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post #1 of 15 (permalink) Old 10-13-2018, 06:21 PM Thread Starter
 
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Need pushrod length advise.

So I have been trying to figure my pushrod length. I purchased the lite valve springs and a adjustable push rod. Also using a home made solid lifter. I set my cam to the closed position set my adjustable rocker (stock rockers with 7/16 studs and poly locks) to zero lash. This is my results. First picture stock pushrod second picture adjustable pushrod. I am using dry erase marker. I cannot get a clean line all the way across. I was thinking because it is not a roller rocker. anyone else come across this problem with stock type rocker arms? any suggestions? (Do the make low profile roller rockers so I can use the stock valve covers w/o spacer or double gaskets?)
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Last edited by RMTZ67; 10-13-2018 at 06:34 PM. Reason: more info
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post #2 of 15 (permalink) Old 10-13-2018, 06:44 PM
 
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"...Do the make low profile roller rockers so I can use the stock valve covers w/o spacer or double gaskets?..."


May have to use the 5/16" thick gaskets. But the Scorpion Endurance Series rockers are said to be low profile. Don't know exactly how much, if any, clearance you'd have with thin gaskets. One guy on the Summit site said they fit under his stock height covers, but doesn't mention what thickness gaskets he used.

https://www.summitracing.com/parts/s...w/make/pontiac

https://www.summitracing.com/parts/e...w/make/pontiac

Last edited by bigD; 10-13-2018 at 06:56 PM.
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post #3 of 15 (permalink) Old 10-14-2018, 02:02 AM
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Try using a Sharpie instead of a dry marker, or maybe even a paint marker and check while it's still a little wet so you can see where the rub pattern really is without the color "flaking" off. Also, it helped when I did mine if I held the edges of the retainer so that the valve couldn't turn. When those springs compress, sometimes they also will twist the valve a little and that will mess up the pattern. FYI you need to get the pushrod length right WITH the rockers you plan to use, so if you're contemplating a change - buy the rockers first, then do your measurements. Your second photo doesn't look bad from what I can see of it --- how was that length compared to the stock pushrod? Another thing to be careful of: Make sure to check the clearance between the outer edges of the spring retainer and the underneath/inside of the rocker. Use a piece of wire to check. You want adequate clearance in there throughout the full rocker arm range of motion - no touching allowed - and 0.060 minimum is even better. The Scorpions I had (the ones that FAILED on me) were really tight to the retainers. For the purposes of checking rocker to retainer clearance, tap lightly on the top of the valve with something like a non-marring mallet to make sure the valve locks are fully seated in the retainer so that the retainer is at its 'maximum' height, otherwise you might think you've got plenty of clearance when you really don't.

Bear
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post #4 of 15 (permalink) Old 10-14-2018, 05:08 PM Thread Starter
 
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Quote:
Originally Posted by BearGFR View Post
Try using a Sharpie instead of a dry marker, or maybe even a paint marker and check while it's still a little wet so you can see where the rub pattern really is without the color "flaking" off. Also, it helped when I did mine if I held the edges of the retainer so that the valve couldn't turn. When those springs compress, sometimes they also will twist the valve a little and that will mess up the pattern. FYI you need to get the pushrod length right WITH the rockers you plan to use, so if you're contemplating a change - buy the rockers first, then do your measurements. Your second photo doesn't look bad from what I can see of it --- how was that length compared to the stock pushrod? Another thing to be careful of: Make sure to check the clearance between the outer edges of the spring retainer and the underneath/inside of the rocker. Use a piece of wire to check. You want adequate clearance in there throughout the full rocker arm range of motion - no touching allowed - and 0.060 minimum is even better. The Scorpions I had (the ones that FAILED on me) were really tight to the retainers. For the purposes of checking rocker to retainer clearance, tap lightly on the top of the valve with something like a non-marring mallet to make sure the valve locks are fully seated in the retainer so that the retainer is at its 'maximum' height, otherwise you might think you've got plenty of clearance when you really don't.

