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I don't know if I've asked or read about this but some info in a response Mark Parker made about his valve clearances in his all alloy engine had me wondering.

If a cam manufacturer asks for .010" cold clearance for say a Triumph 650 750 performance cam, are they expecting or would they like to see this same .010" when the engine is hot? So many variables could change this dimension from heat expansion in a stock vs. modified engine that I can't see this spec not changing between engines. Would it be safe to assume that the cam manufacturer designed the cams ramps etc. around the .010" and the only way to insure this would be to come back and set the lash hot? Otherwise, whether one used iron vs. alloy barrels or steel vs. alloy pushrods would determine what lash one ended up with hot. I've never checked a Triumphs lash hot when using a performance cam so don't know. Thoughts? Mark R.

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High performance US auto engines with mechanical lifters always are lash adjusted hot..The engine is only cold for a short time so it only matters if the lash is reasonable when not warmed up...
I think it's safe to say do check the Triumph clearance fully warmed up, set it to minimum clearance, then do a cold check ....Then you will know for sure, any other opinions on this are meaningless unless comparisons have been made


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I always thought the standard was to set the valves in liquid cooled engines at operating temperature and the valves in air cooled engines cold.
I remember back in the day every VW shop had big fans to get the engine cool enough to set the valves during tuneups.


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Yes VW is normally set cold as are some other air and liquid cooled pushrod engines.I'm just suggesting to check it cold and hot to see what goes on. In my mind what goes on with a fully warmed engine is most important...


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Hillbilly...what you say makes sense to me since it only really matters when the engine is up to temp as long as the valves have some clearance cold to maintain compression.

David your thoughts are sort of what I always assumed but until recently I didn't think real hard about it but if a cam maker says set the lash at .010" cold is he assuming that it will stay at .010" when the engine is hot? Is this what they want to see? Is the stated lash important to the cams performance and perhaps longevity? An what about changing to an alloy barrel or steel rods like Mr. Parker did...he said he now has to set his cold clearances at zero to get them within spec when hot.

I guess maybe the question should go to the cam maker...I've seen .002-.004-.006-.008 & .010" clearances on just Triumph twins. .010" clearance on a 650 intake that requires .002" will make for a noisy engine and more tappet and valve wear so the specs must be important to the cams design and all.

Going back to what Hillbilly said makes the most sense, I've just never heard anyone mentioning it or at least I never paid attention until recently. Maybe I'll have to call a cam grinder and hear what they have to say, what I'd like to hear is that no matter what construction of your engine and it's expansion cold vs. hot considerations...we want to see 'X' clearance when to running temp. Anything else would seem to be doing a lot of assuming, right?

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The manufacturer assumes that everything is at it came from the factory when recommending valve clearances. I don't presume to know why Triumph recommends 0.002" and 0.004" on 650 twins but 0.006" and 0.008" on triples, much less why BSA specs 0.008" and 0.010" on A65, but I assume that the clearances tighten up with heat.
The last time I assumed anything was with a '78 Bus engine. I assumed that it came with the stock hydraulic valve lifters, until it pulled a seat out of a head because I hadn't checked clearances.


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Ok David, I went and googled some VW forum on the Vanagan and then a performance VW parts source and found some interesting info. Their alloy performance pushrods were made of 3/8" dia., .090" wall 2024 T3 and said to have expansion rate such that when the valves were set cold at .006" the hot lash would end up at .002". They went on to say if using chromoly push rods on these engines (solid lifter) the lash would need to be set cold at near zero and would open up to around a clattery .020" when hot. The same source sold chromoly push rods also but maybe they were for hydraulic lifters...I failed to check that out.

So perhaps a Triumph with a cold lash of .010" with stock iron barrels and alloy push rods would be similar to the VW and close up a bit when hot and may have been part of the design criteria... so I'm back to the necessity of checking hot lash for an alloy barreled engine with steel or alloy push rods but I kind of doubt that the cam maker expected a cold clearance of .010" to remain at .010" when hot but I've been wrong before.

I'm back to square one so I'll have to make a call I guess to see what hot clearance the manufacturer was looking for with their cams, then doing like Hillbilly suggested to find a cold clearance that ends up at the recommended clearance hot in a non stock engine. I was originally looking at the steel push rods but with the huge difference in cold vs. hot lash in an all alloy engine I'm going to stick with alloy. MAP even supplied alloy push rod tubes for his alloy barrels to keep the proper crush to preclude oil leaks. Sure is a lot of growing and shrinking going on in these ICE thingees.

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Originally Posted by DavidP
The manufacturer assumes that everything is at it came from the factory when recommending valve clearances. I don't presume to know why Triumph recommends 0.002" and 0.004" on 650 twins but 0.006" and 0.008" on triples, much less why BSA specs 0.008" and 0.010" on A65, but I assume that the clearances tighten up with heat.

