Technical Hemi Gurus, Camshaft Gurus: Need Valvespring Help!?!

Hey Gang,

First off, I have attempted to speak with the camshaft manufacturer, but I'm not really satisfied with their answers...

I am building a high-revving 350-something cubic inch early Chrysler Hemi, for drag racing, and top speed runs with USFRA. Crane spec'd me a single pattern solid roller camshaft with 250° duration @ 0.050" lift, and 0.530" gross valve lift. When I ordered the cam, I told them that my two BIGGEST limiting factors were keeping net lift near 0.500", and keeping open spring pressure under 450 lb's. The Crane tech spec'd a spring with 150 lbs on the seat, and 350 lbs open.

Then three weeks later when I got the actual camshaft, the cam card said that I needed a spring with 225 lbs on the seat and 542 lbs open...far too much pressure for my stock Chrysler 300 rocker arms, and quite different from what Crane's tech had told me on the phone.

So I called Crane back, and spoke with the same tech who helped me order the camshaft. He said the cam card was wrong, and that the cam I had required a spring with 150 lbs on the seat and 389 lbs open. I asked him why that number was different than the first number he told me, weeks before, and he said I probably heard him wrong. I asked him why the numbers on the card were so dramatically different, and he said that the spring spec'd on the card was probably for something like a small block Mopar, and not a shaft type rocker like on the hemi. I didn't want to argue that his logic was backwards (the hemi rockets are heavier).

Anyway, now I am completely lost as to how much spring I should run with this cam. I've tried talking to Crane's Chase Knight (the Hemi guru), but he invariably calls me at 10 minutes to 5:00, and then I can't get him back on the phone. I've talked to Gary @ QEC (73RR), and he said the 150/389 spring "should be" adequate, but that only experimentation will tell for sure (and he said he usually defers to the manufacturer's recommendation).

Anybody on here running a similar solid roller on a Chrysler Hemi? What are you running for spring pressures? Any help or ideas would be greatly appreciated.

Thanks,
Casey

 

i have run 275 pounds on the seat with 300 rockers with no problems. the real problem is running that much lift with a stock length valve. there is little room under the retainer. and you cant remove material from the head. going with a 100 long valve makes for a more usable combo. also the spring choices are better. geometry becomes a problem so stands that move the shaft up and out a hundred thousanths put things back in line. of course new pushrods are needed. its not cheap just bite the bullet and spend the cash. you wont regret it. these valve train issues have always been around for the hemi.

 

High reving is a subjective term,
But high RPMs are usually limited by valve train components. High rev & high quality means only one thing high money.

Next time a tech guy answers the phone at the Cam place's phone center ask them how many valve trains they've set up - and swapping parts doesn't count. Then ask them how many engines they've built. Ask how many cams they've ground.

There's a few places where you can call and talk to someone who stops what they are doing, puts their tools down and talks to you, even the guy who has or will grind your cam.

 

With 0.025" lash I'm only actually opening the valve 0.505". I was under the impression that I wasn't really getting into custom rocker territory at that point. That's why I ordered the cam I did. I'm pretty sure I can make this setup work, I just don't know because I haven't done it, and the people who have aren't talking. I guess it's an old "racer" mentality. 275 lbs on the seat is a ton; that's gotta be pushing 600 lbs open, yeah? Everybody talks like these stock rockers start snapping at anything over 450 lbs...maybe I'm worrying for nothing...

I get what you're saying, but I'm not sure how arguing with tech guys is going to get me any closer to an answer. And I really tried to give my business to one of the smaller vendors. None of them were really interested in supplying me with a cam for the motor I wanted to build. My combo, in all honesty is going to be pretty mild, and I am totally ok with that. It should spin about 7,000 rpm and make about 500 horsepower. I'll be totally happy with 500 horsepower in my 2,000 lb car. Everybody else wanted me to make the jump to full gonzo insane race motor. Schneider said he wouldn't make me a cam unless I built the motor with at least 12.5:1, and he said that really I'm being plain silly not running way more compression and Alcohol. He recommended something like 278° @ 0.050" duration and over 0.600" lift. Evidently he missed the part where I said I wanted to retain stock rocker geometry. I can't afford to break off another $5,000 OR have a motor that needs to come apart every few runs. I don't feel like what I'm trying to accomplish is that crazy, either...

