies.  

Ron M


-----Original Message-----
From: glen english LIST <glenlist@...>
To: main@JabCamit.groups.io
Sent: Mon, Apr 26, 2021 5:07 pm
Subject: Re: [JabCamit] head recession and valve clearance

ahhh OK. I have roller hydras.

So I am told that engines of my gen, the push rod ends are press fit on
and can be removed and the rod shortened.

I need about 0.5 to 1mm.


On 27/04/2021 7:03 am, Jay Scheevel wrote:
> I don't think anyone said anything about hating hydraulic lifters. The problem is that Jabiru did a poor job engineering their hydraulic lifter system, at least in the Gen 3, non-roller version, so a fix was needed.
>






glen english LIST
 

Hi Ron
thanks for the write up, the story and hostory you metnion is most interesting.
I come from an era and experience of Nissan/Datsuns and overhead cams, so push rods, lifters etc are all new to me .

The roller + hydraulic lifter is a super superior mechanical solution IMO.

The point about the cam lobe profile is different is a really good point, since there is a 2nd order function working in there- the spring rate of the resultant system.

While the hydra permits a load of slop, if the lifter should fail and return to a fully compressed maximum clearance position, , enough clerance could develop such that the ball end falls out. trouble from there on.
For that reason, I'll choose to set my system up for no more than 1mm compressed/bled valve clearance. Given the mechanical advantage of the rocker, that has the lift 0.6mm out from fully compressed posiiton.

Interesting that Jabiru suggest 0.2 to 0.3 COLD clearance for solid lifters, but no spec for hydraulic lifters. The 0.3mm COLD has some wiggle room for wear and thermal expansion .

I renewed my bushes and lost about 0.1mm on the rockers, also.

I'll need to get my push rod lengths sorted on a couple of cylinders.
Interesting that jab went from 217 to 215mm. That in my engine would leave a mile of slop and clearance (certain chance of bending something) if the lifter failed with 2mm of clearance available between the rod end and the ball socket.....

**********
TALKing about bushes- in the latest GEN4 revision, the bushes are gone- now roller needle bearings on a 10mm rocker shaft.....There was a string of bush failures... But no roller at the valve stem end, to my knowledge.
******

On 4/27/2021 12:10 PM, Ron Milan via groups.io wrote:
Glen:  I can tell you that the cam shaft lobe profile for a hydraulic lifter characteristically is an accelerated ramp where by the solid lifter uses a constant velocity lobe profile.  Back "in the day" one could get a bit more power from the solid lifter engine.  Many of the folks on this list have commented that they feel that they experienced an engine performance gain with the switch to the solid lifters keeping all other engine related parameters the same.
In our application I am not convinced that we are as concerned with the last morsel of power as much as we are with reliability (hence Jay's comments in the previous post).   There is definitely more regularly required maintenance with the solid lifter valve train---ONE MUST ADJUST THE VALVES!   This is even more prominent in our horizontally opposed air cooled engine design. There is also a potentially accompanied gain achieved by a warning that if the valve clearance has changed a great deal one should be alarmed (THIS WOULD BE INDICATIVE OF AN INTERNAL ENGINE PROBLEM).  This potential wear clearance is often masked by the somewhat generous lash adjustment of the hydraulic lifter valve-train and ONLY shows up after a significant amount of wear has occurred which has exceeded the lash adjustment capability.
Today's hydraulic roller valve trains offer a tremendous amount of power gain.  The camshaft lobe profile can be VERY accelerated, thus allowing a longer duration of valve opening and potential power gain without sacrificing longevity of the valve-train components involved.  This phenomenon was touted by Pete Krotje during an  interview with Dan Johnson.  Pete touted better climb performance, smoother engine idle and other positives with the "NEW" hydraulic roller tappet gen-3 engines.  I know that back in the day we could gain the most performance with the use of roller tappet/roller valve train components.  Today's automobile manufacturers have mostly, if not exclusively, employed the use of roller valve-train components---for what this is worth.  Many of these automobile engine manufacturers have used a fully roller valve train with not only roller tappets but also roller rocker arms that use not only a roller at the valve stem; but, also use needle bearings where they articulate on their respective rocker arm shaft.  I believe that Jabiru still uses a bronze bushing on the rocker arm shaft and no roller at the valve stem end?  Someone update me if I am behind the times here!
Anyway, I did get a bit of air time today social distancing at 4500' MSL.  I had blue skies and <5 mph wind so the flight behind my 3300 Jabiru was a success.  My oil level was exactly on full during my post flight check and I have little to complain about with my hydraulic flat tappet 3300A engine so far.  I am however starting to notice an occasional oil drop forming about the right distributor area (shaft seal?) I will have to do further investigation at some point in the not too distant future.
All stay safe,  and hopefully have calm air or only a tail wind with blue skies.
Ron M


wmax351@...
 

I'm wondering if this might be ideal: pressurized oil feed to the cam lobes from the solid lifters.
https://www.summitracing.com/parts/hrs-91118-1/make/chevrolet


edmund@...
 

