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Discussion Starter #1
So received my rockers yesterday and can't get "acceptable" results.

I'm using the 90 degree method and the roller tip is way on the edge of the valve.

When I use the current setup I can center the pattern but its VERY wide from what I've read.

The rocker angle at closed is at a sharp angle, this would make the components work really hard..

Not sure what to do at this point. This is just a street thumper weekend cruiser.

Ideas?

383 sbc, xr288 cam, comp 1.6 full rollers, valves are 0.100 extra (install height is 10 thpu shy of 1.8 spec for comp beehives)..

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7.250 pushrod wear pattern:

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Discussion Starter #2
Wondering all things considered if 1.5s might buy me some real estate on the valve tip for better geometry.

If I shorten the valves and pushrods to widen the gap between the valve and rocker stud (the valve and rocker stud are like a triangle, lowering the 2 sides widens the gap) the spring install height suffers.. unless I consider different spec beehives with a reduced install height?
 

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Wondering all things considered if 1.5s might buy me some real estate on the valve tip for better geometry.

If I shorten the valves and pushrods to widen the gap between the valve and rocker stud (the valve and rocker stud are like a triangle, lowering the 2 sides widens the gap) the spring install height suffers.. unless I consider different spec beehives with a reduced install height?
Nope, the 1.5 won't be any different, it has the same length from center pivot to roller tip....the difference in ratio comes from moving the pushrod cup closer or farther away frm the center pivot.

That current pattern will eat the guides right out of it.

a lash cap might get you enough surface to not get too close to the edge, but that would require a new retainers in 10°, the 10° locks with lash cap recess, and the lash caps......and still might not work out.

What you really need is a different rocker, one with a shorter pivot length. Straub has Harland Sharp make them for his sales, Crower also makes a backset rocker that would do a similar job.
 

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This kinda crap happens all the time.
The angle of the studs and the angle of the valves make the tops of the studs and the top of the valve closer together the longer they get.
Like said above, the fix is a back set rocker or really long studs and really long pushrods so the centerline of the rocker trunnion and roller tip are running down hill toward the valve. That's a crappy way of doing because that causes other problems too. Or shorten the pushrod and do the best you can and live with it. .040-.060 wide pattern on the valve is a good place to be but sometime you have to compromise and deal with it at .100 wide and less guide life.
 

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I’d take a look at both the height of the stud and pushrod length.

Lots in play here as studs come in variable lengths both in the bottom thread to the head boss and in the upper rocker end. To this end the use or not of sheet metal guides which result if used in the stud sitting higher above the boss than when sheet metal guides are not used.

The .1 longer pushrod is just a starting point for aftermarket aluminum heads. Factory GM heads use standard length pushrods as they don’t thicken the casting wall cross sections for added strength as the outside suppliers of aluminum heads do. Plus some totally race made heads add .2 inch to this dimension, so there is a lot to keep track off.

Changing rocker ratio will not have much effect as the ratio difference is all on the push rod side of the rocker.

Bogir
 

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Those appear to be the Comp Aluminum rockers that are their budget rocker. Not to be a downer - I bought a set of them and at 15K miles the bearings were toast. I was perturbed to find out that they weren't rebuildable. I abought a set of Scorpions and have never looked back.

I'd follow Eric and John's advise - grab a set of rockers to resolve the issue - they'll be more money, but well worth it in the end.
 

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That current pattern will eat the guides right out of it.

What you really need is a different rocker, one with a shorter pivot length. Straub has Harland Sharp make them for his sales, Crower also makes a backset rocker that would do a similar job.
The Straub rockers are not that much coin. It took them while to get me mine, and I ended up using what I had on hand. So I have a brand new set, still in the plastic if you want.
As far as saving money goes, I have learned the true meaning of "It costs more to go slow"
Buy once, and don't look back. Or buy twice, and pay the price!
 

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Discussion Starter #8
Well how would I spec rockers with so many variables? Is there a trunion to roller center spec one can look for?

