Stock Pushrod Length for a 304
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Michael Mayben
IHPA Tech Moderator - Retired & No Longer Online
Which pushrod...a ball /ball (boat rocker) or a ball/cup (welded rocker)?
Search on this sub-forum using keyword "pushrod length" and you will get at least nine returns.
Search on this sub-forum using keyword "pushrod length" and you will get at least nine returns.
Sorry 'bout that, ball/ball for boat rockers.
I have a constant "ticking" noise and the machine shop will look at it tomorrow. He found his receipts from 2000 and he took 0.045" off both the head & block. The rods now are 8.850" and I'd like to be able to tell him what the stock ones were.
Thanks michael!
I have a constant "ticking" noise and the machine shop will look at it tomorrow. He found his receipts from 2000 and he took 0.045" off both the head & block. The rods now are 8.850" and I'd like to be able to tell him what the stock ones were.
Thanks michael!
Robert Kenney
Super Moderator
Here is what you are looking for in case you were unable to find it. Link to a post with the desired data.
http://www.forums.IHPartsAmerica.com/gas-engine-tech/1988-pushrod-length.html
http://www.forums.IHPartsAmerica.com/gas-engine-tech/1988-pushrod-length.html
Hi guys,
to refresh everyone, I have a fresh 10 year old rebuilt 304 that sat for about 10 years before I got the truck running this past fall. I had about 400 miles on it before I took it for a highway run of about 1 hr keeping my eye on both the temp and oil press gauges. When I got off the highway the motor now makes a constant ticking noise. Always. I checked a conrod bearing and all the clearances and are ok. I checked oil pressure in the block and head and have 50psi w/a drill at about 1800rpm. I checked the fuel pump and it is good and I disconnected the belts to keep the water pump from turning. It has a slight wabble. I checked the pushrods and they are all straight and have the same number marked on them (I didn't measure them) the lifters all look good and can't be compressed.
I only measured one of each but....
My new rods have 8.850 written on them. I used a 12" vernier caliper and they measured from tip to tip 9.087".
I have an extra 304 and I pulled a stock pushrod out and measured the same way and got 9.224".
The stock set-up came out of a 9 post rocker assy. And my current motor has a 5 post set-up. The stock rods are a 3 piece unit with a straight shaft and the "balls" are welded in place 180 degrees apart.
The machine shop looked up their records and told me they took off 0.045" from both the heads and block for a total of 0.090". The difference between the stock and new pushrods are 0.137".
I have a schneider cam and the new lifter measures 2.298" long w/the vernier caliper. The stock lifter measures 2.291" long.
The pushrod cups on the new measure 0.402" deep and the stock cup measures 0.444" deep. A difference of 0.038"
the stock rod in both lifters is a little deeper in the stock lifter.
Rod lengths (new / stock): 9.087" / 9.224" = 0.137"
lifter lengths (new / stock): 2.298" / 2.291" = 0.007"
lifter pushrod cup depth ( new / stock): 0.402" / 0.444" = 0.042"
so we have 0.137" - 0.007" - 0.042" = 0.088" difference in lifter/pushrod lengths between a stock and well worn 304 and a freshly re-built 304 w/0.090" shaved off the block & heads.
Can it be a linear relationship between the lifters/pushrod and the amount taken off the head/block?
I still am using only 1 of each.
I will get a feeler gauge and check clearance between rocker/valve at some point.
Thanks!
to refresh everyone, I have a fresh 10 year old rebuilt 304 that sat for about 10 years before I got the truck running this past fall. I had about 400 miles on it before I took it for a highway run of about 1 hr keeping my eye on both the temp and oil press gauges. When I got off the highway the motor now makes a constant ticking noise. Always. I checked a conrod bearing and all the clearances and are ok. I checked oil pressure in the block and head and have 50psi w/a drill at about 1800rpm. I checked the fuel pump and it is good and I disconnected the belts to keep the water pump from turning. It has a slight wabble. I checked the pushrods and they are all straight and have the same number marked on them (I didn't measure them) the lifters all look good and can't be compressed.
I only measured one of each but....
My new rods have 8.850 written on them. I used a 12" vernier caliper and they measured from tip to tip 9.087".
I have an extra 304 and I pulled a stock pushrod out and measured the same way and got 9.224".
The stock set-up came out of a 9 post rocker assy. And my current motor has a 5 post set-up. The stock rods are a 3 piece unit with a straight shaft and the "balls" are welded in place 180 degrees apart.
