I bought a set of used Comp Cam 1.6 roller-tip rockers which came with pushrods from a PFF member in the Mall a couple months ago. I assumed it was This kit that I was buying. Yeah yeah, that was my first mistake. Assume nothing.
I've finally gotten around to wanting to install them.. so when I opened the package today, it took me about five seconds to notice that several of the pushrods were bent. Thanks guy.
Upon closer examination, it appears that these are also not the proper Comp Cam pushrods (6.165" in length) to use with these 1.6 rockers, but are instead probably original stock pushrods with a length of around 6.135". It's not a huge difference in length, about .030" or so. However, this will make a difference with valve-train geometry... but how much I don't know.
Obviously I'm not going to use these bent pushrods, but for anyone who has experience using 1.6 roller-tip rockers in a 2.8 (with stock cam), will it be noticeable and/or damaging to the valve guides or whatever to use stock pushrods if they're perhaps .030" too short than they possibly should be?
Is there an "ideal" pushrod length for use with 1.6 rockers in a 2.8, or is it not all that critical with an otherwise stock engine?
[This message has been edited by Patrick (edited 05-09-2015).]
I'm using 1.6 roller tips with stock cam in a 2.8. I used my stock push rods and that was several years ago with no problems. I also used the lock nuts with the allen set screws so they can be adjustable. I like to run them a little lose but not to the point of tapping. I wouldn't worry about .030 short or long since this can be made up for with the adjustable lock nuts if thats what your using.
Spoon
------------------ "Kilgore Trout once wrote a short story which was a dialogue between two pieces of yeast. They were discussing the possible purposes of life as they ate sugar and suffocated in their own excrement. Because of their limited intelligence, they never came close to guessing that they were making champagne." - Kurt Vonnegut
You said it yourself, "assume nothing". A pushrod length checker is an invaluable tool and there really is no excuse to skipping this part. You could ballpark it with your eyes, I'm sure. But valve train geometry is important here because the incorrect length will result in damaged valve stems. The roller tip must be centered over the tip of the valve stem otherwise it will likely distort the edge of that stem tip and furthermore prevent the valve train from seeing adequate oil to reduce wear, as well as diminish the valve's ability to spin. So, not checking means pulling the heads and getting a valve job down the road, at the minimum. All because you wanted more out of your engine. I only used my PR length checker once, but I'm quite glad I spent that extra $20. Again, assume nothing. If your motor saw any kind of machine work done to the heads or block in the last 30 years, odds are, it needs different pushrods. Better safe than sorry, anyway.
I also used the lock nuts with the allen set screws so they can be adjustable.
Ummm... I don't quite follow you. The factory rocker arm nuts are adjustable, right?
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Originally posted by Spoon:
I wouldn't worry about .030 short or long since this can be made up for with the adjustable lock nuts if thats what your using.
I don't believe that's quite correct. Adjusting the rocker nuts more so affects the hydraulic lifter preload. The length of the pushrods contributes to the overall valve train geometry, such as where on the end of the valve stem the rocker arm makes contact. The goal is have the tip of the rocker arm spend most of it's time in the center of the end of the valve stem. If the rocker is pushing down while off to one side or the other, it contributes to valve guide wear (among other things)... so I've been led to understand from watching a few YouTube videos.
[This message has been edited by Patrick (edited 05-09-2015).]
You said it yourself, "assume nothing". A pushrod length checker is an invaluable tool...
Viperine, you posted while I was typing out my last response. You've brought up some good points.
I was hoping for a shortcut (in regards to knowing the "ideal" pushrod length for this application), but yes, every engine will no doubt be a little bit different.
[This message has been edited by Patrick (edited 05-09-2015).]
Use stock to effect the 1.6 ratio. Use longer to effect more duration and so on. I'm running regular pushrods with 1.6 that I ordered, but not before they shipped longer "standard" gm rods. I called and challenged them on this, and they shipped the stock length, so they may have shipped the incorrect rods to the p.o.
I only used my PR length checker once, but I'm quite glad I spent that extra $20.
$20 for the tool seems reasonable enough, but unless I'm looking in the wrong area of the Comp Cam website, it appears that ordering a "custom" length set of pushrods is about $150 or so. Is that right, or is there a more economical alternative?
I gotta be honest... the minimal return (in power) from investing $150 just for pushrods in this 2.8 wouldn't be worth it.
[This message has been edited by Patrick (edited 05-09-2015).]
The tool itself is $20. Pushrods are another matter. You'll need to find out what length you need before you start pricing the actual pushrod set. I needed 16 custom length pushrods for my small block 406 with a moderate lift cam and comp cam's magnum rockers (which are 1.53 ratio. GM claims stock is 1.5, however, actual value is something like 1.45). Anyway, I was able to find hardened pushrods with multiple feature improvements over stock, for less than $100. But my initial search, before I knew the true length I needed, made it look like I was going to spend much more. Once you get it, use summit's website to show you all of your options for the specific length and I bet you'd be surprised. I can't imagine my set of 16 quality pieces would cost less than a stock replacement material/style pushrod set of 12 for a v6.
