I am thinking of going with a biger cam, .510,.536 lift. I have been told that I will need to use 4V valve springs. I have the 351C 2V head, do I need to change springs? and what is the max lift for 2v head and 4v heads

 

You will definitely need different valve springs which are matched to the cam. The cam manufacturer will have a set of springs which will work with the cam you purchase. I don't have the exact numbers for stock 2V heads handy but IIRC it's around .490" with stock springs. The stock 4V heads may have had different springs which allowed more lift but your best bet is still to get the matched springs from the cam manufacturer.

 

I'm running .585 lift with roller rockers and the appropriate springs and retainers. You just need to verify the valve train geometry when assembling.

 

Well I am using a .498/.510 lift now. Maybe I just need more duration.

 

I am running a hydraulic roller with 0.595 lift. I needed the spring seats cut in my CHI heads for the springs to fit.

 

I was using the matched valvsprings for the comp cam 268H with stock valves, locks and retainers. No machining just a spring change. But the 268H only lifts to .494 at the valve.Thanx.

 

So the general consensus is, change my valve springs when I change the cam?

I have been told that my lift is pretty good .498/.510 but my duration sucks
204/214

I'm just looking for a little lope and some more pull

 

Where do you want your power? The cam that you have will give you lots of power at low RPM. If you increase the duration, you will get more power at higher RPM, but lose a little at low RPM.

If you want more power at highway speed, then another 10 degrees duration will help. It will also increase the overlap and decrease your fuel mileage.

Your lift isn't too bad, if you replace the cam with one with similar lift you will not have to change the springs.

 

how did that cam perform the 268h .494 lift

 

I think I will keep my cam, I just changed the rear to a 3.50:1 and put a higher flowing fuel pump on it(It seemed to run out at the end of the track). I'll see how she does at the track on Friday

 

How did you do at the track 66ford400? That .510, .536 cam sounds like the one that is in my 400. Is that the SVO cam you have? I just had to have the valve springs changed for the higher lift.

 

I like my comp cams 268H. With 402ci's this cam is more of a towing cam with excellent midrange. It has a throaty sound and a little lope. I have 9.8 to 1 mech compression ratio and with the 268 duration and a intake close of 60*'s I have a dcr of 8.2 or so. I just purchased a straight cut timing gear set and I plan to retard my cam 4.5 degrees to get away from a slight pinging problem. Infact i have my base timing set at 4* so I won't ping, but I realy want to run 12-14*'s of base timing. Since my cam has 4* adv ground into the cam it will end up with -.5* adv. With a closing agle of 64.5*. this helps lower my dcr to about 7.8 something. So I should be able to run 14* base timing with 87 octane fuel. I have a ton of torque with this cam, and I would hazard a guese of 325+hp. I have no problem breacking my 35x15.5-15 Swamper TSL/SX's loose with a stab of the throttle in low gear (I have an C6 auto). don't believe the hype of split duration cams. I doubt anyone could tell the differance from the drivers seat. Just my 2 cents. Thanx.