Recently I have been researching a number of Forums and Web Sites trying to get some light about the LS1 valve train. The reason is the consensus about how weak the valve train of the LS1 engine seems to be. I have read about different cam swaps (HOT CAM vs. The Ultra variety of Other Choices), rocker roller ratios, valve springs strength, coil bind, breakage, valve weight (heavy vs. light), titanium retainers, keepers valve locks, different heads with different CMF’s, CC’s volumes, Millin, head gaskets made out of different materials and thickness, La Bamba, Rock-n-Roll, Salsa, Mash Potatoes vs. French Fries…%$#@&*^%$#@ I think that I am loosing iiiiiiiitttttttttt.

O.K. here, these are my questions:
1. How light vs. heavier do the LS1 Valve train needs to be in order to make a difference? Do I need to replace all the materials of: the push rods (chrome molly), rocker rollers (aluminum/stainless steel), retainers (titanium), springs (silicone…), and valves (NaK filled) etc,etc,etc…
2. Why it is not recommended to use an aftermarket cam if you use roller rockers of a 1.85 ratio? Yeah I just read that out of the CMOTORSPORTS.COM about the Comp Cams 1.85 roller rockers.
3. If you make some parts of the valve train lighter and others not, is there a possibility of explosion or implosion?

All I wanted was to have fun Stree/Strip once in a while by buying a Corvette, and then making the vette's valve train stronger, put a mild cam so I would not jeopardize the drivability (replacing the valve springs X so many miles)and then be worrying about the computer codes, transmission failure and gear ratios. HELP! ANYONE…

 

I think that by usisng a little common sense when choosing a cam, you won't have any problems. I went with something a little larger than a stock Z06 cam with not too much more lift.
My cam is 218/224 @ .552/569 @ 115 LSA. with ported zo6 heads and chrome moly pushrods and Manley springs. I think the stock Zo6 springs would of worked out well also. I didn't have any tuning problems whatsoever. My car is pulled 410
rwhp on a Mustang chassis dyno. Oh yeah, swap out the timing chain and thermostat and oil pump while the motor is apart.

 

This is what I bought so far; GM Hot Cam (Lobe .308 ht.), Com Cams roller rockers 1.85 ratio, Manley 7.4 push rods, Sdpc 1423 springs with ti retainers, double roller timing chain and ported blue printed oil pump. With the cam/roller rocker combo my valve maximum lift will be about .571. All the information that I have gatter says that valve spring trouble start at .580-.590 lift. Is that true or not?
Also would it help the valve train combination to have lighter valves vs. the factory ones.

 

Valve springs break because of fatigue. Aftermarket springs are designed with these constraints.
1: They must remain the same basic height to conform to the valvetrain geometry.
2: They must handle greater than stock lift.
3: They must be stiffer to gain greater pressure to avoid floating with aggressive cam profiles.
The only way a spring designer can comply with the above 3 constraints is to use a stiffer alloy. When that happens the alloy is inherently more brittle. When you have a more brittle spring they will tend to fatigue sooner and break sooner. Because of this stiffer springs should not be run more than 10-15k miles, as a suggestion. Some have gotten more, some have gotten less. I foresee some problems with the parts combo you have selected.
1: The 1.85 rockers will hit your valve covers unless you modifiy the covers.
2: The double roller timing chain is a good choice for a timing set, but you will have to modify your balancer to use it. It requires machineing the rear hub shoulder back about 3mm. Otherwise when you install the spacers to give clearance to the front chain to the oil pump, the balancer will bind on the face of the oil pump.
3: I checked on the springs and they are hardened chrome steel. They are great springs but are going to be more brittle than stock and subject to breakage at an earlier age than stock.
4: The 1.85 rockers will give you a more aggressive ramp for a given lobe profile and that can cause quicker breakage.

If you are looking for an upgraded valvetrain and want to remain as reliable as stock I would suggest to do what some of the guys here have done. Go with a set of LS6 Gold Stripes good to ~.570 lift. and an LS6 cam or something like a 220/220 @ .553/.553 lift cam and LS6 lightweight valves. Lightweight valves require less spring pressure to keep them from floating. Cams with a less aggressive ramp will give a longer spring life. And I would stay with the stock ratio rockers.

Having said all that if you need to go with what you already have, I would install the items, checking for piston to valve clearance but you will probably be ok with stock heads, valves, and the HotCam profile. Make sure you heat cycle the springs at least twice before you run it up. Always make sure your oil is at least 180 degrees before you go to high rpms. And check your springs for signs of weakness or fatigue from around 6k miles and up.

 

I appreciate the advice. I don't think I could use the LS6 Golds due to the Cam profile that I have unless I change the roller rockers for 1.7 or 1.8s. But after reading your tread on Valve Spring problems I am re-thinking the set that I would like to get for my 2001 vette. Thanks

 

All very good questions.

A flat recommendation that you not use an aftermarket cam with 1.85 rockers is incorrect and an over simplification of the issue. The issue is lift. With my set-up of CompCam Pro-Magnum 1.85 roller rockers and the 273 grind cam (220/224 530/534) I am running a net lift of 577/581, which is typical lift type cam. Match that up with a set of springs to handle .600 lift and you are good to go, say Comp 918's. I went with the Comp 921 duals, good to .650 lift, for the extra insurance of dual springs. Now you could get the same lift with just the cam ordered to the right grind, but I also like having a set of true roller rockers. I did not like having to modify my valve covers to make them fit, but it did not end up being a big deal. Check my site in the sig for pictures of the modified valve covers. Supposedly with the Crane 1.85s you dont have to. I put the cam in over the winter and have been running it regularly at the strip with this setup, not to mention my usual spirited driving on the streets. I do give the engine extra warm up time now, to at least 120deg coolant temp to make sure I have oil on everything.

The LS1 valve train is decent at stock, or just above stock horsepower, without raising the rev limiter. To define its limitations you just have to take a good look at what the LS6 valve train upgrades are. Just switching over to factory assembled LS6 heads/valves/springs with the 1.85 roller rockers, in addition to LT headers/exhaust, put me about even with the average cam only car with headers.

So to call the LS1 valve train "weak" you have to state in what context you are talking about. As designed, it's good. If you throw on an intake-headers-exhaust, tune it up to 320-335 rwhp and DONT raise the rev limiter, it is sufficient.

But now you have done your homework, got some feedback, you should have a good idea. Think about what your end goal is for the car, then get the right stuff.

Good Luck!

 

You are right. I did not clarify my statement enough. My recommendation was to use a higher lift cam than the HotCam but use 1.7 rockers to yield a net lift around .550. This will keep the lift in the range for the Gold Stripe springs as others have done to keep a reliable valvetrain to ~100k miles. Also I'm wondering what the difference in hp/tq gain would be going from .550 to .570 using stock LS1 heads. They only flow about 3cfm more in that range difference. I would go with greater duration as you have done.

 

Thank you All for your feed back. I am new at this. That’s why I like to read threads and ask questions before I keep expending Dinero (MOney). When I said that the valve train of the LS1 is weak I meant to say that it is probably the weakest link (of the chain) in the engine designed. And I could be wrong but all I have read till now may indicate that. So what I would like to do before I make my C5 Twin Turbo or Supercharge it is to strengthen the valve train so it could handle the extra HP. I know I am going to change Heads to low compression heads, also work on the Trany and maybe the differential as well but that will come later. Any advice is well taken. Thanks in advance ZUUUUKUUUUPOWWWW!!!!