Found my cam base lobe dimensions... advice?

[Rhedalert]

I have been looking for this piece of paper for 100 years. I've been running a Comp Cam re-grind for about 60k miles now, and always had a somewhat noisy valvetrain (even though lift is a modest .460 @ the valves). I took measurements of the base circle of my re-ground cam lobes and came out with the following:

intake lobes: 1.250
Exhaust lobes: 1.227 (more ground down here due to additional exhaust duration)

Stock is 1.290? I had some trouble finding the exact measurement. If that's the case then I should look to extend my pushrods by (approximately...I know since the valves are splayed it will effect the numbers, but for simplicity's sake):

Intake: 1.290- 1.250= 0.040/2 = 0.020
Exhaust: 1.290- 1.227= 0.063/2 = 0.0315

Is this enough to be concerned about looking to have custom length pushrods made?

[SappySE107]

I would run longer exhaust at the very least. Intake is borderline.

[3400-95-Modified]

yeah I've found there is almost .080 of preload on a stock pushrod/cam setup.

If I could find my papers from when I did the stock vs milzy setup I found out that I didn't NEED custom pushrods with that cam, but I did it anyways to keep the factory preload.

[Rhedalert]

Cool, thanks all. I figured the factory preload had to be fairly large (.050 and up) since I still had some preload, even with my exhaust lobes being so much smaller @ the base. But .080, damn!

Who's been making good pushrods lately?

[3400-95-Modified]

Ben or Smith Brothers...

This was my original e-mail to smith bro's

Well in trying to determine the length of pushrods that I need I have come up with a few numbers, I measured my pushrods and got 5.747 for the intake and 6.077 for the exhaust, these are ball to ball pushrods with a oil hole on them. 5/16 ball and a 5/16 shaft with a 0.1 dia oil hole

Maybe you can help from prior experience, but I am trying to get the right length pushrod for my 05 GM 3400 SFI motor with a Stage 1 Milzy Motorsports cam. The one measurement I can tell you about the cam that will help is the base circle is .070 smaller in diameter, so if I'm guessing right I would need a .035 longer pushrod than stock correct?

So the numbers I came up with in the end are 5.782 and 6.112 for length.
Theoretical length that is due to the oil hole.

Let me know if those measurements sound about right and if so, do you have pushrods that would fit my application. They do not run against a steel pushrod guide so I don't "need" hardened ones. I would need 6 of each for a quote.

Thanks
-Jonathan Chmura

and this is what I ended up doing...

Ok well in doing some research and doing a bunch of different measurement methods I have come up with the pushrod lengths I need. Now I need 6 of each and they are 5/16 ball and a 5/16 shaft with a 0.1 dia oil hole, these measurements are straight off of the pushrod with the oil hole in it. As you refer to as the Theoretical length. Drop me a price and how to order and I'll be in touch. (correct me if I'm using the wrong part number)

Intake 5.782 (X6) NR54B-BB
Exhaust 6.112 (X6) NR54B-BB

I came to these numbers by trying your Zero lash method, and then asking around and finding out what others have done. The zero lash method gave me a pushrod that ended up being shorter than the stock one... and that just didn't make any sense to me. I then did some math and someone told me to use A^2+B^2+C^2 to get the length I need since my valves are splayed like a big block. He then tested that formula with the stock length hypotenuse, and a 1" splayed amount and got the straight length, then adding .035 to that for my cam loss the pushrod length only grew .036, So I can go with
.035 to .036 longer and be good with it and retain stock valve train preload....

If you understand any of that cool... If not well Just thought I would fill you in on why I got those numbers.

SO after all that crap my point is, I was told to do a zero lash and then add .030 to the length for preload and that came up shorter than a stock pushrod and this was after removing .035 from the base circle arleady... so its way more than .035 preload to begin with and IIRC it was close to .080 but I would have to find all those numbers again and I don't know where I put my zero lash numbers.

And this length pushrod worked fine, and I also sold this whole setup to someone on this board.

[Rhedalert]

Thanks for that info. The big discrepancy is if the factory specified preload is required. Most people go with 030 preload but with us it's supposed to be much greater. I have enough preload (as did you originally) but did you notice any change in valvetrain noise or performance with the change in pushrods?

Thanks!

[3400-95-Modified]

The pushrods I ended up getting had the same preload as stock, didn't have any extra noise, the cam I have now has a little extra valve noise but that may be due to just the high lift and radical duration alone, I'm not sure what Ben does for preload on his setups since this is one that he measured out and sent to me.