Just got a call from the guy doing my head work/assembly saying that the LT4 springs may not give adequate seat pressure........ He was asking if I had a cam card for it, and I told him that I didn't think it came with one. Can anyone help me on what specs he would need?? I know some people think that these springs are marginal for the cam, but I'm not planning on revving the motor past 6........ I'm tired of chasing parts but holy ****. This is ridiculous. I'll probably ask him to install the springs anyway, and if he won't do it I'll find someone who will.

But anyhoo, can anyone give me the specs on an LT4 HOTcam that would come on a cam card??

John

 

lift is .525 int and .525 exhaust w/ 1.6 RR. duration at .050 is 219 and 228.

I have other numbers if you need them, but those should suffice.

My guy said the springs were on the edge, but OK.

 

Do you have any specs on seat pressure??

John

 

They should work, but they are marginal. My brothers has had no problems what so ever. It has been 8 mths already. Plus, he revs to like 6200-6400. You definetly neev to rev the hotcam to extract maximum power.

Someone else can tell about the specs. but I know max lift with 1.6 rockers are at .525 I/E. FYI LT4 springs are rated up that only.

I have never heard of failute before.

Good Luck

 

I found this online:

One of the most obvious features of the LT4 over the LT1 is the higher 6300 rpm redline. Since the redline was increased 500 rpm, the engineers had to improve the valve springs significantly. They did this by using an egg-shaped, single-coil spring with 100 lbs. of seat pressure, as opposed to the LT1's 85-lb. pressure. The closed seat pressure is 260 lbs.

http://www.malcams.com/legacy/misc/lt1lt4.html

 

Thanks Chris, I think that will help out!!

John

 

Well nevermind guys........ I told the guy earlier that if he really felt like the springs were not ok to get some other ones. Apparently he thought that the LT4 springs were just a big steaming pile of **** because he wasted no time in getting new ones. Oh well.........

John

 

Keep in mind that the factory LT4 used lighter valves. Your engine builder is smart and cautious. Will they work with stock valves? I have no personal experience, but I suspect so or we would have heard about it by now.

Rich Krause

 

When I changed to the HOT cam in 98, I ditched the springs also. Had a couple checked and they didn't even make it to 525. Needless to say I didn't use them.

Don't know if they changed the springs since then as lots of people use what comes in the kit. I didn't feel comfortable with them back then.

Real LT4's had sodium filled valves which weigh a lot less than LT1 valves.

 

I used the ones that came in the kit. Had zero problems and took her to 6400 quite often. I think I bought my kit in 99 or 00, not sure if they changed them or not.

 

For $45(cost of upgraded springs) I think it's cheap insurance. Although that was $45 that I don't have.

The guy came highly recommended and does some work for race applications, so I have to trust him on this one.

Now the question, if I need to rev this motor to 6400, will the bottom end handle it?? I know it would when it was newer, but I have 125k miles. Thoughts??

Also, I would have run the stock springs and not thought twice about it, but that's just me.

John

 

The Hot Cam springs seem to work with no probelms of valve float or coil bind if set up like they reccomend but on paper, you would want another spring.

You would like to have more seat pressure from them but if you shim them ANY more, you will coil bind.

You did the right thing by getting different springs. People have ran them with no problems but they are just so close to "NOT WORKING" that I would reccomend a diff. spring.

NightTrain66

 

I agree. Your engine builder is just trying to look out for you.

Remmeber the LT4 springs were designed with the stock LT4 cam in mind which is NOT the same as the Hotcam. Even with the 1.6 rockers the LT4 cam only had .470 lift, much less than the .525 of the Hotcam.

Also as Rich mentioned the LT4 had lighter, hollow valves.

Now you see why everyone says the LT4 springs are marginal with the Hotcam. Tons of people have used them with no problems but that does not mean they are the optimal part for the job either.

Edit: I see you bought better springs, good choice. They will probably hold their pressure better as well since they aren't being pushed to their absolute limit. You can also sell the LT4 springs to recoup some of the cost, they're worth ~$30 a set and they're great for someone who wants to run 1.6 rockers with a stock cam.

 

I ran the LT4 springs on my stock cam for a while. I think they are great choice for anyone using 1.6 rockers/stock cam, but they are puny springs. Springs are pretty cheap insurance (unless we're talking solid roller ).

Ryan

 

Well, I'm not even sure what springs the guy got for me, but I am going to find out. I'll also see if I can get some pictures of the heads up. I'm real excited to see how they look after cleaning and assembly