 

I sell lots of cams and parts and build engines every day--250 at 050 for a 350 CI is a stout little cam--sounds good. Spring pressures depend on many factors--first is the lobe design--newer, computer designed lobes usually require more pressure --older more gentle ramps can get away with much less. Weight of other parts such as valves ( guessing you have heavy 3/8ths stems), retainers ( you should use titanium in any race engine) and rockers-( you are stuck with heavy on those) all comes into play.
I would say that your ideas about exactly what you want and will wind up with are a little different--folks call and always want a "high winding" combo when most are not experienced enough to know what they really need or will be enough. A small CI Hemi with 250 at 050 will be a stout unit suitable for most any need. Use titanium retainers period--they add RPM and insurance against valve float--no race engine should be without them. Now..on pressures--the same cam can be run with a wide range of pressure --as long as you have enough to control the design of that lobe at the RPM that you will be turning. On a street application you would use less to keep roller wheels where they belong--on a drag unit you use higher all depending on RPM. Older Crane catalogs have a neat chart that shows what pressures with what RPM range--it is very good info. I Usually set a solid roller like yours ( guessing that is an older gentle ramp design) at approx 225-235 and 550-580 open for a full tilt race application--should turn all you want within reason--On serious drag applications is is NORMAL to see 250 seat and 700 plus open but..lifter wheel axle bearings start to have issues with higher pressures--that is what all of these new bushed lifters is all about--many drag engines have crazy high spring pressure these days and lifter failure is very common--folks tend to carry everything to the extreme and thus problems. As an example I have a 355 CI SBC on a FED---I have a 255 at 050 solid roller with approx 560 open--I turn it 7200 easy as pie with cheap lifters--no problems. You probably have Morel made lifters--they are great USA made and will handle medium pressures well as long as you don't let it float the valves--that Kills lifters
So I would say that your combo will run just fine at the 380 or whatever they said--but I would be very careful at first and just see what happens--it may not turn 7000 but you may only need to turn it 6000 to make it work I would feel much better with higher like 225 and 550 range for a true high winding and chances are that 7000 is just a guess and Much less RPM will get the job done.
There is NO substitute for high quality light weight rockers, longer valves and higher spring rates but if you are limited to using stock rockers --then just reel in your expectations and have fun--do what Crane guy says--keep it near 400 and TEST the combo--do what it likes until--you can buy the parts you really need.

 

Racer X is right--I see no problem with pressures in the range of 235 and 500 and that should work just great with your cam and not be limiting factor--just use the titanium retainers for sure
You can't science out a combo on paper--you build , you run, you test, you TUNE and then you change and go some more--explore the limits YOURSELF and do not depend on old wives tales about what a part will take---can't sleep at night? Well then do like all the other sleepless guys and spend the h%$# out of some cash OR do like us cheap skates and race and run well with parts others say can't work but only after you have worked it out by running and testing not reading.
I really think that you can set it all up , turn it less than you were thinking and that it will do just wonderful ----Hotheads owner is a treasure of solid info on older Hemis--call him as well
Good Luck sounds like fun!

 

dusterdave is right on. Check where your coil bind is at that lift. That's why the .100 longer valve helps with spring choices. Put a rev limiter on it and run it. I built mine to the max because repairing a blown up engine 2 or 3 times is more costly than doing it once. Mine has been to 9K several times this summer. Then I fixed the rev limiter . Go for it and guys will be calling you for answers afterwards you'll be someone who did it - not heard from your buddy who knew a guy.

