I am wondering how come the tune-up specs listed on this site call for .018H and .030H while my 63 shop manual calls for .012H and .018H. I recently set mine by the shop manual and they just don't seem as loud as I am accustomed to hearing. I must add that I mistakenly set mine cold and do not know if that could be the reason they are so quiet. On the specs, I seem to recall that we always used 12&18 years ago. What's the real deal guys?
63 409-425 valve lash specs
- Thread starter BuzGuy
- Start date
I have always set mine cold. The gap left is for the growth of the metal when it reaches operating temp. The exhaust side will grow more then the intake, that is why the difference. Am I wrong guys??? My roller sets at .028 intake and .032 exhaust I think. Its been a while.
Donnie
Donnie
Ron, Like everything, there are different opinions on this. I subtract .002 for cold setting on both intake and ex. ...cam card calls for .014 hot ,, I set cold .012
You guys are really making me blow the cobwebs out on this one. There are many opinions on how this is to be done. I never have used a "Hot" setting. I really have never heard of a "Hot" setting to tell you the truth. The point of a valve lash setting on solid lifters at all is for the growth of the metal when the engine is up to operating temp. To set your lifters with a hot engine is not going to be very accurate. Heat is not even through out the entire engine. Whoever said that you only need 0.002 as a difference between hot and cold is way off. Steel grows 0.00002 for every degree over 68 degrees. Now times that by 110-115 degrees for the difference between cold and operating temp and you know a max growth. Exhaust side is much hotter then intake, which is why the difference in lash settings. I do not think I would advise anyone to set the lash with a hot engine. If there is a more expierenced engine builder on here to agree or disagree with my responce, please do so. I need to stay up on this. My current toys have hydrolic lifters, but I need to be refreshed every now and then.
Thanks
Donnie
Thanks
Donnie
I apologize for being way off. I assumed we are talking about a fresh engine on initial start up. I set .002 tight then bring engine to operating temp. , then re-set at spec. I guess that is incorrect according to some experts, but has worked for me . Like I said,, lots of opinions. I won't be changing my procedure based on something read in a magazine article. I have adjusted the valves on an engine with solid lifters in the past and I know what works for me.
All verrry interesting! When I was a kid with my new 62 409 adjusting the valve lash was part of the fun. I read those magazine articles on how to and how not to adjust solid lifters - do it hot & do it running. Tried it that way. Not for me. I gave some thought to hot vs cold and decided that the logic didn't ring true to my way of thinking. The engine is all metal (some cast iron & some steel) and will expand when going from cold to running temperature at nearly the same rate. Everything has a build tolerance + or - a certain percent, rocker arm ratio, cam lobes (not just opening & closing points for one lobe but all lobes probably have some difference, cam bearing clearance, etc. I dedided the only thing in my control was to do what worked for me so I adjusted the valves on my engine by warming up the engine, took my little P&G valve gapper and ran the valves with the engine not running.
We seem to each have a way to do things and if it works thats what counts.
I doubt if a few .001 one way or another in valve lash makes much difference on the street & the engine probably doesn't know or care.
I do like the sound of running solid lifter engine.
We seem to each have a way to do things and if it works thats what counts.
I doubt if a few .001 one way or another in valve lash makes much difference on the street & the engine probably doesn't know or care.
I do like the sound of running solid lifter engine.
Written specifically for the 30-30, Z-28 and LT-1 sbc cams, but interesting.
"30-30" AND OTHER OEM SB SOLID LIFTER CAM VALVE ADJUSTMENT
(Revised 12/15/2005)
By John Hinckley and Duke Williams
The traditional method of adjusting valves one or more cylinders at a time with each cylinder at TDC is fine for hydraulics and for most solid-lifter cams, but NOT for the factory "30-30" solid-lifter cam used in '64-'65 L-76 365 HP and L-84 375 HP (FI) Corvette engines (and in '67-'69 Camaro 302/290 Z/28 engines); this cam has VERY long clearance ramps that are .017" high, and at TDC for any cylinder, both the intake and exhaust valve for that cylinder are still on their ramps, NOT on the cam's base circle, which is why the Service Manual for all cars so equipped says specifically to set them "hot and running".