The machine shop looked up their records and told me they took off 0.045" from both the heads and block for a total of 0.090". The difference between the stock and new pushrods are 0.137".
I have a schneider cam and the new lifter measures 2.298" long w/the vernier caliper. The stock lifter measures 2.291" long.
The pushrod cups on the new measure 0.402" deep and the stock cup measures 0.444" deep. A difference of 0.038"
the stock rod in both lifters is a little deeper in the stock lifter.
Rod lengths (new / stock): 9.087" / 9.224" = 0.137"
lifter lengths (new / stock): 2.298" / 2.291" = 0.007"
lifter pushrod cup depth ( new / stock): 0.402" / 0.444" = 0.042"
so we have 0.137" - 0.007" - 0.042" = 0.088" difference in lifter/pushrod lengths between a stock and well worn 304 and a freshly re-built 304 w/0.090" shaved off the block & heads.
Can it be a linear relationship between the lifters/pushrod and the amount taken off the head/block?
I still am using only 1 of each.
I will get a feeler gauge and check clearance between rocker/valve at some point.
Thanks!
Robert Kenney
Super Moderator
The only reliable way to verify lifter preload is by installing an adjustable pushrod. Idealy verify each location but a couple on each side should be enough to get a ball-park answer.
Basically adjust the rod as short as possible and install in a location that you have made sure is on the heal of a lobe(tdc compression stroke is generaly close enough) and adjust the rod longer until it makes good contact with the lifter socket and rocker arm socket. Remove it and measure it's oal, add .050 to that and that is the length rod I would use.
Also compare your existing rod to the measurement you got fron the adjustable one and see where you are now.
You say the shop decked the block .045? Sure you are at zero deck and not running the pistons proud of the deck at tdc?
Basically adjust the rod as short as possible and install in a location that you have made sure is on the heal of a lobe(tdc compression stroke is generaly close enough) and adjust the rod longer until it makes good contact with the lifter socket and rocker arm socket. Remove it and measure it's oal, add .050 to that and that is the length rod I would use.
Also compare your existing rod to the measurement you got fron the adjustable one and see where you are now.
You say the shop decked the block .045? Sure you are at zero deck and not running the pistons proud of the deck at tdc?
Dealbreaker74
Member
It sounds like you're a little tangled up with all of mods done to that motor. And you didn't mention the head gasket thickness. Adding that dimension will increase the pushrod length. Don't panic. There are ways out of this.
If you don't have adjustable pushrods for measuring, you can do what I did. Probably not any easier than Robert's plan, but it worked for me. And doing it this way, it isn't necessary to know the dimensions of lifters, or the amount removed from the heads/block.
I somehow lost track of the exact material removed from the heads and block deck. (that sometimes happens when it takes four years to rebuild a motor.) so I mocked up a stock pushrod on the heel of a cam lobe and made a Mark (photo 1). Then I tightened the rocker assembly which compressed the lifter cup (photo 2) and made a second Mark. Its hard to see it in the pic.
I have a friend who works at a place with a waterjet cutter. I had him blast shims of various thicknesses of aluminum (photo 3). When I measured the distance between my marks, it came out to .130" (photo 4). So I chose a set of shims cut from .100" material which left me with .030" of preload on the lifters when the rocker assembly was tightened down. So far, the results are good. I have about 500 miles on the engine and it hasn't ticked like my '74 is prone to do. And if you don't want to do the shim route, you can have pushrods made to order using your new dimensions.
If you don't have adjustable pushrods for measuring, you can do what I did. Probably not any easier than Robert's plan, but it worked for me. And doing it this way, it isn't necessary to know the dimensions of lifters, or the amount removed from the heads/block.
I somehow lost track of the exact material removed from the heads and block deck. (that sometimes happens when it takes four years to rebuild a motor.) so I mocked up a stock pushrod on the heel of a cam lobe and made a Mark (photo 1). Then I tightened the rocker assembly which compressed the lifter cup (photo 2) and made a second Mark. Its hard to see it in the pic.
I have a friend who works at a place with a waterjet cutter. I had him blast shims of various thicknesses of aluminum (photo 3). When I measured the distance between my marks, it came out to .130" (photo 4). So I chose a set of shims cut from .100" material which left me with .030" of preload on the lifters when the rocker assembly was tightened down. So far, the results are good. I have about 500 miles on the engine and it hasn't ticked like my '74 is prone to do. And if you don't want to do the shim route, you can have pushrods made to order using your new dimensions.
