Rocker arms and actual lift at valve

I'm assembling a low deck 511 with Trickflow 240 heads, Hughes engines rockers and comp solid roller. After getting the rockers installed I thought about checking actual lift at the valve vs cam card. Well it wasn't as close as I hoped... Even after trying 2 different length pushrods it's about .050 less than the cam card of .631 with the 1.5 ratio. I even checked the Hughes with a couple spare blue Mopar rockers I had and they were closer actually almost perfect. I was on the fence between buying Harland Sharp and the Hughes rockers now I'm kind of bummed. Would the correct set of HS's be a better option for the Trickflow heads? Or am I worrying about something not that significant?

What are you seeing for actual measured lift at the valve with zero lash?

There was recently a thread over on Speed-talk where someone was seeing a significant amount of deflection of the retainers…….which was skewing the true “at the valve” lift result.

You could probably test for this by using a fairly stiff feeler gage trapped between the rocker and the valve and measuring off that vs just measuring off the retainer.

I measured net lift on only one set of Hughes rockers, and they were the older version that didn’t have the notch cut in the top.
They were 1.6’s.
With checking springs they calculated out at just under 1.6……like 1.58 or 1.59.
With 600lbs spring force they were barely over 1.50…….like 1.51.

I’ve never checked the TF specific HS rockers, but I have checked a few of the “normal” BBM sets.
Those checked closer to .05-.06 higher than the nominal ratio with checking springs, and still slightly higher than nominal with full spring force.

One set of 1.6’s on some Indy SR heads were 1.67 with checking springs, and still 1.63@.700 lift with 700lbs on it.

Hey Dwayne thanks for the reply that's a good idea this is the cam you spec'd for us and I spoke to you earlier this week. Lift at the retainer is approx .580. How much of a difference would be considered "normal" between cam card and actual?

Ok thanks that answers my question. I'm sure all manufactures are different.

Rockers are all over the map in terms of the true ratio. You might be bummed but odds are that you would see zero power difference between 1.5 and 1.6 rockers on that engine. I've done a lot of rocker arm testing with the TF heads and the extra lift doesn't always mean that you'll make more power.

If you’re seeing .580 at the valve, with the lash set to zero, then the effective ratio is only 1.38.
I doubt there would be a “ton” of power left on the table leaving them in place, but I think all things considered for your combo, having the net ratio closer to a true 1.50 should be worth “something”.
Whether that’s 5hp or 15hp, there’s only one way to know.

At this point, you have to decide if you’re willing to spend the money for different rockers or not.
If your heads have the TF SR spring package, and you’re going to try different rockers, I’d step up to the HS 1.6’s.

If you’re looking for an option that’s friendlier on the wallet, buy 8 Hughes 1.6’s and put them on the intakes.

You can always start with what you have and change them down the road too.

Looks like the individual Hughes rockers would cost roughly $256.
If considering that option…….I’d buy one 1.6 and one 1.7, and mock them up and check for true net ratio, and how they impact pushrod clearance.
Then decide on which ratio to buy.

If the 1.7’s are close to 1.6 net……and the pushrods aren’t too much of a fit problem…….I don’t see any reason not to go that way.

Btw, the old MP blue rockers were Cranes.
The few sets of those I measured(1.5’s) were in that 1.55 ratio range when using checking springs.

I went through something kinda similiar. I was using ball/cup pushrods and Crane rockers, which require quite a bit of adjuster to show in order to get oil to the pushrod. With changing pushrod length you probably are already on one of the issues if using ball/cup pushrods, the push rod kick-out from the ball adjuster will take out lift, so the longer the pushrod the better. I was losing over .030. I went to ball/ball pushrods on my current build with the cup adjuster and have eliminated most all the kickout. I also went to a the bigger pushrod 7/16-3/8 taper, to keep down any deflection, and I am only using 400lb springs. I do think the deflection happens more than some think, from just what Dwayne described in going from check springs to your real springs you do see a difference.

I will say that like Dwayne and Andy the lift loss may not be as big an issue. I would check the scrub on what you have to see where that is, as I think this can lead to some gains if you are measuring .100 or more. The bad part is, the only way to fix is to raise the shaft. I found sometimes the rocker you use can help you out as some are shorter. When the rocker goes up it also goes out on the valve tip, a shorter rocker can help out. On mine going from a Harland to the Crane allowed me to just use a .250 spacer to fix my scrub. The motor tended to carry rpm better after that change. There are plenty of threads on here discussing it-mine is below.


https://board.moparts.org/ubbthreads/ubbthreads.php/topics/2891437/re-valvetrain-issues.html

I'm not sure this is of any help but I live with valve lifts and springs where you can use the stock stamped rockers. I mocked up enough of a block that I could measure the lift of a stock rocker keeping everything else the same. I took a whole pile (literately) of lifters and measured the true lift. The lifts were all over the map. What I ended up doing was grouping them into groups with relatively close lifts. Racer Brown used to recommend using the higher lifts on the exhausts so that's what I did.

I wrote down all the results but for the life of me I can't find it. Some day.....

