CAT3

iTrader: (9)

Whats the benefits if any over one of the springs to the other? Which will provide longer life with a cam near the .590 lift?

Charlie.

SStrokerAce

iTrader: (2)

It has more to do with the agressiveness of the lobe more than anything.

There are some cam lobes Comp has that really require alot of seat pressure to keep the lifter on the cam lobe. The 977's are what you use then. It doesn't really have to do with valve lift. There are lobes as small as 214 deg @ .050 that need these springs. The XE-R lobes are meant to use a 977 spring because the ramps (where the cam transions from 0 lift onto the lobe) are very aggressive. That's how they get more lift on the same duration.

True guys have run the 987 and 918's on the XE-R lobes no problem. The 977's need to have a better lifter.

Now as far as life goes. The 977's will keep a higher spring pressure during their service life so even if they fall from 155lbs on the seat to 130lbs on the seat they are the same as the 987's and 918's new. The other side of that is that they will be harder on the valve seats and pushrods. Good pushrods help that out though.

Bret

CAT3

iTrader: (9)

Bret are you talking about the 978 or a different one being the 977?
So, with the 978 I would need new lifters? I thought it was safe to run those springs...dayum.

Jorday

I have seen posts about this recently. You probably won't get away with the 978 springs with stock lifters. As mentioned above, many people are running the XER lobe profiles with less spring pressure than the 978 springs.

v8maro

iTrader: (4)

978's & stock lifters are fine, stock rockers = a nono
-Steve

SStrokerAce

iTrader: (2)

? The stock lifters are going to go before the rocker arms will. The rockers might flex but the lifters will collapse, it would be a good idea to upgrade the rockers, but that's one hell of a plunge.

Bret

SStrokerAce

iTrader: (2)

The 978 is a close spring to the 977, the 977 is good up to .600 lift, the 87 is not. It's basically a higher spring rate 987 so there is more pressure over the nose of the cam. (Max Lift)

The 977's are the best choice, they will control the valves really well in the 6500-7000rpm range.

Bret

CAT3

iTrader: (9)

Ok, I didnt even see the 977's on thunders page. So Bret, using the 9 7 8 springs, this is the one you say needs to use an upgraded lifter?
Anyone have the PN for Shubecks Lifters?

Jorday

I made a little bit of a typo up there. The 977 spring is the one that I think is iffy with the stock lifters.

SStrokerAce

iTrader: (2)

You might as well get the Comp R's if you are going to upgrade the lifters, because the Schubecks are just a modified stock lifter.

Anything will more than 130lbs on the seat will need a upgraded lifter. The 977's especially. It's not only the seat pressure but the over the nose pressure will kill stock lifters.

Forget about the 978's because you are going to run more valve lift than they can handle if you set them up to work like a 977.

Bret