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Pretty cool having a buddy make rocker stand shims!
Do you think you can say that you have a 1 of a kind valvetrane?
I had a good friend who worked for the komatsu plasma cutting division but he moved on...
Someone also mentioned valve seats. Would a valve not sitting properly cause a tick? Would a bleed down test prove anything?
I can't pinpoint one thing making noise and I have had a valve cover off and listened to everything w/a stethoscope. They all sound the same.
I'll keep going and let you guys know.
Thanks!
Do you think you can say that you have a 1 of a kind valvetrane?
I had a good friend who worked for the komatsu plasma cutting division but he moved on...
Someone also mentioned valve seats. Would a valve not sitting properly cause a tick? Would a bleed down test prove anything?
I can't pinpoint one thing making noise and I have had a valve cover off and listened to everything w/a stethoscope. They all sound the same.
I'll keep going and let you guys know.
Thanks!
Robert Kenney
Super Moderator
Personally experienced IH sv rockers hiting the valve cover to the point that a dimple could be seen on the outside. Never could point a finger at the fault. All stock valve train components were used except for the cam which was only a bit over stock lift wise. May be worth a look for witness marks.
Dealbreaker74
Member
Yes, the waterjet is a sweet rig all right!
The valve seats should all be of a uniform height if you've had a valve job done. Then whoever assembled the heads ideally should have used a height mic and the necessary shims to set all of the spring heights to whatever number called out by the spring company. If all of this was done, then you shouldn't see any valve tips lower or higher than the rest. Remove one of the rocker assemblies and put a straight edge across all of the intakes and then exhausts and see if you can see any daylight under the straight edge. If not, then you might try my idea of measuring the pushrod deflection with the rocker assembly loose, then tight. If you see more than say .070" between tight and loose, then I'd say your machine work has resulted in moving the rocker rails too close to the block deck. Your pushrods May be too long. You might need shims like me. I have some extras, but we need to know if this is really what's going on.
Then again, the opposite might be true. With the rocker rails cinched down, can you move any of the pushrods? The pumped up lifters should allow them to spin, but not migrate up and down at all. Of course, some of those rods will be pushing valves, so they should be nice and tight anyway. Rotate the motor by hand and see if any are noticeably loose.
There's a lot of variables going on here. Because you don't know the exact history of this engine, it really needs to be logically diagnosed one thing at a time. If you don't find anything wrong by doing the above, then it makes sense to put a dial indicator down each lifter bore and see the height of each cam lobe as a helper rotates the crank through the nose of each lobe. This is a pain, but like checking everything else I suggested, its a solid diagnosis, not a guess.
And if you want to set your mind at ease, buy one of those oil filter cutters. They'll allow you to pop the cover off your filter and examine the element for trash. Cams and lifters are magnetic, so if a lobe is trashed, you'll see specs sticking to a small magnet as you drag it through the folds. If it comes up clean, you'll know you're still okay.
Keep in touch!
The valve seats should all be of a uniform height if you've had a valve job done. Then whoever assembled the heads ideally should have used a height mic and the necessary shims to set all of the spring heights to whatever number called out by the spring company. If all of this was done, then you shouldn't see any valve tips lower or higher than the rest. Remove one of the rocker assemblies and put a straight edge across all of the intakes and then exhausts and see if you can see any daylight under the straight edge. If not, then you might try my idea of measuring the pushrod deflection with the rocker assembly loose, then tight. If you see more than say .070" between tight and loose, then I'd say your machine work has resulted in moving the rocker rails too close to the block deck. Your pushrods May be too long. You might need shims like me. I have some extras, but we need to know if this is really what's going on.
Then again, the opposite might be true. With the rocker rails cinched down, can you move any of the pushrods? The pumped up lifters should allow them to spin, but not migrate up and down at all. Of course, some of those rods will be pushing valves, so they should be nice and tight anyway. Rotate the motor by hand and see if any are noticeably loose.
There's a lot of variables going on here. Because you don't know the exact history of this engine, it really needs to be logically diagnosed one thing at a time. If you don't find anything wrong by doing the above, then it makes sense to put a dial indicator down each lifter bore and see the height of each cam lobe as a helper rotates the crank through the nose of each lobe. This is a pain, but like checking everything else I suggested, its a solid diagnosis, not a guess.
