[importsmasher]

I just changed the heads on my 67 full size wagon from the original #143 to a set of 1974 #46 heads. (see http://forums.maxperformanceinc.com/...d.php?t=633800). As part of the swap, I changed to the later style, longer pushrods. I got the car all back together and torqued the rocker nuts down, and i have slop in the valve train. I can move the pushrods up and down. The engine runs, but (obviously) has severe valvetrain clatter. I got these heads as part of a package deal, and they were freshly rebuilt. They are stock (not milled), the engine is stock, everything is stock. The only answer I can come up with for the pushrods seeming too short is that whoever built the heads put valves that were too short in them. I have a 73 service manual, and I can't find any information on installed height. Can anyone provide a measurement I can make with the heads on the car? I guess my only option (other than paying to have the heads re-re-built...) is aftermarket rocker studs and making the valvetrain adjustable....

Any suggestions?

Thanks,
Importsmasher

[Bill Boyle]

Valve length and installed height are two different things. You probably know that but your question was a bit confusing to me. Installed height pertains to length of spring when the retainer and keeper are installed. Too short of a valve reduces the installed height, however +.050 keepers are available.

A stock rebuild of those heads would probably specify an installed height for heads for a 67 400. Those numbers can be found in any Chiltons covering that period. If the heads were rebuilt to today's standards of performance, it is likely, that 1.600' was or should be the installed height using modern aftermarket dual springs. As for pushrods, you should be able to use stock type pushrods for a 400 for 1967. To eliminate the clatter, go with an adjustable valve train using BB studs and 7/16" poly lock nuts. Too many unknowns to not go this way.

[screamingchief]

Originally Posted by importsmasher

The only answer I can come up with for the pushrods seeming too short is that whoever built the heads put valves that were too short in them.

Well first thing first,shorter valves would require shorter pushrods,not vice-versa.

Taller valves would thus require longer pushrods as SOP.

If you used the 9.130" to 9.170" "stock" length pushrods with the #46 heads,then that should be the right length,of course assuming the stock length valves are still in those heads.

Now a valve job can sink the valves a little deeper,and thus make the valves appear just a bit longer,but typically that's supposed to be dealt with in the process of a proper valve job.

And typically a head surfacing "clean-up" cut helps cancel out that problem as well.

What rocker arms are you using on this?

Anyhow,OE IH for the '73-'74 #46 heads should be 1.586" int./1.590" exh. as I recall.

Not sure what your problem is,but IMO it's always a good idea to convert to an adjustable valvetrain whenever practical.



HTH

Bret P.

[johnta1]

Are you sure the pushrods are the longer /later ones?

The pushrod lengths:

The 2bbl pushrods you had: ~ 8.71875" (8 23/32")
The longer style you need: ~ 9.171875" (9 11/64")

[importsmasher]

Yeah, that's what I am going to do. I was asking for the installed height of the valve spring in order to determine if someone put in valves with too short of stems. The stock nuts are hitting the shoulder (when I torque them down) before taking up all of the slack in the valvetrain. I have the correct 9.1XX" pushrods, and the stock 1.5 ratio rockers. That's what confuses me, all the parts are correct; the only thing I can think of is that someone put in the wrong length valves.

I am going to order a set of ARP studs and install them. Thanks for the replies.

Importsmasher

[importsmasher]

screamingchief, I understand what you mean shorter valves would require shorter push rods. I guess I didn't explain it correctly. I think I do have shorter valves, becasue there isn't enough adjustment in the rocker arm to take up the slack, so it "seems" like the pushrod is too short, but in reality, I need to be able to adjust the rocker arm lower to take up the slack.

Thanks again,
Importsmasher

[screamingchief]

Originally Posted by importsmasher

screamingchief, I understand what you mean shorter valves would require shorter push rods. I guess I didn't explain it correctly. I think I do have shorter valves, becasue there isn't enough adjustment in the rocker arm to take up the slack, so it "seems" like the pushrod is too short, but in reality, I need to be able to adjust the rocker arm lower to take up the slack.

Thanks again,
Importsmasher

I get what your saying Is,but how your saying it is a bit confusing here.

Apparently me & Bill were more concerned about explaining the IH ~ valve length relationship.

See it's entirely possible to have a shorter valve length with the stock IH.

Vice-versa is true as well,you can have a longer valve with the stock IH.

Also you can have a stock length valve with a shorter/taller IH.

Or any combination therein.

Thus you cant rely 100% on the IH to determine the valve length.

IH is relative to the combination of parts being used in the valvetrain assembly.

Only way to be 100% certain of the valve length is to pull down a head and actually measure the valve(s).

Now anything that would move the rocker arms fulcrum height could affect this as well.

Are we 100% sure those #46 heads are indeed from '74?

I ask as there is an earlier pressed stud #46 head casting ('69 290 hp 400 cid).

Anything under the rocker studs other than the guideplates??

Not using thicker than stock head gaskets???

Odds are the adjustable valvetrain will fix the problem,but it never hurts to figure out why that is so.

Bret P.

[importsmasher]

Yeah, sorry I am not explaining it very well, but it seems you have the idea.

I hadn't thought of the fact that you can have different valve length/installed height combinations. I was just trying to figure out a way to determine if my valve stem tips were lower than they were supposed to be, and spring height seemed like a good idea.

Yes, these are definitely 1974 #46 heads. The casting date is J223. They came with my 74 GTO, but I have no need of them for that car. They have screw in studs, not press in. There is nothing but the guide plates under the studs. I used standard Fel-Pro head gaskets. I can't think of anything other than the length of the valve stems that would cause this issue. I really don't want to remove a head and measure a valve (and even if I did, and found that they were too short, I can't afford to have the heads re-done with the proper valves), so I plan to go adjustable valvetrain...I just ordered my ARP studs.

Thanks again for the help!
Importsmasher

[screamingchief]

Originally Posted by importsmasher

I hadn't thought of the fact that you can have different valve length/installed height combinations. I was just trying to figure out a way to determine if my valve stem tips were lower than they were supposed to be, and spring height seemed like a good idea.

Well,on some engines it's extremely common to reference that measurement (btw that's known as the valve stem tip height),but it's not a commonly referenced specification on the pontiac heads at all.

Valve tip height is far more important a concern on engines with shaft rockers and such (buicks,FE fords,mopars,et-al),as on those engines as often it's not all that easy to accomodate any significant changes in the valve tip height/rocker geometry/pushrod length relationship.

And it also often assumes nothing else has been changed either,as you would be measuring the tip height from a "known" location like the spring pad or such.

Anyhow,I know the Crane HD stamped pontiac 1.5 rockers came with some thick 7/16" ID parallel ground/hardened flat washers that could be used for a deal like this,they included them so one could "adjust" the stock rockers with the bottleneck studs,they included some HD locknuts as well,but that deal never really seemed all that good a choice to me.

I always just converted to the 7/16" BBC studs and locknuts or poly-locks.

I cant even remember the last time I tried to use the OE rockers,studs,& nuts.

Bret P.

[importsmasher]

Well in case anyone is interested, I got the ARP studs and 7/16 lock nuts on the car, and all is well. The valvetrain noise is gone, and the car is running really well.
Thanks for the input!
Importsmasher

[johnta1]

Cool!

[screamingchief]

Yeah,glad it worked out for you.

Kinda felt it would do the trick,always has for me.



Bret P.