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#1
05-05-2020, 01:05 PM
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PIston to valve clearance ??
What's a safe range of valve lift with KRE 74cc heads with a normal felpro gasket, .041 crush, and not worry about clearance issues. TRW L2359 flat top pistons.
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67 Firebird Convert 455 +.060 TH400 74cc KRE d-ports piston dished 16cc H-beam rods Comp Cam 305-AH-8 cam 108* LSA 253/260 @.050 duration .577/.594 lift w/1.65 rockers Ford 9" 3.50 Detroit Locker M/T Sportsman Radials 31x18x15 on Convo Pro 15x15s |
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#2
05-05-2020, 01:51 PM
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That question can not be put in such ball park terms due to how much impact your Cam pick will have!
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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#3
05-05-2020, 02:20 PM
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Valve timing and lift will change clearance but a minimum clearance spec at any given time can be targeted
As far as what that number should be CAN be a matter of opinion but as a rule of thumb if a piston is chasing a valve closed I like to see a bit more clearance there as possible valve float delays closure which in hand reduces clearance at that point in time, Yeah I know ya should spring it to control the valves just a small built in safety factor Conversely if a valve opening is chasing a piston away from TDC you can live with a touch less clearance
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........... The More You Follow The Herd The Less You Can Be In The Lead .......... |
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#4
05-05-2020, 08:10 PM
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Cam specs are in my signature.
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67 Firebird Convert 455 +.060 TH400 74cc KRE d-ports piston dished 16cc H-beam rods Comp Cam 305-AH-8 cam 108* LSA 253/260 @.050 duration .577/.594 lift w/1.65 rockers Ford 9" 3.50 Detroit Locker M/T Sportsman Radials 31x18x15 on Convo Pro 15x15s |
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#5
05-06-2020, 07:45 AM
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I got close once about 20 years ago with a 276/284 @ .050" cam on a 110LSA using the TRW Super Duty replacement pistons. Those have really small valve reliefs in them. The cam had close to .750" lift and it would "bump" the pistons if I rotated it thru without the head gaskets in place.
I'm betting you have PLENTY of clearance with those parts........
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If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
| The Following User Says Thank You to Cliff R For This Useful Post: | ||
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#6
05-06-2020, 07:52 AM
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Do you have these heads?
You say you have the Cam! If so then why are you so reluctant to do the work and place some clay on a oiled up piston top, drop the heads on without the head gasket and rotate the motor thru 2 full revolutions to see what the heck you have?!! I myself have run as tight as .052" on a race motor fighting for compression and that's as tight as I felt comfortable with when you factor in thermal factors and rod stretch, others I know have gone down to .048" which to me is crazy!
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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#7
05-06-2020, 10:02 AM
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Or use a light spring on the valve assemble with lifter cam and put a dial indicator on the valve retainer and then push the valve down and measure clearance. You can even map it using a degree wheel. Usually 8-12 BTDC or ATDC are the closest areas. That also gives you a reference point of future cam swaps. Many of the cam companies have a chart with lone lift at specific degrees 104,106,108,110 to compare.
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Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune [email protected] 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs 1964 Corvette Coupe 327 4 speed |
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#8
05-06-2020, 10:26 AM
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Thanks all. I do plan to do a check this weekend or sooner. Was just trying to get a feel on what to expect. I've heard both ways when doing a clearance check. Use solid or my regular hydraulic lifters?? Solid seems to make more sense.No deflection.
__________________
67 Firebird Convert 455 +.060 TH400 74cc KRE d-ports piston dished 16cc H-beam rods Comp Cam 305-AH-8 cam 108* LSA 253/260 @.050 duration .577/.594 lift w/1.65 rockers Ford 9" 3.50 Detroit Locker M/T Sportsman Radials 31x18x15 on Convo Pro 15x15s |
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#9
05-06-2020, 12:26 PM
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With large cams my closest clearance was at 10 degrees ATDC.
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| The Following User Says Thank You to Old Man Taylor For This Useful Post: | ||
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