I have recently acquired an incomplete 312 build...The gentleman I purchased from had been gathering parts and seems most are complete. The block has been machined .60 over included sonic testing, with cam bearings installed. The deck set up with pistons.004 in and using 10.00 cc head gasket with the new dome forged pistons milled from 10 to 4 and connecting rods from Probe Industries. The crank had been ground 20/20 and all the assembly balanced including damper. Looking at the cam grind sheet from it appears to be set up using the smaller 1.43 rockers for some reason although he supplied new 1.54's. My question would be should I use the new 95# valve springs he also supplied or would the stock 70# springs be better/safer? I am just worried about cam wear and break in mostly.

Regards,
Gary

Gary;
If you post the cam specs you will probably get some good opinions on the valve seat pressure.

Rono

  Ron Lane,  Meridian, ID

Cam specs:
218 Grind/Oregon Cam Grinding
108 lobe separation..intake and exhaust center line  108
lift int./ex. .293
duration @ .002 tappet rise int./ex 354
duration @.020 tappet rise int./ex. 259
at .026 tappet rise int./ex 250
at .050 tappet rise int./ex 226
at .100 """191
at.200"""128
Gary

Sheet is a bit confusing not showing 1.54 rockers for lift it has 440 lift at 1.5 rockers and 469 at 1.6 rockers/duration shows225 int/ex. .050...lobe separation 108 int./ex...lobe lift 293
Gary

With that cam, you want the 95lb springs, maybe even a little more. That is a pretty mild cam and any reasonable amount of spring pressure will not cause a failure.

Since you know who the manufacturer is, Oregon Cams, your best course of action is to consult them and find out what they recommend.



Lawrenceville, GA

Thanks I will call them Monday

Gary

Gary.  Camshaft 'stuff ' is a subject that is the basis of a lot of threads in the Archive of this Forum.  In an attempt to help with what you wrote in your initial question here are a couple of pieces of info. 

A camshaft supplier's ADVERTISED duration is measured today at .006 for a camshaft using hydraulic lifters and .020 for a camshaft that uses solid lifters.  There's another number called 'lash point', that can vary widely depending again with the type of lifter and the valve lash used with the solid lifter rocker arm mechanism [if a rockerarm is used  ].   In my recollection, Iskenderian was responsible for establishing the comparing of camshafts at the .050 DURATION measurement.  My understanding is the .050 measurement came about because the ramps on the cam lobes can be misleading as to when a valve actually has significantly begun lifting or all but closed.

While the FoMoCo 239, 256, 272, 292, 312 'little' y-block species were used in various vehicles produced between '54 and '64, the 1.43:1 rocker arms were used for 9 of those production years and 1.54:1 rockers were only used for 2, 1956 and 1957.  Since most y-block engines came with the 1.43 rocker arms, aftermarket camshaft suppliers generally provide valve lift specs expecting the purchaser to be using the 1.43 units.

One of the threads last year involved numerous members' discussion about selecting and obtaining a camshaft for a rebuild.  The thread was four pages in length and very informative pertaining to the y-block cam AND what Oregon Cam is offering.  Ken at Oregon Cam was referenced as a contact person.  Click the link below. 
http://forums.y-blocksforever.com/Topic111517-1.aspx

In that same thread was a link that Miker supplied to an article in the June 2006 edition of Popular Hot Rodding Magazine.  Consider reading the link below for one of the most comprehensive articles I've seen in a glossy monthly magazine on camshaft insights.  The title of the article is, 'Be The Camshaft Expert'.  David Vizard was the author with some assistance from a Johnny Hunkins.
http://www.hotrod.com/how-to/engine/0607phr-camshaft-basics/#__federated=1

As Charlie suggested above, connecting with Oregon Cam is a good way to get an answer on what springs to use with the cam they've supplied.  Short of that, consider the engine rpm range you anticipate using in your 'Bird.  Methinks valve float is the primary concern and rpm is the principal determiner.

Hope this helps. 


NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

As a general rule, seat pressure does not wipe out a camshaft; it’s the over the nose pressure that’s critical.  This number can be either measured with a valve spring tester or derived mathematically if the spring rate (lbs/in) is known.  It’s possible for a 95# seat pressure spring to have less pressure at full camshaft lift than a 70# seat pressure spring depending on manufacture, coil wind, construction, etc. assuming installed heights for each are the same.

Lorena, Texas (South of Waco)

I'm with Ted, it's over the nose pressure that can hurt both a cast or steel cam. I bought one of those inexpensive spring pressure testers from Summit that you use with drill press or even a vice. To measure the spring heights I make different length PVC tubes the fit inside the springs until I get the open and close valve demension I need. For "open" its just a little math with the cam and rocker ratio. I can check every spring before goes on the head this way.
I guess tinkering is a passion I have and I really like building the engines we race. Sorry none are Y's but I doesn't change what I would do..Good Luck.

56 Vic, B'Ville 200 MPH Club Member, So Cal.