Hi, folks,
I am not a total newb, I have assembled a couple engines, but I have never checked pushrod length. I would like to ask everybody on the forum who has done it, do you need to check all 16, and then, like, take the average, or what? Can I just use a pushrod checking tool on one rocker, and call that the pushrod length? And, can you do it with no head gasket, and then just figure the compressed gasket thickness into the length of the new pushrods? Thanks,


Scott

 

I just used an old stock p-rod and a Moroso checker tool (ProForm sells these also) - like $10. I tried using the adjustable p-rod but with the engine in the car is was a big waste of time. IMHO the adj p-rod is for the serious builder with the engine on a stand while the checker tool is fine for most of us. All u need is to get the rocker tip center so it doesn't side load the vlv stem. There's no measurement numbers for this.
The checker tool is snap - just measure with a feeler gauge on the side with space. If space is between p-rod and rocker arm then stock p-rod is too short by the feeler gauge distance. If the space is between the valve tip and the rocker arm - then the stock p-rod is too long and needs to be shorter by the feeler gauge distance.

Why do u want to measure this without a head gasket? It just makes it 10 times more complicated. Just wait until u get the heads on with gaskets and torqued, then measure for p-rod length. I would only be able to guess how to measure p-rod length using a checker tool but without the head gasket.

Just measure a couple of p-rods until u feel comfortable with some consistent numbers. U shouldn't have measure all of them.

Good luck,
cardo0

 

Ideally pushrod length should be such that the tip of the rocker passes across the center of the valve stem twice during its travel...when the valve is either fully open or fully closed the rocker tip should be toward the inside of the valve stem; when the valve is halfway open the rocker tip should be toward the outside of the valve stem. Set your checking pushrod to whatever length gives you this geometry, making sure that there is no retainer-to-rocker contact when closed. Obtain 16 pushrods of this exact length and you should be OK.

 

You should do it with a head gasket, but the rest depends.

If you had the block decked and the heads are new, you probably don't need to check more than a couple. However, if the valves are not in the same position from one valve to the next (due to each valve seat being ground by a machine shop), you may find differences and need to average them out.

Also, the checker tool is of no use if it doesn't match the rocker arms you are using. The rocker arm makes a big difference in geometry- brand-to-brand differences in design, ratio differences, even differences from the various styles from the same design (like Comp's pro magnum, aluminum, roller tip, or long slot ball/socket type).

If your build is very mild, it might not be necessary- but if you find out that you should be using something besides stock length, you'll be glad you checked.

 

I thought I would have to change all the springs over to checking springs, and then back to the regular valvesprings. It seemed like that would be a real PITA while torqued down on the engine, in the car. I'm brand new to the whole checking the pushrod length thing. The last engine I did was a MOPAR 440, they have shaft mounted rocker arms with an adjustment on the rocker arm itself, not like a SBC at all. It sounds like that checker tool will make my life a whole lot easier. It may not be quite as accurate as using an adjustable pushrod checker and checker springs, but I am using stock stamped rockers, and I am under the impression that the pushrod length isn't quite as critical as with roller tipped rockers. Still, I'd like to get it pretty close, and your description sounds like it will fit the bill. Thanks a bunch, man, all I've been able to find on the internet about this is stuff oriented toward roller tipped rockers. I have seen those checking tools that you describe, but had no idea how they were used, and really couldn't find anything about them, so thanks again for squaring me away.


Scott

 

True enough, stock rockers flex so much that perfectly spec'd pushrods are not so perfect under the full load of a real valvespring. You'll probably be fine, but it doesn't hurt to check.

I'm not even sure if the checking tool is intended to match stock rocker arms or some given brand/model roller tip or full roller arm.

 

Using stock stamped steel rocker arms, with brand new Edelbrock E-Street heads, do you think I'll be ok with Cardo0's technique?


Scott

 

What springs are you using, and how rowdy is your camshaft? Is it roller or flat tappet? Hydraulic or mechanical?

 

valvesprings are the ones that come with the heads, don't know the specs, only that they should be adequate for the cam I'll be running, Comp Cams XE256H, hydraulic flat-tappet.

http://www.summitracing.com/parts/CCA-12-256-4/


What started this whole thing off is that Edelbrock says you need to use .100" longer than stock pushrods with these heads, and I have gotten alot of advice from this forum saying that you should really check the length, and order new pushrods based on that. I am now thinking that using that blue plastic checker along with an adjustable pushrod could be a very easy way to measure for and order new pushrods. Any input from you guys is super welcome.


Scott

 

quick answer from the road...

Only one cylinder needs to be checked.

The plastic tools are inaccurate enough to be useless.

The cylinder needs to be set up completely...head gasket, torqued, rocker, etc.

 

I suggest that you check them then. Those springs might be far too stiff for a flat tappet cam, you should really do your homework there. Get the spring specs (should be with your heads, or call the Edelbrock tech line) and call Comp to see if they're compatible.

I have a pair of Edelbrock Performer RPM heads on the 409 SBC in my '76. When I installed the flat tappet cam in the engine three years ago, I had to get some "Z/28" springs (the ones originally designed for the high-revving 302 smallblock that was in the Can/AM 1969 Z28) for the Edelbrock heads. They worked perfectly and only cost around $25 a set, plus about $15 or so for new stock style retainers. They matched the springs specified for my cam, which I believe is the same set of springs your cam calls for. Get this much right, wiped out cam lobes are no fun.

I swapped in a roller cam this summer and the Edelbrock springs turned out to be a perfect match for the new cam, so back in they went- along with the Edelbrock retainers.

Anyway, with the right springs, stock rocker arms should be fine with your cam, but you should consider getting some longer slot arms since you're running a pretty good lift with that cam. You should like it, it's a good strong cam for a fun street car.