There is, however, a better way to adjust the valves with a "30-30" - you can set them "cold and not running" by setting the intakes at 90 degrees ATDC and the exhausts at 90 degrees BTDC - so the lifters are on the base circle, not on the clearance ramps. This has been confirmed with cam lift/crank-angle diagrams and analysis of the GM drawing lobe data, and I've done mine this way - results in a nice mechanical "singing" sound, no "clacking", it runs better, sounds better, idle is more stable, and throttle response is improved. Several other Z/28 owners have followed this procedure as well since we developed it, and all of them have seen the same positive results.
Set them cold at .023"/.023". The actual measured (stamped rocker arm) ratio at the lash points is actually about 1.37:1 (not the design 1.5:1, which is a “theoretical” number), so the clearance ramp, which is exactly .017" high on the lobe, is all taken up at .02329" clearance; .030" clearance with the valve closed is too loose - the ramp ends/begins before the .030"clearance is taken up, resulting in the valve being lifted off and returned to the seat at greater than ramp velocity. This will contribute to valve seat recession, and can cause valve bounce at the seats at high revs - it will also be noisy.
You can adjust two valves at each 90-degree rotation point, starting at #1 TDC, turning the crank 90 degrees at a time seven times (measure and mark your balancer first at 90-degree intervals from TDC). Removing the plugs simplifies rotating the crank, but you were going to change them anyway, right? Proceed as follows:
TDC #1 - 8E, 2I
90 deg. - 4E, 1I
180 deg. - 3E, 8I
270 deg. - 6E, 4I
0 - 5E, 3I
90 deg. - 7E, 6I
180 deg. - 2E, 5I
270 deg. - 1E, 7I
Start at TDC #1, then rotate 90 degrees at a time, setting at .023" cold. If you like, you can then go back after you're done to each cylinder's TDC position and check clearance on that cylinder's two valves, and you'll find that they've closed up to approximately.021", indicating that both valves are still on the ramps at TDC, as I pointed out in the beginning.
Trivia - the point of max inlet lift on the "30-30" cam is at 110 degrees ATDC and 118 degrees BTDC on the exhaust side, so the lobe separation angle is 114 degrees (angle between points of max lift, not the geometric center of the lobe - the lobes on the "30-30" cam are asymmetrical).
Addendum (May 19, 2003), Lash settings revised 12-14-2005
This procedure should also be used for the LT-1 cam. The exhaust is “on the ramp” at TDC. The inlet is not, but just barely. With the Duntov cam this indexing procedure may be used, or both valves may be set with the cylinder at TDC of the compression stroke, or all 16 valves may be adjusted at TDC #1 and TDC #6 as outlined in the 1963 Corvette Shop Manual. The Duntov cam has shorter clearance ramps than the 30-30 or LT-1 cam.
This indexing procedure on page 1 may be used with ANY cam to assure that the lobe is on the base circle, and MUST be used for cams with very long clearance ramps.
The following inlet/exhaust valve clearances are recommended with the engine cold and not running. The difference between “hot” (engine idle speed) and cold clearance on a cast iron pushrod engine is negligible, so clearances can be set cold, which is more convenient. These clearances are computed by multiplying the height of the clearance ramp (which was determined from analysis of the GM drawings that list lobe data to five decimal places every cam degree) by the 1.37:1 measured lash point rocker ratio. The computed number is then rounded down. The factory clearances are derived from multiplying the maximum height of the ramp above the base circle by 1.5, except the 30-30 cam. The clearances of .025"/.025" listed on the drawing were derived from this formula, but the rationale of the published .030"/.030" is unknown. It is speculated that the higher clearance was specified to solve idle stability problems on FI engines as the larger clearance decreases effective duration slightly, but is definitely tougher on the valvetrain. Idle speed on 30-30 cam FI engines should be set at whatever RPM is required to achieve stability, and this will probably be in the range of 1000-1200
When running hard, such as sustained WOT, the exhaust valve head will heat up considerably. About 80 percent of exhaust valve cooling is through the seat, but the stem temperature will also increase, which will cause the stem to grow and decrease running clearance. This is why exhaust clearance ramps are typically higher than inlet ramps – to allow for more stem growth and maintain acceptable running clearance to ensure the valves fully seat. Since the inlet valve is cooled with every fresh intake charge, its temperature and clearance will remain more consistent over the entire engine operating spectrum.
