High Rpm Power Loss After Switching Back To 1.6 Rockers

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... As far as the flat spot @ wot is not valve float, it'll just flat fall on its face and never pick up. ... THEN Check your pressure too. And the 1.7s give you more lift which gives you more top end. More duration gives you bottom end and more LSA gives you more of both basically.

I like simplifications that help general understanding. Unfortunately, except for the valve float statement, the above is not correct. Cam and lifter dymamics are more complicated than this.

Lift - (Changed by lobe shape or rocker arm ratio) - Helps more air in and out across the power band IF the heads flow better at the higher lift, if the springs do not bind, and if there is enough piston to valve clearance.

Duration - (not significantly affected by rocker arm ratio) - allows more time for the air to flow in or out and helps more at high RPM due to the valve timing overlap.

LSA Lobe Separation Angle - this combined with duration affects idle quality and can move the torque band in the RPM range. If you like a lopey idle, you want overlap, but your computer will measure incoming air better and idle better with a wider LSA and less overlap.

Opening and closing rate - The faster, the better IF your valve train can handle it. Ideally, you want the valve at peak flow lift as quickly and ask long as possible. But if things move too fast, the lifter may not stay on the lobe, and the valve may float or even bounce. Noise and loss of power are just two consequences of this problem. If it gets bad enough, things break.

SO- leaving the 1.7 rocker on the exhaust side may help the flow on the exhaust port side. It is not unusual for Fords to need this help more than on the better flowing intake port.

The question I have is why were things noisy with 1.7 lifters? You do not list what cam you are using and what valve springs, but if there is clearance and things are lined up (AKA correct Geometry and clearance), 1.7's should not be noisier than stock stamped lifters.
 
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I like simplifications that help general understanding. Unfortunately, except for the valve float statement, the above is not correct. Cam and lifter dymamics are more complicated than this.

Lift - (Changed by lobe shape or rocker arm ratio) - Helps more air in and out across the power band IF the heads flow better at the higher lift, if the springs do not bind, and if there is enough piston to valve clearance.

Duration - (not significantly affected by rocker arm ratio) - allows more time for the air to flow in or out and helps more at high RPM due to the valve timing overlap.

LSA Lobe Separation Angle - this combined with duration affects idle quality and can move the torque band in the RPM range. If you like a lopey idle, you want overlap, but your computer will measure incoming air better and idle better with a wider LSA and less overlap.

Opening and closing rate - The faster, the better IF your valve train can handle it. Ideally, you want the valve at peak flow lift as quickly and ask long as possible. But if things move too fast, the lifter may not stay on the lobe, and the valve may float or even bounce. Noise and loss of power are just two consequences of this problem. If it gets bad enough, things break.

SO- leaving the 1.7 rocker on the exhaust side may help the flow on the exhaust port side. It is not unusual for Fords to need this help more than on the better flowing intake port.

The question I have is why were things noisy with 1.7 lifters? You do not list what cam you are using and what valve springs, but if there is clearance and things are lined up (AKA correct Geometry and clearance), 1.7's should not be noisier than stock stamped lifters.

You know your stuff, very in depth. But that was just the basics of what Howards Cams explained to me a while back. And I've done a half million cam swaps and that's kinda how is worked out as well. The manufactures catalogs I have point in the same direction too if you compare specs to the rpm range and description of the cam. However, I completely agree with what you said. Its logical, I was just putting things in more simple terms.
 
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Not going to get in the middle of this **** match.

Barney is a troll that mostly googles crap and posts tons of wrong and/or states the obvious. He is hated on the Corral and sad to say he found his way here.

lol, well lets see, i have 8 "likes" here after being here a short time.

i have several "friends" on the corral and one just posted a friend request to me the other day. there are a few a holes on the corral and if you are there, your quote above proves that you are obviously one of them.
 
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Here's another question (hehe)... if/when I open up the valve covers again, I was considering putting the 1.7 rollers back on... but just on the exhaust side, leaving the stock rockers on the intake. Is this a great idea or not ?
Plenty have done it with success. How much are you preloading the lifter when you install the rockers? Too much preload can make them noisy.

Also, if you're using the stock EFI valve cover, you might be making contact with it in a few spots. The Cobra 1.7 Rocker arms are cast aluminum and not forged like many others. As such, they've got to be made a little "bulkier" to promote the needed strength. Take a peek on the inside of the cover and see if there are any worn shiny parts. Best way to combat this is to clearance the inside of the rocker cover with a dremel and/or run two rocker cover gaskets to give yourself a little added clearance.

