I have read with interest the 30-30 and Other OEM Solid Lifter Cam Valve Adjustment by Duke Williams and John Hinckley revised in Dec of 2005. Is this proceedure also recommended for the (I believe) Duntov cam in my (stock) 327/ 340hp 62 and can anyone attest to it's effectiveness in a similar car? It seems to me I read somewhere that they are now back to recommended cold lashing to the service manual specs at TDC of .008/.016. for the Duntov cam and the 90 Deg. adjustment is only for the 30-30 Z/28 Cam. Can someone set me straight on this.
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Re: Cold Valve Lash 62 327/340hp
The Dec 2005 revision clearly listed recomended clearance specs for the Duntov cam and two other indexing options beyond what is recommended for the 30-30 and LT-1 cams.
The other two indexing options only apply to the Duntov Cam because it has much shorter total duration including the clearance ramps.
To give you and idea, here are the approximate durations in degrees - from the beginning of the opening clearance ramp to the end of the closing clerance ramp. Subtract these numbers from 720 and you have the total degrees that the cam is on the base circle.
Duntov 380(I), 420 (E)
LT-1 490 (I), 540 (E)
30-30 540 (both)
From the paper:
Addendum (May 19, 2003), Lash settings revised 12-14-2005
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.
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.
Duke -
Re: Cold Valve Lash 62 327/340hp
Tom;
It would be best to wait to hear from either Duke or John on this directly.
I, like you, have a 340 hp with the Duntov - only a 63 version. I used to always set mine cold at .008" Intake and .016" Exhaust using the old Sevice Manual method (cyl. 1 and 6) and that always worked quite well for me. A few months back I did the 90 degree method as described in Duke's/John's instructions that Duke was kind enough to send me. I worked with my son's assistance as I was intimidated into thinking it was a two man job. It's more work, but the results seem satisfactory. May be it was my imagination, but the engine seems to run slightly smoother and the tappet sound more even. Performance is about the same. I have been having other issues with heat soak and carburation so I can't tell what exactly is helping or hurting when I make changes.
Stu foxComment
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Re: Cold Valve Lash 62 327/340hp
Thanks Stu, I didn't get an email notification of your post. This new Discussion board format SUCKS...The old one was much better where you could view all the posts. It took me forever to find my post and your answer.
All I got from Duke was a reprint of his essay, which really doesn't answer my question. I am going to lash the valves cold at .008 and .016 and take whatever that gives me. I am not going to trash my detailed enging compartment with a hot lash. The only thing that is likely to happen if I try the Duke's 90 degree proceedure is that I will break something in my high dollar original 327/340 engine.
I appreciate your post..
Tom CheairsComment
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Re: Cold Valve Lash 62 327/340hp
I don't see how the paper doesn't address your questions, but whatever...
It discusses hot and cold clearance - why it basically doesn't change between the two conditions - and listed two optional indexing methods that can be used with (only) the Duntov cam. These two optional indexing methods do not apply to the 30-30 or LT-1 cams.
One thing I have not done is verify from the lift data on the engineering drawings that the #1 and #6 TDC positions result in the the specfied valves to adjust in the 1963 Shop Manual to be indeed on the base circle, so I am trusting Chevrolet on this without verification.
I have verified that both valves for the Duntov cam can be set at TDC of the compression stock. This doesn't change the number of points the crankshaft must be indexed at (eight) to adjust all 16 valves, but it may make keeping track easier.
I always recommend that you prepare a table/checklist on a piece of paper that lists the valves to adjust at each 90 degree crank position beginning at TDC #1, like this:
TDC #1 - 8E, 2I
90 deg. - 4E, 1I
180 deg. - 3E, 8I
270 deg. - 6E, 4I
TDC #6 - 5E, 3I
90 deg. - 7E, 6I
180 deg. - 2E, 5I
270 deg. - 1E, 7I
A couple of years ago I was timed at this procedure. Another person told me which valves to adjust from the table/checklist I wrote on a tablet and kept track of the crank position. I rotated the crank and set the valves. Not including installing and removing the valve covers, I (carefully) adjusted all 16 in less than ten minutes. This was with a 30-30 cam so I only had to use one feeler gage. It might have taken me a bit longer if I had to swap gages as is required for the LT-1 and Duntov cams.
I could probably cut my time down another minute or so if I rearranged the order at each crankshaft postion to minimize the number of times I had to move to the other side of the car.
DukeComment
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Re: Cold Valve Lash 62 327/340hp
Thanks Duke, I do understand now. And please accept my apology for being so dense at the outset. I will plan to set the valve clearances "cold" at TDC at the hot clearance values as per the manual (which I do not have for my 327/340hp motor) but I would think it is the same cam in the 63 340hp engine and .008 and .016.
You are a valuable asset to our forum and I appreciate very much your help.
Tom CheairsComment
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Re: Cold Valve Lash 62 327/340hp
For now I recommend you set both valves for each cylinder at TDC of the compression stroke or use the indexing method recommended for the 30-30 and LT-1 cam.
The '63 Corvette Shop manual really only recommends the method where you set eight specific valves at #1 and #6 for the hydraulic lifter cam.
For the Duntov cam I am doing a layout to determine if the specific valves listed are on the base circle at these two positions. I worked on it until midnight last night when I became to tired to complete it as it does take some thinking to do correctly.
DukeComment
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Re: Cold Valve Lash 62 327/340hp
Tom
For what it's worth I set the valves on my 62 340hp motor using the revised method and have put close to 17 thousand miles on the motor. Have readjusted the valves once and only because I wanted too.
TerryComment
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Re: Cold Valve Lash 62 327/340hp
Duke;
You are a workaholic, you are, Ha! We do appreciate your efforts immensly. I, for one, look forward to what you come up with on this. I hope I didn't scare Tom off from using your 90 degree method. It took my son and I longer as it was our first time and we wanted to be sure we did it right. My next time will be faster, but I'll never be able to match your speed. I'm slow with a feeler gauge because I usually want to go back and compare the feel with the previous valve I set.
Could I interest you in a set of valve clips to hot set Chevy valves with? Ha! Remember those days? I still have them in my tool box and I think the last time I used them was about 1956! Even though they are "blued" spring steel, the last time I looked at them they were rusting away. I offer them to some "newbies" now and then to see if they will bite and really try to use them. That's one procedure you only try once and be happy if you don't come away with oil burned hands.
Stu FoxComment
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Re: Cold Valve Lash 62 327/340hp
I completed the layout and verified that the #1 and #6 optional indexing method for the Duntov cam that is discussed in the copy of the paper currently floating around in cyberspace will not yield accurate results.
The optional method of adjusting both valves at TDC with the Duntov cam is still valid, but it will not work for the 30-30 and LT-1 cams.
I've revised the paper and started a new thread on the subject.
No thanks on the clips - no need!
DukeComment
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