I enjoy building engines so don't mind having some parts down the road but at some point its gotta stop.

I'm gonna get a long 7/16 unc rod and use a reg nut to see what kind of results I'd get with a silly tall stud.. but just seems wrong. How does one navigate this bag of unknowns?
 

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Discussion Starter #9
Tx, pm me how much and the specs.. I have 3/8 and 7/16 studs currently.. guess I'd prefer 7/16 :)

The Straub rockers are not that much coin. It took them while to get me mine, and I ended up using what I had on hand. So I have a brand new set, still in the plastic if you want.
 

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What I do, is measure with calipers looking for “B” in the drawing.
Start with the valve at half lift. Measure outside of the valve tip to outside of the stud 90’ to the valve stem. Write that down.
Subtract 1/2 the valve tip diameter, then subtract half the stud diameter and you have your center of trunnion to center of the rocker roller tip measurement to aim for. Then go shopping for as close as you can get to that.
When the parts arrive, do the usual half lift method for push rod length and order that length in your favorite brand.don’t forget to factor in the pushrod base radius.
I use Engine Pro and Trend a lot.
 

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Discussion Starter #11
Thanks, is there a term for that spec? Can't recall seeing it before but now that I've run into this it should be right up there with the ratio!

Since I have the current rocker on i could measure it and subtract what I need to move it in, since its at the exact tip at half lift, I could subtract half the valve diameter (11/64?) and shop off that.. then I can fine tune it with pushrod length...

What I do, is measure with calipers looking for “B” in the drawing.
Start with the valve at half lift. Measure outside of the valve tip to outside of the stud 90’ to the valve stem. Write that down.
Subtract 1/2 the valve tip diameter, then subtract half the stud diameter and you have your center of trunnion to center of the rocker roller tip measurement to aim for. Then go shopping for as close as you can get to that.
 

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614049

Thanks, is there a term for that spec? Can't recall seeing it before but now that I've run into this it should be right up there with the ratio!

Since I have the current rocker on i could measure it and subtract what I need to move it in, since its at the exact tip at half lift, I could subtract half the valve diameter (11/64?) and shop off that.. then I can fine tune it with pushrod length...
I call it back set. I don’t know if that’s proper but no one has said otherwise so I guess it’s correct enough to figure out anyway.
according to you picture, I’d guess your still .020-030 to far to the exhaust.
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Distance "B" in the above drawing is referred to as "pivot length".
I'm thinking 1.450"/1.460" is the common SBC dimension, looks like you need at least .050" less than that.
 

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Eric,
The small block fords are close at I think 1.510? Is that right? Which means many are too long to start with when cheap rockers are made to fit both SBC/SBF.
 

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Discussion Starter #15
Man fantastic info fellas, thanks so much, learned a lot today .. I'll keep u posted.. def going to need longer studs and pushrods too by the looks of things.
 

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Discussion Starter #16
Tx again Eric, Found a catalog with jesel rocker specs listing pivot length. Any clue what else might work off the shelf?

These are 200cc Asian castings, copy of something im sure.

I'll measure the length today and get back, thanks.

Distance "B" in the above drawing is referred to as "pivot length".
I'm thinking 1.450"/1.460" is the common SBC dimension, looks like tou need at least .050" less than that.
 

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Tx again Eric, Found a catalog with jesel rocker specs listing pivot length. Any clue what else might work off the shelf?

These are 200cc Asian castings, copy of something im sure.

I'll measure the length today and get back, thanks.
STR 11600 is the PN from Chris Straub. I gave $339 for them. They are made by Harland Sharp special for these heads.
It took awhile to get them, so I just used what I had, and it worked. I still have the set, but am going to use them on my next build, but it wont be for awhile...
Call Chris and see if they are available now, if not let me know maybe we can work something out if thats the way you want to go. I also have a set of Crower 1.5s 7/16 stud that are used, and I will let them go for cheep. PN 73601-16 These may, or may not be the ones E was talking about...
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