SoCal Jet Boats

Tech Talk => Engine Mechanical / Electrical => Topic started by: Mark on August 20, 2008, 06:57:29 AM

Title: Measuring for new pushrods?
Post by: Mark on August 20, 2008, 06:57:29 AM

The new Dart heads require pushrods that are 0.20-0.25" longer than stock, they recommend measuring for an exact fit -- but fail to mention how to do this.

The motor is a 4 bolt Mark 4 BBC and I'm using around a 0.55" lift hydraulic cam and long slot stamped rocker arms.  Is there a normalized height or angle you set the rockers to so the pushrod length can be determined?

Thanks, Mark

Title: Re: Measuring for new pushrods?
Post by: Ralph Brunt on August 20, 2008, 07:44:28 AM

valve train geomotry
http://www.compcams.com/Technical/FAQ/ValvetrainGeometry.asp (http://www.compcams.com/Technical/FAQ/ValvetrainGeometry.asp)

Title: Re: Measuring for new pushrods?
Post by: jet boat performance on August 20, 2008, 09:01:09 AM

Good info from Comp ! Mark order or buy a "checker" or if you have Two old pushrods (long and short) you can cut them in half and thread in a stud to creat a length checker ,once you get the geonmetry right then simple measure the OAL and order accordingly , Summit usually has a good selection ,we buy from Smith Bros in Oregon ,inexpensive and custom lengths, great service! Tom

BTW I think your going to find the length needed is considerably more than .025 ,more like .250 (1/4 inch) and your right Dart doesn't put that info out there but valve train geometry should be checked on every build
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fus.st12.yimg.com%2Fus.st.yimg.com%2FI%2Fchucker54_2012_78206102&hash=ee604dfdd986c881f49588bc34c191c62b3a5c93)

Title: Re: Measuring for new pushrods?
Post by: Mark on August 20, 2008, 09:39:03 AM

Thanks for the info.

My problem is that I'm using stamped steel long slot rockers, not rollers like in the described procedure.  The stamped steel rockers have a slightly curved contact face that seems to "slop" across the valve stem surface rather than rolling in an easily seen pattern.

Sorry about the confusion over the added length.  Force of habit to never leave a leading decimal point on a dimension.  A drafting teacher 35 years ago is to blame for this  :)

Thanks, Mark