The rocker arm nut should be tightened until a light drag is felt on the feeler of the same thickness as the recommended clearance. Then the clearance may be verified by inserting a .001” larger gage, and if it does not go the clearance is between the two gages, which is just right. Note that the inlet clearance specification for the 1963 Corvette was tightened to .008” to give a bit more effective duration. This does not need to be “factored” anymore. We recommend this tighter clearance for all 327s, and it is optional for 283s for a little more top end power though the effect may not be noticeable. Normal engine service will usually result in slight loosening of the clearance, and Chevrolet service recommendations from the sixties call out a lash check every 12,000 miles as part of a normal tuneup.
Duntov cam (283) .010”/.016” (lobe clearance ramp heights: .008"/.012")
Duntov cam (327) .008”/.016” (lobe clearance ramp heights: .008"/.012")
30-30 cam .023”/.023” (lobe clearance ramp heights: .017"/.017")
LT-1 cam .016”/.023” (lobe clearance ramp heights: .012"/.017")
Note: Clearances/clearance ramp heights are listed inlet/exhaust.
Interesting facts: The LT-1 cam exhaust lobe is the same as the 30-30 cam lobe (both sides identical), but the point of maximum lift is indexed four degrees earlier at 122 deg. BTDC. The LT-1 inlet lobe is the same at the L-72 cam lobe (both sides identical), but the point of maximum lift is indexed two degrees later at 110 deg. ATDC versus 108 deg. ATDC for the L-72. The LT-1 inlet/L-72 lobe also has greater asymmetry than the 30-30 lobe. The LT-1 cam was, therefore, not "all new", but incorporated two proven lobe designs with indexing refinement to broaden torque bandwidth, and the early phased exhaust event compensates for the small blocks' relatively restrictive exhaust port. The Duntov lobes are symmetrical and identical other than the exhaust lobe having .004" greater clearance ramp height. At any point on the opening and closing flanks (the portion of the lobe above the top of the clearance ramp), as measured from the point of maximum lift, the design exhaust lobe dimension is exactly .00400" greater than the inlet lobe.
"30-30" AND OTHER OEM SB SOLID LIFTER CAM VALVE ADJUSTMENT
(Revised 12/15/2005)
By John Hinckley and Duke Williams
The traditional method of adjusting valves one or more cylinders at a time with each cylinder at TDC is fine for hydraulics and for most solid-lifter cams, but NOT for the factory "30-30" solid-lifter cam used in '64-'65 L-76 365 HP and L-84 375 HP (FI) Corvette engines (and in '67-'69 Camaro 302/290 Z/28 engines); this cam has VERY long clearance ramps that are .017" high, and at TDC for any cylinder, both the intake and exhaust valve for that cylinder are still on their ramps, NOT on the cam's base circle, which is why the Service Manual for all cars so equipped says specifically to set them "hot and running".
There is, however, a better way to adjust the valves with a "30-30" - you can set them "cold and not running" by setting the intakes at 90 degrees ATDC and the exhausts at 90 degrees BTDC - so the lifters are on the base circle, not on the clearance ramps. This has been confirmed with cam lift/crank-angle diagrams and analysis of the GM drawing lobe data, and I've done mine this way - results in a nice mechanical "singing" sound, no "clacking", it runs better, sounds better, idle is more stable, and throttle response is improved. Several other Z/28 owners have followed this procedure as well since we developed it, and all of them have seen the same positive results.
Set them cold at .023"/.023". The actual measured (stamped rocker arm) ratio at the lash points is actually about 1.37:1 (not the design 1.5:1, which is a “theoretical” number), so the clearance ramp, which is exactly .017" high on the lobe, is all taken up at .02329" clearance; .030" clearance with the valve closed is too loose - the ramp ends/begins before the .030"clearance is taken up, resulting in the valve being lifted off and returned to the seat at greater than ramp velocity. This will contribute to valve seat recession, and can cause valve bounce at the seats at high revs - it will also be noisy.
You can adjust two valves at each 90-degree rotation point, starting at #1 TDC, turning the crank 90 degrees at a time seven times (measure and mark your balancer first at 90-degree intervals from TDC). Removing the plugs simplifies rotating the crank, but you were going to change them anyway, right? Proceed as follows:
TDC #1 - 8E, 2I
90 deg. - 4E, 1I
180 deg. - 3E, 8I
270 deg. - 6E, 4I
0 - 5E, 3I
90 deg. - 7E, 6I
180 deg. - 2E, 5I
270 deg. - 1E, 7I
Start at TDC #1, then rotate 90 degrees at a time, setting at .023" cold. If you like, you can then go back after you're done to each cylinder's TDC position and check clearance on that cylinder's two valves, and you'll find that they've closed up to approximately.021", indicating that both valves are still on the ramps at TDC, as I pointed out in the beginning.