Truth be told....rocker arms are noisy to begin with, so it's no wonder you're finding your stock stamped steel arms much quieter.
 
Some solid advice in here other wise the pissing match continues just like the 408 thread . Never ceases to amaze me
 
Here's another question (hehe)... if/when I open up the valve covers again, I was considering putting the 1.7 rollers back on... but just on the exhaust side, leaving the stock rockers on the intake. Is this a great idea or not ?
hello;

if you had shims under your 1.6 rockers and you no longer have them shimmed exactly as they were when it ran good with them previously, then one very simple, intelligent test you can do is install ALL the 1.7 rockers again with the same shims you used with them before.

if it runs good on top end with no "miss", then it's reasonable to "guess" through simple logic/deduction. that the problem is caused by improper shimming of the 1.6 rockers.

if it continues to have a similar problem then it is definitely something other than the rocker adjustment that is causing the prob which suggests it's most likely fuel or electrical.

i read that you did not change any setting, but maybe some wires got bumped in the rocker changing process. hard to tell from behind a computer.

simply changing the exhaust rockers only is not the best approach, until you determine the cause of the prob and correct it.
.
 
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lol, well lets see, i have 8 "likes" here after being here a short time.

i have several "friends" on the corral and one just posted a friend request to me the other day. there are a few a holes on the corral and if you are there, your quote above proves that you are obviously one of them.

This isn't Facebook.. Who cares.
 
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@Gearbanger 101 good point about checking the valve covers for contact. There may be a thick gasket available for this, but using yellow weatherstrip glue between two and they will not come apart. Ever. I was also thinking to check if they are hitting on the springs.
But I am wondering if something was bent when it was making noise and that is why it will not rev with the stock rockers.
 
Seems that alot of people misunderstood what happened here.

Stock 5.0 (stock cam), did 1.7 roller rockers at same time as gt40p heads. Did not need any shims at that time, torqued about 3/4 turn after zero lash on the 1.7s, no issues ran great but was noisy. I already cleared the valve covers by modifying the oil fill baffle, there is no valve cover contact at all. Re checked, played with them, re-read install instructions etc.. noise wouldn't go away (they were 'used' already). Took it to the track ran 13.8. This was a few months ago.

A couple days ago, I put back the 1.6 stock rockers on, I didn't check the preload, for some reason assumed they'd also need no shims. Had high RPM power loss during short test drive. So today I put 1.7s back on the exhaust since I read this is good to do, and also re-checked the 1.6s that stayed on the intake. Turns out I made a bad assumption and they needed 60 thou shim to torque at 3/4 turn after zero lash (were over a full turn without). Car runs great now, good power, and noise is less than with all 1.7s, but a tad more 'sewing-machine' sound than if it had all stock rockers. I'll leave it like this for now, play with it a bit, burn some tire, maybe take it to the track and see if it improves my time.
 

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Huhu...I thought I remember someone here saying that a few posts back? :chin
Yes I saw comments eluding to the possibility that the adjustment may be the cause of the running problem in posts 3, 6 and 28.

the test suggested in post 28 would have definitively determined the excessive preload as the cause.
 
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Yes I saw comments eluding to the possibility that the adjustment may be the cause of the running problem in posts 3, 6 and 28.

the test suggested in post 28 would have definitively determined the excessive preload as the cause.
The test in your post wouldn't work, I was pretty clear that I hadn't run these heads with the 1.6s yet. Even so, I'd rather measure turns (like i did) instead of putting something on and hoping it would work, already learned my lesson on doing that here.
 
The test in your post wouldn't work, I was pretty clear that I hadn't run these heads with the 1.6s yet. Even so, I'd rather measure turns (like i did) instead of putting something on and hoping it would work, already learned my lesson on doing that here.

Dave, it is best to ignore googlemeister barney. He gives out more bad and wrong advice than good. This being another example.
 
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The test in your post wouldn't work, I was pretty clear that I hadn't run these heads with the 1.6s yet. Even so, I'd rather measure turns (like i did) instead of putting something on and hoping it would work, already learned my lesson on doing that here.
sure it would have. it would have determined that your problem was due to improper preload which is exactly what you found out when you shimmed your 1.6. rockers. its a simple deductive test procedure.
 
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