The Cal-look Lounge

As some of you know I am in the progress of building a screamer type 4 (66x105)

My question is if somebody have experience with chevy springs. Im considering using them along with my stainless steal (48/38) valves. Anybody have an idea of what maximum rpm would be before valve float with these springs? CB says 9000 rpm, can that be true?

Another thing, does anybody know if its possible to get higher lash caps than the standard ones cb is selling. My pauter vavle train arm is hidding the retainer before the roller touches the "standard" lashcap.

Hope someone can help me on this one..

Regards, Jakob..

Link to the engine build: http://cal-look.no/lounge/index.php/topic,14531.0.html

berg and cb have larger caps ;)

Limit of springs to valve float will depend on your chosen cam and the rocker (ratio) you have chosen; and actual ratio.
Even with that information, the rpm of valve float event will be pure speculation ... too many variables: valve weight, retainer & lock weight, spring installed height & pressure, spring pressure @ maximum lift, etc.
Some may give an estimate, but that's all it will be. :-\

What is the weight of the lifter , also very important

Udo

What Chevy springs? There are several available. Also, at what installed height? And what does your cam need and how big is your RPM window according to your calculations? No need to go big unless you need to. A typical Chevy springs is around 140lbs at the seat and 350-360lbs over the nose. The K800's will give you around 150lbs at the seat and 430-440 lbs over the nose.

I have Udo heavy lifters, about the same size valves as you, FK87 style cam and Scat 1.4 (1.44) and have taken my engine up to 8200 rpms without any issues. "Chevy" springs from Summit installed at 150lbs and 365lbs over the nose. Ran the same springs for 2 seasons, only checking them each winter. Took them out this Easter and they was spot on.

BB

Thanks for the replies..

A little more information...

Cam is web251
Rockers are pauter 1.48
Lifters are scat light weigt, think they are 94 grams.
total lift is 15,7 mm.
Estimated power output somewhere between 5000-9000.

I have ran the engine with steal valves and the new CB650 double springs, installed them so I had 1,7 mm clearence at full lift before coilbind. Have spun the engine to around 8500 rpm. When I took it apart (it leaked between cylinder and head) The 4 exhaust valves had hitten the piston (had around 2,5 mm clearance between piston and valve, measured with clay)

I have a couple of options here the way I see it.

First option:

I have actually oredered a set of titanium valves (48/38) I can use. But they are for chevy style locks, wouldnt it be to much to run titanium valves and chevy springs, what do you think?

Second option:

My other option is to use stainless valves and chevy or K800 springs. If I cut 1 mm deeper in the heads and open up the spring area 1 mm I can with the chevy springs have 1.7 mm "air" at full lift (15.7 mm) before coilbind.

Must admit im a little scared of using the tit valves, if they hit the piston im afraid the head will break of uposit the steal valves wich will "only" bend.

And like one of you said, its all a bit of guessing when it comes to valve float, so many variables. So im most keen on using the stainless valves first, then when I know more about the engine I could allways change to tit valves..

Hope some of you can help me choose the right decission for my application.

Best Regards, Jakob

What rpm they can take...? the single most important thing is that the cam is designed correctly, or you need the stiffest springs in the world...

I would say there is no way with steel valves and 94 gramm lifters up to 9000 , even not with k-800 .
I have now for the first time my 94 gramm lifters (because i have no 60 gramms any more) and will try to get 9000 with titanium valves and k- 800 in my new engine

Udo

k800 with SS valves and heavy lifter would be OK around 8000rpm to keep them last a while!
other way is to use special valves with smaller stem thus less weight or better Ti
I think that 1..7m before coil bin is too tight (well on a  race engine you can go with),your springs may loose a lot of pressure quikly!
JR

"K800" springs as in the K-Motion brand, or just another V8 type spring (i.e. 1.460")?

If you're talking about K-Motion springs, you may want to go a different route, as there are much better springs on the market these days. Check out the PSI brand springs (http://www.psisprings.com/) and/or contact the folks at Precision Products Performance Center (http://www.pppcenter.com) - they know their stuff!

--Eric

As far as I know the Web 251 cam is designed to be used with standard type 4 rocker arms. When used with ratio rocker arms the acceleration of the  valve/valve spring will be much faster than the cam was designed for. This will result in spring flutter or floating springs. Ramp design of the cam have a huge effect on the valve train components and using the right rocker ratio for the specific cam is critical when making a high rev engine. Like Udo says lifter weight is also huge factor along with valve train components in general. Stronger springs will most likely move the problems elsewhere and break more or other parts. Pauter rocker arms will mostlikely have a limited life spann in this combo.

/Rolf

Cams for use with 1.25:1 or 1.5:1 rocker arms (lift shown with 1.5:1)               
251   324º   285º   0,630"   16,00   108º   Large displacement, carbureted dragster and pro sedans
   54ºBTDC   90ºABDC   90ºBBDC   54ºATDC      .050 check
 ;)

I have found out with a lighter lifter you can make 500 rpm more on most applications . 94 is heavy weight :-)

Udo

udo becker lifter 60gr? ;D