Literally every piece of the valvtrain flexs, stretchs, bends, something! From the hold downbolts, to the shafts, rockers flex, retainers flex, and all this can be seen in the design of very high end valvetrain components that are stronger to combat this. My Jesel setup with a gross lift of .867 lost .040 versus checking springs that checked spot on. Even the cam flexes, hence the bigger diameter core cams used on some race motors. Ater seeing that .040 loss of lift i decided to go with a lighter spring, taking about 50 lbs of seat load off the spring at rest. That showed less deflection of .030, a savings of .010 in net lift.

What you're seeing is not unusual
If you want them to be correct, perfect, check all of them on the motor with lightweight checking springs and write the results down and then contact the rocker arm maker and see if they will make you as many new ones you need to get your motor correct on the lift at the retainers
It can be done, but not quick and easy

On the Edelbrock Victors I run, Hughes 1.6 rockers measure close to 1.60 when using a checking spring. When measured with the 600+ lb open-load roller spring, all the deflection in the valve train drops the net ratio to 1.54-1.55.

I checked out some Hughes 1.7 at the same time, although I use their 1.6 rockers. Unloaded they were in the high 1.6s, but against the roller spring they dropped closer to 1.60, losing more ratio than the 1.6 rockers. I suspect this may be the result of Hughes changing their design to include a "trench" down the backbone of the rocker body. I have the early style without the "trench" and believe it's stronger (less flexible) under a load.

FWIW, I passed on my measurements to Hughes and suggested they still offer the early design as a "heavy duty" option, but never saw any response from them.

One last comment is that Hughes rockers have a regressive ratio curve, meaning they start out much higher than the advertised ratio early in the lift, then the ratio drops off as the lift increases. Think of it as starting out at 1.7 off the seat and ending up at 1.5 near peak lift, so it averages out to 1.6 overall. Some rockers are linear, some are progressive, and some are regressive.

All this ratio stuff also depends on the shaft location with respect to the valve tip, the relative length of the adjuster screw, the angle of the adjuster screw, the rocker body fulcrum length, etc. Fun, fun, fun...

Found a pic showing the new style Hughes rocker on the left and the original style on the right, for anyone who isn't familiar w/ them

Thanks guys for all the responses. It's crazy to think all the engines being built and things like rocker ratios may not be close to the cams we think we have! Lol. Obviously I haven't ever really given much thought to until now. Anyway, the rockers I have are the new design. They are a really nice rocker. Not knowing whether or not they will make more/less power, at this point in the build, I would rather try a different brand getting closer to the lift desired. At least I'll know it's closer. Plus doing it know will be easier then doing it down the road after I've had a chance to think about it. Going to a 1.6 might be an option also. However I wouldn't be comparing the same ratios if I did go that route. It really depends what is available in the HS flavor. Not looking to promising at Summit or Jegs for either ratio I'll have to call around later. The trick flows I have are set up for .700 lift as they were the only set available at time of purchase so they do have the heavier springs I believe.

I've been all the way down that road and wrote an article about it: https://www.motortrend.com/how-to/trying-find-extra-power-rocker-arm-testing/

Wow good write up. I find it interesting that the HS had burnt the push rod ends. Were they the only ones tested without and with push rod oiling? I will definitely get oil thru push rods now with either rocker assy we end up with. The engine you are testing has a more aggressive camshaft than mine. With a true 1.6 ratio we would end up with .673 lift at the valve with zero lash. That is .093 more than current lift. As you mentioned in the article about the trade off with more lift is extra wear and strain on components... In my situation should probable check ptvc if different rockers are chosen.

All the stuff that David Vizard preaches, FWIW, is that the exhaust is more duration-sensitive than lift-sensitive. If, as Dwayne was suggesting, you can bump up the intake ratio to Hughes' 1.6 or 1.7 (advertised) to get the additional intake lift you want for under $300, that could be worth checking out.

FWIW, my suggestion for swapping out the 1.38 net ratio rockers for something that’s in the 1.5-1.6 net ratio range ……in this application……..has almost nothing to do with my concern about the max lift change/increase.

Hmmm...

I will agree. My concern isn't getting maximum lift out of the camshaft chosen just more of an accurate lift. That bugs me. Or closer than it is.... If that makes sense? The HS's in either ratio wont be available until mid Jan. Unless I find some on the shelf somewhere.

Excessive clearance between peak lift and spring coil bind comes to mind...

I thought I saw some HS for Trick Flow heads available from Summit or eBarf recently

Also, I have a spare pair of Hughes later design 1.6 rockers you can borrow if you want to check the lift with those

Thanks Brad I really appreciate the offer but we'll either wait until some are available or go ahead and start it as is. The engine is ready to go with the 1.5s now only thing I should do after reading Andy's article is get some oil thru pushrods eventually. We have bam lifters with push rod oiling. It's on an engine run stand so parts aren't too difficult to swap out later. Finally getting close between waiting on machine shops and collecting parts this will be almost a 3 year project. lol.
The normal bb rockers are available, not the E series for Edelbrock and TF heads.
Just noticed you said for the TF heads. I'll check ebay. Thanks.