To those with cams.

[3400-95-Modified]

Now I need to get custom length pushrods for my engine since I got a Milzy stage one cam. I know on his site that it says you dont need pushrods but if you measure the base circle of the cam from a stock one its smaller, therefore you will loose hydraulic preload on the lifters if you stick with the stock size. Now my question is, can I go and order a set of pushrods that are the base circles radius difference, longer? If your confused I'm thinking that I measure the base circle, get the radius and then just add that to the length of the stock pushrods and I should be set right?

I know how to check valve geometry but nothing else is changing except for the cam base circle. I could understand that I would need to do much more research if I decked the heads, or used longer valve stems or something weird like that but the only change here is the cam.

Any info appreciated.

[rickykline]

whats the difference size of base circle on the milzy cam? noone else is running custom pushrods at least noone i know...

[3400-95-Modified]

I think its .070 dia base circle difference on a stage one, I will recheck that tonight. If they are not running custom pushrods then they are not getting full lift. Or they will float the valves easier, there is approx 1.5 turns of hydraulic preload on the lifters STOCK, so I don't want to take that away, Obviously there is room to take up the .035 base circle radius difference but the preload is there for a reason, taking it away will result in sooner pump down of the lifters loosing lift and getting float.

[AaronGTR]

You're using the stock pedestal rockers that automatically set the height and lash right? Then I'd say yes, all you need is to take the difference in radius of the base circle of the stock cam to the new cam and add that to the length of the pushrods. That should give you the same amount of hydraulic pre-load. You are only talking about less than 1/28 of an inch though so I don't know how much difference that will really make. It would probably matter less with the hydraulic pre-load but more for the end lift, since after a 1.6:1 rocker it would give .056 more lift at the valve (about 1/18").

[Superdave]

I was wondering the same thing since i'm getting a regrind. Just add the base circle difference to the pushrod length and order 'em up...?

[3400-95-Modified]

To answer your question yes I'm using the stock rockers so yeah they auto adjust, but only if the pushrod is the right length. But I guess your info makes me fell like I was thinking along the right track. I'll remeasure that difference with a more accurate tool and then post my findings.

[3400-95-Modified]

Just measured a stock cam and the milzy one once again with cheapo plastic calipers, I didnt bring a good set home so I'll bring the cams to work instead.

Stock cam base circle was ~1.285 Dia
Stage 1 cam base circle was ~1.215 Dia

so that is a .070 difference like I thought. So that would mean a .035 longer pushrod should take care of it.

If anyone has a stock cam to double check my measurement that would be good.

[Superdave]

so not to go off on a tangent or anything.. but since most of us change the LSA and all.. i'm sure degreeing the cam in is a must right?

[3400-95-Modified]

Unless you have setup for an adjustable cam gear degreeing the cam will not help you. Most companies will determine the degree you should run for optimum performance and grind the cam to fit that. Since the 3x00 motor is timed by a pin on the cam, changing that by a few degrees means you need to machine out the timing gear and then make slightly offset collars to go over the pin to move the gear 1 or more degrees in a certain direction.

I guess regrinds are a different story, I'm not sure how milzy grinds his cores to fit, but I'm sure since nothing has been mentioned about it, its not something we need to worry about.

[jackal2000]

MMS cams install straight up

[3400-95-Modified]

No they dont. Your base circle is missing material it needs to be compensated somewhere and if you think it doesn't then you don't know how to build a motor. Even Ben will back me on this statement.


Back on topic

Ok well I asked Smith brothers and they told me to build the motor and using an adjustable pushrod to set the pushrod to zero lash and then to add .030 to that for proper hydraulic preload.

Is this a normal amount of preload, and enough??

[sprucegagt]

I guess regrinds are a different story, I'm not sure how milzy grinds his cores to fit, but I'm sure since nothing has been mentioned about it, its not something we need to worry about.

No they dont. Your base circle is missing material it needs to be compensated somewhere and if you think it doesn't then you don't know how to build a motor. Even Ben will back me on this statement.

Seems to me your contradicting yourself. But if your using stock rocker arms, I don't see where .035" of pushrod length will make a difference. Stock rockers aren't anywhere near as critical with pushrod length as say roller tip rockers.

Jackal was saying that you install Milzy's cam straight up (aka 0*). So no need to jump on his case.

[3400-95-Modified]

Seems to me your contradicting yourself. But if your using stock rocker arms, I don't see where .035" of pushrod length will make a difference. Stock rockers aren't anywhere near as critical with pushrod length as say roller tip rockers.

Jackal was saying that you install Milzy's cam straight up (aka 0*). So no need to jump on his case.

Ok yes maybe I did jump on jackal since I didnt know what he ment... this thread was about pushrod lengths to begin with so thats what I thought he was referring to.

and how do those two quotes contradict each other?The first quote I was replying to superdave on how cams are ground degree wise, since milzy starts with a blank and can grind anything and a regrind may have limitations. The other one has to do with a base circle diameter for pushrod length... Not even remotely alike.

[sprucegagt]

and how do those two quotes contradict each other?The first quote I was replying to superdave on how cams are ground degree wise, since milzy starts with a blank and can grind anything and a regrind may have limitations. The other one has to do with a base circle diameter for pushrod length... Not even remotely alike.

Okay maybe they weren't contradicting. But now your just being confusing. Jackal answered your question about Milzy's cam grind, but you jumped on him about pushrod length instead. So what are you getting at?

[SappySE107]

How does .035 in pushrod length not matter as much with stock rockers vs roller tip?