I know this isn't a Corvette question, but there are some pretty smart folks on this forum, and I can't seem to figure this one out on my own.

I am contemplating buying a set of Edelbrock E-street aluminum heads, 5089, to install on my 'vette's 350. I will be keeping the stock "929" cam. Can I use my existing pushrods and rockerarms (or at least new stock replacements)? They are advertised as having pushrod guides, and requiring hardened pushrods, but can I just get rid of the guides? Also, there is some question about the length of the pushrods. Do I need .100" longer pushrods, or not? Why would I need longer pushrods anyway? The instruction manual mentions it, but is ambiguous about it, and none of the many advertisements even mention it, one way or the other.


Scott

 

If they have pushrod guide plates yes you should use them. As far as longer pushrods you need to measure with a pushrods length checker to get the right geometry. I would not put an engine togther without doing this. You cannot just use .100 longer rods or what they say. You need to measure and get what the engine needs. I have AFR heads and mine are .100 longer, that is what it needed.

 

I agree with Gordonm, always check your individual application.

But my Edelbrock RPM heads instructions said the same thing.....0.100 additional length pushrods.

When I read that, I was wondering why. The best guess I could think of is that the modern head gaskets are slightly thicker than the factory head gaskets. Either that or the valves are slightly longer than stock.

The weird part, when i replaced my big-block pushrods and rockers with Comp Cams high performance stuff(keeping the stock heads)....they measured 0.100 longer too! Maybe the factory got it wrong?

 

I'm sorry if this comes out sounding snippy, but I don't have any problem understanding the concept of "If an engine needs longer pushrods for some reason, then you need to get longer pushrods." What I'm really driving at is this: Does this head need longer pushrods, or not? And if so, then why? Is there something about these heads that changes the valvetrain geometry?

Also, this is basically going to be a stock engine with aluminum heads. My stock heads don't have pushrod guides, do they? Then why do these heads need pushrod guides (for my purposes)?

I guess what I'm really looking for is somebody who has run these heads and knows something about them. I want to run the stock valve train, is there a way to do it?


Scott

 

You can do what you want and think what you want. I will tell you what you have to do.

Guide plates and hardened pushrods are needed for those heads. You need to get a adjustable pushrod and put that in and watch the travel of the rocker arm tip over the end of the valve. Light valve checking springs are what you also need if it is a hydraulic cam.

The rocker tip should move an equal length on each side of the valve tip when you rotate the motor. No other magic way to do it, no one can tell you what length to use you need to figure that out for your particular application

 

Do what you want. Your stock engine went out the door as soon as you put aluminum heads on it. The rocker arm geometry may or may not been correct on the stock heads and it may or may not be on the Aluminum heads. I would want the correct geometry on mine so it lasts a long time and I don't have problems. If you want to risk it then by all means run the stock un hardened pushrods with no guide plates.

 

the aftermarket heads have a thicker deck surface and the. valve spring seats are raised for a better port contour thereby requiring a longer pushrod. use the correct length pushrod or have reduced performance and risk engine damage.

 

I am not sure, but I think I am detecting a little hostility here. Maybe it's because you think I am a sarcastic jerk. (rereading my last post, I guess I can understand why someone would get that mistaken impression) I assure you I am not being sarcastic, I would really like to know the answer to these questions I am asking. It's just that I am not asking how to determine proper pushrod length. I already know how to do that.

If I were to go to the junkyard, and take a cylinder head, in good condition, off of a, let's say, 1980 chevy 350 engine, I could take it and bolt it onto another 1980 chevy 350, install the rockers and pushrods, screw down the rocker stud bolt till the lash was right, bolt on the valve cover, and walk away, couldn't I? Well, why can't I do that with the e-streets? Not a rhetorical question here, I am curious as to what the particular thing is about these e-street heads is that changes the valvetrain geometry, neccessitating a longer pushrod. I have looked around on the internet, can't find an article or anything that really goes into it

One thing I have to disagree with you about, tho. I don't think guideplates are neccessary on these heads at all. CarCraft did an article comparing the e-street heads to the vortec heads, instead of getting hardened pushrods, they removed the guides, and ran the valvetrain from the vortec heads, which did not have hardened pushrods. They didn't mention what length the pushrods were, but I am sure that they were the length that they needed to be, tho. (OK, now, that last sentence WAS sarcastic, sorry.)


