cam specs?
- Thread starter 78IH
- Start date
- Status
Robert Kenney
Super Moderator
Here's the deal on v8 balancing. Anything you do that changed the piston or rod weight will/can through the rotating assembly out of balance. Especially changing the rods to a different version or style.
This is a general rule and I have never build an engine with out balancing but have had a few that I fixed because a guy didn't balance. Even a grocery getter will run to a rpm that can have harmful harmonics.
This is how I do it not how every one does it. If the guy building the engine is ok taking the risk of an out of balance engine well I guess you have to let him/her go with it.
This is a general rule and I have never build an engine with out balancing but have had a few that I fixed because a guy didn't balance. Even a grocery getter will run to a rpm that can have harmful harmonics.
This is how I do it not how every one does it. If the guy building the engine is ok taking the risk of an out of balance engine well I guess you have to let him/her go with it.
If he builds race motors and has a good reputation, then I would assume he knows how to balance an engine...
Actually, if he does race engines, then, every engine he does should be balanced.... As robertk stated / implied if he did not balance...
I was "worried" about the "average guy" at xyz machine shop.
I had a flywheel / pressure plate (corvair) balanced (supposedly) many years ago. It had a "vibration" at exactly 4500 rpm (nowhere else in the rpm range). Of course, I only felt it when I ran the engine to the redline (5500). And, it lasted the 50 - 60,000 miles until I replaced it with another "pair" balanced by another person -- no vibration idle - 5500 rpm.
Actually, if he does race engines, then, every engine he does should be balanced.... As robertk stated / implied if he did not balance...
I was "worried" about the "average guy" at xyz machine shop.
I had a flywheel / pressure plate (corvair) balanced (supposedly) many years ago. It had a "vibration" at exactly 4500 rpm (nowhere else in the rpm range). Of course, I only felt it when I ran the engine to the redline (5500). And, it lasted the 50 - 60,000 miles until I replaced it with another "pair" balanced by another person -- no vibration idle - 5500 rpm.
Last edited:
When I brought it in, I was going to use the sealed power cam and the same springs if they were still good. Its week five now, and I can afford a performance cam and springs. For the last week ive been calling to see where he is at. But they say he is busy, I left messages about my situation. $175 isnt too bad, ive got my fingers crossed that he hasnt got too far. Ill call tomarrow about the balancing. The rods are at the shop, they are different rods for a 392 with cap screws. There was somthing in the bb FAQ about how near the end of production there was a standard rod for 345 and 392s borrowed from the 392. But that they could even be mismatched without adverse results. These are those rods. Im really learnin now. Can balancing correct this? Should I bring in a old piston and rod?
Robert Kenney
Super Moderator
In the balance department, it doesn't matter if it is bowtie or blue oval or IH. They all balance the same and use the same Bob weight calculations. Again I always assume on the safe side and while it May seem that I state the obvious I am only looking out for a any possible problem. Sounds like you are in good hands.
I hear stories of 152 and 196 scouts running so loudly that the driver needs ear plugs.
my 152 is as smooth at 2000 as it is at 4200 and I can cruise all day long at 65-70 with no ill ear affects. 
enjoy your new engine.
Robert Kenney
Super Moderator
I see we are a little out of sync on our posts.
after the new rods are weighed small end and big end with the bearing the piston and one ring set. Are also weighed and all parts are matched to the lightest one small end to small end etc with exception of the rings and bearings.
If you are replacing parts the old ones are no longer relevant.
Yes if you change rods to the newer type they May be very close as the parts are interchangeable by IH parts books but checking can't hurt.
One example is tim potters engine. It was machined in an attempt to lighten the reciprocating and rotating parts so the rods were modified so they are no longer IH spec weights. We are changing rods so all needs to be checked. Bad thing here is that the rod weight change made it necessary to lighten the crank excessively so it May be to light to balance with the new rods without adding mallory (carbide based heavy balance material) to the counter weights. That is when balancing can get pricey. You are not likely in that situation but I thought I would add the info.
after the new rods are weighed small end and big end with the bearing the piston and one ring set. Are also weighed and all parts are matched to the lightest one small end to small end etc with exception of the rings and bearings.