Trivia - the point of max inlet lift on the "30-30" cam is at 110 degrees ATDC and 118 degrees BTDC on the exhaust side, so the lobe separation angle is 114 degrees (angle between points of max lift, not the geometric center of the lobe - the lobes on the "30-30" cam are asymmetrical).
Addendum (May 19, 2003), Lash settings revised 12-14-2005
This procedure should also be used for the LT-1 cam. The exhaust is “on the ramp” at TDC. The inlet is not, but just barely. With the Duntov cam this indexing procedure may be used, or both valves may be set with the cylinder at TDC of the compression stroke, or all 16 valves may be adjusted at TDC #1 and TDC #6 as outlined in the 1963 Corvette Shop Manual. The Duntov cam has shorter clearance ramps than the 30-30 or LT-1 cam.
This indexing procedure on page 1 may be used with ANY cam to assure that the lobe is on the base circle, and MUST be used for cams with very long clearance ramps.
The following inlet/exhaust valve clearances are recommended with the engine cold and not running. The difference between “hot” (engine idle speed) and cold clearance on a cast iron pushrod engine is negligible, so clearances can be set cold, which is more convenient. These clearances are computed by multiplying the height of the clearance ramp (which was determined from analysis of the GM drawings that list lobe data to five decimal places every cam degree) by the 1.37:1 measured lash point rocker ratio. The computed number is then rounded down. The factory clearances are derived from multiplying the maximum height of the ramp above the base circle by 1.5, except the 30-30 cam. The clearances of .025"/.025" listed on the drawing were derived from this formula, but the rationale of the published .030"/.030" is unknown. It is speculated that the higher clearance was specified to solve idle stability problems on FI engines as the larger clearance decreases effective duration slightly, but is definitely tougher on the valvetrain. Idle speed on 30-30 cam FI engines should be set at whatever RPM is required to achieve stability, and this will probably be in the range of 1000-1200
When running hard, such as sustained WOT, the exhaust valve head will heat up considerably. About 80 percent of exhaust valve cooling is through the seat, but the stem temperature will also increase, which will cause the stem to grow and decrease running clearance. This is why exhaust clearance ramps are typically higher than inlet ramps – to allow for more stem growth and maintain acceptable running clearance to ensure the valves fully seat. Since the inlet valve is cooled with every fresh intake charge, its temperature and clearance will remain more consistent over the entire engine operating spectrum.
The rocker arm nut should be tightened until a light drag is felt on the feeler of the same thickness as the recommended clearance. Then the clearance may be verified by inserting a .001” larger gage, and if it does not go the clearance is between the two gages, which is just right. Note that the inlet clearance specification for the 1963 Corvette was tightened to .008” to give a bit more effective duration. This does not need to be “factored” anymore. We recommend this tighter clearance for all 327s, and it is optional for 283s for a little more top end power though the effect may not be noticeable. Normal engine service will usually result in slight loosening of the clearance, and Chevrolet service recommendations from the sixties call out a lash check every 12,000 miles as part of a normal tuneup.
Duntov cam (283) .010”/.016” (lobe clearance ramp heights: .008"/.012")
Duntov cam (327) .008”/.016” (lobe clearance ramp heights: .008"/.012")
30-30 cam .023”/.023” (lobe clearance ramp heights: .017"/.017")
LT-1 cam .016”/.023” (lobe clearance ramp heights: .012"/.017")
Note: Clearances/clearance ramp heights are listed inlet/exhaust.
Interesting facts: The LT-1 cam exhaust lobe is the same as the 30-30 cam lobe (both sides identical), but the point of maximum lift is indexed four degrees earlier at 122 deg. BTDC. The LT-1 inlet lobe is the same at the L-72 cam lobe (both sides identical), but the point of maximum lift is indexed two degrees later at 110 deg. ATDC versus 108 deg. ATDC for the L-72. The LT-1 inlet/L-72 lobe also has greater asymmetry than the 30-30 lobe. The LT-1 cam was, therefore, not "all new", but incorporated two proven lobe designs with indexing refinement to broaden torque bandwidth, and the early phased exhaust event compensates for the small blocks' relatively restrictive exhaust port. The Duntov lobes are symmetrical and identical other than the exhaust lobe having .004" greater clearance ramp height. At any point on the opening and closing flanks (the portion of the lobe above the top of the clearance ramp), as measured from the point of maximum lift, the design exhaust lobe dimension is exactly .00400" greater than the inlet lobe.