And if you want to set your mind at ease, buy one of those oil filter cutters. They'll allow you to pop the cover off your filter and examine the element for trash. Cams and lifters are magnetic, so if a lobe is trashed, you'll see specs sticking to a small magnet as you drag it through the folds. If it comes up clean, you'll know you're still okay.
Keep in touch!
Dealbreaker74
Member
Hey, this is exactly right. I'm an air head for not mentioning it. When I shimmed my rocker pedestals, I had some interference with the rocker arms hitting the valve covers too. Made some stupid noise. I was able to "dress" the offending ones on the belt sander. If I recall, they were at the ends of the covers....like #1, 7, 2 and 8. I only had to grind two of them.
Good catch, Robert!
Ok,
ran the truck for about 5 minutes to get it in the garage.
Took off the valve covers and hooked up the starter trigger.
My feeler gauge goes only down to 0.004".
Basically a go / no-go for the gauge is as follows:
1,3,5,7 bank:
#1 intake - yes, #5 intake - yes all others - no
2,4,6,8 bank:
#2 exhaust - yes, both #4 exhaust & intake - yes but the intake has a lot more friction, #6 exhaust - yes
I tried all of them at least 6 times to make sure I got them all w/the valves closed and I'm not sure if they are in tdc compression or exhaust stroke.
Does this sound like I'm onto somethin'?
ran the truck for about 5 minutes to get it in the garage.
Took off the valve covers and hooked up the starter trigger.
My feeler gauge goes only down to 0.004".
Basically a go / no-go for the gauge is as follows:
1,3,5,7 bank:
#1 intake - yes, #5 intake - yes all others - no
2,4,6,8 bank:
#2 exhaust - yes, both #4 exhaust & intake - yes but the intake has a lot more friction, #6 exhaust - yes
I tried all of them at least 6 times to make sure I got them all w/the valves closed and I'm not sure if they are in tdc compression or exhaust stroke.
Does this sound like I'm onto somethin'?
Dealbreaker74
Member
I'm not sure, but I think you are putting the feeler gauge between the valve tip and the rocker wear surface? There shouldn't be any air gap there if so. The nature of hydraulic lifters is to eliminate all the lash. Is that what's going on?
Yup, but it's not an "air gap". I can force the feeler gauge between the rocker arm and valve tip. There is friction there but I can put the gauge between them. When the valve is open I can't force 'em between the two but when the valve is closed I can.
Now I only have a 0.004" gauge so maybe when I get another set that goes down to 0.001" maybe I can get it between all rocker arms and valve tips?
I'll try tomorrow to see what the largest gauge is that I can fit between the rocker arms and valve tips. Machine shop guy said anything over 0.005" will cause noise.
So if 5 out of the 16 has "clearance" for the feeler gauge would it be an issue of pushrod length or lifters or something else?
Now I only have a 0.004" gauge so maybe when I get another set that goes down to 0.001" maybe I can get it between all rocker arms and valve tips?
I'll try tomorrow to see what the largest gauge is that I can fit between the rocker arms and valve tips. Machine shop guy said anything over 0.005" will cause noise.
So if 5 out of the 16 has "clearance" for the feeler gauge would it be an issue of pushrod length or lifters or something else?
Dealbreaker74
Member
Okay, so we're talking about the same thing. Good. And your machine guy is right. Any running lash here will make noise.
The fact you have .004" of slop here is the mystery. The measurement should be at least .040" the other way.
So either the valves are too short (the stems are often "tipped" or ground square to stem) from the valve job performed. Or the pushrods are too short, or the rocker pedestals are too high. Or maybe a super-thick head gasket was installed.
Of all the possibilities, I'd look at the work performed on the valve stems. If you could find out what the shop's procedure is when dressing the tips, it might shed some light on this. If it was a shop that hasn't dealt with IH motors, perhaps they didn't know the valve train is non-adjustable. On a GM product, you can just crank the nut down a little more on the rocker. Not so IH.
We really have to know more about the machine work performed on this motor. If all of the parts are original to the build (rocker assemblies and pushrods in particular), then all I can think of is the valve stems are too short now.
