Valve adjustment on…Linamar?

[WheelHorseVH 95]

Hey guys, couple of questions with pictures that follow. First, looks like my 520H has a Linamar LX790 in it. Was this possibly the factory original in the 1996 model because Onan was already taken over by Linamar? Or is this a replacement engine?

 

Second, I want to do the de-carbon and valve adjustment on this machine. I have the service manual from this site (for the P220G which I assume is the exact same as the LX790) and it shows the procedure fairly well. What I want to know is, how much disassembly is there and can it be done with the engine installed or does everyone pull the engine? It looks to me like quite a bit has to be removed. All tins, air cleaner, carb and intake (along with all linkages), exhaust, ignition module or coil, anything I missed?

 

Finally, please see pics below looking down from the top of the engine with the air cleaner assembly removed. The valve cover on the rear cylinder looks like it might have sat in the rain a few times before it found its forever home with me. Anything I should worry about with that?

 

I really want to do this job but want to make sure I do it right and am well prepared on how many hours it will take. Thanks in advance for the help and sorry for the long post.

 

[Ed Kennell 35,857]

I don't have any knowledge on the Linamar.    I was able to decarbon the P-220 in my '88 520H  without removing the engine.   It is a challenge on the rear cylinder, but can be done.

 

[RED-Z06 2,122]

The rear cylinder is tough to get at but with patience its doable in chassis.

 

To do the valve lash...its a task.

 

Pull the air filter box, the sheetmetal up top.  Youll need to pull the muffler and exhaust manifolds.  Once that's off, unclip the governor rod, and unhook the choke.  Then remove the intake manifold/carb.  Now you can get to the tappet covers.  Grab a gasket set online for the tappet covers, intake and exhaust..i usually put a thin coat of "the right stuff" on the intake and tappet cover gaskets for extra piece of mind.  Then reassemble.  Its a solid hour job once you've done it a few times.

[WheelHorseVH 95]

@RED-Z06 solid hour job for someone who has done it a few times would be like 4 hours for a newbie, no? Not too bad. Do I need a valve spring compressor tool? I ask because I know the lash adjustment does not but I have heard you should do intake seals while at it. Also what is the right stuff? Thank you.

[RED-Z06 2,122]

4 minutes ago, WheelHorseVH said:

@RED-Z06 solid hour job for someone who has done it a few times would be like 4 hours for a newbie, no? Not too bad. Do I need a valve spring compressor tool? I ask because I know the lash adjustment does not but I have heard you should do intake seals while at it. Also what is the right stuff? Thank you.

Cant say ive ever done valve seals on one but ive had to pull a valve once on one, i used a wrench for leverage.

 

 

[lynnmor 6,798]

The Linamar is the exact same engine, production was moved to Canada because of the emissions nonsense in the US.  I believe that you have a replacement engine.

 

I spend many hours to do the job right.  Check the compression before starting the work to see if additional work might be needed.  I have never encountered an Onan that really needed a decarbon, but I guess it happens.  Soak every fastener with penetrating oil repeatedly for days before disassembly.  A shop vac is useful for cleaning as you proceed.  Check the intake manifold for leaks where the two halves meet.  You might want to clean out the carburetor and replace the accelerator pump.  Glass bead the exhaust and paint it.  Paint the valve covers, as you can see they collect water.  If you are replacing the intake valve seals, be sure to plug the drain holes to prevent parts from falling inside the engine.  Be sure that you have a torque wrench suitable for the light torque specifications required.

[WheelHorseVH 95]

Cannot thank you guys enough for the continued support, first an update then a few questions. I disassembled more tonight. I am taking the time to clean surrounding areas and cover all holes tightly, like to carb and the crankcase vent. I am also thoroughly cleaning and repainting things I remove then bagging and labeling them. I have a gasket set on the way from onanparts.com so right now I am happy taking my time. Its really satisfying knowing that by the time I am ready to do the actual valve adjustment, there will be a whole bunch of clean and freshly painted parts (down to the bolt and screw heads) sitting in baggies ready to reassemble.

 

For my questions…

 

I confirmed that the exhaust bolts are not seized and will come out. Is it good practice to use new bolts for such a heat cycled part? Or is it ok to reuse them? How about intake? Regardless of the answer, should I use anti seize on any of them?

 

Thank you.

