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Thread: NEW INSTALL, CAM & LIFTERS

  1. #11
    Registered Member BamaNomad's Avatar
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    RD: I found this spec for the '70 LT1 camshaft.. including lash specs. Your 0.026 on the exhaust may not allow sufficient expansion for a hot engine??

    OEM part #3972178 is the original LT-1 setup. 242/254 @ .050 with 316/336 advertised, with a 116L/S. Lift @ valve .459" x .485". Lash settings of .024"-intake and .030"-exhaust.

  2. #12
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    BamaNomad, lash specs on solid lifter cams are for a fully warmed up engine. So it's not about expansion, it's about matching the lash to the camshaft design.

    It's up to you to figure out how much to "fudge" the cold lash. Usually it's .002-.003" but it varies with the engine and camshaft. Aluminum vs. iron heads are also a factor.

  3. #13
    Registered Member BamaNomad's Avatar
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    Rick,

    I don't want to get into a long discussion on this, but If not for thermal expansions how would you explain why there's a difference between the hot AND cold lash specifications on a solid cam? (AND adjusting the lash on a HOT/running engine is a very messy job!)

    My comment on this to RD was based on his exhaust valve setting of 0.026 versus the spec of 0.030. Every solid cam I've used over the last 50 years has had different lash settings, and yes those differences are based on the engine/cam design and the specific application of the engine! My own experience with solid cams began with a Lunati cam which matched the '67 Z28 specs in a bored HTC/CSC 302 in a record running '67 Camaro, and continued with 'stock' '68 Z28 (302), stock '69 Z28 (302+0.030) and a '70 350 LT1 engine (two of them), so all of those were Chevy engines from the '67-70 timeframe. As far as any other brand solid lifter engines, I know nothing and don't pretend to. Currently the only solid lifter engine I own is in the '69 Z28 (and I might be changing this to a 'roller cam' design in the future). I installed a 350/350 hydraulic cam in the last LT1 I rebuilt (because IMO it's a pain having to adjust lifters in a street engine).
    Last edited by BamaNomad; 02-22-2021 at 06:25 AM.

  4. #14
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    explain why there's a difference between the hot AND cold lash specifications on a solid cam?
    I don't think you'll find any cold lash specs. What you do is set the initial lash with an educated guess and then when warmed up, check and set again. There is a difference but it's not spec'd and cold lash is not an accurate predictor of hot lash.

    adjusting the lash on a HOT/running engine is a very messy job!
    There's an easy answer for that. Don't adjust lash on a solid lifter cam while the engine is running. For that matter there's normally no need to adjust hydraulic lifters with the engine running either.

  5. #15
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    I has been rears since I ran the valves on my 67 Camaro SS 350 it has a Duntov 30/30, it even went 1500 miles of Power Tour in 17.

  6. #16
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    Quote Originally Posted by BamaNomad View Post
    RD: I found this spec for the '70 LT1 camshaft.. including lash specs. Your 0.026 on the exhaust may not allow sufficient expansion for a hot engine??

    OEM part #3972178 is the original LT-1 setup. 242/254 @ .050 with 316/336 advertised, with a 116L/S. Lift @ valve .459" x .485". Lash settings of .024"-intake and .030"-exhaust.
    Yeah I'm a little tight on the exhaust side, but it seemed noisy at .030 setting cold. But the engine runs great, and trying to get them all set at near operating temp would be too hard and I like to have the plugs out. I would like to just put a hydraulic cam in it and forget it, but holy crap this engine pulls hard and I haven't even ran it to 6500rpm that it would easily go to. It is such a great engine that Chevy sold as a long block 50 years ago, and the angle plug turbo iron heads came separate. The one I bought for $1000 in 1989 had never been run. It currently has 700 miles on it, and is one the best SBC you could by from GM back then.camera phone 363.jpg

  7. #17
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    A 30-30 Duntov cam is noisy, I thought many liked that. Just like they like the random misses at idle. And I agree with markm, you don't have to adjust the valves often. It's just not necessary.

  8. #18
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    adjusting hydraulic flat tappetsi

    I have always used 1/4 turn after zero lash with new lifters and have never had an issue.

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