Re: Roller Cam Lash Reduction
[Re: Moparrob68]
#2875337
01/17/21 02:16 AM
01/17/21 02:16 AM
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Joined: Aug 2003
Posts: 43,099 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,099
Bend,OR USA
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Iron heads or aluminum? I've raced a lot of loose lash cams like that one, both flat tappet solids and solid rollers, with .006 to .012 tighter hot with no bad results that I know of Most of them ran quicker tighter than looser like the cam card called for Running them tighter makes the motor think the cam is bigger, looser acts smaller
Last edited by Cab_Burge; 01/17/21 02:17 AM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Roller Cam Lash Reduction
[Re: Moparrob68]
#2875504
01/17/21 01:25 PM
01/17/21 01:25 PM
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Joined: Jul 2004
Posts: 19,317 State of confusion
Thumperdart
I Live Here
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I Live Here
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Posts: 19,317
State of confusion
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Been tightening up my lash on solid flat tappets and my current roller .010-.012 forever w/zero issues.....
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
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Re: Roller Cam Lash Reduction
[Re: old_racer]
#2875692
01/17/21 07:08 PM
01/17/21 07:08 PM
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Joined: Oct 2007
Posts: 4,205 New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,205
New York
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If you have the intake PV clearance advancing should help
Boffin Emeritus
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Re: Roller Cam Lash Reduction
[Re: hemienvy]
#2875786
01/17/21 10:10 PM
01/17/21 10:10 PM
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Joined: Jan 2004
Posts: 8,233 fredericksburg,va
cudaman1969
master
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master
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Posts: 8,233
fredericksburg,va
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It really has nothing to do with PROPER valve lashing, .030 is proper on that cam. A softer ramp on any lobe profile will be just that, softer. There is zero valve lift at all until lash is taken up, so altering the lash has zero effect on valve open time. The take-up ramps are not part of the lift profile. So you’re saying that if adjusted to .015 instead of .030 won’t affect lift? Roll that cam around to total lift, then crank that adjuster down another .015 (light spring) won’t that make the valve that amount farther off the seat?
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Re: Roller Cam Lash Reduction
[Re: cudaman1969]
#2875806
01/17/21 10:53 PM
01/17/21 10:53 PM
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Joined: Aug 2003
Posts: 43,099 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,099
Bend,OR USA
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The rocker arm ratio has a lot to do with how the motor reacts to any change in the valve train, especially lift and duration off of the seats I ended up with Isky RR602 solid roller lifter grind for wedges that had the slowest opening ramps I have ever seen when degreeing that cam, it was horribly slow getting to .050 lifter rise, HORRIBLY slow It ran fine in all three motors that I had installed it in but it was not as fast in the 60 Ft. times or on the top end MPH in the 1/4 mile with better cams in the same motors Don't forget that a lot of cam development was done way before computer where use for that function, a lot different technology back then I think Mark Heffengton was one of the first, if not the first, to use modern technology in designing solid roller drag race cam lobes back in the early 1970s
Last edited by Cab_Burge; 01/17/21 10:57 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Roller Cam Lash Reduction
[Re: Cab_Burge]
#2875857
01/18/21 12:32 AM
01/18/21 12:32 AM
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Joined: Jan 2003
Posts: 6,135 Melbourne , Australia
LA360
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master
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Melbourne , Australia
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I don't think an old shelf cam like that is going to beat up anything with the right spring on it. It's not going to be an aggressive lobe by any means.
Personally, I wouldn't mess around with the lash too much, unless I had some way of determining it was an improvement (Engine dyno for example). I have seen people tighten it up and even loosen it up to about 0.040"- 0.042" and make gains.
Alan Jones
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Re: Roller Cam Lash Reduction
[Re: rebel]
#2875972
01/18/21 10:33 AM
01/18/21 10:33 AM
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Joined: Aug 2005
Posts: 759 Southington Ct.
turbobitt
super stock
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super stock
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Southington Ct.
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Keep in mind that when you tighten up the lash you are really just getting into the Accel/Decel ramps of the cam where the lobes are really lazy so you may just be adding a bunch of overlap and hurting engine vacuum and throttle response. .
With that being said, some of the newer cam profiles with more aggressive ramps and tighter spec lash settings are really critical to lash settings because Accel/Decel ramps are much shorter/smaller and require that tight lash setting.
AG.
1970 Challenger w/572 Hemi street car and my pride and joy.
1986 T-Type with 272 Stage 2 Buick V6 engine - True 8 second street car. Just updated the engine and put down 928 HP @ 35# boost to the ground on chasis dyno.
1976 Cee Bee Avenger Jet Boat - 460 Ford powered.
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Re: Roller Cam Lash Reduction
[Re: hemienvy]
#2876149
01/18/21 03:44 PM
01/18/21 03:44 PM
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Joined: Oct 2007
Posts: 4,205 New York
polyspheric
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master
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New York
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Tighter lash extends duration in both directions (the tappet begins to move earlier and stops later) to add degrees to the intake opening BTDC and exhaust closing ATDC: overlap. Whether this significantly affects reversion, etc. is a different question. What does not change: LSA (assuming the lobes have symmetrical ramps in both directions).
Boffin Emeritus
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Re: Roller Cam Lash Reduction
[Re: hemienvy]
#2876316
01/18/21 09:51 PM
01/18/21 09:51 PM
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Joined: Aug 2005
Posts: 759 Southington Ct.
turbobitt
super stock
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super stock
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Posts: 759
Southington Ct.
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turbobitt:
"Keep in mind that when you tighten up the lash you are really just getting into the Accel/Decel ramps of the cam where the lobes are really lazy so you may just be adding a bunch of overlap and hurting engine vacuum and throttle response. "
This is completely wrong. You are not adding any overlap. I believe I am right. As stated, the EVC and IVO overlap increases with less lash, especially on a lazy high lash lobe profile. I have done many cam profiles, too many to remember all the idiosyncrasies of each lobe. I dug this one up from a project I was working on a few years ago comparing Comps "TC" Lobe family with a more aggressive "QRI" lobe Family. AG.
Last edited by turbobitt; 01/18/21 09:52 PM.
1970 Challenger w/572 Hemi street car and my pride and joy.
1986 T-Type with 272 Stage 2 Buick V6 engine - True 8 second street car. Just updated the engine and put down 928 HP @ 35# boost to the ground on chasis dyno.
1976 Cee Bee Avenger Jet Boat - 460 Ford powered.
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