Edited February 29 by WheelHorseVH

[RED-Z06 2,122]

47 minutes ago, WheelHorseVH said:

Cannot thank you guys enough for the continued support, first an update then a few questions. I disassembled more tonight. I am taking the time to clean surrounding areas and cover all holes tightly, like to carb and the crankcase vent. I am also thoroughly cleaning and repainting things I remove then bagging and labeling them. I have a gasket set on the way from onanparts.com so right now I am happy taking my time. Its really satisfying knowing that by the time I am ready to do the actual valve adjustment, there will be a whole bunch of clean and freshly painted parts (down to the bolt and screw heads) sitting in baggies ready to reassemble.

 

For my questions…

 

I confirmed that the exhaust bolts are not seized and will come out. Is it good practice to use new bolts for such a heat cycled part? Or is it ok to reuse them? How about intake? Regardless of the answer, should I use anti seize on any of them?

 

Thank you.

If they are in good shape, wire wheel and reuse should be fine, ive used Stainless serrated flange bolts a few times when the old bolts were badly erroded from exhaust leaks, but ive never had one stick or break off on one...yet.  I dont use anti-sieze, you can, i dont personally on them.  Kohler commands i do, much smaller hardware prone to snapping off.

 

The only onan bolt ive ever had a problem with was head bolts, i usually run them down soft with my impact then finish them with a ratchet, just have a feel for them...the one time i used a torque wrench it pulled the threads out on a couple 

[lynnmor 6,798]

Onan calls for a drop of oil on the threads, anti-seize may cause the bolts to be over tightened and possible stripping.  If you use it, use your judgement and a much lower torque value.  I have had manifold threads in the block strip easily, my answer to that is to bottom tap the holes and use longer bolts. Check length without the washer first to be sure they won't bottom out, cut the new bolts for a custom fit.  It is good practice to run a tap in all holes to completely clean the threads.

[RED-Z06 2,122]

4 hours ago, lynnmor said:

Onan calls for a drop of oil on the threads, anti-seize may cause the bolts to be over tightened and possible stripping.  

Thats always been my fear, especially with aluminum blocks and smaller fasteners, you lose that "feel", and walk right past the yield point of the fastener or pull the threads.

[WheelHorseVH 95]

On 2/28/2024 at 5:23 AM, lynnmor said:

Check the intake manifold for leaks where the two halves meet.  You might want to clean out the carburetor and replace the accelerator pump.  

If the intake is leaky, do I use the right stuff form-a-gasket? And you reminded me, when I do a cold start, warm up a couple min, then try to gradually push the throttle up, it dies. I need to go up to full throttle fast and back down to sort of rev the engine a bit. Then it works fine when fully warm. Is that a bad accelerator pump or am I not letting it warm up enough?

[lynnmor 6,798]

I use MotoSeal 1 to seal the two intake manifold halves together.  It is of little value to just smear it on the surface, it needs to be used with the intake split and then screwed back together.  There is some information on this forum.  You can test for leaks by spraying a fuel on the intake while running and see if engine performance changes but I don't recommend living dangerously.  Another and safer test is to remove the intake and seal the carburetor mounting surface with a gasket and flat plate clamped in place, then invert and pour gas, kerosene or diesel fuel in intake to see if it leaks.

 

It does sound like you have a lean condition caused by restricted fuel or air leaks so check the manifold, vacuum hose and then the carburetor.  Debris in the carburetor or a bad accelerator pump (if equipped) are common problems.

[RED-Z06 2,122]

2 hours ago, WheelHorseVH said:

If the intake is leaky, do I use the right stuff form-a-gasket? And you reminded me, when I do a cold start, warm up a couple min, then try to gradually push the throttle up, it dies. I need to go up to full throttle fast and back down to sort of rev the engine a bit. Then it works fine when fully warm. Is that a bad accelerator pump or am I not letting it warm up enough?

I did mine last year, mine fell in half.  I used motoseal 1, drilled and tapped the intake, threaded in screws and nuts, fixed it up nice

 

https://www.wheelhorseforum.com/topic/102458-how-are-yall-fixing-onan-intake-manifolds/#comment-1121349

[WheelHorseVH 95]

Got my onanparts.com order of gaskets today. Kept working on disassembly and cleaning. Take a look at pic below and tell me what you think. I gently removed the exhaust and intake, vacuuming up before and after and putting in paper towels to protect from debris. 
 

