Gen 2 Hybrid Pushrod Length Help, and Base Circle

[ghrarhg]

I have a gen 2 2.8 with a 3400 top end, and an engle cam. I'm measuring for pushrods, and i'm getting some silly numbers. I just want to make sure I'm not losing my mind. First 2 questions:

1) What are the stock lengths of the gen 2 pushrods. I don't have a caliper large enough to measure right now.


2) I've found that the exhaust seem to be in the 6.25 range and intake in the 5.95 range for most hybrids, is this with stock cams?

I'm getting closer to 6.416 or so exhaust and 6.116 on the intake side. This is with comp lifters. Seems like I have .166 more than everyone else.

My engle cam has a base circle of 1.202 plus or minus .002 on all lobes. According to my measurement on the stock cam, this makes it about .120 smaller than the intake and .060 smaller than the exhaust base circles on the stock cam.

Based on the difference in base circle, I really don't understand how my pushrods seem to be so much longer. Can anyone post a link to the proper method in case I'm missing something. I could see coming up short if I was doing it wrong, but not long???

[ghrarhg]

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[ghrarhg]

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[kitabel]

It's very difficult to anticipate the exact pushrod length until you have the rocker geometry done. Even if the new cam is stock lift and the valves are stock, simple seat wear will raise the stem height.
Assuming you favor the Miller "mid-lift" method, you may need lash caps or a height change to the rockers to get this. Don't be surprised if the intakes and exhausts are different.
At this point, the best PR length is whatever gives you a small adjustment - the length in inches is not relevant.

[gsEnterpries]

kinda off topic but, how is that Engle cam working out. Im asking cause I want to get one but I rather hear somenews about'em first

[ghrarhg]

I haven't fired it up yet. I was trying to get some pushrod advice (see above). I just ended up ordering custom pushrods, so hopefully they'll show up by this weekend, or early next week at the latest.

Bottom line is, it's probably going to be mid week next week (if everything shows on time) before this thing fires up. I will post an update as soon as it does.

[ForcedFirebird]

It's very difficult to anticipate the exact pushrod length until you have the rocker geometry done. Even if the new cam is stock lift and the valves are stock, simple seat wear will raise the stem height.
Assuming you favor the Miller "mid-lift" method, you may need lash caps or a height change to the rockers to get this. Don't be surprised if the intakes and exhausts are different.
At this point, the best PR length is whatever gives you a small adjustment - the length in inches is not relevant.

Agreed. Since the Gen 3 top ends don't have adjustable rocker arms (unless you go aftermarket) pushrod length is critical, specially with cam MFGR's having different base circle diameters. I got a custom reground cam and it just so happened that the Gen2 pushrods were a perfect fit. I would suggest putting the motor together and counting the turns from zero lash to the rocker pedestal seats on the head. You should have about 1-1.5 turns for a good fit.

and kitabel, I KNOW for a fact that the intake and exhaust pushrods will be different lengths since these are canted valves