 

Thanks DusterDave. I appreciate your advice, and I think I will just get this thing together already and see what she does.

I finally did manage to get Chase Knight from Crane on the phone. His recommendations fell in between the other three. He said the 225/542 spring was overkill for what I want to do, and echoed your sentiments about valve train weight, saying to go with an 11/32" valve stem and while he didn't say to run a titanium retainer, he probably assumed it was a given. He said 160 lbs closed, 400 lbs open, and a limit of 6,500 rpm was a good starting point. I think if I'm going to experiment beyond that, I'm going to experiment with a rev kit...

As for coil bind, I've been round and round with the lift number. It's going to take a special spring for sure. I'm looking at beehives, trying to find something with a wire diameter that won't bind at the factory 1.700" installed height. The beehive retainer will help with rocker arm clearance, and I know the top of the guide has to be machined down a little. They say 0.500" is the limit. I'm not pushing it by much.

 

titanium is expensive and not real good for the street. i have run them. manley makes a hollow stem valve that is right between stainless and titanium for weight. thats what i run now with a titanium retainer and locks. the problem with the hemi stuff is all the guys that ran it back in the day have not stayed current with the new pieces available. the parts and combinations today are far superior.

 

Hot heads carries johnson roller lifters. They made a experimental set with holes drilled in the the bodies to oil the axle. I have been running them all this year with no problems. Call bob and get a set. This is exactly what i mean about people not staying current on technology.

 

Now much longer valve can you go without geometry problems on stock early Chrysler rockers?

 

I agree just stay with stock vales IF you use stock rocker--foget the Hotrod Magazine Beehive mania--That ain't how you do a Hemi--hes said Race so he needs Titanium retainers --couple hundo at Doug Herberts--I also agree with Crane on that pressure--I just rev'd a big hyd roller 6400 on dyno last week with 440 open so .....You can't get it perfect on paper first--just do it and run it then tune it--If you don't have the cash to do a Hemi valvetrain right by tossing a couple thou at the rockers, longer valves etc then you Have to settle down, use stock stuff, keep pressures reasonable and go with it.
That cam lobe should be doing all it can by 6400 anyway
Good Luck!!! Oh ..Rev limiters are Hell on parts and are rougher on parts than a little over reving anyday! Skip those silly things and drive! I mean--ya just can't let an engine sit against the rev limiter for even a few seconds without it beating the heck out of stuff--they should be called a Rev ALERT system--you keep an engine against one and it will destroy itself fast--they are made to be sold not used by good drivers

 

dont forget about putting a toe loop on your gas pedal. i use a shift light set at 200 rpm below were i want to shift and a rev limiter 500 above were i want to shift.. i use my right foot as the first rev limiter and my msd as the back up in case of a drive line failure. a blown hemi at full throttle is faster at reving when something breaks than your brain recognising the failure then reacting in a way to stop it before more damage occures.

 

As I've said before...a blown alcohol hemi will turn 11,000+! Think about it; if that is in fact true building what you want is basically easy, not cheap but easy. I agree that "old hemi racers" probably haven't kept up with the latest "stuff". I certinally haven't. If I raced again (I won't) I would need to start over not mechanically but parts wise.

 

Nice to hear that a SBF will tolerate 700lbs open. If you try that with an EarlyHemi you will break rockers.
I'm not even sure that I'd try it with a fin welded on the stock parts.
Remember guys, you simply cannot go to a catalogue and buy the 'good' stuff for an EarlyHemi without a second mortgage. Fords? Yes. Shiverlays, Yes. B&RB Mopar? Absolutely, but when Casey needs to keep the stock rocker gear on his 354 then all of the super-whiz-bang goodies are useless and this includes trying to cheat with .100 long valves that will require rocker stand surgery.
Beehive springs are useful on an EarlyHemi when you are at the 0.500 lift mark. The smaller diameter retainer provides some needed space under the rocker. Can you use 'normal' diameter retainers? Sure, but you better be damned sure that you have clearance. Bad stuff can happen.
But, being an 'old' Hemi guy you are probably right and I should start my career over with all of the new super-cool catalogue parts....on second thought, I'll let someone else experiment with broken parts and I'll focus on reliable but older technology, on what are usually expensive rebuilds.

