I've read on the board about too stiff valve springs rounding off lobes on a hydraulic flat tappet cam. I'm wondering how this could affect my set up. I'm running a stock shortblock, iron gt40 heads I picked up second hand (I know he bought them from ford motorsports and installed them on a roller block) with a comp hydraulic flat tappet cam, and 1.6 roller rockers. I don't see iron gt40s in the 2009 Ford motorsports catalog so I don't have any more info about them. Does anyone know if there were more than one version of the gt40s available aftermarket w/ different spring rates?
According to the 1996 motorsports book, " These fully loaded head assemblies consist of our M-6049-L302 GT-40 heads and M-6090-L302 valve train kit" Which show to have the M-6513-A50 springs, Which shows 110 LBS @ 1.820 height And 240 lbs @ 1.400 Height. But the only true way to know what you really have is to check the spring. You will also need the specs of your cam manufacture to see what they recommend.
The dual springs on the GT 40s' can kill cam lobes on break in with a flat tappet hyd.If you pull the damper spring(inner) you should be fine but... the springs wont take a huge lift/duration cam...just aint strong enough.
The main concern with strong springs and flat tappets is only during the break-in period. Once you get past that, you can use just about any spring that doesn't coil-bind. They recommend that if you want to run very strong springs on a flat cam, that you break it in first on a set of light springs. Then swap in the stiff springs afterwards. Or in the case of dual springs, break-in with only the outers, then install the inners later. That is what I did.
The Lightning's 351's had a flat tappet cam and GT40 heads. I can't find any spring specs though for em. Compare the rates posted above with what Comp recommends to see how close they are.
Valve Springs Trashing Cams The last 2 API specification upgrades on automobile motor oils have removed much of the trace elements that used to help lubricate the sliding surfaces on flat tappets. Those trace elements cause the catylitic converter to become less effective. They don't have to worry about lifter wear anymore primarily because cars use roller lifters now. If you read the Hot Rod Article some years ago it will go into all the details. Hot Rod Magazine reccommended using Diesel oil because they still used flat tappets. I've used Shell Rotella in my race car ever since. It only looks to come in 15W-40. The new 2007 diesel oil specification (JG-4 I think) for the new catylist equipped engines also reduced much of these trace elements so I don't know what the deal is now. If you watched any of the Cup series races earlier in the year you saw a bunch of engine failures due to lifters / camshafts. They have coated the surfaces to make up for what is lacking in lubrication properties of the oils since the rules only allow them to use flat tappets. Of course the spring pressures and forces are extreme in this application. If I had to break in a new cam on the race car I'd use lots of lube and take the inner springs out. I still have some 2006 Rotella I would also use unless someone could convince me the new spec was OK.
I think it is the removal of Zinc that has the effect on flat tappets. I believe it also includes synthetics. Kendall has an oil we can use if I remember right. Have to look into it.
Found a link to Shell rotella's new spec for its oil. Its back up to around 1500 ppm Zinc contrary to the reports in 2007. Cant verify it on the Shell site though. I'll keep looking.
So from what I am reading I use my old springs for break in. I just bought a new cam and new springs. I was just going to install both at the same time.
Most streetable cams shouldn't require that precaution. I would say durations less than 230 degrees at 0.050" lift and 0.500" of lift probably don't have springs that could wipe out the lobes if you use plenty of the break in lube. Yhis is just an opinion so don't go to the bank with it. I'd love to know if Darren found any more about the Rotella specs.
Diesels haven't used flat tappet cams for decades. I don't know where Hot Rod got that from. Even the old 71 series Detroits had roller cams. Those date back from the 1930's. If anything the zinc phosphate was to lengthen the life of the rod and main bearings. These used to be changed out at about 250,000-300,000 miles (with the engine in the truck) with nothing else done to the motor.
Here is the link to the latest tech article on Hot Rod on this issue. http://www.hotrod.com/pitstop/hrdp_0702_pitstop_zinc_oil_additive/index.html
The last cam i broke in i used 80# on the seat springs, Although this wasn't a performance cam i didn't have any problems. I have also found Lucas has a new product that may be easier for most to get and use, Although i have never used this product i do believe in Lucas products. http://www.lucasoil.com/products/display_products.sd?iid=82&catid=9&loc=show&headTitle=%20-%20Engine%20Break-In%20Oil%20Additive%20-%20TB%20Zinc%20Plus
My P heads ate my cam after about 3 years. Ran fine most of that time, and break-in went noneventfully. All of a sudden, 3 years later, I am driving around town and start to get a light tap. Then over the course of 15 miles driving, it gets so loud that I am turning heads at the intersections. Get home, start pulling stuff apart, and I have lost almost 1/4" on one of my lifters and rounded out a lobe. That was on a mild cam and stock springs from a 97 Explorer GT40P head. Can't say for sure that it was the springs, or maybe the zinc, or possibly both, or something else. But when I rebuilt the engine, I got different springs and converted to roller lifters so I would never have to go through that all again.