P.S. the term "custom" may be a little misleading. It really just means "not stock length", because the typical set is purchased at all 1 length. The only issue you may have, is that length is checked with the tool AND a solid type lifter. I took an old lifter, took it apart, and removed the spring. I then added washers to simulate lifter pre-load and reassembled the lifter without the spring. This gives you a very accurate reading. But requires the intake be removed so you can access the lifter. Wow. I feel bad now. Valve train geometry requires more than removing valve covers. Might want to consider that. Hope this has been helpful.
You'll need to find out what length you need before you start pricing the actual pushrod set... I can't imagine my set of 16 quality pieces would cost less than a stock replacement material/style pushrod set of 12 for a v6.
The only "stock replacement material/style" set of pushrods at Comp Cam for the 2.8 appear to be These for $26 plus shipping. Price is right but the selection of lengths is limited... to one
The next step up is These for $113 plus shipping. There are more sizes available, but nothing any shorter than 6.2" from what I can see.
The sets of pushrods that were about $150 (for 16) at the Comp Cam website were These.
I'm beginning to understand why people modding the 2.8 just say the heck with it and use the stock pushrods with the 1.6 rockers. I agree that perfect length pushrods would benefit the valve train geometry, but for the minimal gain in ponies to be had with the 2.8, it just isn't worth the expense IMO.
[This message has been edited by Patrick (edited 05-09-2015).]
Rocker arms increase or decrease ratios by changing where they pivot. A higher ratio rocker, like your new set, pivots closer to the pushrod side. A lower ratio pivot is closer to the valve side. I think. Trying to visualize it. Brain is on overload. Haha. The length of the pushrod is variable just because centering the roller to the valve stem is dictated by the length. You could actually increase valve lift by using all of your stock valve train components and simply over tighten each rocker nut past zero lash + lifter preload. But you put serious pressure on the cam and risk damage, should any single component fail. I've had a faulty lifter snap a stock rocker clean in half, and subsequently bend and snap a pushrod before I realized it was a lifter problem. Personally, I was dissuaded from using rocker arms as the sole attempt to increase performance after reading an article on how they usually cancel themselves out by changing more camshaft specifications than just the lift. You wind up changing every aspect, including duration, and some of the changes will not allow the new ratio to do what you would expect it to. I forget the specifics, but the article was backed by several dynoes with many different ratios on a single engine. This was the whole reason I selected the 1.53 magnum ratio for myself. The 1.6 wouldn't have any gain to justify the cost. I tend to rant a lot, and I apologize, but I do like being thorough. And obviously, they still make these fancy rockers, so there must be a reason, that I at least hope exceeds "demand".
I don't believe that's quite correct. Adjusting the rocker nuts more so affects the hydraulic lifter preload. The length of the pushrods contributes to the overall valve train geometry, such as where on the end of the valve stem the rocker arm makes contact. The goal is have the tip of the rocker arm spend most of it's time in the center of the end of the valve stem. If the rocker is pushing down while off to one side or the other, it contributes to valve guide wear (among other things)... so I've been led to understand from watching a few YouTube videos. ;)
Perhaps this link will help you out. Also notice the factory locknuts vs aftermarket. I did not read anything about changing pushrod length in this article. http://www.hotrod.com/how-t...r-rocker-ratio-test/
They didn't bother covering that important aspect of valve train geometry, but it was interesting to see the figures nevertheless. Going to 1.6 rockers from 1.5 increased HP by 1.5 % at 3000 RPM. Using that same percentage increase with the 140 HP 2.8 in our Fieros, we'd only expect to gain about 2 HP at 3000 RPM. I didn't use the HP figures shown for 6000 RPM because a stock 2.8 just isn't going to be breathing efficiently at that high of an RPM. (I also didn't use the "average" readings for 4500 RPM as they would've been thrown off by the readings for 6000 RPM.)
It's because of this rather low potential increase in pony power that I'm not all that keen to be spending much for "perfect" length pushrods. Would I like the valve train to be perfectly aligned? Absolutely, but with such a minimal increase in performance, it needs to be done with minimal expense... or not at all IMO.
Here's a couple of videos that explain about checking pushrod lengths. The first video is very short...
This video gets into it a bit more...
And this fella really goes into detail...
[This message has been edited by Patrick (edited 03-22-2021).]
If you are using a stock cam I would be very surprised if a different length push rod is needed. When using an aftermarket performance cam the base circle is often smaller than the OEM cam. To keep the rocker centered on the valve stem a longer pushrod is required. The 1.6 rockers move the pushrod end further away from the pivot but do not change the relationship of the valve stem/rocker tip. The valve opens a little further but this will still hit the same spot on the valve stem head. Stock will be just fine - really.