The CAMit conversions kits are available..... From Kevin in the UK.
--
Jabiru SK G-EWBC  Builder/Owner with CAMit 2200 and GT Propeller


David Amsler
 

When I installed Ian's CAMit drop in solid lifter conversion in my 3300, about 8 years ago, the camshaft was left the same and got about a 15% power increase, which Ian said was typical.

It was noted at the time that the smaller tappet surface area of the hydraulic lifters and the drop in conversion lifers was too small for the cam profile and the cam would ride the outside edge of those lifters for part of the cycle which is why those lifters developed burrs on outside edge that the manual said to remove when survicing them.  The real solid lifters had a larger tappet surface.

David A.

On Tue, Apr 27, 2021 at 7:08 AM edmund via groups.io <edmund=comberfamily.co.uk@groups.io> wrote:
The CAMit conversions kits are available..... From Kevin in the UK.
--
Jabiru SK G-EWBC  Builder/Owner with CAMit 2200 and GT Propeller


wmax351@...
 

" I can only say that one jabiru owner in the past used an off the shelf chevy lifter and it turned out to be slightly oversized which apparently led to premature spaulling of the cam lobe, so if you do make the change, you will need to purchase adjustable rockers and make sure the OD of the solid lifter you use is consistent with the OD of the hydraulic lifter you are replacing. "

Looking at the clearance specs in the overhaul manual, it appears that with the maximum lifter/lifter bore clearance allowable, puts the minimum lifter diameter of 0.836. The actual bore should be 0.8433-0.8441, so that is on the tight end if the lifters really are 0.842.

Does anyone have a lifter out that they can measure? 


Ron Milan
 

David: Your noted  power increase seems to consistently common, I can always appreciate a power increase myself as long as it is NOT at the expense of reliability or longevity.  

I am however confused by your verbiage of "drop in" and limited lifter diameter.  The original JABIRU solid lifter engines required that the lifters be placed (inserted) in their respective engine case half bores prior to mating the two haves together.  This was because these solid "lifters" were of mushroom design with the cam shaft lobe mating surface being of much larger diameter than the portion of the lifter that reciprocates in the bore(s) of the engine case.  

When Jabiru migrated to using the hydraulic lifters, they utilized a lifter design where the body of the lifter was completely consistent from top to bottom.  The design was completely parallel, thus the lifter had the advantage of being able to be inserted from the outside of the assembled engine.  This design is analogous to the Chevrolet Corvair design and that of many other common engine manufacturers.  The small Briggs & Stratton air cooled in valve flat head engines utilized the mushroom design requiring that the lifters be installed into the engine prior to final assembly or camshaft install pending on the style of engine.  This design is not totally uncommon, seemingly more common in the air cooled engine world.

I cannot visualize how any "drop in" replacement could have any larger base than that of the original parallel bodied lifters.   If I correctly understand your post, any lifter would be too small to properly mate with the lobes of the camshaft?   Engine manufacturers do purposefully design the lifter/lobe mating so that the lobe is offset from the center of the lifter thus causing lifter(s) to rotate in their bore(s).  Roller tappets are centered over each camshaft lobe and they are necessarily locked from rotation.   I most prefer this roller design and only wish that I has a roller tappet set-up in my JABIRU, I feel that this is superior to any solid lifter design (the mushroom design of yesteryear or a drop-in replacement design from CAMIT today).  

If I correctly understand your post; any lifter (original "hydraulic" or "solid lifter drop in" replacement) utilized in an engine of the flat tappet hydraulic era design will suffer edge wear because of the design flaw of too much lobe to lifter offset?

Please clear this up for me!

Thank you,
Ron M


-----Original Message-----
From: David Amsler <EnergyHawk@...>
To: main@...
Sent: Tue, Apr 27, 2021 7:45 am
Subject: Re: [JabCamit] head recession and valve clearance

When I installed Ian's CAMit drop in solid lifter conversion in my 3300, about 8 years ago, the camshaft was left the same and got about a 15% power increase, which Ian said was typical.

It was noted at the time that the smaller tappet surface area of the hydraulic lifters and the drop in conversion lifers was too small for the cam profile and the cam would ride the outside edge of those lifters for part of the cycle which is why those lifters developed burrs on outside edge that the manual said to remove when survicing them.  The real solid lifters had a larger tappet surface.

David A.

On Tue, Apr 27, 2021 at 7:08 AM edmund via groups.io <edmund=comberfamily.co.uk@groups.io> wrote:
The CAMit conversions kits are available..... From Kevin in the UK.
--
Jabiru SK G-EWBC  Builder/Owner with CAMit 2200 and GT Propeller


wmax351@...
 

"It was noted at the time that the smaller tappet surface area of the hydraulic lifters and the drop in conversion lifers was too small for the cam profile and the cam would ride the outside edge of those lifters for part of the cycle"

This is what Kevin told me. So that problem exists with the hydraulic lifters as well.

From what I've read, the chevy lifters seem to have a range of 0.841-0.843. And the clearance for the lifters on a car engine is generally 0.003" at most. The 0.19mm/0.0075" maximum clearance specified by jabiru is quite a bit larger.