OK hard core race engine builders, I have a question. I bought a slant six head with big valves. The valve stem length is also about .250 longer then stock. Put the head on a dummy block, with a .528 lift cam, and the rocker geometry sucks. The rocker shaft need to be raised, and moved toward the valves. I know a couple of ways to cure the problem, but would like to hear what others have done.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

I have not done this, but I did expect to run into this problem when time comes for me to put bigger valves in , so I have put some thought into the subject.


My plan is to cut the rocker shaft saddles off until they are flat. Then use aluminum blocks with saddles cut into them. This will allow differnt heights, plus some movemment side to side to help possition them over the valves right.

I dont know if you understand my meaning. But if you have seen Max Wedged rocker setups it will become clear.


I have not built a /6 sense back in early 1980. And I have been on hold waiting for a court seattelment to help with the money end of things. SO I have not yet put my mill to the head yet & done test to see what size this & that will be needed. With a quick look at some of my engines it became very clear that most people are probably running around with very bad rocker placement. This can cause way more problems than most people figure. And I am betting that many are even loosing power over it.

What really surprized me was checking a stock engine just how much differnce there was between each rocker on the ratio. I havnt pulled any rockers to see if this is possible, but I have even given thought to putting bushings in them & running a smaller shaft so that ratio can be changed. With them being a stamping I dont know if this is possible, but we do it to the Factory Big Block ajustable rockers (Isky type iron) to make up for wear & correct ratio's.

If your trying to get by with using the factory pushrods you can even mess with camshaft base circle diameter to help get you in reach.


If the Big Block & /6 rocker shaft is the same diameter, you might even be able to buy the block like I was refering to. The Billit aluminum Hold down they sale for the BB is much like I am talking. Just turn them upside down & you have a stand for the shaft that would set on a milled flat rocker pedestal. Look about half way down the page & there is a set of hold downs like I am speaking of. I dont know that this will work, but it will give you the idea & something to get you started with.

http://www.440source.com/rockerarms.htm


There may be a much easier way than this. BUt it is pretty much the same way places like Jessel use to install there $1000.00 rockers on differant head designs. Although instead of using little blocks they use a whole pieces of aluminum that bolts down to the milled flats. Then the top side of the plate is configured for each type rocker setup they use.

Right here is a thread where they are taking Indy EZ BB Mopar heads & cutting the rocker standes down to install Jessel rockers. You can go through it & see how I am talking about cutting the rocker stands flat.

http://board.moparts.org/ubbthreads/sho ... ost3204113



If one was to use upsidedown cup blocks like the billit hold downs I linked to, you may have to machine some kinda register on or for them some way to keep them from moving around. But with the shaft & maybe some shouldered bolts this may not be needed.


The height that will be needed will be different for bigger & smaller camshafts, or defferent base circle heights of the camshaft. This could require shimming of the blocks or making defferent height blocks altogether.

Even if the Billit hold downs will not work, they could be used with shims to figure what height the blocks should be.


Jess

A lil OT, but what is the stock slant rocker ratio anyway? Just curious.
-Jesse

Theoretical is 1.5, but in the real world varies greatly.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

If you are familiar with the old 413 big blocks they had bolt on rocker stands. I ran into this same problem on a 440 with shaft mount chevy roller rockers. I milled the cast rocker stands off the 440 heads and used the 413 bolt on stands, to get the shaft hight I needed. I was thinking of doing something similiar to the slant head, or maybe a set of W-2 stands. I need to check some specs.
Would be much easier to do this, if I had free access to a machine shop, like I did while working as a tool and die maker.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Hey Charlie,

This is the the method that sounds best to me - good rundown, Jess.

The Coxes did this on their motors, and made different height spacers/pads for different valve/cam setups. I like that Jesel setup too.

Lou

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Home of Slant6-powered fun machines since 1988

I do too. It's to bad they don't have a setup for the slant, at about $100

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Try a set of the 1.6 rollers if you have them. I know Mike has used them to correct misalignment before.

He and Blaine did the mill the stands off and make aluminum ones too.

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Official Cookie and Mater Tormentor.

Don't have those, and can't afford them. I got this head a couple of years ago, with some other parts. If it wasn't for this problem it would be a cheap/easy upgrade for the engine in my Valiant. I think I will hold off for now, and then do the "bolt on" rocker stand mod, in the future. I wanted more compression (stock head) and needed to get one head milled, any way. So thought "mill this head and get big valves to boot".

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225