Thanks Cecil, I knew the way I have been doing it came from someplace creditable.
Thanks Cecil,
We have always mapped the lash ramps and used a clearance that is just under the ramp height like .002-.004 and set hot. And they sing as opposed to rattle.
On an iron engine is is not as big of a deal because the expasion directions for the most part offset eachother when adjusting hot verses cold. On an aluminum engine they must be adjusted hot.
Either way the optimum setting is hot and using a clearance just short of the ramp.
And there as many opinions as there are stars in the heavens so what ever works for you.
We have always mapped the lash ramps and used a clearance that is just under the ramp height like .002-.004 and set hot. And they sing as opposed to rattle.
On an iron engine is is not as big of a deal because the expasion directions for the most part offset eachother when adjusting hot verses cold. On an aluminum engine they must be adjusted hot.
Either way the optimum setting is hot and using a clearance just short of the ramp.
And there as many opinions as there are stars in the heavens so what ever works for you.
Hi fellas; I was hoping for specifcally 409-425 stuff but you guys with the small-block/LT info sure gave a lot to learning the how and why of this. Its no doubt the guy who reduces the settings for cold is doing the wrong thing as am I. When you think about the valve stem and push rods heating up they sure do get longer and will require MORE clearance rather than less to compensate for a cold setting. I also like the idea of warming the engine before setting but this is just not possible after a teardown although its good for the situation of re-adjustment which I am in now but I guess you gotta work fast. I am wondering if that hi-tech approach explained by odskydog is right when it says the difference between a hot engine and a cold engine with cast iron heads is negligible. That is hard to believe because I went back and looked at my original 63 shop manuel again. First off, it calls for .012 and .020 not .018 on the exhaust as I stated in my therad opening above. I misread the thing because there is also a spec for "sustained high speed running" and that is .018 and way up at .030 for the exhaust valve which must get a lot hotter at high speed... so much for that remark that there should no difference in hot and cold settings for a cast iron head engine - - last I heard all these 409s had cast iron heads. AND if you like valve lash noise as I do, then opening them up for high speed running even if you just drive around town and to shows can't hurt a thing... OR COULD IT?
Hey Clyde.... I still have my P&G Valve gapper in the original wooden box on my garage shelf. 
I haven't used that DA....M thing in years. I remember when I had my '63/425HP impala I would always come up against a 70 GTO with about a hundred kids in the back seat of it and they would always make a remark that the '409" fender emblems were bogus, Until I mashed the pedal through the carpet . Needless to say,I would always leave them in the dust. The guy would always wing the motor and sidestep the clutch and just sit there and dig 2 grooves in the pavement. AH !!! The good old days !!!!!! I would go over to my friends house after a trip to the store and he would always adjust my valves so that the motor didn't sound like a diesel. He would say..... Did you race that Goat again???
The car is pictured in my album.
Butch
I haven't used that DA....M thing in years. I remember when I had my '63/425HP impala I would always come up against a 70 GTO with about a hundred kids in the back seat of it and they would always make a remark that the '409" fender emblems were bogus, Until I mashed the pedal through the carpet . Needless to say,I would always leave them in the dust. The guy would always wing the motor and sidestep the clutch and just sit there and dig 2 grooves in the pavement. AH !!! The good old days !!!!!! I would go over to my friends house after a trip to the store and he would always adjust my valves so that the motor didn't sound like a diesel. He would say..... Did you race that Goat again??? The car is pictured in my album.Butch
I think there is a lot of bunk in that reference above... I read what Ronnie sent and I wonder - - how or why would a flat lifter under tremendous spring pressure could ever come crashing into the cam? I also wonder why Chevy/GM has clearnces of .018 and .030 for sustained high speed running. If and cam crashing gets done, you would think it would certainly happen during high speed/RPM running.
I set my valve clearance hot or cold, never had a problem. If any of you think you can predict how the various components of an engine will grow, or not, at operating temp, well that's one up on me. You can lash tight and kill a little bottom end or lash loose and, with traction, pick up 60'.