The big thing I noticed was the carbon. Tons of it in the exhaust manifold, soft and as expected. However, caked and wetish on the back of the intake valve? Why would that happen? Does this mean i need to do a full decarbon? I was ready to abandon that for the valve lash and reassembly. 

[RED-Z06 2,122]

If yours is a "accelerator pump" style carb, they tended to run a shade rich, if you idle alot, youll get carbon built up.  Id personally just do the lash, run it...put a load on it, get it good and hot, help burn the carbon away

[lynnmor 6,798]

Carbon on the back side of the intake valve was likely caused by oil leaking past the valve seal.  It doesn't look too bad but if you want to fix it the heads need to come off to remove the valves.  Personally I would run it, even with new seals there will be some carbon buildup.

[lynnmor 6,798]

Another thread reminded me to tell you about the heat shields rubbing the intake manifold.  Remove some metal from the shields where the might touch so they don't eat into manifold.

 

[WheelHorseVH 95]

Got it, thank you for the additional mention on the tin, I will check that as well. Tonight I got the rear cylinder valves dialed in to spec: .005 on the intake and .013 on the exhaust. For both, I went by the manual and ensured that .002 over did not fit. I turned the engine one full rotation from each valve’s fully open position to take the tappet off the cam lobe but now wondering if 2 rotations would be better. I also did a lot more cleaning with the holes plugged, using a shop vac with a small crevice tool as you suggested, @lynnmor.
 

Ignore the 3x5 index cards, I was using them to act as valve covers. I used toothbrush sized brass and nylon brushes. All of the old fuel line was ripped out and is getting changed along with the filter. I also am putting in new vacuum lines going to the vacuum gauge and to the little air cleaner sensor. I know, I know…no one cares about either of those two things but I love getting things back to working order. I removed the valve covers, sanded the rust off and hit them with rust reformer flat black. The intake and carb got external cleaning, was extra gentle with them because I REALLY do not want to have to split the intake.
 

Perhaps a topic for another thread, but I see nothing special about that intake. Why did Onan not make it out of pipe stock with flanges? A longitudinally split aluminum casting held together by thin, peened “bosses”? What design standard were they following? I’m not even an engineer but it’s hard to imagine that no one raised their hand that day.

 

Questions I would appreciate input on:

 

What is the torque spec on valve covers? 
Should I use a dremel non-metal wheel of some sort to get ALL traces of gasket material off? You can see what I have in the picture.

A local shop will ceramic coat my exhaust and the heat shield above it for fairly cheap, like well under $200 but need 3 weeks on turnaround. Worth it?

 

Thanks as always guys. @lynnmor asking you questions and posting pictures of my progress is my way of giving back to Redsquare! People will always be able search and find your advice. Thank you sir, you are a font of knowledge.

[RED-Z06 2,122]

43 minutes ago, WheelHorseVH said:

Got it, thank you for the additional mention on the tin, I will check that as well. Tonight I got the rear cylinder valves dialed in to spec: .005 on the intake and .013 on the exhaust. For both, I went by the manual and ensured that .002 over did not fit. I turned the engine one full rotation from each valve’s fully open position to take the tappet off the cam lobe but now wondering if 2 rotations would be better. I also did a lot more cleaning with the holes plugged, using a shop vac with a small crevice tool as you suggested, @lynnmor.
 

Ignore the 3x5 index cards, I was using them to act as valve covers. I used toothbrush sized brass and nylon brushes. All of the old fuel line was ripped out and is getting changed along with the filter. I also am putting in new vacuum lines going to the vacuum gauge and to the little air cleaner sensor. I know, I know…no one cares about either of those two things but I love getting things back to working order. I removed the valve covers, sanded the rust off and hit them with rust reformer flat black. The intake and carb got external cleaning, was extra gentle with them because I REALLY do not want to have to split the intake.
 

Perhaps a topic for another thread, but I see nothing special about that intake. Why did Onan not make it out of pipe stock with flanges? A longitudinally split aluminum casting held together by thin, peened “bosses”? What design standard were they following? I’m not even an engineer but it’s hard to imagine that no one raised their hand that day.

 

Questions I would appreciate input on:

 

What is the torque spec on valve covers? 
Should I use a dremel non-metal wheel of some sort to get ALL traces of gasket material off? You can see what I have in the picture.