If you are replacing parts the old ones are no longer relevant.
Yes if you change rods to the newer type they May be very close as the parts are interchangeable by IH parts books but checking can't hurt.
One example is tim potters engine. It was machined in an attempt to lighten the reciprocating and rotating parts so the rods were modified so they are no longer IH spec weights. We are changing rods so all needs to be checked. Bad thing here is that the rod weight change made it necessary to lighten the crank excessively so it May be to light to balance with the new rods without adding mallory (carbide based heavy balance material) to the counter weights. That is when balancing can get pricey. You are not likely in that situation but I thought I would add the info.
There still seems to be some confusion on the subject of balancing an engine - based on the repsonses from the participants (and my "reading" of the responses...).
I will attempt to state my "simplified" view:
robertk -- you can delete my post (or pm me and I will delete it) if you find it too far out of line...
Pistons --
if you look at the "bottom" of a piston, you should see two "raised metal bosses". The pistons should weigh the same amount. So, the "balancer" should weigh all the pistons. The piston that weighs the least amount will be set aside and all the others will have "metal" ground down from these bosses until all pistons are equal weight.
Rods ---
all the large ends (piston to crankshaft) and all the small ends (rod caps) should weigh the same amount.
This means not the complete rod, but the two separate pieces.
I do not know if the rod bolts / nuts are included -- I am not aware that the rod bearings are part of the calculation, either; as robertk stated... (I have very limited experience compared to robertk.)
crankshaft ---
this is a "gray area". You can have the crankshaft polished / balanced (assuming the skill level of the machinist is "up to it"). If you do this, you probably need the harmonic balancer and the flywheel also dynamically balanced -- based upon IH "dynamically" balancing assembled engines as an unit on the assembly line.
In my particular case (30 years ago), a new crankshaft was polished / balanced (the orignal crankshaft broke). "we" (mechanic and I) also made a decision to not use a harmonic balancer (stock for the engine), but to use a solid steel crankshaft pulley (from an "earlier" version of the engine) -- which was also balanced as part of the "package".
Hth to explain "things".
I will attempt to state my "simplified" view:
robertk -- you can delete my post (or pm me and I will delete it) if you find it too far out of line...
Pistons --
if you look at the "bottom" of a piston, you should see two "raised metal bosses". The pistons should weigh the same amount. So, the "balancer" should weigh all the pistons. The piston that weighs the least amount will be set aside and all the others will have "metal" ground down from these bosses until all pistons are equal weight.
Rods ---
all the large ends (piston to crankshaft) and all the small ends (rod caps) should weigh the same amount.
This means not the complete rod, but the two separate pieces.
I do not know if the rod bolts / nuts are included -- I am not aware that the rod bearings are part of the calculation, either; as robertk stated... (I have very limited experience compared to robertk.)
crankshaft ---
this is a "gray area". You can have the crankshaft polished / balanced (assuming the skill level of the machinist is "up to it"). If you do this, you probably need the harmonic balancer and the flywheel also dynamically balanced -- based upon IH "dynamically" balancing assembled engines as an unit on the assembly line.
In my particular case (30 years ago), a new crankshaft was polished / balanced (the orignal crankshaft broke). "we" (mechanic and I) also made a decision to not use a harmonic balancer (stock for the engine), but to use a solid steel crankshaft pulley (from an "earlier" version of the engine) -- which was also balanced as part of the "package".
Hth to explain "things".
71 Scout 2
New member
The 1800-5000 is the usable rpm range, or basically the camshaft's powerband. Peak hp will typically occur between 300 and 500rpms lower than the upper listed limit. So in this example peak hp shall be anywhere from 4500 to 4700rpms (per chassis dyno with a warmed up 345 and that cam).
Not putting anyone down, but just because someone builds "race" engines doesn't mean they'll automatically do everything to your "street" engine that they do to their "race" engine. Sometimes these people see this as "easy" money and will do only what is required unless instructed to do more.
Personal opinion, but as others have mentioned, if you're spending a fairly large sum of cash on the build, another $100-200 is worth it in my book for a smoother (probably longer living) engine.
