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Sat Jun 30, 2012 4:06 pm

High rev, heavy duty, whatever you want to call them. Is about a 110 all that singles can take or can they also be used for a 120?

If they cannot typically handle a 120, are there valvetrain mods/lightening that I can do to make it work? (aluminum pushrods, truly light lifters, retainers, keepers, valves)

I had a lot of people tell me that bone stocks wouldn't work with my FK7, but they've been in for four years and 50,000 miles. I'm glad I listened to the ones that said they would work. I like to partly attribute my good fuel consumption, quiet operation, and low idle speed to low tension valve springs.

Sat Jun 30, 2012 6:36 pm

I always thought the same thing, lighten everything and you could still get the tension you need with only the single springs. My 1776 with a Engle 120 and single high revs has been fine, but I rarely hit 5500rpm.

Sat Jun 30, 2012 7:54 pm

I run single HD springs on a 1835, engle 120, solid rocker shafts, stock rockers, aircooled.net HD alum. pushrods and elephant foot adjusters with a 6k redline and I have had no problems so far for 40k miles.

Sat Jun 30, 2012 8:05 pm

I just stripped down an 1835 that had a 120 with 1.25's and stock singles, the result was two broken intake springs, a valve head wedged into the head, and a hole punched in the top of a mahle piston, cracked cylinder and a twisted con rod, all in 100km of driving.

The springs were stockies so I would think HD singles would be better but I would have reservations of going above 4500-5000 rpm

Sat Jun 30, 2012 9:17 pm

I forgot to mention, that my set-up uses 1:1 rockers with the 120 and single HDs.
With my close ratio tranny, I'm at 4000rpm on the interstate, and I have full confidence shifting at 5000-5500.

Sun Jul 01, 2012 10:49 am

Awesome! About that 1835, someone was bold to even run all of that with stock springs! I wonder what's the largest cam you could get away with is.

Sun Jul 01, 2012 12:18 pm

How do you know you have stock springs?
Are you just judging by the progressive wound coils?

A lot of aftermarket heads have come with stronger springs going back 20 years, so it will be difficult to identify the springs without measuring them

Most do have the same wire diameter (bout .165?) but the number of coils and free length varies.

Sun Jul 01, 2012 12:49 pm

66brm wrote: I just stripped down an 1835 that had a 120 with 1.25's and stock singles, the result was two broken intake springs, a valve head wedged into the head, and a hole punched in the top of a mahle piston, cracked cylinder and a twisted con rod, all in 100km of driving.

The springs were stockies so I would think HD singles would be better but I would have reservations of going above 4500-5000 rpm

Within 100km...sounds like coil bind to me, either way that engine had bigger problems then the wrong springs for that to happen.

Sun Jul 01, 2012 1:16 pm

More likely that fatigue failure set up by spring harmonics is what killed it, but obviously stock springs were a bad choice. I have singles in my 1915, working just fine for several years now. Most people don't realize that the inner ones have hardly any pressure to them, they mainly reinforce the outers.

Sun Jul 01, 2012 1:16 pm

dan97019 wrote: 66brm wrote: I just stripped down an 1835 that had a 120 with 1.25's and stock singles, the result was two broken intake springs, a valve head wedged into the head, and a hole punched in the top of a mahle piston, cracked cylinder and a twisted con rod, all in 100km of driving.

The springs were stockies so I would think HD singles would be better but I would have reservations of going above 4500-5000 rpm

Within 100km...sounds like coil bind to me, either way that engine had bigger problems then the wrong springs for that to happen.
like what?

Here is a rough idea
stock 120-130 open
brazil/cb 170 open
bugpack 190 or even 200 open
bugpack duals 250-300 open

as you can see duals are twice as strong as stock, HD singles could be 160-200 depending on what spring and how close to bind they are.
you get the most out of em' if you set them up to be say .080 to bind open, if you just bolt stuff together it's a big old roll of the dice.

Sun Jul 01, 2012 2:57 pm

I had scat singles on my fk8 for many years & never an issue with them,there what roy said they put on my mofoco 042's. unless you need the extra spring you dont need the extra spring.

Mon Jul 02, 2012 12:21 am

I chased an upper RPM problem for almost a year, and it would have been a lot less if I didn't listen to my dad say singles are all I need. Put dual springs on her and wow, runs up to 7k rev limit no problems. Started with an fk42 wouldnt pull on the top end, switched to a eagle 2246 and the vlave float got worse. Upgraded to duals on the new heads, whole different animal. Use the search feature and look up singles vs duals, HUGE debate.

Mon Jul 02, 2012 1:25 pm

it's not always the spring, it's not always the cam, it's sometimes the combo, or junk springs or just not set up quite right. sometimes the rockers can also add to the problem,some have a lot of un needed extra material being thrown back&fourth adding to the issue.I rework my stuff, lighten it&coat it.
I helped a guy with his bug a few months ago, it was having issues(induced issues by an exspert)well the motor was just about toast.as in got so hot the rings came off the pistons& the valve springs could be depressed with just a finger.so it's not always singles wont work, but those singles wont work.

Mon Jul 02, 2012 2:35 pm

Far more engine damage happens from not having enough spring then from having too much.

My general rule of thumb is anything larger then a W-100 cam with dual carbs needs dual springs. A W-120 cam needs dual springs.

Mon Jul 02, 2012 2:52 pm

Just know this, there is no one right answer to this question except stock for stock.
Everything else is on an as needed basis, the variables are so vast that I could sit here and write about this until my computer fries.
Things like cam ramp angle, lift, push rod type and weight, lifter weight, valve weight, spring design, cam duration, the materials of all the above, and max RPM are all part of this equation.

Sorry to sound so bold, but it is what it is.

Mon Jul 02, 2012 2:58 pm

I rebuilt my 1904cc into a 2161cc engine last year. changed everything but the heads. I had CB 044 heads with single HD springs. I used the Engle 120 cam w/1.25:1 rockers. I thought the heads would be ok. I could not rev the motor past 5000rpm without getting valve float. Phoned Greg Timms and ordered his stage 2's and haven't had a problem since. also gained tons more power and will rev past 6500 with no problems.

Mon Jul 02, 2012 6:33 pm

Yeah, I guess my question wasn't all that well thought out. I think I was just thinking the W-series of cams. No ratio rockers or VZ cams.

Patrickvw, what are the specifics of your valvetrain combo? Do you think your setup is on the heavy side?

I wonder if I should get my heads cut for duals and just run singles until I run into an issue.

Mon Jul 02, 2012 10:28 pm

the engle 100, 110, and 120 have similar lift rates, the 110 being the harshest IMO. So they would all require similar springs with the same engine and RPM limit. 200LB open should be enough for 6k rpm unless you use heavier than stock valvetrain parts. Throw on higher ratio rockers or go up to a E125 and then you probably would need VW duals or stronger springs of some kind

most aftermarket lifters/rockers/pushrods/retainers are heaver than stock, so it is easy to end up adding a lot of weight, so maybe some combinations would need stronger springs to reach 6K, but not all.

making sure the springs are a good tight fit on the retainers and at the head is an old trick that also helps, most springs aren't a real tight fit at the head anyway so cutting 2/3 of the spring boss down should not make it much worse

Mon Nov 19, 2018 5:36 pm

How can you tell the difference between a stock springs and a HD Hi Rev single springs?

Mon Nov 19, 2018 5:51 pm

By measuring them.
Compress to bind, back off .080, read the force with a scale.

You can also just measure all the physical dimensions of a spring and get very close too. Free height, wire size, OD, number of turns.