Quote:
Originally Posted by goatasaurus rex
cliff,
whats the deal. i had to have mine shimmed to 1.630 to get 140/350. this was done by a experienced cylinder head guy using a rimac machine.
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The older 995's were a completely different spring,Comp changed the seat and open pressures completely,and instead of changing the part number to reflect that,the new specs just superceded the old specs,if those pressures are what you measured,yours are likely the older stock 995's.
The "new" 995's are listed as 130 lbs @ 1.700" and 372 @ 1.150",and like Cliff says,they often measure more as SOP/OOTB as they'll loose a few lbs after a bit of run-in time.
The "old" 995 specs were 115 lbs @ 1.700" and 340 @1.150",and from what I know of this deal,those "old stock" 995's usually check right at those specs,or a few reports stated they might check in just below that.
Like I said,those springs have been discussed a bunch here already,and I was hoping that there was no need to spend time re-typing all that info here,do a search on 995 and you'll get all the info.
And as for the lunati #73949 spring,I'm not entirely sure it's not the same spring as the crower #68405-16 spring,with lunati just listing that #79349 spring at the 1.650" IH instead of 1.700",those lunati springs are rated as 120 lbs. @ 1.650" and 265 lbs. @ 1.250" their CB height is listed as .950" and the rate as 363 lbs.
The Crower #68405-16 is rated at 129 lbs. @ 1.650" and 278 lbs. @ 1.250",CB is .980" and their rate is 382 lbs/in.,so those two part numbers are very close to each other according to their ratings.
As stated for "healthy" applications most will install the Crower springs @ slightly less than the 1.700" IH,mine were installed @ 1.687" and that got 115lbs.,this set-up is good for up to .630" lift easy while leaving the proper retainer to seal clearance.
That was with +.100" ('67 to '70 5.100" appx.) length valves in #96 heads.
I'm going to be using the Crower #60210 hydraulic with those #96 heads,and that Crower hydraulic is somewhat close to the .050" specs of the OE 041/RAIV hyd. cams,except that it has slightly more lift,less seat duration,and a tighter LSA,all for a bit less total overlap than the 041 cam has (yet more OL @ .050").
And FYI I'm using a set of HS 1.65 roller rockers with this cam for a lift of .531"/.551" (.547"/.567" if you consider the HS 1.65 rockers measure closer to 1.70 ratio) based on the .322"/.334" lobe lift.
Though those #96 heads were originally set up to be used with a Crower custom solid cam #E-27941,that solid cam is 256°/260° @ .050" and had quite a bit more lift than the current hydraulic has,and the solid was intended to be run with the 1.65 rockers as well.
That custom solid cam has a lobe lift of .360"/.365".
That custom Crower solid cam found it's way into my racecar's 406 instead of the streetcar's 455,that 406 engine uses the "old" spec 995's @ 1.700".
As you can see,the old spec #995's are very similar to the specs those #96 heads were set-up to use with the #68405-16 Crower springs and that #E-24971 custom solid cam,so that was a natural choice given the parts I already had on hand,that 406 engine had a comp 292 magnum hydraulic when I got it,and I'm not a fan of that style of grind,so in went that solid cam!!!
The race engine is intended for higher RPM's,as it has the better bottom end (eagle rods/forged pistons) and it will see regular use over 6000 RPMs,the "street" 455 on the other hand has a cast bottom end,so it will never see over 5400 RPM likely,thus it got that hydraulic cam to act as a defacto "rev-limiter" of sorts.
I'm practical to a fault at times,this is just an example of that.
HTH.