.

 

Thanks for saving me having to explain myself on the beehives Gary! And yeah, pretty much. Not to mention that I'm trying to build this motor with as much old tech as possible. I can't afford to be competitive with the modern stuff anyway, but trying to go 160 with mostly period stuff is a good challenge. Thanks for all of the input you guys!

 

so there you have it either go with a stock type set up or go all out with all the new parts. now that was easy. its all what you can afford. i started out going the cheaper route then i paid again to buy the better parts. here is a quote from herb mccandles as he told me many years ago when i was building a stroker wedge. no one ever has the money to do it right the first time but they always find the money to do it right the second time. i never forgot it. that quote has saved me a lot of money over the years.

 

I can appreciate what you're saying. And I've spent a hell of a lot of money so far to not just keep on going, but where do you stop?

I know I said I'm going to "race" this thing, but I'm not going to be competitive in any class, and I'm ok with that. I already went from (initially) building a 350 horsepower street hemi to building a much stouter motor that will spend VERY little time on the street, all because I want to know what it's like to run wide open on the salt just one time. But at the end of the day my combo is still going to be pretty darned mild.

If my intention is to stick with a stock rocker arm assembly, then I will have to adjust my expectations slightly, and be happy with what I've put together. That's where I'm at, and I'm ok with it. I think it's going to be pretty damned quick for a hemi wearing stock valve covers. And I can't wait to find out.

 

A hemi is never a cheap date. Good luck and keep us posted. A word of caution on the adj rockers. The lock nut is prone to cracking and stripping by over tightening. The threads are a unique fine count. They are hard to find seperate. Go easy on them.

 

You might get good info from Chris Nielson @ 801-451-7745. He is a veteran cam grinder for early Hemis. He designed the specs for the Thumper cams that Comp Cams sells.

 

You told me that once before I remember. Something like in the "teens" of inch pounds, right!?! That's crazy lite. I will be careful. I'm not going to lie, these factory 300 rockers, by the time they're rebuilt, almost seem like more trouble than they're worth. The good news about early hemi's though, is if I change my mind BEFORE I break something, I know I can sell it for every penny I've sunk into it. The market for this stuff makes for a pretty incredible safety net...one I'm not used to...

 

Thank you. I will give him a call.

 

Sorry, kinda late to the game here.

Donnie Johansen helped me chose a solid roller cam with the following specs.

Intake 260 degrees duration @.050, .549 lift. With the .026 lash it makes .523 lift.

Exhaust 254 degrees duration @.050, 567 lift. With the .026 lash it makes .541 lift.

Seat pressure is around #185 with a spring rate of 566.

That being the case I had to beef things up a bit. I had a friend weld a set of TR Waters tabs on the exhaust rockers and then had to hone them to fit the new hard chromed rocker shafts. I tried running it with adjustable pushrods,breaking a couple and bending a few more. I had 73RR convert my rockers to adjustable and then I made up a set of 3/8 solid pushrods. She's staying together now.

If your made of $$$ you can always buy the billet aluminum rocker setups. I'm not so I modified.

High reving and early hemi are not usually used in the same sentence as the valvetrain is so darned heavy.

Here's a thread i did with pics about beefing up the hemi valvetrain.

http://www.jalopyjournal.com/forum/...valvetrain-in-the-digger.673636/#post-7483276

 

Oh yeah, starting at 185# on the seat and a 566 rate that puts me around 490# open.

 

Then there are mousetrap spring revkits that install on the rocker shafts. I've no experience with these nor have heard how successful they were.

