96speed

Long story:

Made a dyno and the engine stopped revving after 5800rpms (would still rev up, but lost power. 411rwhp @ 5800). After pulling the heads and consulting with a few different people, I'm led to believe my 977s were not enough spring so I'm stepping up to 943s. The old setup barely cleared my promags, but the 943s (@ 1.9" tall and 1.55" OD) do not clear the rocker by ~.2".



Short story:

Stud mount promags will not clear comp 943 spring with LT1 heads.

Can I have the promags clearanced (seems like they would get MUCH weaker by the amount of material needed to be removed), or is a shaft rocker setup mandatory ?

Ryan

HardcoreRM125

Switch to a conical shaped spring like Bee Hives or something similar. They use a much smaller retainer, and will clear on stock LT1 heads.

Wckd94Z

96speed,

nice color i always wondered what an ss spoiler would look like on my car, along with some draglites. anyway, what're the specs of your cam? if you're running under .600 i'd run 918s, that's what I'm running.

Ram Air 383

I'm running stainless Hi-Tech Comp Cams 1.6 stud mounted rockers with CC 943 springs on LT4 heads. The clearance is fine.

My friend is running even bigger springs and he had to get Crower rockers (stud mounted) which are specifically clearanced for big springs.

Turbo6

If the 977's and the 943's are the same diameter. The problem is the installed height. You didn't mention what your installed height is for the old springs, but if the installed height is different then you will need longer pushrods. If the rockers fit on the old springs, and the new springs are the same diameter, then they will fit when you get the correct length pushrods for that installed height. I have personally run the comp pro-mags on my car with Comp pacalloy springs that were 1.55" without clearance issues.

Jason Short

He can't. Ryan forgot to mention that this is a solid roller motor. The 918s are not near enough spring for his cam.

Same thing here.....its not the lift that soley dictates what spring you run. The lobes on Ryan's cam are way too aggressive for a 918 spring.

This is near the same setup as I used to run and it worked with the 943s as well. I was under the impression that the ProMag's and HiTech's were the same design (different material). I also ran the HiTech rockers and I had no clearance problems.

Hey Ron How is the new motor treating you? The 977s have a 1.46" O.D. whereas the 943s do have a larger 1.55" O.D. All the 977s I have used in projects have fit LT1 heads without machining the spring seats; however, the 943s require machining.

Ryan, check your pushrod length. I am certian you will need longer pushrods.
If you need to borrow my length checker, I can send it to you.

Jason

96speed

Thanks for the info, and compliment Wckd !

Like Jason pointed out, I don't have much option besides the rocker arm.

Jay: Thanks for the offer bro, but I actually have one . I'm waiting until everything is installed on the car before I start to think about the pushrods. Luckily, we have a local place I can pick those up the next day .

I'll look into the crowers and into the Hitech promags. I didn't know there was a difference either. In fact, I assumed most of these things were made by the same supplier.

I'll post an update to my findings .

Ryan

96speed

Need a little more input .

Crower makes some clearanced rocker arms. They have a couple options...

The standard studmount rocker is clearanced for 1.56". I don't know if the shape of the spring retainer from different manufacturers is fairly standard. IOW, does 1.56" of clearnace mean that any spring/retainer under 1.56" will fit?

They have another rocker that has longer arms with a total clearance of 1.65". They even have another rocker arm made for .100" longer valves (I forgot to mention I am in fact running +.100" valves) - the rocker is backed (by offseting the stud back in the trunion) .050" to accomodate the longer valve and correct geometry. Backing the rocker arm body away from the spring seems like it would also (as a side benefit for me) give a little more clearance to the standard 1.56".

It seems black and white that the +.100 rockers are exactly what I would need, but I don't want to just pull the trigger on a set of rockers only to find they don't fit and I'm stuck with a 15% returning fee .

After reading up, I'm about 80% sure those are the rockers I need, but would like some backup.

Ryan

Mindgame

The Crower enduro stainless rockers will clear 1.55 springs & I'm sure the Comp Hi-techs will too. Harland Sharp and Crane also have widebody aluminum rockers that will work. Just throwing a few options at you.

Just looking at the picture, you DO need a longer pushrod. That may very well take care of the interference.

Good luck Ryan.

-Mindgame

1racerdude

Get longer push rods and lash caps if need be. The caps come in different thicknesses from different manufacturers so check to see what will clear.

96speed

Mindgame: Does the rocker have to sit on the bottom of the stud? I assumed it does. However, if it can be "suspended" by the valve and pushrod, my problem is much simpler than I thought.

Come to think of it, if the rocker had to sit on the bottom of the stud, we'd never have to set lash - just bolt them tight and shut the hood. I feel kind of dumb now .

Thanks guys. I think I got it....

'Dude: The rocker tip is going to be at the top 1/4 of the valve tip at half valve lift. I will be close to going over the edge of the valve tip. Is this what a lash cap is for - making this work?

Ryan

Jason Short

Ryan, now you're getting it The rocker arm doesnt sit on the base of the stud.....the pushrod elevates it up on the stud. Just watch how the roller rides on the valve tip. When we talk on the phone next I will go over how to measure correctly for pushrod length. That rocker is going to sit about 1/2-3/4" higher on the stud than you have in that pic

All the clearance will come back! Pushrod length controls alot of geometry factors in your valvetrain.....that's why it is so vital to have the right length.

I got your voice message today....I'll call you tomorrow!
Jay

1racerdude

No
If ya have to go with a longer than normal PR then the caps will raise the stem end to keep the geometery correct.
I "know" ya havent checked it, but before ordering PR's ya need to check the geometery and see if the rockers hit.(no they don't sit all the way down on the stud) Make sure ya got enough stud sticking through or ya will break them with the poly locks.Ya can get long studs.

96speed

Jay: Cool man. Give me a ring before 2 or after 5:30ish CST. Gonna try out my new driver tomorrow .

'Dude: How many threads do you like to see? Here's a pic I mocked up:



You can't see the top of the stud - maybe 3-4 threads. (Yes, the rocker needs a new trunion clip) The pic shows the lowest I can get the rocker before it contacts the retainer. This is with me eyeballin' it. The tip of the rocker is sitting at the top 1/4 of the valve tip. Would slapping a lash cap on top make things ok? A lash cap would raise the stem, lifting the tip of the rocker, which would bring the rocker tip back to the middle, right?

Ryan

1racerdude

That doesn't look right.
What is your installed height? Are they stock studs?
Ya are probably going to have to get stud's because it looks like the PR end needs to go up,that would pull the tip back to the stud side. Then if ya need to raise the stem end and the PR end to clear the throat of the rocker the lash caps will go up .050-.075 depending on who makes them.The contact line for the tip should be as close to center as possible and the sweep line should be as narrow as possible.
Jason can get ya plumbed up on the geometry checking without me having to write two pages here or Google it and get a tutorial for the procedure.