In my (limited) experience you'd assume correctly. I can't speak for other OEMs but I have set up and run numerous valvetrain tests for the engine OEM I work for. We've done a lot of testing with instrumented pushrods varying valve clearance to come up with OEM clearance specs. The goal has always been to see how close we can get to zero lash under operating conditions.

It perplexes me how a cam manufacturer could provide clearance specs without knowing what other components are in the valvetrain but I suspect customers would complain if no specs were given.

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Originally Posted by mondtster
Originally Posted by DavidP
The manufacturer assumes that everything is at it came from the factory when recommending valve clearances. I don't presume to know why Triumph recommends 0.002" and 0.004" on 650 twins but 0.006" and 0.008" on triples, much less why BSA specs 0.008" and 0.010" on A65, but I assume that the clearances tighten up with heat.

In my (limited) experience you'd assume correctly. I can't speak for other OEMs but I have set up and run numerous valvetrain tests for the engine OEM I work for. We've done a lot of testing with instrumented pushrods varying valve clearance to come up with OEM clearance specs. The goal has always been to see how close we can get to zero lash under operating conditions.

It perplexes me how a cam manufacturer could provide clearance specs without knowing what other components are in the valvetrain but I suspect customers would complain if no specs were given.

Mondster...I assume your efforts to get close to zero lash is on non hydraulic systems (obviously) and since you said 'pushrods' we're getting close to talking apples to apples here. Very interesting, thank you, are your OEM engines air cooled and pushrods alloy or steel? All aluminum engines? Any reason not to mention OEM?

Perplexing is right, in the case of Brit bikes the expansion rate of stock vs. modded engines appears to be huge from what I'm learning. Replacing iron barrels with alloy and alloy pushrods with steel would appear to be worse case scenario so I'm not sure why anyone would use steel pushrods in this case. I hope Mr. Parker chimes in on his use of steel pushrods in his very special all alloy BSA, in light of his comment on how much his clearances open up when hot. Maybe I need another posting on steel vs. alloy pushrods.

On a side note in regards to expansion in a hot engine, I'm using MAP steel con rods with their zero deck pistons so that I can tighten up the squish to a minimum knowing or assuming that the alloy MAP cylinders will grow more than the steel rods the hotter the engine gets. Heat expansion may also be the reason my stock T140 barrels are equipped with stainless alloy studs since certain SS alloys expand at almost the same rate as aluminum...seems like a good idea in the effort to keep near constant torque on our hot running heads but again I'm assuming. To bad the factory installed those same studs upside down with the tits up but that's another story.

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For what ever it is worth: BSA unit singles tend to be quite clattery (not sure that is actually a verb). Rupert Ratio, which is the bible for unit single owners, says the unit single engines grow when they get hot. He suggests (at the reader's own risk) setting the clearance at nil (just enough clearance to be able to turn spin the pushrods with your fingers) when cold, as the clearance will increase when the engine warms up. I tried it and it worked for me.

Ed from NJ

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My Triumph street bike , the single engine and dual engine Triumph LSR bikes have steel pushrods. They all use a custom length made up by Smith Bros...I could shorten the alloy rods myself but that didn't happen. Running half the lash of alloy rods..


79 T140D, 89 Honda 650NT ,61 A10 .On a bike you can out run the demons
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But a V8 engine is a good start for me
Think I'll drive to find a place, to be surly"
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Originally Posted by MarksterTT
Mondster...I assume your efforts to get close to zero lash is on non hydraulic systems (obviously) and since you said 'pushrods' we're getting close to talking apples to apples here. Very interesting, thank you, are your OEM engines air cooled and pushrods alloy or steel? All aluminum engines? Any reason not to mention OEM?

Perplexing is right, in the case of Brit bikes the expansion rate of stock vs. modded engines appears to be huge from what I'm learning. Replacing iron barrels with alloy and alloy pushrods with steel would appear to be worse case scenario so I'm not sure why anyone would use steel pushrods in this case. I hope Mr. Parker chimes in on his use of steel pushrods in his very special all alloy BSA, in light of his comment on how much his clearances open up when hot. Maybe I need another posting on steel vs. alloy pushrods.

On a side note in regards to expansion in a hot engine, I'm using MAP steel con rods with their zero deck pistons so that I can tighten up the squish to a minimum knowing or assuming that the alloy MAP cylinders will grow more than the steel rods the hotter the engine gets. Heat expansion may also be the reason my stock T140 barrels are equipped with stainless alloy studs since certain SS alloys expand at almost the same rate as aluminum...seems like a good idea in the effort to keep near constant torque on our hot running heads but again I'm assuming. To bad the factory installed those same studs upside down with the tits up but that's another story.

