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heavy valve spring question?

G

gwstang

Member
Don't kick me...but this is on my son's 350 cheby (in the '56 in the pic by the stang). It did wipe a couple of lobes as I have everything apart. I looked up the valve spring pressure for the comp cam springs and they are a whopping 432 lbs. :wtf This was a higher lift cam, but not a monster. Just a slight lope at idle. Should I put the oem springs back in (that I still have) to use with the new camshaft or just reuse the monster springs (Valve Springs, Single, 1.255 in. Outside Diameter, 432 lbs./in. Rate, 1.153 in. Coil Bind Height, Set of 16).

New Camshaft is Hydraulic Flat Tappet, Advertised Duration 266/266, Lift .440/.440

Need some of you experts' opinion/help please :bowdown
 
I'd call Summit and ask for the recommendation. 432 lb rate seems high for a street cam, and could have factored in the wiped lobes. For camparision, I'm planning a build of a BBC now that has .550 lift and more aggressive ramps on the cam, and it is calling for 350 lb/in springs. It will only be spun to 5200, so no need for mega rate springs. The Lunati I'm putting in the 5.0 for the Stang uses 250 lb/in springs, and it's a 220/220 @ .512 lift roller.

Be careful what oil you use, flat tappets need the zddp content to be 1200 ppm zinc even after break in - again, IMO.
 
It does seem high, the beehives I'm running are only 370# and I have a total lift of .555"
 
And Mark is racing, so spinning higher rpm than your son will.


(note lack of reference to grenade broken engines)
 
"apollard" said:
And Mark is racing, so spinning higher rpm than your son will.


(note lack of reference to grenade broken engines)
Click to expand...


Thanks Buddy!
 
Hey everyone. We went ahead and put some lower # springs on today.. Those heavy one's are such a bitch to compress for removal that I just reached for a large 1/2 socket to fit over the top and handed my son the BFH and a couple of whacks later and the keepers just sit on top and lift the spring off. :roll I knew there were some crane cam springs in the shop...just had to find them amongst the mess. :shrug Now to install the new cam/lifters etc... Oh yes, we have the bottle of zddp stuff to help protect the new stuff. ( I went ahead and got several for future oil changes).
 
"I'm planning a build of a BBC now that has .550 lift and more aggressive ramps on the cam, and it is calling for 350 lb/in springs."

What is the BBC going in?
 
26' Boat. I wantneed about 100 hp more.

Should be easily gained, as the existing cam is bascially a stock chevy truck motor cam, 192/202 @ .050, .400/.440 lift. Boats need both HP up high and large amounts of torque down low to get on plane. They are also basically a big water brake dyno - the engine is under pretty much full load at all times, there is no coasting or cruise. No need for vac advance (in fact, most boats- even carbed- run electronic advance curves that top out around 32 degrees).

The big issue with boats, however, is idle water reversion. The cooling water is injected into the exhaust just after the manifolds to cool the exhuast (really hot surfaces in a fiberglass boat = not good). Get the overlap wrong, in either number of degrees or timing of events, and you'll suck that water back into the engine. In extreme cases, the oil will get milky from it - and you'll weaken valves, which love to let go at WFO @ 5000 rpm. :hide

Raising the idle will help, but most outdrives can't handle high shift speeds - the Bravo I run needs to be well under 900 rpm. You can also switch to a water jacketed exhuast that does not mix the water into the gas stream, but those are loud as hell and I like to ski / tube /etc. A straight piped 454 isn't relaxing to me.

So, picking the right cam is much more critical than building a 400 hp 454 street engine (which is a cake walk). I could easily get a cam that won't revert and will get me the 400 hp I want, but I'm picky and don't want to leave 30 hp on the table. I want to be right on the line of reversion, and get max HP I can given the wet exhuast and need to idle at 800 rpm.
 
Thanks, I'm learning before I blow something up - like a 7k boat engine. There are some great forums out there like this one with lots of folks that build engines for a living on them - engines as in 1200hp supercharged 540 ci monsters - and that's 1200 hp that is run WFO for 30 minutes at a time, not a 8 second run. Here's an example, it's a work of art to watch him put together
http://forums.boatfreaks.org/showthread.php?t=16735
 
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