bent pushrod, 18psi of boost
May 22, 2011 | 03:13 PM
#11
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single digit dreamer
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From: omaha ne
OK,So same way as a ls style rockers.The lifter was preloaded a little more with the 918's then stock I would guess.This is likely a matter of just changing the PR's I would guess,but the more I look at the way its bent just seems a lil suspect.Maybe somebody can share a picture of another PR thats bent.Preferably in a scenario where the problem was corrected.
my mind is going with things like maybe i chunked a piston and that got in the way of the valve and bent the pushrod... aren't 918's pretty mild as far as after market springs go?
oh well. i have a set on the way and should be ready to test again on tuesday or so.
May 22, 2011 | 04:13 PM
#12
Yeah,918's are a relatively mild performance spring.I don't think the piston hit the valve cause,I'm sure it would've popped the lock.I mean it is a possibility but,just not a likely suspect IMO.Do you know if the bend in the PR was on the upper portion by the head or the lower closer to the cam?I wanna guess the cam side.
May 22, 2011 | 07:59 PM
#13
How high is the owner trying to rev the little 4.3L? The hydraulic roller small-block derived engines have notoriously heavy valve-train and coupled with relatively low spring pressure and high boost, I wouldn’t be surprised if the engine tried to float the valves and under so much boost it just bent the pushrod. The lifter preload shouldn’t change just swapping the springs, as the installed height of the valve-stem didn’t change, only possibly the spring height depending on the retainer/lock combination. That being said, if he ever found the need to pull the heads; I would have the heads machined for screw-in studs and guide-plates, so he would have a stronger fully adjustable valve-train, especially if he ever decided to move up to a stronger set of valve-springs. Better pushrods may help or just be a band-aid if the engine is trying to float the valves; if this is what’s happening, I would increase spring pressure or at least look at installing a REV kit to keep the heavy hydraulic roller lifters under control and possibly extend the rpm capability a little. The problem is I don’t know of anyone that currently offers an out-of-the-box REV kit for the 4.3L V6 and it may require the modification of a kit designed for a SBC. Installing a good set of hardened steel pushrods is still a wise investment.
Just some food for thought, whatever the case, the little engine is running very well. Good luck!
Just some food for thought, whatever the case, the little engine is running very well. Good luck!
May 22, 2011 | 10:17 PM
#14
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single digit dreamer
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From: omaha ne
pushrod bent toward the cam. the hole in the head help to keep the top strait.
we are not reving it high at all. stock cam. looking at the logs it goes to 5500rpm in 1st and 5200 in 2nd.
everything i am hearing says just try the pushrods. thanks.
we are not reving it high at all. stock cam. looking at the logs it goes to 5500rpm in 1st and 5200 in 2nd.
everything i am hearing says just try the pushrods. thanks.
May 26, 2011 | 05:50 PM
#20
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single digit dreamer
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From: omaha ne
got the 7.2" comp pushrods in there. nice and quiet now.
took it for a spin, ran it thru the gears a few times with no issues. pulls nicely. now we need it to stop raining so we can goto the track.
took it for a spin, ran it thru the gears a few times with no issues. pulls nicely. now we need it to stop raining so we can goto the track.