Markster,

You are correct, the tests were performed on solid tappet engines. The engines in question are liquid cooled diesels so we're talking mostly iron and steel with very little aluminum. I'd prefer to leave my employer out of things although you can probably figure it out based on my location and the information I've given.

I'm wondering if the discussion of checking lash while the engine is hot is an attempt to remove the variables that would otherwise be a factor with setting the lash cold when you have unknown valvetrain components. Perhaps the best procedure on a modified engine would be to initially set the lash hot then allow the engine to cool and measure the lash cold to see where you would need to set it in the future. Perhaps this is something I should consider doing myself when the initial valve adjustment and cylinder head retorque is done on the t140 engine I just finished up.

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I was reading tuning tips by circle track racers, mostly pushrod Chevys....They all do the valves cold now because it's less messy and close enough. Iron blocks with iron heads ,the lash tightens up as the engine warms.With iron block with aluminum heads the lash loosens as the engines warms...For more power out of the turns they increase the lash, this eliminates the clearance ramps giving more effective duration.. It's also hard the the valve train..Nothing to do with Triumphs.....
Mondtster, do you post on Wild Guzzi?


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I guess that going back to engineering first principles the primary objective is for the valve to follow the cam at all conditions of engine revs, temperatures of engine components etc.
So ideally you need zero valve clearance (lash) at all conditions.
However with dissimilar metals for pushrods, barrels etc there is going to be differential expansion going on as the engine warms up.
So as well as wanting zero valve clearance one also wants for the clearance never to be negative--otherwise compression fails.
If you are using components made from different materials from standard then perhaps the best way is to measure the clearances hot and cold.
If the clearances hot are less than cold then set the cold clearances as (cold clearance minus hot clearance) plus, say, two thou.
The two thou is to allow for variations over time to ensure that the clearance never goes negative.
If the clearances hot are greater than cold by more than two thou then set the clearances as zero.
If the clearances hot are greater than cold by less than two thou then set the clearances at two thou.

I remember when I was riding BSA A7s and A10s the recommended clearances(set cold) were 8 thou inlet and 10 thou exhaust but the manual said something along the lines of---for fast riding increase the clearances to 10 thou inlet and 16 thou exhaust.

Just gotta try to keep the valve following the cam as much as possible!
Just my two cents worth of course.

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zero lash aka hydraulic lifters/tappets....most are good for 7000 rpm these days...


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Originally Posted by Hillbilly bike
Mondtster, do you post on Wild Guzzi?

I do more reading than posting on there but yes. I use the same handle everywhere that I participate so if you see it, it's me.

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Thanks guys, a lot of good input. I found that on my stock '66 T120 the clearances tightened up as the engine got hot. I set the intakes way to tight once and remember thinking that this is one quiet Triumph, then about 3 miles later when coming to a stop it died on me and had barely enough compression to restart and make it back home...so that's aluminum pushrods and iron barrel.

I went to the source and called Jim at Megacycle and asked him what lash I would want with the 1065 cam (.010' cold lash) when hot and mentioned the alloy barrel and steel pushrod concern. He understood the situation and said to absolutely check the lash hot and probably stick to aluminum pushrods. And he had to look up the cams profile in his book for a hot recommendation, he said something about the cam having a .015" ramp on the closing side (mostly just talking to himself) so not sure the thought process or exactly what that meant lash wise but he then said to adjust the intakes to between .012"-.013" right after coming in hot and since the exhaust valve would already be cooler then when running (so shorter by .002"-.003" probably) just add .002"-.003" to the intake clearance I get after the engine cools down and of course after I had already set intake when hot. So pretty much Hillbilly's, Tridentman's and mondster's recommendations with addition of exhaust difference.

Jim did add that this lash recommendation was specific to this cam profile and that if I wanted recommendations for any of their other cams he'd look them up for me, he was very pleasant and willing to help.

Hillbilly & Tridentman...I'll have to think about the comments you made about increased lash for more power and high speed running because I've always thought that on Triumphs one would increase the lash to reduce effective cam duration for more low end on smaller, tighter tracks, Norris told me this almost 50 years ago when I bought his 'R' grind cam. Did I get this wrong? He should have told me to buy his street cam with much smaller numbers but that's another story.

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Originally Posted by edunham
For what ever it is worth: BSA unit singles tend to be quite clattery (not sure that is actually a verb). Rupert Ratio, which is the bible for unit single owners, says the unit single engines grow when they get hot. He suggests (at the reader's own risk) setting the clearance at nil (just enough clearance to be able to turn spin the pushrods with your fingers) when cold, as the clearance will increase when the engine warms up. I tried it and it worked for me.

Ed from NJ
I borrowed a friend's BSA starfire once and it was the most clattery bike I have ever heard but it was also very fast!