A local shop will ceramic coat my exhaust and the heat shield above it for fairly cheap, like well under $200 but need 3 weeks on turnaround. Worth it?

 

Thanks as always guys. @lynnmor asking you questions and posting pictures of my progress is my way of giving back to Redsquare! People will always be able search and find your advice. Thank you sir, you are a font of knowledge.

The intake is smooth inside, and has shaped turns for smooth flow, but its also designed to maintain velocity, long runners mean good torque, the small volume means fuel isnt apt to pool up at low speed.

[lynnmor 6,798]

Sounds like you are doing it right.  Two turns on the crank would get you right back to where you started, one turn like you did is perfect.  I hope you downloaded the Onan Service Manual the torque specs are in there.

 

Don't be afraid to pop the top off the carburetor, often the gasket can be reused.  With the top off you can flush out any debris collected in there.  It is possible to dislodge some debris from doing your work and there is nothing like pulling it all back apart after you had it running.

 

The flat intake was likely designed to keep engine height to a minimum.  If you test the intake for leaks and it has none, I wouldn't split it.  I finish all flat surfaces with a 8" good quality mill file kept flat on the part, of course one needs to be very careful to not do damage with it.  A rotary tool is something that I would not use.

 

I use Rustoleum High Heat spray paint on the exhaust, I find it better that some expensive header paint.  Of course the ceramic coating you propose should be better, but I find that the Rustoleum is good enough, YMMV.  I use Dupli-Color Engine Paint with Ceramic Semi-Gloss DE1635 for all of the engine tins.

 

That little air filter sensor often fails because of the nipple breaking off from the heavy factory vacuum hose, find a thin, lightweight and flexible hose to protect it.

 

 

[RED-Z06 2,122]

Of all the hi temp paints ive tried; the only one ive used that lasts is this stuff, my exhaust can glow and this stuff hangs right in there, and resists rust.  Do a good prep, strip it clean then good wipedown with a degreaser, ill usually warm the exhaust with a torch  prior then do a couple even coats.  Give it a couple hours then a short run at part throttle to get it to the smoke point, then let it cool, then run it full power...and fully cure.

 

PJ1 16-HIT Flat Black Hi-Temp Spray Paint (Aerosol), 12 oz https://a.co/d/if9Ue0O

[WheelHorseVH 95]

@RED-Z06 thanks for your suggestions. I have “the right stuff” on the way now for a thin layer on the gaskets for valve covers and intake. Do you put a thin layer on both sides of the gasket or just one? If just one, flange side or engine side?

 

@lynnmor I actually sent the manual to my local Staples yesterday and got it printed and spiral bound for $17 so I can have it in the garage with me. Picked up lightweight hose for the vacuum sensor and will tie a small gauge wire around it to keep it on the nipple.

 

All valves now are set to spec. They were all tight, is that weird? I guess I would expect them to require tightening over time, not loosening. Anyway, I removed the packing from the crankcase breather and checked it out and it looked fine. Like a stainless steel brillow pad, clean. So I repacked it and closed it up. 
 

I absolutely hate the pre-insulated crimp connectors you get at your local auto parts store so I’m chopping these terminals (in pic) off of the wires going to the ignition coil and going to re-do them with heavy gauge open barrel ring terminals that grab the insulation and the conductor like a factory crimp. I did this to my 1973 VW a couple years ago and haven’t worried about one coming loose since.

 

The big thing I did tonight was the worst idea I have had. Earlier in the day I sprayed the Rustoleum rust converter gel all over my muffler, having abandoned the idea of a full ceramic coat and gone towards using the rustoleum hi heat paint. They tell you not to let it dry but I messed up and I left it on a little too long. Came out to the garage and my muffler was a mess. Runny, tarry slime combined with a hard crystalized white coating. I did this because I don’t have a blaster and couldn’t find anyone near me to do it fast. So tonight I sat there and hand sanded and dremeled the thing and then primered with rustoleum hi heat primer.

 

I didn’t take any pictures but I should have. Right now I would gladly go back and pay the money to have it blasted and coated for me. Not a fun task if you don’t have access to a sandblaster, even one of the little suction types I used to have.
 

I will continue posting here til I am done with this task in case this helps anyone instead of me just only taking from this forum. Thanks guys.