Scott

 

OK, makes sense to me. Thanks for the info. Also, thanks for actually reading my question and answering it, instead of trying to tell me how to measure pushrods.


Scott

 

hmmmm, that IS weird. It must have something to do with the rocker itself, if that's the only other thing that changed.


Scott

 

vortec heads use guided rockers if you have guided rockers you don't need guide plates.

 

Alright, so what would be the best way to go here, keeping in mind that I'm kind of a cheapskate. I guess I could go with hardened, +.100" pushrods, and use the crappy old rockers I prsently have. Or, I could get regular pushrods, +.100", remove the guides, and used a self-aligning rocker arm. Which would be cheaper? I like the idea of using new aftermarket rockers with a more accurate ratio, are there any cheap ones you guys can point me at?


Scott

 

try summit or jets both have some inexpensive roller rockers. the guided rockers are more expensive. keep your guide plates most all aftermarket pushrods are hardened anyway

 

Guideplates better imo.

 

I am installing an older set of Performer heads and having a lot of the same questions.

First, there is a difference in the casting between the stock and the Edelbrock heads. The stock heads have this little hole that each pushrod fits through. This hole can also limit the geometry. The Edelbrock head has a large hole that encompasses both pushrods and has plenty of clearance. Because of the size of this hole, I can see a greater need for guide plates.

I too bought the recommended .100 pushrods. However, the recommendation is for use with the stock stamped rockers. I decided to go with Harland Sharp rollers. I can see that with rollers it is critical to measure the geometry. The stock rockers do not have such a fine point of pressure like a roller.

I am disenchanted with Edelbrock "tech support" because when I called them regarding this matter they said I should go ahead and buy the .100 even with the rollers. "It couldn't hurt", he said.

Shipping costs hurt but I would buy and mount the heads and do a test fit with the stock pushrods and stock rockers. Then determine if you need longer or not before you buy your hardened pushrods. I am going to go with Comp Cam High Energy series .

Its hard to do all this in one easy purchase.

 

The right way is to check things and be sure all fits properly. In general when a company builds a head and they use parts and dimensions different than stock they do know about what needs to be different because they made the head to different standards and they tell you this,use .100 longer push-rods. In most cases these heads use .100 longer valves to accommodate higher valve lifts and stronger valve springs. Guide plates are the way to go and you do need a way to guide the movement of the push-rod and this is the best way to do it. The idea with the push-rods are to have the contact be in the middle of the valve stem at 50% of your valve lift, and to do this you adjust the push-rod length.

 

Yep the OE 80 stuff'll fit back together & run just fine ... and well, maybe you could get away with it on a new alum head, maybe not.

I suspect the root of the issue lay in the rocker arm itself.

Me thinks those who makel Alum heads are rather confident the installer will choose some sort of ROLLERIZED rocker ... rather than a very forgiving "SHOE" rocker [both C3 & later self-align OE are shoe rockers (with No roller tip)]. Pushrod length is nowhere near as critical with shoe rockers as it is with a roller riding across tip (& possibly riding onto a retainer from improper length PR). Me thinks the Al head maker thinks you will probably be using aftermarket rocker with a rollerized tip, so maker writes instructions accordingly. Additionally, Al head's rocker arm boss may/may not be higher than OE. sbc design is about 60 years old ... plenty smart/dumb/sophomore guys already worked this stuff out long ago.

again, measure what length YOUR combo requires.

 

hardhead here.
It just sunk in ... 929 cam with Edelbrock alum heads on a 350.

why? 929 is tiny ... that's stock OE L48 cam ... tiny.

 

No hostility at all, worded it so you would listen, apparently you didn't, you want some magic pushrod fairy to tell you what length to use instead of the proper procedure I outlined. The Harland Sharp rockers are nice I would just go without guide plates and ordinary pushrods .100" longer and it should work perfect

 

Maybe a little reading right from Comp Cams will take a little sting out of your attitude

http://www.compcams.com/Products/CC-...rods%27-0.aspx