Bear
So this is what I ended up doing. Tell me what you think? I further stuffed foil into the xtra lifter I had purchased and squeezed it in the vise until I could get the locking pin with no more compression. Put it on a valve with the double springs and this are my results. And a picture with the adjustable pushrod asd the original. engine was decked 0.30 and heads were milled slightly and oem 0.41?? gaskets.I thought about roller rockers but do not want to add double gaskets or spacer.I currently have 5/16 gaskets to clear the poly locks. The low profile rollers BigD pointed out are a little pricey seeing I have drum brakes all around and could use the cash to install 4 wheel disc brakes before stuffing the motor in my way of brake booster,lines etc. So I will use what I have and finish up my engine build.
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post #5 of 15 (permalink) Old 10-14-2018, 09:57 PM
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The pattern in the first photo looks to be centered pretty well. The second one is just a tad bit "high" on the valve - biased towards the intake ports. Both patterns look awfully "wide" to me. Compare them to the photo I'll attach that shows the contact pattern on my most recent build.

Use those light checking springs and the adjustable pushrod and do an experiment: Mark the top of valve like you have been, make sure the lifter and adjustable pushrod is on the cam base circle (zero lift). Back off the adjustable pushrod so that you know it's way too short. Set the rocker onto the stud, start the nut but leave it completely loose for now, and looking at it from the side so that you can get a good view of exactly where the rocker tip is touching the valve, move the rocker up or down on the stud so that it touches the valve as close to the exact center as you can get it. Hold the rocker in that position and finger tighten the rocker nut down to meet the rocker. Now, continuing to hold things like they are (the pushrod should still be way loose at this point) --- lengthen the pushrod until it seats in to the rocker and takes the slack out. If you did everything right, at this point everything should be snug, all the slack taken out of the pushrod->rocker->valve, and the rocker should be touching the valve dead center on the valve stem. Now "run it through" and see what kind of pattern you get. It'll probably be slightly biased off center - that's ok - what we're doing is establishing a base line starting point to work from. Make some sort of mark, count turns, whatever --- so that you know exactly where this setting is on the adjustable pushrod so that you can come back to it any time you want to.

Now clean every thing up, remove the parts, and LENGTHEN the pushrod by exactly two turns, and make another test pattern. Did it get better or worse? If it's worse, then go back to your baseline setting and then SHORTEN the pushrod by two turns --- better or worse than your baseline pattern? What we're doing here is trying to figure out if "pushrod nirvana" is to be found with a length that is longer than our base line or shorter. Once you know that, then start over - go back to the base line and start running patterns in whatever direction that is that looked better than your baseline (longer or shorter) but making smaller changes - lengthening (or shortening if that's the right direction) by only one turn, or even a half turn --- until you get as close as you possibly can to patterns that look like the ones in my picture.

Here's a couple of tricks that should help you get a better and more readable pattern. I already mentioned holding the valve so that it can't turn. Another thing that helps, is every so often as the valve is opening and closing, stop and 'wiggle' the rocker arm back and forth side to side across the top of the valve. What you're doing is wiping some of the ink off so that the pattern will be more obvious when you next remove the rocker to look at it. In fact, now that I think about it --- it's worth installing a rocker at the baseline length and then doing that 'wiggle' thing to make a marking - then take the rocker off and looking at the pattern without turning the engine over at all --- just to see if your baseline setting really does have it centered and also to see how wide the contact patch is that the rocker makes with the valve. That patch might be 'wider' just from the contour of the rocker tip.

Feel free to holler or PM me if you want to if none of this makes sense. Maybe we can link up or something and I can help walk you through it.

Yes, it's tedious, time consuming, and you may have to make multiple tests at the same settings to get confidence that what you're seeing is correct. However getting this right is important and it's worth the effort.

Good luck --- let me know how it goes.

Bear
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post #6 of 15 (permalink) Old 10-16-2018, 08:09 PM Thread Starter
 
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Originally Posted by BearGFR View Post
The pattern in the first photo looks to be centered pretty well. The second one is just a tad bit "high" on the valve - biased towards the intake ports. Both patterns look awfully "wide" to me. Compare them to the photo I'll attach that shows the contact pattern on my most recent build.

