Hello I have a Z-303 cam and it says Requires valve spring pressure 120 lbs. close 340 psi open and may require longer pushrods. I have gt40p heads Is there any valve sping for this lift that will fit this heads with out mechaning if not help me on learn how to read specs on valve springs so I want get a set thats not to small. thnaks Jim Duration @ .050 228 Int & Exh Lift .552 Intake & Exh 112 LC
Sorry, that is above my head. It sounds as if you have a Ford Motorsport cam. Try contacting them directly or an authorized dealer. That should give you your answer since you are using Ford heads. Best of luck. Seth
The springs that come on GT40P's are good for only .500 lift. That's also where these heads stop flowing, so unless you have a good bit of port work and possibly larger valves that cam won't help you. If your heads are reworked I'd call the cam manufacturer's tech line for a suggestion on springs. That's why they get paid the big bucks. Those spring pressures you listed are not uncommon.
I know this is a ford motor sports cam and I know about the gt40p .500 flow limit. but i have read with port work that this heads do put out flow gains up to .600 lift.
Yes. The main restriction is the hourglass shape of the valve bowl just above the valves. This shape increases flow velocity at low lift/ low rpm. Open that up and these heads flow like crazy, with a slight loss of low rpm torque.
Go over to Comp Cams web site, look in their catalog under springs; has a pretty good explanation of spring terms and dimensions. Then jump to the spring chart page, should find what you're looking for. Also, check out the valve spring upgrade kit from Trick Flow at Summit, I dont remember the specs offhand but I know alot of people use them with the alphabet cams on GT-40 heads. Or go over to The Corral web site and do a search, they have a ton of info on GT-40's
Yes TFS has a set that will fit with out mechaning the head If i remeber right it is only up to a .540 lift and i need one for a min of .552 lift Tfs does have another kit for .600 lift but i am not sure it they will work with my heads. thanks Jim
Valve Spring Pressure...hmmm...I'm pretty sure that means you use a pressure gage. This is how you find out whether a spring is good, needs to be replaced, etc. First, you find out the height of the spring whenever the valve is closed. You may be able to find that in a professional ShopKey program or a Chilton's Manual. Then, you take a bench vise, pressure gauge, and each spring, and compress the spring along with the guage, inside the vise, until you compress the spring to the height of the spring when the valve is closed...as I referenced earlier. Then, take the reading and compare it to your manual. If it is within 5-8% of what is referenced...you're in the green. If your springs are not to spec, definately replace them, especially if you are using a high-performance camshaft. Car buffs, let me know if my information is accurate. I'm fixing to test the valve springs on my car's 200ci. Thanks, Jeff
Thanks Jeff that is some good info to know, but what i was wanting to know is how much pressure you nee for X amount of lift would it be ok to run a spring made for a .600 lift on a cam with .552 lift?
I would think so...But I dont know what they would do to your valves. What for more replies...sorry. Jeff
I think I found some:bananaman from crane and it don't even require machining up to a .585 lift. The kit is Part Number: 44308-1 http://www.cranecams.com/?show=browseParts&lvl=2&prt=34&action=partSpec&partNumber=44308-1 The springs only Part Number: 99841-16 http://www.cranecams.com/index.php?show=browseParts&action=partSpec&partNumber=99841-16&lvl=3&prt=122