Oh, and are you sure the rockers aren't also hitting the covers like Robert suggested? Has nothing to do with this problem, but it will cause more tail-chasing with valve train noise.
just re-read the earlier posts...are these the original pushrods or not? If your numbers and Robert's are correct, your current ones are .107" too short. That's a problem if true. Your valve stems are probably fine. Its your pushrods that you should be looking at.
The fact you have .004" of slop here is the mystery. The measurement should be at least .040" the other way.
So either the valves are too short (the stems are often "tipped" or ground square to stem) from the valve job performed. Or the pushrods are too short, or the rocker pedestals are too high. Or maybe a super-thick head gasket was installed.
Of all the possibilities, I'd look at the work performed on the valve stems. If you could find out what the shop's procedure is when dressing the tips, it might shed some light on this. If it was a shop that hasn't dealt with IH motors, perhaps they didn't know the valve train is non-adjustable. On a GM product, you can just crank the nut down a little more on the rocker. Not so IH.
We really have to know more about the machine work performed on this motor. If all of the parts are original to the build (rocker assemblies and pushrods in particular), then all I can think of is the valve stems are too short now.
Oh, and are you sure the rockers aren't also hitting the covers like Robert suggested? Has nothing to do with this problem, but it will cause more tail-chasing with valve train noise.
just re-read the earlier posts...are these the original pushrods or not? If your numbers and Robert's are correct, your current ones are .107" too short. That's a problem if true. Your valve stems are probably fine. Its your pushrods that you should be looking at.
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Robert Kenney
Super Moderator
Depending on how good you are at distinguishing between true lash and the lifter plunger depressing because oil has bleed out of it you seem to have a normal situation. Till you can get your paws on an adjustable push rod I think it is a guess..
Many times a lifter can give you an indication it is fully extended and leaving lash like you have measures. Shoving a .004" thick gauge in between the valve and rocker will surely depress the lifter plunger. That is not true lash.
With very light pressure and the friction of your finger on the end of a rocker see if you can feel clearance up and down. No then you are ok.
From reading your new pr length of 8.85 and the rough 9.95 the shop removed correct amount for .045 deck and .045 head milling.
Dealbreaker74
Member
Robert's right about the machine work. .045"+.045" is .090". I thought your pushrods were too long by .107", so this get things back in the ballpark. But when you add in the head gasket, you still might be too short. I agree an adjustable pushrod will give the definitive size. I'd check both heads to be sure.
Alright, called the local speed shop and will pick up an adjustable pushrod length tool for $24.
I'll loosen the 5 posts and remove 1 pushrod at a time or should I remove all 8 or doesn't it matter?
I'll then torque the stands to the 12 ft*lbs and extend the tool until it touches the rocker arm and is just barely snug. I'll try to gently rock the rocker arm and eliminate any movement if there is.
I'll then loosen the shaft and remove the tool. I'll use my vernier calipers to measure the end to end oal and add what to that, 0.030", 0.040", 0.050"?
I'll try do that to all 16.
Now getting back to the feeler gauge test, all the rocker arms where tested around the same time w/the starter indexing them. Shouldn't all the lifters have lost the same amount of oil due to drainage? Most I couldn't fit the 0.004" feeler gauge.
Do you know what the rocker arm post hole should measure out at? How about the shaft od?
Someone keeps telling me that it very well could be the rocker shafts/arms/springs/spacers.
I'll loosen the 5 posts and remove 1 pushrod at a time or should I remove all 8 or doesn't it matter?
I'll then torque the stands to the 12 ft*lbs and extend the tool until it touches the rocker arm and is just barely snug. I'll try to gently rock the rocker arm and eliminate any movement if there is.
I'll then loosen the shaft and remove the tool. I'll use my vernier calipers to measure the end to end oal and add what to that, 0.030", 0.040", 0.050"?
I'll try do that to all 16.
Now getting back to the feeler gauge test, all the rocker arms where tested around the same time w/the starter indexing them. Shouldn't all the lifters have lost the same amount of oil due to drainage? Most I couldn't fit the 0.004" feeler gauge.
Do you know what the rocker arm post hole should measure out at? How about the shaft od?
Someone keeps telling me that it very well could be the rocker shafts/arms/springs/spacers.
Rocker shafts: michael has a thread that shows a good shaft and a bad shaft. The bad shaft was bad because it was worn where the rocker arms pivot. They wore because of a lack of lubrication. Is that the only way these things fail, they develop "low spots" or "grooves". Can there be any wear under the spacers or springs on a 5 post?