Use those light checking springs and the adjustable pushrod and do an experiment: Mark the top of valve like you have been, make sure the lifter and adjustable pushrod is on the cam base circle (zero lift). Back off the adjustable pushrod so that you know it's way too short. Set the rocker onto the stud, start the nut but leave it completely loose for now, and looking at it from the side so that you can get a good view of exactly where the rocker tip is touching the valve, move the rocker up or down on the stud so that it touches the valve as close to the exact center as you can get it. Hold the rocker in that position and finger tighten the rocker nut down to meet the rocker. Now, continuing to hold things like they are (the pushrod should still be way loose at this point) --- lengthen the pushrod until it seats in to the rocker and takes the slack out. If you did everything right, at this point everything should be snug, all the slack taken out of the pushrod->rocker->valve, and the rocker should be touching the valve dead center on the valve stem. Now "run it through" and see what kind of pattern you get. It'll probably be slightly biased off center - that's ok - what we're doing is establishing a base line starting point to work from. Make some sort of mark, count turns, whatever --- so that you know exactly where this setting is on the adjustable pushrod so that you can come back to it any time you want to.

Now clean every thing up, remove the parts, and LENGTHEN the pushrod by exactly two turns, and make another test pattern. Did it get better or worse? If it's worse, then go back to your baseline setting and then SHORTEN the pushrod by two turns --- better or worse than your baseline pattern? What we're doing here is trying to figure out if "pushrod nirvana" is to be found with a length that is longer than our base line or shorter. Once you know that, then start over - go back to the base line and start running patterns in whatever direction that is that looked better than your baseline (longer or shorter) but making smaller changes - lengthening (or shortening if that's the right direction) by only one turn, or even a half turn --- until you get as close as you possibly can to patterns that look like the ones in my picture.

Here's a couple of tricks that should help you get a better and more readable pattern. I already mentioned holding the valve so that it can't turn. Another thing that helps, is every so often as the valve is opening and closing, stop and 'wiggle' the rocker arm back and forth side to side across the top of the valve. What you're doing is wiping some of the ink off so that the pattern will be more obvious when you next remove the rocker to look at it. In fact, now that I think about it --- it's worth installing a rocker at the baseline length and then doing that 'wiggle' thing to make a marking - then take the rocker off and looking at the pattern without turning the engine over at all --- just to see if your baseline setting really does have it centered and also to see how wide the contact patch is that the rocker makes with the valve. That patch might be 'wider' just from the contour of the rocker tip.

Feel free to holler or PM me if you want to if none of this makes sense. Maybe we can link up or something and I can help walk you through it.

Yes, it's tedious, time consuming, and you may have to make multiple tests at the same settings to get confidence that what you're seeing is correct. However getting this right is important and it's worth the effort.

Good luck --- let me know how it goes.

Bear
Thanks for your response. I will try your advice and tricks this weekend see if anything changes and i'll be sure to post the results.
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post #7 of 15 (permalink) Old 10-17-2018, 06:46 PM
 
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Competition Cams roller tip rockers are like factory rockers except has the roller tip. They also have the long slot for the rocker arm stud if you use a high lift cam.

You will note that you may need thicker gaskets due to the polylocks - which you already know about. These are not full roller rockers which are typically larger and need taller valve covers.

https://www.summitracing.com/parts/c...ac?prefilter=1
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post #8 of 15 (permalink) Old 10-17-2018, 07:10 PM
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If you're seriously considering going with roller tip rockers that don't also have roller fulcrums, you might want to watch this first:

https://www.motortrendondemand.com/d...er/0_bhpycxdw/

Bear

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post #9 of 15 (permalink) Old 10-17-2018, 09:05 PM
 
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Originally Posted by BearGFR View Post
If you're seriously considering going with roller tip rockers that don't also have roller fulcrums, you might want to watch this first:

https://www.motortrendondemand.com/d...er/0_bhpycxdw/

Bear

The video shows a small block Chevy capable of 7,000 RPM's. In the first comparison, stamped vs roller tip, the stamped showed a very slight advantage from 5,000 and up and they also made comment that the difference was believed to be the flex in the rocker arm studs. The stamped rocker arm used a 7/16" rocker arm stud while the roller tip was only available for use with the smaller stock Chevy 3/8" rocker arm stud. Time - 9:20 & 12:20 on the video. So for all intense purposes, the stamped vs roller tip is the same with regards to performance and you won't be spinning a Pontiac to 7,000 RPM's.

