nascar fan

I recently purchased the new cast iron Bowtie cylinder heads for my '94 5.7L 350 engine. I also purchased the Bowtie vortec intake, shorty headers, HEI dist., 1.52 roller rockers, Howard Cams PN# CL112031 .475/.475 lift flat tappet cam with Delphi lifters etc. etc.

The pushrods I purchased were standard (7.9) +.100. I was assuming that the vortec heads were similar in height to my stock heads.

When I went to adjust the valves, the adjusting nuts bottomed out on the rocker studs, indicating that my pushrods are too short. I'd like to avoid the task of locating/and/or purchasing a pushrod length finder, and the delay involved with measuring and reordering pushrods.

I am hoping one of you is an experienced engine builder, and can just tell me what size pushrod to use. I think it will be in the range of 8.4 to 8.5 inches. (Height of stock head + difference in vortec design)

I have read the process of marking the valve stem with a marker and turning the engine over to center the roller on the valve stem. I tried it, but the directions for installing and adjusting the valves said to soak the roller rockers in motor oil for at least 30 minutes. They were so oily that I couldn't get that process to work. A visual inspection of the roller to valve contact looks fine.

I'm finding out there is no substitute for experience. Can anybody help me???

sofakingdom

iTrader: (1)

There is no difference, that I know of, in the push rod length used with Vortec heads; the 062 & 906 at least. They're the same as any others.

Start by determining if you have a push rod length problem, or a stud height problem.

EVERYBODY that ever asks this question starts out with attempting to rebel against the known fact, that THE ONLY WAY to know what the right push rods for YOUR combo is, is to MEASURE IT. There is absolutely no way to guarantee that anything anyone else has ever found, will apply to your build. That's fantasy land. Put it out of your head and move on.

The expense of a push rod length checker is negligible. In fact you can make one by simply cutting a push rod in half and welding a piece of ¼"-20 allthread to one half and a ¼" nut to the other. But as cheeeeep as they are, it's not hardly worth the effort.

Same for re-ordering push rods; you'll have to wait for that regardless of how you find out what length to get.

http://www.summitracing.com/search/D...?Ns=Rank%7cAsc

You DO NOT want the little plastic thing type, you want one that looks like a push rod.

Order a couple of solid lifters at the same time as you order the checker.

This IS NOT how it's done!!!

Find the length that gives you the NARROWEST POSSIBLE witness mark on the valve stem, REGARDLESS OF where on the stem it lands. Remember, IT DOES NOT MATTER if it's near the exh side, near the int side, or what; you're looking for THE NARROWEST POSSIBLE mark. The right length will be the next incremental length shorter than that; they come in .050" increments.

If your rocker nuts still bottom, you need either longer valves, different studs, or machine work (cut the bosses down some more). That IS NOT a reliable indicator of ANYTHING WHATSOEVER to do with push rod length.

Sonix

iTrader: (1)

Sofa pretty well nailed it.

The adjustable pushrod checkers basically come in two sizes (for an SBC). I believe they are considered the "flat tappet" size and the "roller" size. I own the flat tappet size.
Just an FYI - I ended up something like .130" longer or something along those lines. Custom made pushrods come in .050" increments, and are high quality and expensive (custom made...). HOWEVER, I found that some *Ford* standard length pushrods were within .010" or something of what I required. Just an FYI - You may not require custom made ones, if you open your mind to using other styles. As long as the diameter & length are right, you're fine.

nascar fan

I am still waiting for an experienced engine builder. These vortec heads are not stock items. They are the latest version of bowtie high performance heads. They flow as well as the aluminum fast burn heads, but cost much less because they are made of cast iron. The part number is 25534421. Check them out.

I am thinking that if an engine builder ran into this situation, he would remember the size of the pushrods he installed. There is nothing wrong with the rocker studs or valves. These heads are brand new.

I ordered a pushrod length finder from Summit. But I doubt that I will ever need it again. I'm in my late 60's.

Thanks for your replys.

sofakingdom

iTrader: (1)

So help us understand what you're REALLY trying to say here.

Here I am, trying to help you by telling you the truth, and I don't particularly find the implication of this comment to be showing very much gratitude. I'll be happy to let you continue to flounder, like you already are, if you'd prefer.

I am thining that if an "experienced engine builders" ran into this situation, he would do EXACTLY as I just described, which is EXACTLY what I ddi the last however many times I've needed to set up a valve train. Doesn't matter whether the parts are new or not. It's pretty common, really; these things aren't just, pull em out of the box, bolt em up, and drive off. Those of us who ARE "experienced engine builders" know that you CANNOT predict what the optimum push rod length for ANY engine is, until the engine is built, and that the farther it is from "stock", the more likely it is to need some specialized attention. Those of you who ARE NOT "experienced engine builders" might like to "think" that it can be done that way, but you would be wrong.

Measure what you need and get the right thing. And of course as said above, by the voice of experience, if you can't get optimum push rod geometry with the components you have now, be prepared to do some troubleshooting and re-work. As of now, you have ABSOLUTELY NO WAY WHATSOEVER to be sure that there's "nothing wrong with the rocker studs or valves", as far as their geometry; all you can "know", is that they're still under warranty. You don't really even have any way of knowing whether they're broken or not.

