ive been doing my own wrenching for years but am just now doing my first complete engine build. its a 383 sbc. i have afr heads im installing scorpion roller rockers. the issue im having (honestly im not sure its an issue yet) is that when i set all of the rockers on the rocker shafts several of them sat so high that i couldnt start the poly locks on the threads. i havet gone through to adjust them yet and its completely possible that when i start rotating the engine that they will plop right on. i watched about 10 videos on how to install them and on every one they sat all of the rockers on and started the poly locks by hand. is this an issue or do i just need to rotate the engine?
Did you make SURE...that the rocker axle is in the correct position ? That is, the machined flat on the axle is "up" while the rocker is over the studs. The axle is round, but has a machined counterbore for the nut to rest properly. This counterbore NEEDS to face up, or toward the adjusting nut. Another possibility is that your pushrods are too long for the combination of rockers and lifters. Have you measured to obtain the correct pushrod length ? This task is clearly written in most cam catalogs. Having the correct pushrod length has another effect. It will provide the "correct" angle for the rocker arms to sit atop the valves. Too short or too long a pushrod will lessen the performance of the cam. You will lose lift and to a small degree duration with the incorrect pushrods. Mike
I agree with Mike. Make sure the axle is oriented correctly. I've had this problem as well. Sent from my SM-G950U using The H.A.M.B. mobile app
While we're on the subject of roller rockers on SBC, I don't want to hijack this thread, but does anybody doing this restrict the oil low through the pushrods up to rockers?
I've used roller rockers on several builds, but never restricted oil flow to the top end. I think that's something done on race engines, but don't see it done for street use.
I have also used many sets of roller rockers on SB Chevy street engines having no issues with the trunion oriented correctly & with the correct length pushrods. In my experience, top end oil restrictions are only used in race engines to prioritize more oil to the mains & not flood the rocker boxes @ high RPM’s Sent from my iPhone using H.A.M.B.
Thats because some of them are setting on top of the cam lobes. IF you could start them all with your fingers at one time you'd have bigger problems then roller rockers, you'd have flat cam lobes...
^This is what I suspect as well. If it's on the nose of the lobe your gonna have a****** of a time, don't stress the fastener threads. If you are using a conventional SBC firing order 1-8-4-3-6-7-5-2, no 4-7 swaps etc. Rotate the crank to, confirmed, #1 TDC. Adjust cylinders #1 and #6 Rotate 90°, adjust #8 and #7 Rotate 90°, adjust #4 and #5 Rotate 90°, adjust #3 and #2
i appreciate the replies guys. i got it figured out and it turns out the issue is that im dumb. i didnt have the lifters seated all the way. i barely laid a finger on them and they settled right down and everything is as it should be. the problem with working alone is that you always know exactly who the idiot is
The question was asked about restricting oil; I know hydraulic cams put up a lot of oil but solids not so much. Oil for cooling the springs is important especially on racing engines, not drags, and we would never restrict ours. I have heard long ago guys added pipe cleaners to the pushrods..
There is a difference between being dumb and lacking some specific knowledge because you don't have first hand experience. The willingness to to learn is a great sign of intelligence. Now you have both knowledge and experience and apparently humility.............great combination. So don't beat yourself up, I guarantee we have all learned from making mistakes. I still do............Got a PHD in it While you are doing this, observe the movement of the rocker arm across the face of the valve tip. It should be near the center of the valve. Also it should look kinda level, not at any severe angle. When changing parts, you have to check everything to insure you have the correct geometry. Don't****ume the parts are correct just because they bolt or slip into place.
@evilokc, no joke. Two things are wrong with Mike's suggested method, one a lot more than the other. 1. That is not the correct firing order. 1-8-4-3-6-5-7-2 is. 2. If you adjust the valves on pairs of cylinders (ie 1 & 6) one of those is going to be on the valve overlap portion of the exhaust/intake cycles. This is not optimal adjustment on an engine with hydraulic lifters, and if you have solid lifters chances are you'll have 4 cylinders that won't have enough compression to work at all. Aggressive cams and solid lifters adjusted this way could result in valves kissing pistons. I always start with all rockers very loose, then adjust number 1 at TDC between compression and combustion. Then turn the engine EXACTLY 90° and adjust #8, turn 90° and adjust #4, then 3, 6, 5, 7, 2. I typically mark my harmonic dampers at TDC and every 90° so I don't have to guess.
This video posted above is completely wrong in that "center up the roller tip contact on the valve tip and geometry is correct", this is the same bad information that has been and keeps getting passed around the hotrod community but was never correct in the first place. "Centered" is a thirdly or fourthly on the list of priority, if even that high on the list... It really needs to be stamped out of existence, just completely wrong. Want to do it right?? This is the only correct video you will find, unless someone has also posted a copy of the same method/information detailed in it.... (187) Push Rod Geometry for Engines - YouTube
Eric, I watched both videos, and I think your video does an excellent job of explaining setting up a rocker arm, but I think you are reading something into the other video that just isn't there. The guy explains that when you have the relationship correct, your roller will traverse the the center of the valve stem. Could he have elaborated a little better....probabably so, but he isn't saying anything thats problematic. As for whether the pushrod length determines rocker geometry or rocker geometry determines pushrod length..........its just simply phrasing something differently but but meaning the same thing. If someone buys a new set of roller rockers and screw in studs and uses their old pushrods, they may or may not have correct geometry. In this case, the length of the pushrod determined geometry even if its wrong. So buying new pushrods woul determine the new geometric relationship. I think there was enough information in the first video that someone setting up some rocker arms understands the importance of relationships. I do think your video gives a clearer understanding of how it works though.
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