The roller tip provides the advantage of less wear on the valve stem tip and runs cooler as it rolls across the tip vs being dragged - which is also where you get your wear. Time - 12:54 on the video. This may not be a big advantage on a lower lift cam using moderate valve spring rates.

My personal opinion is to go with an aftermarket stamped steel rocker for lifts in the .500" and under range. The aftermarket pieces are better quality, a true 1.52 ratio (whereas the factory rockers are said to be closer to 1.48), have the long slot in the fulcrum so you don't have to worry about bind, and have the grooved balls for better oiling. I used them on my last 400CI build - no issues. Comp Cams XE274H with .491" lift.

Going more radical, up in the .550" lift range or under, AND valve spring pressures do not exceed 350 lbs open. I have never had the need for full roller rockers as I have never built an engine with a roller cam or on the verge of a race only engine. I am however using the Comp Cams roller tips on my 455 build. I have both the 1.5's and 1.65's to experiment with, but max cam lift on the solid cam will be under .540" with the 1.65's. And it is not about power advantage, but the smoother operation of the roller on top of the valve stem tip versus stamped.

Price of course is the consideration. I don't think the extra $spent on roller tip rockers is really needed for most cam choices short of the roller function across the top of the valve stem tip. I would invest in a set of new stamped rockers for the reasons I pointed out over the stock factory rocker arms. Save the difference and put it somewhere else in the build.

Comp Cams' Magnum Roller Rocker Arms
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post #10 of 15 (permalink) Old 10-18-2018, 08:50 PM Thread Starter
 
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The video shows a small block Chevy capable of 7,000 RPM's. In the first comparison, stamped vs roller tip, the stamped showed a very slight advantage from 5,000 and up and they also made comment that the difference was believed to be the flex in the rocker arm studs. The stamped rocker arm used a 7/16" rocker arm stud while the roller tip was only available for use with the smaller stock Chevy 3/8" rocker arm stud. Time - 9:20 & 12:20 on the video. So for all intense purposes, the stamped vs roller tip is the same with regards to performance and you won't be spinning a Pontiac to 7,000 RPM's.

The roller tip provides the advantage of less wear on the valve stem tip and runs cooler as it rolls across the tip vs being dragged - which is also where you get your wear. Time - 12:54 on the video. This may not be a big advantage on a lower lift cam using moderate valve spring rates.

My personal opinion is to go with an aftermarket stamped steel rocker for lifts in the .500" and under range. The aftermarket pieces are better quality, a true 1.52 ratio (whereas the factory rockers are said to be closer to 1.48), have the long slot in the fulcrum so you don't have to worry about bind, and have the grooved balls for better oiling. I used them on my last 400CI build - no issues. Comp Cams XE274H with .491" lift.

Going more radical, up in the .550" lift range or under, AND valve spring pressures do not exceed 350 lbs open. I have never had the need for full roller rockers as I have never built an engine with a roller cam or on the verge of a race only engine. I am however using the Comp Cams roller tips on my 455 build. I have both the 1.5's and 1.65's to experiment with, but max cam lift on the solid cam will be under .540" with the 1.65's. And it is not about power advantage, but the smoother operation of the roller on top of the valve stem tip versus stamped.

Price of course is the consideration. I don't think the extra $spent on roller tip rockers is really needed for most cam choices short of the roller function across the top of the valve stem tip. I would invest in a set of new stamped rockers for the reasons I pointed out over the stock factory rocker arms. Save the difference and put it somewhere else in the build.

Comp Cams' Magnum Roller Rocker Arms
The video was very informative and I feel as you do about using the aftermarket stamped steel rockers. I currently have stamped steel rockers with the long slots and also purchased the 7/16 studs and poly locks. I am going to try Bears tips and tricks on measuring my pushrods and see how it matches up against what I have already tried and see if anything changes. I am thinking the steel rockers tend to leave a wide line unlike the thin line left by roller rockers. have you tried measuring pushrod length with steel rockers? and did you get similar wide lines like in my prior post?
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