Oh, one more thing- when I measured mine, I needed 0.200" longer than stock pushrods with a similar cam and the Edelbrock Performer RPM heads- and they also suggest 0.100" longer than stock as a baseline. If you end up needing the same length, I'll make you a heck of a deal on the 0.200" longer pushrods as I took them out when I swapped to a roller cam and don't need them anymore. They're just sitting on a shelf now.

 

Bill!!! You caught me sneaking around behind your back!! LOL!!

Whew. If it's only one cylinder, I can deal with it. Quick question tho. I have been wondering how the fact that there is no oil pressure in the lifter is accounted for. Is this the whole reason for the super light checker springs?

Ya know, if I go thru all of this hassle to do it the right way, and it turns out that I need .100" longer than stock pushrods, I am going to be soooooooo pissed off!!!!! But at least I'll have the peace of mind, right? Thanks, all of you, I feel better about the situation now.


Scott

 

Yes, you've got it. No oil pressure is the reason you need the light springs.

Also, you can use compressed air (through the spark plug hole) to keep the valves closed while you swap springs. This way, you don't have to torque/untorque the head lots of times while you swap springs, measure, etc....

Are you planning on checking piston to valve clearance?

 

That is something to think about. And not that big of a deal to do before installation. Thanks, I'll look into it.


Scott

 

I'm going back and forth by PM with Billla, he's kinda holding my hand for this project, and he hasn't mentioned anything about it. Thinking about it, tho, I guess it wouldn't hurt to check it with some modeling clay on the piston, with the head snugged, no gasket, just for the peace of mind. Every time I try to suggest cutting corners, Billla smacks me on the wrist (figuratively) and tells me to do it right. I think I'll be ok if I just listen to him. See ya,


Scott

 

Two rules to live by:

1. If you can't afford to fix it, don't measure it.

2. Measure EVERYTHING.

In other words, you got into this because you wanted to get the most out of your money, your time, and your sweat. If you can't afford to do it a second time, check everything! Zen-like car crafting is about double checking everything and having no surprises when you take it out to fry the hides the first time. A guy I know here didn't do it, and he made it a few blocks before the valve heads came off of #7. The interference was very slight, but enough to destroy his engine. You should verify your valve timing while you're doing all this, just in case there was a mistake. Isky ground the wrong cam for my on a special order one time, and I caught it by accident when I was verifying that the timing set was installed on the right slot/dot. Simple human mistake, the used the wrong pattern when they ground the cam. They fixed it for free of course, I'm just glad it didn't get caught any other way-like a crappy running engine or catastrophic failure.

 

I grew up hearing my father and my grandfathers saying things like "Measure twice, cut once." "If the foundation is off by an inch, the roof will be off by a foot." "There are two ways of doing things: the easy way, and the right way.", so I really should know better than to cut corners. But on the other hand, I've never been one to just take things at face value, either. If there is a better, easier way to do things, I want to know about it. I think what it boils down to is just my lack of knowledge on the subject. One of the ways that I learn things, is to ask "Can I get away with this shortcut?", and if I am lucky enough to be dealing with someone who is knowledgeable, and has enough patience, I will get an answer, something like "No, and here is why not........." or "Well, yeah, if you're willing to take the chance.". Billla has been pretty patient with me in this regard, as well as you others, and I appreciate it, I am really learning alot.

I figured the pushrod length would need to be measured for all 16 valves, (after all, you don't just measure one main bearing clearance and assume the rest are within the same spec, do you?) and that seemed like alot of work, it is a relief to hear that only one cylinder must be measured.

I am beginning to think that since my project is going to involve new cam, lifters, pushrods, valves, springs, retainers, locks, heads, timing chain and sprockets, pretty much every single piece of the valvetrain except the rocker arms, I might as well just get new rocker arms, too. What the hell, right? Any recommendations for new stamped steel rockers, good quality to price ratio?


Scott

 

Do you have an opinion about the Comp cams K-kit?

http://www.summitracing.com/parts/CCA-K12-234-2/

It's not really much more than the cam and lifters kit, and it includes beehive springs, supposedly matched to the camshaft. The timing set isn't a double roller, but I think it still might be worth it. what do you think?


Scott

 

I'll defer to the experts on that question. I call the cam companies to get recommendations and then plug their suggestions into a desktop dyno program to see what the result looks like. Then, I call the same company again two or three times, on different days and different times of day to try to see how many answers I get and see how they compare, and try again using Comp Cam's free download software. I usually end up picking a little milder than average unless the DD simulations suggest there's a strong advantage and nothing significant lost by bumping up a bit.

With a flat tappet cam, I'd search all the car forums I could find for either a good used set of comp pro magnum full roller rocker arms, their roller tip rockers, or Crane gold roller rocker arms. Stay away from any other brand if you go roller tip, but many companies make good full roller rockers- find some you like and post up to see if anyone has had trouble with them. I'd avoid CAT and the Chinese ones on ePay.

If the timing set was a good name brand, it will be fine. Cloyes stock replacement timing chains will outlive most performance builds, to tell you the truth. Beehives are great so long as you get the right ones for your cam.

EDIT: The springs in that kit don't look like beehives, but that doesn't mean they won't be fine. It's not a radical cam.

 

The pushrods only come in 0.050" increments, and it's unlikely you'll be all that far off so long as you measure to confirm you'll be in the ballpark. You're running hydraulic lifters anyway, so there's some variation in effective length on each stroke of the lifter anyway. On a street engine, if you're off .050" it likely won't hurt much, but if you're off 1/4" your valve guides will take a beating. SBC guides aren't exactly known for longevity anyway. Measuring all of them isn't a bad idea, but you will end up buying pushrods of all the same length anyway.