Valve train geometry
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==Overview== | ==Overview== | ||
Valve train geometry is an important aspect of building a performance engine. If done correctly, having the correct geometry will increase power and reliability. | Valve train geometry is an important aspect of building a performance engine. If done correctly, having the correct geometry will increase power and reliability. | ||
==Measuring a pushrod== | ==Measuring a pushrod== | ||
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Overall or "actual" length doesn't always equate to the pushrod length as specified by the manufacturer, odd as this sounds. The difference is in whether the pushrod was measured by overall or actual length (longest measurement of the three), "theoretical" length (about 0.020" longer than actual length) or "gauge" length (longest of the three). | Overall or "actual" length doesn't always equate to the pushrod length as specified by the manufacturer, odd as this sounds. The difference is in whether the pushrod was measured by overall or actual length (longest measurement of the three), "theoretical" length (about 0.020" longer than actual length) or "gauge" length (longest of the three). | ||
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===Chevy small block=== | ===Chevy small block=== | ||
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*Stock hydraulic flat tappet SBC- 7.8” | *Stock hydraulic flat tappet SBC- 7.8” | ||
| − | *SBC OEM hydraulic roller pushrods are 7.2” long. When using shorter | + | *SBC OEM hydraulic roller pushrods are 7.2” long. When using shorter GM OEM roller lifters from the 3.1L or 3.4L V6, or the 2.2L inline 4 cylinder engines, start with 7.500" pushrods. These lifters are mostly only used when converting a flat tappet block to use an OEM roller cam, although they might be an advantage in a roller block due to their lighter weight. |
*Crane retro hydraulic roller- 7.046" | *Crane retro hydraulic roller- 7.046" | ||
*Retrofit roller lifter pushrods are 7.300". | *Retrofit roller lifter pushrods are 7.300". | ||
===Pontiac V8=== | ===Pontiac V8=== | ||
| + | Stock pushrod length- 9.130". It has been published that if using Chevy lifters, the pushrod length is 9.290” as a starting point. However, caution must be used if Chevy lifters are going to be tried in a Pontiac engine because the oil band is in a different location. This could effect oiling. There are aftermarket lifters advertised for use in both Chevy and Pontiac engines. These should also be checked but the assumption is that the oil band is correctly located for both applications. | ||
| − | + | ==Things that can affect pushrod length== | |
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| − | ==Things that can | + | |
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A large number of variables are involved in determining the correct length pushrod for your application. Pushrod length is affected by any of the following: | A large number of variables are involved in determining the correct length pushrod for your application. Pushrod length is affected by any of the following: | ||
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==Mid lift theory of valve train geometry== | ==Mid lift theory of valve train geometry== | ||
| + | ;Info from Jim Miller<nowiki>:</nowiki> | ||
| + | *[[Media:MILLER ROCKER GEOMETRY.pdf|Rocker Geometry]] article from the AERA (Automotive Engine Rebuilders Association) quarterly magazine, '''''Engine Professional''''' by Jim Miller | ||
| + | *[[Media:MILLER ROCKER HISTORY MID LIFT.pdf|History of Mid-Lift]] By Jim Miller | ||
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| + | ;Hotrodders forum threads<nowiki>:</nowiki> | ||
| + | *[http://www.hotrodders.com/forum/mid-lift-rockers-206836.html?highlight=MID+LIFT+MILLER Miller mid lift rocker theory] | ||
| + | *[http://www.hotrodders.com/forum/rocker-arm-199353.html Rocker arm geometry] | ||
| − | + | ;Example of instructions for Miller Mid-Lift PA Series rockers | |
| + | *[[Media:Miller pg 1.png|Page 1]] | ||
| + | *[[Media:Miller pg 2.png|Page 2]] | ||
==Tools== | ==Tools== | ||
| − | [[File:PUSH ROD LENGTH CHECKING TOOL | + | [[File:PUSH ROD LENGTH CHECKING TOOL 004.JPG|thumb|left|400px|Homemade adjustable pushrod length checking tool]] |
<br style="clear:both"/> | <br style="clear:both"/> | ||
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| + | [http://www.homemadetools.net/forum/adjustable-push-rod-length-checker-5 Instructions] for making an adjustable pushrod length checker. | ||
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| + | Other homemade pushrod length checking tools at [http://www.homemadetools.net/tag/push-rod HomemadeTools.net] | ||
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| + | Miller uses a MID-LIFT G-TooL to measure for geometry. It is quite different from the other devices on the market, like from Comp Cams and others that are used to estimate pushrod length. | ||
==Resources== | ==Resources== | ||
| + | {{Note1}}Also see wiki page [http://www.crankshaftcoalition.com/wiki/Valve_train_points_to_check '''Valve train points to check'''] | ||
| + | *Circle track article ''[http://www.circletrack.com/techarticles/ctrp_0611_rocker_arm_valvetrain_geometry/viewall.html Rocker Arm Geometry And Valvetrain Alignment], A Detailed Explanation Of Valvetrain Alignment Goals'' by Bob Bolles, from February, 2009 CT mag | ||
*Lunati article [http://www.lunatipower.com/Tech/Valvetrain/HowToVerifyValvetrainGeometry.aspx How to verify valve train geometry] | *Lunati article [http://www.lunatipower.com/Tech/Valvetrain/HowToVerifyValvetrainGeometry.aspx How to verify valve train geometry] | ||
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*Wiki page [http://www.crankshaftcoalition.com/wiki/Category:Adjust_valves Adjust valves]<br><br><br><br><br> | *Wiki page [http://www.crankshaftcoalition.com/wiki/Category:Adjust_valves Adjust valves]<br><br><br><br><br> | ||
[[Category:Engine]] | [[Category:Engine]] | ||
| − | + | [[Category:Camshaft]] | |
[[Category:Cylinder head]] | [[Category:Cylinder head]] | ||
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| + | {{develop1}} | ||
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