thurman_merman

I needed more lift for an upgraded camshaft and the comp 981 springs are only good for .490 lift. I did more searching and made a few phone calls and this is what I did. Cam is a comp xe 08-503-8, 224/230 .503/.510 112lsa +4.

​​​​​*edit* Manley has a bad reputation lately for broken springs, I'm switching mine out for a set or pac 1201 or 1201x for peace of mind.

Here's what I have found. The Manley springs 22410 drop in and fit great. They will work with the factory retainers however, because of the overall height of the factory retainers I could only get about .460 lift before they hit the valve seals. After fitting the standard steel Manley retainers 23651 I was able to get .590 lift before hitting the seals, plenty for the .510 I was wanting to run.


I did find out that my engine has been rebuilt at some point so I don't know what, if any, headwork has been done.


I know that its highly unlikely that my factory pushrods would fit after a cam change and after some more reading I found that when you change to stiffer springs you need stiffer pushrods, the stockers cannot take the added force. There are plenty of reports of stock pushrods bending and falling out of their cups or worse, binding into the edge of the lifter and rocker and breaking valve springs causing engine damage. Its worth the $100 to get hardened pushrods.


Factory rocker arms cannot handle more than about .470 lift because of their short slot where it mounts to the rocker stud, also they are known to be inaccurate in their lift ratio. Long slot rockers are an option as well as opening up slot on the factory rockers but I chose to go with a roller tip rocker from Comp Cams 1417. They only needed minor clearancing on the drip tabs which are important for keeping oil in the center section of the rockers. About .030 off the inside to cylinder .750 inch up from bottom and .030 off the end is plenty for clearance.


So that's kind of a newbies guide to valve springs in a d-port alum 113/zz4 corvette head, what I was looking for a couple months ago. I hope it helps someone.


Also, this is a good read about valvetrain.


http://www.aa1car.com/library/perfor...valvetrain.htm

Churchkey

Thanks for the info am getting close to checking for spring bind & stem seal clearance on a pair of 113 heads. New cam is .480 lift with 1.5 full roller rockers.

Using the Manley 23651 retainers: Do they change the installed valve spring height as well or just provide more clearance for the stem seal?

Currently have Crower springs @ 1.750 installed height for correct valve seat pressure.

C409

..... I just built a pair of 113's using Comp 987 springs installed @ 1.750 ... I had the guides machined for positive valve seals ... 987's are 1.430 dia and 138# seat pressure ... I'm seeing .575 clearance between the seal and 740 steel retainer ... if you need more lift clearance , there's always the +.050 keepers/locks ... this set-up is intended for Comp XR276HR with .540 lift with 1.6 rockers .....

thurman_merman

The retainers don't change the installed height, they are just shorter overall compared to a factory retainer and give more retainer to valve seal clearance.

My heads had been rebuilt by the previous owner and I know for a fact that my valves were not correct for my year engine, the retainers may not have been either. Either way the Manley retainers solved my issue and then some.

thurman_merman

I installed positive type seals on my heads too but didn't need to do any machining. What did you have done, cut the protruding guides down to the casting or did you have to machine the casting too? My guides were flush with my casting and that's why I think I was able to have so much extra clearance compared to others corvette owners experiences, I have read that 113 heads give you .525-.530 max.

+.050 keepers are a slippery slope in my opinion. They change your spring installed height and have to be shimmed underneath to get the seat pressure back in check but even worse they bring the retainer closer to the tip of the valve and you really have to check your rocker arm clearance. Especially with those big bodied aluminum roller rockers built for serious pressures, you just may not have the space for the +.050 keepers before the rockers contact the retainer. I was able to stay away from them and I feel more confident with the standard keepers.

cv67

Talk to Mr Tripp at Manley and get the right parts the first time
Hes been at this longer since most of us have been alive
learned the hard way he bailed me out and have one hell of a motor due to it. Sometimes just need to talk to the right person Guy is the man.
You want a pro or a 10 buck an hr sales hole?

C409

..... The O.D. of the top of the factory guide was cut/reduced to allow fitting a more common sized performance valve stem seal that also fits the I.D. of the inner valve springs better than the factory umbrellas ... whenever fitting any aftermarket parts it is the installers responsibility to check every piece for its impact on the other parts around it ... particularly rocker arms , valve springs , and push rods ... serious spring pressures would likely never be needed on 113 heads as the port and valve sizes limit the heads overall power production capabilities long before the range of rpm that would require serious enough valve spring pressures .....