 

......might have to start tinkering with a 'rev-kit', one more thing for the to-do list.....

 

I'm interested in the class you want to run at the USFRA meet at Bonneville. A 354 ci engine will put you in the C category for engines. Will you be running gasoline and carburetors?

 

Thanks Kerry,

That makes me feel a lot better. My setup is pretty mild compared to yours, and you're holding together just fine. Your cam specs do bring up another question. What are you doing to accommodate the additional lift (beyond the 0.500" "limit")? Did you run longer valves and raise the rocket stands at all? You're DOING a lot of stuff that can't be done...I like it!

I'm just planning on running the "muscle car class". They let you go between 130-139.99 your first time out, and if you can make that speed safely, they let you go between 150-159.99. You join the 130mph and 150mph "Clubs" if you make the number. These are considered "street car" classes according to the USFRAwebsite. Either speed will be a feat in a traditional hot rod. Safety requirements are pretty minimal, and only entail the basics such as a 4-pt cage, race seat & harnesses, speed rated tires, etc. The cage required to run an SCTA event really rules out any "dual-purpose" use in such a small bodied vehicle. I'm hoping I don't get "the bug".

 

I am going to suggest that "might" is not the operative word here. I used to think you were a crackpot, now I know a little bit more about you and think you are just crackpot enough to get it done.

I am never sure what someone means when they say high revving, to me it is entirely different than it is to others. In general high revving hemi or otherwise means light valve train. So the suggested light retainers is just a starting place. I don't know what is available for baby hemis in the line of rockers but if I were afraid of the stockers I would be looking for something different.

As for valve springs what the cam grinder suggests is usually a good starting place, maybe call and ask for a different tech and get a better idea. If you think it is too much spring pressure for your setup then send the cam back and opt for a different cam shaft.

I certainly would not be afraid to go with a longer valve and adjusted geometry on any engine if it would keep me from spring bind. Spring bind is bad and I have been told that longer springs are a little gentler on the valve train. That could be just something that someone said but it makes sense to me anyway.

 

You're right Beaner, if a fella needs 'high-revs' (definition left open to individual interpretation) then everything that moves must be put on a diet. In the case of EarlyHemi valve gear, nothing is light weight and other than expensive aftermarket rockers we can only make some structural changes to help the spindly exhaust live a little longer. (side note here...there is a Titanium rocker in the works...). In truth, the aluminum rockers are very bulky and not much lighter but they are roller tipped. We can also re-engineer the rocker assemblies to take advantage of taller springs/valves. Yes, this helps a lot; no, it is not cheap. The basic problem with the EarlyHemi design is that the original 1948 design calls for a spring that is 1.2" tall open and 1.7" tall closed. We do have better wire today so we can usually keep clear of coil bind with a smaller diameter wire and we have much better spring rates than in 1950 so our choice of cam profiles are plentiful. But, until we change the geometry ever-so-slightly long valves and tall springs are not viable options.
There is always a debate on valve springs. Bee-hive springs, as previously mentioned, do offer some help in avoiding parts interference but still need to be within the original parameters with the oem rocker design. The bee-hive spring is also reported to have better harmonics at extended-elevated rpm (think NASCAR).
The simple job of the spring is to keep the valve closed. So as the rpm goes up the spring pressure must also go up to overcome inertia....an object in motion wants to stay in motion...so when the spring reaches its 'limit' then valves don't close and lifters don't stay on the lobes and bad things start to happen. There are also other factors involved of course; ramp design can affect how well the valves sit or perhaps bounce on the seat.
So, EarlyHemi aficionados get to play with what little is available and roll the die. With a little luck we make a good choice the first time and the engine does what we want. Sometimes we need to make changes that are relatively easy; bigger spring numbers and maybe bigger cam numbers are easier than changing compression and often cheaper than port work.
All a fella needs is a well planned and well executed rebuild plan based on solid engineering.

.