Jump to content
Server maintenance Read more... ×
Sign in to follow this  
Tyler06

Just for info xflow spring pressures.

Recommended Posts

Been reading something interesting about cam bearings and thought id put some info together. Anyone that has a hot crossy tell us wat springs you use and cam and pressure...

Me Crow 7338 springs shimmed to 140pd with 597' lift.

Share this post


Link to post
Share on other sites

Solid cam...145 seat 365 on the nose 649 lift 286 duration @ 50. 

 

Roller cam...240 seat and 600 on the nose with 709 lift and 275 duration @ 50th

 

Thinking now days is that they want more seat pressure than nose pressure for a more stable valve train with less stress.I know Ando runs ALOT less seat pressure but he uses a ISKY high frequency spring set aswell.Basics are a lighter valve train uses a lighter spring,but it is still dependent on cam choice.Yours needs the cam bearings to be matched to the cam shaft so don't send your block till you get your cam and ask em to measure the cam shaft and fit the bearings to suit.

Share this post


Link to post
Share on other sites

If you want to rev it with confidence,have no harmonics issues and have less than .600 lift, then there is only two springs for a x-flow.  Isky 295D Tool room springs with 115 on the seat. For lift at .584 I use the 295Ds little brother the 235D at 110 seat.  Tried - tested - proven.  I have never fucked a cam bearing - pulled a shaft mount roller rocker out etc. with these springs and they will go to 7500 all day, every day.  My engines are used in speedway but this spring is equally at home on the street.

 

People will say I'm crazy and have no clue running such low spring pressures and a just a single spring with a damper that is ' way to small to do the job' and that's cool - cause they are the same people that have there engines apart, miss meetings and have constant failures and that is good for me. 

 

I must say that I did not come up with this spring.  The late great Geoff TRUSCOTT was my dear friend and he discovered this spring and he loved it because it does not create valve train harmonics.  I am using the 295D on my roller cam engine - Yes roller cam.  It does have less than .600 lift tho. 

Share this post


Link to post
Share on other sites

Dyno Dave (Dick Johnson's brother that is) did ALOT of research into valve springs and harmonics in the valve train for there clevo's.He used the strobe light and used various testing procedures and found that they could go down in spring rate by alot after doing so as he found the super heavy springs were not needed.They didn't have the same sort of springs we do today but deff alot lighter than the competition was using for sure.

 

Who can remember DJR's clevo's breaking? yeah me neither so he was onto something back then in the early mid 80's.

Share this post


Link to post
Share on other sites

I run Isky 8005a doubles with a damper @140lb on the seat . 250* @050 duration and 612" lift

They lost a bit of tension after run in tho , not sure if this is normal

Share this post


Link to post
Share on other sites

Like Sly and Ando mentioned the spring frequency plays the biggest part when trying to run a lower seat pressure, the higher the spring frequency the better, the spring will go into surge later with a higher frequency. That is why beehive springs are generally better and can run a lower spring pressure, they have 2 advantages, less weight due to smaller retainer and they have many different frequencies and pass through these harmonics quickly so it dosen't go into surge. I am taking Ando's advice and going with the Isky springs he mentioned for a cam with .542in of lift.

Share this post


Link to post
Share on other sites

I run Isky 8005a doubles with a damper @140lb on the seat . 250* @050 duration and 612" lift

They lost a bit of tension after run in tho , not sure if this is normal

That is a bit unusual for an Isky spring.  I find that I can get four years out of the 235D's.  At four years they lose 5lb of seat pressure but I'd still be happy to use them with 105 on the seat.  I usually replace them, the bearings and rings at that time and its good for another 4 years of flogging.  That's in speedway.  They would probably last forever in a street/strip engine as they just don't see the constant high revs like speedway engines do.  It's all dependant upon how many cycles they go through. 

Share this post


Link to post
Share on other sites

they do not require machining of the springs seats.  If you run single groove valves you can buy the 707-sta steel retainers and 255-vsl locators.  You may need to shim them up depending on your installed height. 

If you run multi groove valves you will need comp cams 744-16 retainers and about an hour on the lathe to make them suit the 295D/ 235D springs.

Yes you can run the cam in with them as is as they are only a single spring with a damper and with low spring seat pressures you will not wipe lobes. 

Share this post


Link to post
Share on other sites

grimmy you have some seriously big gonads my friend.  Most cam manufactures recommend run in on outer springs with seat pressures over 120lb.  I would think that at 140 you are pushing the envelope and run the risk of wiping a lobe at some stage.  but hey if you get away with it all well and good. 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×