Apeiron

Quite possibly, but he'd know he should measure because of manufacturing tolerances.

nascar fan

You just made my point. An experienced engine builder would measure the correct pushrod length. I'm not talking .050 or .100. I'm thinking my pushrods are at least 1/2 inch too short. I just want to hear from somebody that has installed a set of these same heads. I could get a ballpark figure from him and go from there. Do you really think GM Performance Parts would sell a new set of heads with the wrong rocker studs, or valves that are too short?

...sorry if I ruffled your feathers.

Anybody else want a piece of me??

sofakingdom

iTrader: (1)

Gee, you really ARE inexperienced, aren't you?

None of these items is "stock".

None of them is a GM product.

They affect your push rod geometry however; and even more critically, they just might affect how far down onto the studs the rockers can go before they bottom out. Which means, the studs on those heads might be "right" for stock rubber rockers, but TOTALLY WRONG for whatever rockers you have. GM had no idea about your rockers when they built those heads.

Whether your valves are the "right" length or not, or whether your studs or machine work are "right" or not, is not a function of GM's setup of the heads; it's A FUNCTION OF YOUR COMBO.

Unless you can find somebody that used those heads, those lifters (or, whoever is making them for Delphi, since AFAIK there are only a tiny handful of on-shore mfrs of flat lifters any more, and Delphi Electronics isn't one of em, since they are long since vanished from production vehicles and are only sold in a tiny fraction of their historical volume), the same head gaskets you're using, whose block happened to have the same tolerance stack-up in its cam tunnel location and in its machine work (deck height), you're going to have a tough time coming up wiht that.

That's why "experienced engine builders" MEASURE valve train geometry, in EVERY engine above phone company van replacement grade that we build. NO TWO ARE ALIKE.

It's really not that hard, or expensive, and you'll have the satisfaction of knowing that it's PERFECT when you get done. The adjustable PR and the pair of lifters you ordered shouldn't have been more than $25 shipped, not worth even bothering with the possibility of somebody else's results not matching what you need. Peanuts.

I've never installed a set of those particular heads; to this point, they haven't seemed like an economically attractive alternative toward accomplishing anything that I've done lately.

nascar fan

Sofa king, You really are a "dick". I'm out of here. I'll get my advice on one of the trucking sites. You people are snobs.

sofakingdom

iTrader: (1)

Sounds good to me... sorry you aren't interested in hearing the TRUTH, but instead, just want somebody to reinforce your misconceptions. People often seem to think that those who tell THE TRUTH are being "unkind" to them or something... I'm kind of used to it actually, I have a wife and adult children, so it happens all the time.

I'm sure truckers will be a great deal more help to you in getting this taken care of for you.

nascar fan

Sofa, I'm back and ready to eat crow. I was not aware that my roller rockers have Adjuster Nuts with Polylocks. Is it possible that the polylocks were bottoming out on the top of the rocker stud? I am away from home and unable to physically check it out. At the time I was installing the rockers, I had them soaking in motor oil, and I was in a poorly lit garage. (If the polylock backs out of the adjusting nut, that would explain why I couldn't adjust the rocker arm further down onto the stud.)

I'm not a mechanic, and now I feel like an idiot. ...sorry about the attitude.

I'll post the results next week sometime.

naval_ned

Comp Cams has some decent videos on valve train geometry and what not that may help you out. Here are some links.

http://www.compcams.com/Pages/417/va...-geometry.aspx
http://www.youtube.com/compcams
http://www.cpgnation.com/forum/comp-...duct-tech.html

sofakingdom

iTrader: (1)

Hey that's OK, if you're willing to man up to a mistake I'm willing to help.

Start with an adjustable push rod. Remove the valve springs from both valves on one cyl and put in some real light "check" springs, light enough that the lifters will stay fully extended and not compress at all. Find the length the adj PR that gives the narrowest possible "sweep" pattern across the valve tips, using gear marking compound or white lithium grease or even a Sharpie to create a witness mark. Don't worry about "centered"; look for the narrowest possible. IMO Comp's instructions are WRONG, but I don't know anybody that works there any more like I used to (and did myself, engr work on a contract basis) so I probably can't get it changed.

That by itself might cure the otehr issues. Come back and report the results and we'll go from there.

InfernalVortex

iTrader: (4)

There are a LOT of VERY experienced engine builders roaming around here. You can snort and puff at them all you want, but it doesnt make what they're saying any less accurate.

If you just want to take stabs in the dark go buy a random length set of pushrods and maybe you'll get lucky. But good pushrods aint cheap and no one around here is going to tell you to go buy X pushrods because they "might" fit.

And just check your poly locks when you get back to it. If you didnt loosen them up and back them out, it's very possible that you're bottoming out against them.

grumpyvette

read thru these

http://forum.grumpysperformance.com/...php?f=52&t=697

http://forum.grumpysperformance.com/...php?f=52&t=181

Curious_George

When I built my 355 engine combo, I had to get slightly shorter pushrods. .050 or .100 can make all the difference when it comes to valve train geometry if you want it right / correct.

CG