When I installed my Comp Cams roller tip rockers, I just used my stock pushrods.
I'm beginning to suspect that's what most people do when using these 1.6 rockers with 2.8/3.4 engines.
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Originally posted by woodyhere:
Stock will be just fine - really.
Oh probably... however, if there were reasonably priced pushrods available for the 2.8 in a variety of different lengths I'd still go through the extra trouble. But as I'm discovering, there isn't... so I won't.
[This message has been edited by Patrick (edited 05-10-2015).]
Oh probably... however, if there were reasonably priced pushrods available for the 2.8 in a variety of different lengths I'd still go through the extra trouble. But as I'm discovering, there isn't... so I won't.
I don't know what you consider reasonably priced, but most pushrod manufacturers offer custom length pushrod options. Comp only has the one length for the V6 kit, because they're made for their rocker kit. It's probably the right length you need for your engine, unless you've milled the heads or deck, or done something similar to alter the stock dimensions of the engine itself. If you don't want to bother with buying a length checker, verifying the length for each rocker/valve in the head, and then ordering custom length pushrods specific to your engine, I'd just suggest buying the $30 Comp set and call it done.
Comp only has the one length for the V6 kit, because they're made for their rocker kit.
If you don't want to bother with buying a length checker, verifying the length for each rocker/valve in the head, and then ordering custom length pushrods specific to your engine, I'd just suggest buying the $30 Comp set and call it done.
Interesting that the 6.165" pushrods that Comp Cam lists for use with their 1.6 rockers are basically the same length as the "stock" 2.8 pushrods offered by some vendors. The reason I say "some" is because when I checked RockAuto's catalog, the lengths mentioned in the blurbs for each brand of pushrod vary from 6.043" to 6.163" to 6.390". 6.163 seems to be the most common length offered.
Hmmm... maybe what I'll do is just swap the injectors for now until I decide ultimately what to do with the 1.6 rockers and/or pushrods. Just doing the injectors for now will at least allow me to see if this alone makes a difference with how the engine performs and with the crummy gas mileage.
However, more feedback on the 1.6 rockers and/or pushrods is certainly welcome. Thanks fellas.
EDIT: Upon further research, I discovered that the various length pushrods are only mentioned in RockAuto's catalog for the '87 and '88 Fiero. For the '85 and '86 Fiero, 6.163" is the only length pushrod offered. I find that rather odd, as I would've suspected that there'd be no difference in the pushrods for all the years that the 2.8 was offered in the Fiero.
[This message has been edited by Patrick (edited 05-11-2015).]
Originally posted by Patrick: EDIT: Upon further research, I discovered that the various length pushrods are only mentioned in RockAuto's catalog for the '87 and '88 Fiero. For the '85 and '86 Fiero, 6.163" is the only length pushrod offered. I find that rather odd, as I would've suspected that there'd be no difference in the pushrods for all the years that the 2.8 was offered in the Fiero.
Well, the 87-88 2.8 does have some differences to the 85-86 2.8. I don't know if the block casting changed then as well or not, but any number of changes could have also required a change in the pushrod length. Too much work to figure it out, I think.
Given the change is so small (most vendors usually sell pushrods in 0.050 length increments, and the differences listed here are less than that), I think it's safe to use either the stock or Comp pushrods, with the stock or 1.6 rockers, and there will be minimal issues resulting due to out-of-geometry valvetrain from either one. Given the engine won't really go past 5500 anyway, and the lift is not that great, I'd just stick with what's available.
Setting the valve lash compensates for *some* variability in pushrod length on iron heads. Once that threshold is crossed, then you need custom length pushrods such as is the case for using a roller cam block (and roller lifters) V6 with iron heads.
[This message has been edited by lou_dias (edited 05-11-2015).]
Given the change is so small (most vendors usually sell pushrods in 0.050 length increments, and the differences listed here are less than that)...
Dobey, are you testing my math abilities? The differences in lengths of the pushrods listed at RockAuto are .120" from the shortest to the middle one, and .227" from the middle one to the longest.
quote
Originally posted by Patrick:
...the lengths mentioned in the blurbs for each brand of pushrod vary from 6.043" to 6.163" to 6.390". 6.163 seems to be the most common length offered.
But yeah, I'll probably end up using a "stock" pushrod length of 6.163" and be satisfied with that.
Originally posted by Patrick: Dobey, are you testing my math abilities? The differences in lengths of the pushrods listed at RockAuto are .120" from the shortest to the middle one, and .227" from the middle one to the longest.
Sorry, I was only thinking of the 6.135" and 6.165" ones mentioned in your OP.
Thanks guy. 
6.163 seems to be the most common length offered.
