GT40p valve springs?

[wgt500]

Well I just got my GT40p heads. My question is.... Will the stock springs work up to 5000rpm? The heads and springs are brand new. That's as far as I probably will push this engine unless I get really excited out there. My Performer cam probably isn't good for much more than that even though my bottom end is good to about 7000rpm.

[Ltngdrvr]

What lift cam?

Stock GT40P springs will be about the same as 5.0 HO springs.

[v8only]

actually, stock p springs are weak, very weak. Not close to the HO springs. the p heads are from a torquey explorer that doesn't rev high. the mustang revs easily to 5500-6000.

Yes, the springs will be good to 5000, but I would expect you'd make power to 5500+, no??

imo you WILL get excited, as that's the entire reason you're building this engine!! at a minimum, put the mustang springs on if they're still good. Otherwise, I went with the tfs valve spring kit. Cheap at just over $100, and cheap insurance against valve float.

[wgt500]

Jeremy, Do you have a part # for the trick flow valve spring kit? Thanks, Dick

[Hooptie]

Just use the comp cams replacement #986-16

[wgt500]

Thanks Hooptie. I'm going to check the open pressure and seat pressure of the stock GT40P springs and see how they compare to the specs. of the Comp Cams 986-16. I will post my findings. Dick

[Matt Paul]

The correct thing to due is use the springs the cam manufacture states.There is more to spings then just lift. Yoy have ramp rate pressure, coil bind, retainer to valve stem height and so on.Just some food for though before you make a mistake.Ill post a pic of what I mean.

http://i201.photobucket.com/albums/a...4/hpim0794.jpg

[wgt500]

Thamks Matt, I'm just running a Performer cam. Edelbrock states it will make power to 6000RPM. Having run it for 200 miles with the stock heads, 6000 seems high. Maybe with the GT40P's, now the cam instead of the heads might determine the power curve. Anyhow, Edelbrock does make a spring for this cam. You make a good point about ramp pressure and the acceleration curve of the valve opening and closing. Now with bind. At only .473" valve lift I'm not too concerned, but you can bet that I will check for it. Thanks.

[Matt Paul]

Thamks Matt, I'm just running a Performer cam. Edelbrock states it will make power to 6000RPM. Having run it for 200 miles with the stock heads, 6000 seems high. Maybe with the GT40P's, now the cam instead of the heads might determine the power curve. Anyhow, Edelbrock does make a spring for this cam. You make a good point about ramp pressure and the acceleration curve of the valve opening and closing. Now with bind. At only .473" valve lift I'm not too concerned, but you can bet that I will check for it. Thanks.

Good to see that you stepped backed and took another look at your situation.Also your motor stops pulling at 5500 due to more then just heads and cam.Low comperssion motor i.e. 9.0:1 or lower, exhaust size and hearders, intake and carb.I understrand at only .473 lift coil bind may not be much of a concern but float a valve and see what happens.

Thanks Matt

[wgt500]

Today I found time to test the stock GP40P valve springs. Seat pressure at installed height is 75lbs.(very weak). open pressure @.500" lift from installed height is 225lbs. which is good for about 4000-4500RPM. (260lbs. safe for 5000RPM). Coil bind takes place at .540" lift. This pretty much confirms the stock springs are disigned to work well within the speed range of the Explorer 5.0 engine for which they were made. I ordered a set of Edelbrock "Sure Seat" springs designed to work with my Performer cam. Dick

[v8only]

nice, fantastic post! firsst time I've seen the #'s layed out like this.

[Matt Paul]

Today I found time to test the stock GP40P valve springs. Seat pressure at installed height is 75lbs.(very weak). open pressure @.500" lift from installed height is 225lbs. which is good for about 4000-4500RPM. (260lbs. safe for 5000RPM). Coil bind takes place at .540" lift. This pretty much confirms the stock springs are disigned to work well within the speed range of the Explorer 5.0 engine for which they were made. I ordered a set of Edelbrock "Sure Seat" springs designed to work with my Performer cam. Dick

Excellent choice but if the budget allows it opt. for the titiumn retainrs and you can run at least 10lbs less seat pressure on the springs and pick up about 200-300RPM.