[RED-Z06 2,122]

1 hour ago, WheelHorseVH said:

@RED-Z06 thanks for your suggestions. I have “the right stuff” on the way now for a thin layer on the gaskets for valve covers and intake. Do you put a thin layer on both sides of the gasket or just one? If just one, flange side or engine side?

 

@lynnmor I actually sent the manual to my local Staples yesterday and got it printed and spiral bound for $17 so I can have it in the garage with me. Picked up lightweight hose for the vacuum sensor and will tie a small gauge wire around it to keep it on the nipple.

 

All valves now are set to spec. They were all tight, is that weird? I guess I would expect them to require tightening over time, not loosening. Anyway, I removed the packing from the crankcase breather and checked it out and it looked fine. Like a stainless steel brillow pad, clean. So I repacked it and closed it up. 
 

I absolutely hate the pre-insulated crimp connectors you get at your local auto parts store so I’m chopping these terminals (in pic) off of the wires going to the ignition coil and going to re-do them with heavy gauge open barrel ring terminals that grab the insulation and the conductor like a factory crimp. I did this to my 1973 VW a couple years ago and haven’t worried about one coming loose since.

 

The big thing I did tonight was the worst idea I have had. Earlier in the day I sprayed the Rustoleum rust converter gel all over my muffler, having abandoned the idea of a full ceramic coat and gone towards using the rustoleum hi heat paint. They tell you not to let it dry but I messed up and I left it on a little too long. Came out to the garage and my muffler was a mess. Runny, tarry slime combined with a hard crystalized white coating. I did this because I don’t have a blaster and couldn’t find anyone near me to do it fast. So tonight I sat there and hand sanded and dremeled the thing and then primered with rustoleum hi heat primer.

 

I didn’t take any pictures but I should have. Right now I would gladly go back and pay the money to have it blasted and coated for me. Not a fun task if you don’t have access to a sandblaster, even one of the little suction types I used to have.
 

I will continue posting here til I am done with this task in case this helps anyone instead of me just only taking from this forum. Thanks guys.

I will usually clean the cover really well, and apply the right stuff to the block, and put the gasket down, then put the cover on..this should allow future removals without ripping the gasket, the block side is more apt to have porosity or imperfections.

[RED-Z06 2,122]

Tight valves is indicative of valve stretch, and/or seat wear pretty normal to find, its good to address the lack of lash before it burns a valve.

[WheelHorseVH 95]

Man I am excited and a bit disappointed. More on that below.

 

Tonight I got it all put back together again, pics are below. Turns out my wife getting pissed about losing her parking spot in the garage made me stop taking my time and get it done. You can see the valve covers with rust removed and protected with flat black rust reformer. Everything got cleaned up with a brass toothbrush at least and shop vacuumed, down to the wire sheath that runs strewn over the block, under the intake and exhaust…which doesn’t exactly make sense to me from a design perspective. @lynnmor, @RED-Z06 not sure if you gents have an explanation for that?

 

I added about half a quart of 30W since it was low on the dipstick. Gently ran a tap through the intake and exhaust bolt holes and ran the bolts themselves through a wire wheel and a die because there was just a tiny bit of raised stuff that the wheel didn’t get. Torqued everything down to spec. My stainless steel exhaust shield and pan head screws were browned so I got new screws and polished out the shield which now looks like new. The exhaust heat shield and exhaust got a coat of high heat primer and paint as I mentioned previously, pics also below. Please note that the pics were taken wet, the real finish is flat black, not glossy.
 

Got the carb linkages back on. Popped on the air cleaner assembly, put the battery back in. Attached brand new fuel lines, fuel filter, vacuum line to the gauge, and thinner vacuum line to the air cleaner sensor so it doesnt break off as @lynnmor mentioned.
 

Then I started it up. As soon as it started running, I could tell that it was just quieter. It was revving high but clean. I just could not figure out why it was idling at 1800 with no choke. I checked out the linkages to make sure nothing was binding and it wasn’t. Then late tonight I figured it out by zooming in on one of my carb pics. I had the governor linkage set to the wrong hole on the carb. So I just finished taking a whole bunch of stuff apart to redo that and am sure it is correct. It is in alignment with the Onan manual in that I used the arm hole in the governor that aligns with WOT on the carb.

 

I got it all back together again just now. The bad part is that it’s too late to actually run it again tonight without disturbing the neighbors or my wife so tomorrow first chance I get, I am going out to start the horse. But I will say, I have never seen a cleaner motor!