It's been awhile (http://www.svtperformance.com/forums/showthread.php?t=201084) since I’ve posted but have finally made the mods to my Cobra. I went with the 165cc AFR's (#1402), 1.7 Scorpion rockers, and used all recommended hardware. The only place I deviated from was the cam. After talking to the AFR tech's I was "talked" into a Comp cam that was not "e" legal but both AFR and Comp tech said would pass a "sniff" test but of course couldn't guarantee it. It's a (Comp P/N 35-351-8) XE270HR 218/224 dur @.050 and .512/.512 lift (.534/.534 with Scorpions) and 114° LSA. AFR wanted a 4* advance on the cam and it came out to 3* so I left it at that. Of course it was close in the p to v area as I had .083 on intake! The exhaust at .122 was much better. I reused my stock roller lifters as they were making no noise and looked in good shape. Beings how I converted from non adjustable pedestal mounts to studs with poly locks I obviously had to do some adjusting. I went to base circle, took out all the play in the pushrod, and gave it 3/4 turn more. Fired right up and clacked "mildly" all the way to operating temp. I only took it off idle (1500-2000rpm) a couple of times on the way to operating temp and it never did quite up. I shut it down, pulled the valve covers, and gave all of the adjusters an additional 1/4 turn. It help but seems to clack on initial firing, and after reaching operating temp. It might just be me but it seems to be ok in between these two points. Ideas? Also two other items I've been troubleshooting...a rolling idle problem that has been there since I bought the car but was never (200-400rpm flux) bad enough to worry about. With the new cam? it would roll from idle (approx 750-800rpm) to almost 2000rpm repeatedly before settling down again. I think I’ve (IAC,salt n pepper connectors, etc) pretty much fixed that problem but this brings up the last issue. Unless I have a lite load on the accelerator the car in any gear (1500rpm and lower) wants to buck. I'm pretty sure the cam is not "big" enough to cause this but I’m thinking it has to do with my idle quality issue. If it wasn't for the noise and this lite bucking the car has really responded to the changes as it even sounds meaner and pulls waaaay harder than it used to. I need to get this fixed so I can get some new dyno and track numbers. Any and all help appreciated. Thanks for listening.
Lifter noise after mods?
- Thread starter SNK-BIT
- Start date
Sounds like the rockers are adjusted wrong.
Loosen up the rockers to zero lash again, you need to prime the lifter real good before adjusting, unplug the coil wire turn the motor over a few times "priming the lifters" check for squishiness each time turning the motor over as necessary per cylinder & once you find zero lash go 1/4 of a turn "not 3/4" lock the locks & your done of course assuming your adjusting each cylinder @ lowest point on the lobe. Too much preload can also making a ticking noise aswell & if you had 3/4 to a full turn like you said that's adding to your problem, take your time & do as I said & you will not hear a single tick or anything & it'll sound like a sewing machine "perfect" when done right
Loosen up the rockers to zero lash again, you need to prime the lifter real good before adjusting, unplug the coil wire turn the motor over a few times "priming the lifters" check for squishiness each time turning the motor over as necessary per cylinder & once you find zero lash go 1/4 of a turn "not 3/4" lock the locks & your done of course assuming your adjusting each cylinder @ lowest point on the lobe. Too much preload can also making a ticking noise aswell & if you had 3/4 to a full turn like you said that's adding to your problem, take your time & do as I said & you will not hear a single tick or anything & it'll sound like a sewing machine "perfect" when done right
Thanks for the reply. I'm as surprised as anyone as to why the lifters are clacking. This is not my first engine build by any means. I adjusted the lifters on the base circle of the cam while the intake was still off. The point being I know the lobe was "down" when I adjusted them. I gave a lite "drag" to the pushrod and then 3/4 turn more pretty much knowing that it would be "overkill". Most "chebbies" run fine with a full turn. I was just making "sure" I would not have to pull the valve covers again. My thought was the lifters might have "bled" down during the head swap, hence me going back and adding the extra 1/4 turn. Thanks for the info about being to far "down" in the lifter. I did not know :bash: this would contribute to the noise. I will back them off, crank it over to "refill" them and go the 1/4 turn. Thanks again. I'll post results.
No luck. I did as suggested one cyl at a time. Loosened in/ex on that cyl and cranked eng over until I saw oil press come up to make sure lifter was "pumped" up. Ran poly's down 1/4 turn and locked set screw down. Did all cylinders that way. I'm sure i'm on "base" circle of cam. Initially it was completely quite then it acts like there is too much valve spring pressure and it bleeds the lifter down and they start clacking again. It's not oil pressure as before I did the heads etc it was at 35lbs idle and still is. I was told the clacking is "normal" by a couple of mechanics after changing heads, pushrods,rockers. I don't know but i'm not real happy with the way it sounds. It's not that it's "that" loud it just didn't make any noise before that I remember. I'm more concerned about the excessive lash beating the rockers or valve stem tips. Anyone else have "Scorpion" rockers? If so are they noisy? Somethings wrong!
Does it sound any different ?
Aslong as you turned the engine over making them good & primed & checking & making sure they were not bled & returning over the motor & making sure of no squishyness then went a 1/4 turn from zero lash they would be perfect, have you checked where the fulcrum touches the valve stem ? You may have the wrong size pushrods or a bent valve, try sticking something to the valve cover & listen to it, like a plastic baseball bat that'
s what I used, put one end on the valve cover & the other to your ear & listen.
Are you do the rockers when the pushrods are @ there lowest pont or there highest point ? Can you lift the rocker off the valve stem after adjusted when the pushrod is @ it's lowest point sticking out of the head ?
Aslong as you turned the engine over making them good & primed & checking & making sure they were not bled & returning over the motor & making sure of no squishyness then went a 1/4 turn from zero lash they would be perfect, have you checked where the fulcrum touches the valve stem ? You may have the wrong size pushrods or a bent valve, try sticking something to the valve cover & listen to it, like a plastic baseball bat that'
s what I used, put one end on the valve cover & the other to your ear & listen.
Are you do the rockers when the pushrods are @ there lowest pont or there highest point ? Can you lift the rocker off the valve stem after adjusted when the pushrod is @ it's lowest point sticking out of the head ?
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