604 Pushrod Length Change ***IMPORTANT -- PLEASE READ***

Let me start by saying I am not a proponent of Crate racing. Since the decision was made to allow blue-printing & resealing with cable ties, the cost advantage touted years ago is lost. There is no longer a cost saving aspect. Especially if you run up front.This post is directed at those in particular who still run GM style bolts and have not had their motor apart. This is also to help those whose engine builder may not be aware. The below post on Facebook brought this information to light this weekend for more than a few people during protest at the I-75 raceway. Direct quote is below as well:

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From GM: Push rod number 10421740 has been superseded by part number 12371041 as depicted on engine as you really have no way of knowing which push rod the engine came with. If the engine has been rebuilt and the rebuilder replaced the push rods with new from the GM they would be the 12371041. As that is what would be shipped unless the early number was specified. With this being said part number 12371041 is 5/16 diameter with a length of 7.192. After confirming this information with GM and Marvin Ford, Zach Shannon has been declared Legal.

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For the Facebook post:https://www.facebook.com/pg/I75motorspeedway/posts/ There is a LONGER pushrod option available as a replacement part. Reference page 38 of the below manual. Optional pushrod replacement number is 12371041. This part is available through Speedway Motors (as well as many others) via the next link.The rulebook is available here http://staffordmotorspeedway.com/wp-...ECH-MANUAL.pdf [PAGE 40]And the parts are available herehttp://www.speedwaymotors.com/GM-Per...-16,70648.html Note the length of the above is 7.191"Take a look at the manual again, this time on page 14. Below is the direct quote:

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P/N 10241740 is used in 88958603 & 88958604 engines. It is a HD pushrod that has a .060” walland 7.122” long and 5/16” diameter.

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Original pushrods in these motors are 7.122" long. The new replacement pushrod is 7.191" long. By some simple math, the new APPROVED pushrods are .068" (68 thousandths) LONGER.Without getting into camshaft/valvetrain geometry, which you are welcome to research yourself, I suggest anyone with a stock-length pushrod immediately order and replace with the 12371041 pushrod before their next race. Without question, this may be why that guy with a blue-printed motor is beating you by a few tenths every lap.Again, this is only in the interest of equalizing competition for all. Is that not what this CRATE engine mess was not intended to do in the first place?Thanks for reading.Links below. Sorry for formatting issues, tried to correct the URLs.https://www.facebook.com/pg/I75motorspeedway/posts/http://www.speedwaymotors.com/GM-Per...-16,70648.html http://staffordmotorspeedway.com/wp-...ECH-MANUAL.pdf

I applaud your post and effort into awareness for all to see.
I have to admit that after reading your post I was somewhat embarrassed about not having any knowledge on this.
My shop is an authorized rebuild center for many different sanctions and I am personally a tech inspector and advisor of tech with many tracks and sanctions across the country.

in our shop we rarely replace pushrods but I do keep a set on hand for replacement even though I have hundreds of used ones up on a shelf

the numbers that you are quoting are different in the respect that
10241740 is a single push rod
and
12371041 is a kit (16) pushrods
the kit (to my knowledge) is simply 16 of part #1024170

the circle track tech manual does specify a length of 7.122" and that is still the spec in the latest version that I have which is 2 versions newer than the one you gave a link to----------there is a newer version in the works and if it has not already it should be released soon-----we can only hope that this dimension has been corrected in the newest version of the tech manual.

I only had 1 pushrod left in my shop kit (12371041) and it did measure 7.191"
I pulled one from a newer engine that just came in for rebuild and it was 7.193---engine had never been touched
I pulled one from a older engine that is here for rebuild and it was 7.191"
I pulled several off of my used parts shelf from various years and they ranged fro 7.190" to 7.193"
I decided to dig really deep---I have an engine way in the back that is still all together and it is a 2005 engine (which would be one of the very first engines---it has been on my back shelf for more than 5 years---the pushrod in it measured 7.190

my conclusion at the moment is that they have always been 7.190ish and the technical manual has been wrong in its dimension----there is also the possibility that when the manual was written the measurement was being taken in a different manner other than total length (speculation)

as a tech inspector we have always used a "known legal" pushrod as comparison rather than an actual dimension as it would be very simple to see one that is a 100 thou too long and even 50 would be noticed if looked close

I will discuss this entire topic with GM officials that are deeply involved in the engineering of this engine and report back if in fact there was ever an actual change but at this point this evening I feel the book is simply mis printed

Brad
www.race-1.com

Brad,Thank you for taking the time to respond. As an anonymous, first-time poster myself, your post really adds validity to the original message. Again, the crate deal is only fair if everyone is on the same page.I'd like to retract part of my original statement. Not everyone should immediately replace these pushrods as I posted earlier. Even though all 604s are 'the same' there is enough variance from castings, to camshafts, lifters and rockers that performance gains from push rod lengths should truly be verified on a motor-to-motor-basis.There has been conversation with other car owners and at least one GM-certified builder in the last few days. There have also been discussions with UCRA officials.First: Car owner (with substantial wins this year) checked a cable-sealed engine. His engine had the 7.122 rods as per the manual.Second: Certified builder pulled rods from a factory sealed engine, again these checked 7.122.From my perspective, without name-dropping, that confirms that the manual-stated length does (or did) exist.Third: Same builder pulled rods from a used cable-sealed engine. These checked 7.191 as per the discrepancy stated.Fourth: Same builder pulled replacement rods from the shelf, and these also checked 7.191. Again,it appears that both rods do exist. My speculation is that either (1) GM has had a part number issue along the way or (2) replacement part manufacturers have done the same.The one glaring issue is that the replacement rods seem to indicate the 355- prefix, whereas the GM part number does not contain this prefix.My understanding is that, at the very least, there will be some clarification from the UCRA group shortly.Thanks again for reading

now you have convinced me that the 7.122 pushrod length exists
after checking the 2005 engine last night and finding it had 7.190 pushrods I was ready to call this a misprint in the book (which has happened in several areas in the past)------but I have just added to our tear down and inspection sheet a spot for pushrod length and we will check every pushrod going thru our shop and/or tech barn from now on.

I thank you very much for sharing this with the public

Brad
www.race-1.com

Won't this increase in pushrods length alter the geometry of the rocker roller pin on the valve tip, basically moving the roller more forward on the tip creating side loading and accelerated valve guide wear? Just wondering.

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Originally Posted by Carlisi

Won't this increase in pushrods length alter the geometry of the rocker roller pin on the valve tip, basically moving the roller more forward on the tip creating side loading and accelerated valve guide wear? Just wondering.

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Depends where it was to start with. i don't believe its enough of a change to cause issues. But like pointed out its a potential performance advantage if the geometry is better with the longer rods.

Guys,
Please read a few threads below
there really was NO difference in pushrod length

Brad
www.race-1.com