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| Pushrod Tech (Page 1/2) |
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La fiera
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MAY 25, 11:38 PM
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sleek fiero
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MAY 26, 10:56 AM
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Rae;
Again great job on this post. really opened my eyes to how important pushrod length is. Bill
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Frenchrafe
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MAY 26, 11:01 AM
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Hi Rei,
Rumble isn't available in France.
Shame I can't see your vids.🙁
Cheers,
Rafe------------------
"Turbo Slug" - '87 Fiero GT. 3800 turbo. - The fastest Fiero in France! @turboslugfiero
https://youtu.be/c4Cu7_2OgYc
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fieroguru
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MAY 26, 06:31 PM
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The LS engines already start with 1.7 and 1.8 ratio.
You can accomplish the same with the LS engines with a proper shim under the rocker arms to dial in the preload with the longer pushrod.
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La fiera
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MAY 26, 08:25 PM
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| quote | Originally posted by fieroguru:
The LS engines already start with 1.7 and 1.8 ratio.
You can accomplish the same with the LS engines with a proper shim under the rocker arms to dial in the preload with the longer pushrod. |
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Yes, but you'll have to get the shims and the pusrods to accomplish the same. If the pusrods are not changed along with the shims instead of increasing lift and duration they will decrease regardless of the rocker ratio. If the preload is at max (no hydraulic cushioning) pushing the plunger all the way down, once that motor revs high enough the oil pressure will pump up the lifters holding the valves open when they are suppoused to be close and then........ Ask me how I know, that's why I gave up on hydraulics years ago.
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pmbrunelle
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MAY 26, 09:55 PM
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I think it is most interesting to optimize to minimize the movement of the rocker arm across the tip of the valve, for long life of valve guides.
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claude dalpe
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MAY 27, 08:28 AM
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I Agree with pmbrunelle and it requires more explanation from you to better understand
Yes the fiera you get more valve opening this way but we can see that the roller of the rocker moves on the valve stem which leads to a valve guide wear
Maybe premature valve guide wear is negligible and worth it ?
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sleek fiero
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MAY 27, 12:05 PM
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| quote | Originally posted by La fiera:
Yes, but you'll have to get the shims and the pusrods to accomplish the same. If the pusrods are not changed along with the shims instead of increasing lift and duration they will decrease regardless of the rocker ratio. If the preload is at max (no hydraulic cushioning) pushing the plunger all the way down, once that motor revs high enough the oil pressure will pump up the lifters holding the valves open when they are suppoused to be close and then........ Ask me how I know, that's why I gave up on hydraulics years ago. |
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This is the reason I set my valves at zero lash as Crower says to for this cam rather than the 1/4 to 1/2 turn of preload most builders use. Definitely don't want valves leaking at high rpm or any rpm.
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La fiera
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MAY 27, 09:58 PM
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| quote | Originally posted by claude dalpe:
I Agree with pmbrunelle and it requires more explanation from you to better understand
Yes the fiera you get more valve opening this way but we can see that the roller of the rocker moves on the valve stem which leads to a valve guide wear
Maybe premature valve guide wear is negligible and worth it ? |
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All rockers move across the valve tips, there's no way around this and Yes, faster guide wear might be an issue. As a matter of fact is an issue regardless of the aggressiveness of the rocker ratio, whether is OHV or OHC. The key to control valve stem and guide wear is to use the right material and the preparation of the valve stem. I do that personally. I buff a coat of dry WS2 on the valve stem and put a light coat of hi pressure/high temp assembly lube and that seems to do the job. Every time I take one of my engines out for any reason, the heads go the the racing shop and get torn apart and inspected by a professional (That particular shop sponsors me with service, no cash) and they keep a record of the stem and guide measurements.
Have you ever seen a hybrid car or any other engine management system that shuts the engine off at a traffic light to prevent the engine from idling? My 2010 Prius has 250 thousand miles and it doesn't smoke or have any sign of valve stem, valve guide or valve seal wear. I'm pretty sure it has some wear because it is inevitable but not to the point the point where the valve rocks and wear the seal out and oil finds its way down the valve stem collecting behind the valve and crating a lump of carbon due to the burning of that oil. And the visible sign is blue smoke out of the exhaust during deceleration and idle.
The point you are bringing is true, valve wear is inevitable but the number one valve stem, guide and seal killer is prolonged idling.
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claude dalpe
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MAY 28, 03:53 PM
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Rei I just want to understand, not say that it's not good what you're explaining
I start my explanation again, when you have the right push rod length the rocker does not move on the valve stem or very slightly but in general the rocker remains in the center of the valve stem which gives normal wear of the guides
Your example of your prius, is good but it's a stock engine my everyday car (honda accord) has almost 300,000 km and doesn't take oil either and it's stock.
In your video we can clearly see the rocker (the longest push rod ) moving on the valve stem (the rocker does not stay in the center of the valve)
Like I said in my other post he there needs to be an explanation why the guys who modify engines adopt this modification probably the engine is rebuilt more often and they don't mind having a bit more wear at this place ?
Watch this little 2 minute video it's well explained
https://www.youtube.com/watch?v=Cqx8Cs6O6Vo
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