I tend to not worry about hot clearances on my 650 Triumph and just do what it say in the repair manual. I did check after a ride once and then screwed the caps back on as tightly as usual. When the engine had cooled I had a hell of a job undoing them again.

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Originally Posted by dave jones
Originally Posted by edunham
For what ever it is worth: BSA unit singles tend to be quite clattery (not sure that is actually a verb). Rupert Ratio, which is the bible for unit single owners, says the unit single engines grow when they get hot. He suggests (at the reader's own risk) setting the clearance at nil (just enough clearance to be able to turn spin the pushrods with your fingers) when cold, as the clearance will increase when the engine warms up. I tried it and it worked for me.

Ed from NJ
I borrowed a friend's BSA starfire once and it was the most clattery bike I have ever heard but it was also very fast!

I tend to not worry about hot clearances on my 650 Triumph and just do what it say in the repair manual. I did check after a ride once and then screwed the caps back on as tightly as usual. When the engine had cooled I had a hell of a job undoing them again.

Dave, I'm with you on a stock Triumph with stock cam but my concern was with an all alloy engine (MAP cylinders) and aftermarket cams (.010" cold lash). The all aluminum parts expand more than the iron barrel engine and then if you use steel pushrods you'll have less expansion and less take up of the all alloy expansion so the worst case scenario. So my question was to find out what clearance was desired with my cams profile when the engine was at running temperature regardless of engine construction...so eliminating all the possible variables. I'll say the resulting suggested clearances wasn't what I was expecting but now I know. Mark R.

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Sorry, Markster. I didn't read your post properly.

Dave

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[quote=dave jones]Sorry, Markster. I didn't read your post properly.

Dave[/quote

Oh, no worries Dave, I appreciate any response and made a note never to tighten down any caps into a hot engine...at least not without a propane torch near by. Scratch that...use a paint stripper heat gun...I can just see someone setting their bike on fire playing a propane torch under their fuel tank. To be honest, I did set my Jeep pickup on fire once doing something similarly stupid...I learn the hard way. Mark R.

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The B series and A75 engine were all ally (albeit with lined sleeves) what do they recommend for valve lash on those bikes?

Fwiw, I’ve just set the cold tappet clearences on my A65 with John hill barrel. For suggests 4 thou in and 6 thou ex. I’m yet to run the bike but a few people have these barrels and I haven’t heard any complaints when using those specs. ( bsa original specs were 8 thou in and 10 thou ex.


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Originally Posted by Allan G
The B series and A75 engine were all ally (albeit with lined sleeves) what do they recommend for valve lash on those bikes?
A75 is .006" intake, .008" exhaust for normal road use. Hele recommended 8 and 10 for the race bikes.


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Normally we see recommended clearances larger on the exhaust side. This would lead one to believe that heat causes the clearance to tighten up.
Are these recommendations reversed when the combination of metals means that the clearance increases with heat?


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Allan, I'm not familiar with BSA's but if you went from iron to aluminum barrels and stayed with the alloy pushrods and stock cams then I'd have to go with recommended clearances and since Hill tightened them up would suggest to me, he either expected or tested for greater heat expansion and for the clearances to grow, so adjusted his cold clearance recommendations.

DavidP, from my experience with all stock Triumph's that was the case...the clearances tightened up with heat...key words are 'All stock'. Mark Parker's BSA A65 experience with his alloy cylinders and steel pushrods would indicate the clearances grew since he had to set them cold at 0.00" clearance which is why I started thinking about this topic. Aluminum cylinders expand more than iron and steel pushrods less then alloy so it stands to reason the hot clearances grew.


Stock engines? I would always go with the manufacturers recommendations on valve lash but when it comes to any variation of component materials that also includes 'aftermarket cams', then I would question cold/hot clearances and the only one who could answer this for me was the cam manufacturer. My question to them was...regardless of engine heat expansion due to component materials, when everything is hot and running with your cam profile, what clearance would you like to see 'hot'? Once set for these hot clearances, I can do as Hillbilly and others suggested, let it cool down and then check and use that clearance for my cold settings from then on. If I had only changed the cams from stock, then I'd probably just set them at the recommended clearance of .010" and ride on.

I will stay with my aluminum pushrods for no other reason then to keep the cold vs. hot lash clearances closer since they will expand as the alloy barrels grow, more so than the chromoly steel ones any way. Many years ago, I heated a stock alloy T120 pushrod in the oven at 250*F (I think) figuring this would be an extreme for this components location in the engine, I believe it grew almost .020" of an inch but it's been a while so I'll just say it grew more than I had expected but then I think I heated it up beyond what it would actually see in the running engine. Maybe I'll try this experiment again some day while heating up my TV dinner...maybe.

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