MILD THUNDER

iTrader: (3)

Good discussion though fellas . It's interesting stuff

MILD THUNDER

iTrader: (3)

I agree . I also think the key with any solid setup, is maintaining the proper lash. I don't think I would want to run a solid on a hydraulic lobe, and let the lash get too big, I can see where that would start hammering stuff

5050

one other thing to think about is solid roller on hydraulic roller cam with like t&d shaft rockers lash doesn’t change with those so if u have a rocker get loose u will hear it and u have an issue and not just a loose rocker so u can find a problem before it’s catastrophic as to where a hydraulic roller would pump up and self adjust some and cover it up until it’s severe. Once you have shaft mounts u will never go back to a regular roller rocker.

Single cat

So my cam much be a a monster. 276 282 @ .50 on 112 lobe with 780 ish with a 1.80 rocker. Lol mite need some inserts for the tail pipes.

GPM

I have an old dyno sheet sitting around where I ran a 276/284 @ .050 .785 lift with a Procharger on a 598. I ran that cam for several years with the Jessel shaft rockers and PAC springs didn't have a problem.

Single cat

Cool deal. I bet it sounded mean.

endeavour32

iTrader: (4)

How may hours were you getting before you needed to replace the springs and lifters? My 572's are running a 258/262 .712 lift cam, with TD shaft rockers. I'm curious what the refresh rate on the valvetrain is going to be. Right now I'm planning on every 150 hours, but I don't know if that is realistic or not.

GPM

I just checked my notes, the springs were Crower 68806, I ran them for 3 seasons until I gave the heads to my brother for his motor, I believe he ran them another 4 seasons. I don't know exactly how many hours that would be. He used the same cam family just 4 degrees less duration. 7/16 pushrods, shaft rockers and good springs seemed to help the valve train to live, even at 7500 rpm.

Rookie

iTrader: (4)

I believe Jim is running 1.85 IN (I think he might be going back to 1.8's) and 1.8 EX. It's really not easy to pin down how many hours he gets before freshening things up cause he will pull the heads to change something up, inspect bores/wear and check spring pressures. His engine has always been an R&D engine. The longest that I can remember was about 4 years the heads actually stayed on. lol

Also, I must note that he uses rocker ratio to obtain lift. As noted other times he uses relatively smaller duration Comp cams that don't have large lobes. He tries to match lift to his porting. Another thing he doesn't put SR on HR cams on everything. I only know ~6 engines out there to have that setup.

Another note, I solved my engines problem of beating the crap out of my valve train. (SR on HR cams) Spring pressure! I against the advise of my head guy, decided to go off the advice of my cam designer and used spring pressures and rates that he recommended. Replaced them last year with my head guys recommendation and haven't touched them since.

Gimme Fuel

So back to something that this discussion has brought up.....

Is running a more mild cam with a 1.8 ratio rocker better than a larger/more aggressive lift lobe and a 1.7 ratio rocker in an endurance application? Consider an application where a mild cam with 1.8 rockers or an more aggressive lobe coupled to 1.7 rockers. Both setups net the same valve lift.

To me, having less lifter movement and a bit higher transmitted pushrod force to the lifter due to the ratio increase seems like it might cause fewer harmonics, or at least lower amplitude ones, than running a larger lobe and a lower ratio rocker. The slight increase in transmitted spring force would also help to keep the lifter solidly on the lobe with no bounce along with the slightly milder lobe profile further reducing lifter bouncing potential and the need for stiffer valve springs to control lifter bounce.

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