IH sv v8's are externally balanced, and will require the flywheel/flexplate you plan on using. If it's a flywheel, get it resurfaced before balancing, if needed. Along with the front balancer hub/hamonic balancer and other internals listed in this thread (repeating robertc I know). Another item that some people don't look at is the pressure plate/clutch assembly on a manual trans vehicle. Most pressure plates aren't balanced to very tight specs. Example, my friend put a new clutch/pressure plate (big name brand) in his vette and it had a odd vibation. Pulled it back out, took it in and had it balanced (don't remember how far off it was, not much), now it's silk. Just more to think about.
On the term of balancing, another opinion I have is weight, or lack of it. I like light weight internals, something IH isn't know for. But you can have weight removed from various parts and places. The mallory metal isn't required when balancing an engine unless you add stroke (and a fair amount) to the crankshaft, or add weight to the pistons and/or connecting rods. So no worries there.
Picture of some connecting rods.
Top connecting rod is a stock 216114r21. The bottom one is a lightened 309253c11. Both weighted roughly the same stock, 960g for the 216114r21 (stock) and 955g for the 309253c11 (stock). That's total weight, of the rods. The 309253c11 weighs in at 860g as pictured and lost a few more grams before everything was finished. The weight loss resulted in no loss of strength. In fact, every gram you can remove from the pistons and small end of the connecting rod will remove stress from the connecting rod, thus making it more durable.
Careful on selecting aftermarket rod bolts for the endcap style rods. IH uses the bolt threads to align the rod with the cap. Most arp bolts are too short, or have a short threaded portion allowing the cap to "float" on the rod. I need to do some digging to see what arp bolts mimic the stock IH bolts.
Not putting anyone down, but just because someone builds "race" engines doesn't mean they'll automatically do everything to your "street" engine that they do to their "race" engine. Sometimes these people see this as "easy" money and will do only what is required unless instructed to do more.
Personal opinion, but as others have mentioned, if you're spending a fairly large sum of cash on the build, another $100-200 is worth it in my book for a smoother (probably longer living) engine.
IH sv v8's are externally balanced, and will require the flywheel/flexplate you plan on using. If it's a flywheel, get it resurfaced before balancing, if needed. Along with the front balancer hub/hamonic balancer and other internals listed in this thread (repeating robertc I know). Another item that some people don't look at is the pressure plate/clutch assembly on a manual trans vehicle. Most pressure plates aren't balanced to very tight specs. Example, my friend put a new clutch/pressure plate (big name brand) in his vette and it had a odd vibation. Pulled it back out, took it in and had it balanced (don't remember how far off it was, not much), now it's silk. Just more to think about.
On the term of balancing, another opinion I have is weight, or lack of it. I like light weight internals, something IH isn't know for. But you can have weight removed from various parts and places. The mallory metal isn't required when balancing an engine unless you add stroke (and a fair amount) to the crankshaft, or add weight to the pistons and/or connecting rods. So no worries there.
Picture of some connecting rods.
Top connecting rod is a stock 216114r21. The bottom one is a lightened 309253c11. Both weighted roughly the same stock, 960g for the 216114r21 (stock) and 955g for the 309253c11 (stock). That's total weight, of the rods. The 309253c11 weighs in at 860g as pictured and lost a few more grams before everything was finished. The weight loss resulted in no loss of strength. In fact, every gram you can remove from the pistons and small end of the connecting rod will remove stress from the connecting rod, thus making it more durable.
Careful on selecting aftermarket rod bolts for the endcap style rods. IH uses the bolt threads to align the rod with the cap. Most arp bolts are too short, or have a short threaded portion allowing the cap to "float" on the rod. I need to do some digging to see what arp bolts mimic the stock IH bolts.
216114r21 rods do use the same bearings, right? This is a biggie. I thought that IH con rod service report said they did but, now I cant remember. All I can check are the part #s for 345 vs. 392. I did change to heavier rods. Please elaborate on this grey area. The crank is balanced with the rest of the rotating assembly when balancing, right? But theres also polishing which sheds oil quiker, making the crank lighter, right? But I wont see the advantages of polishing unless I also dynamic balane? Am I understanding this right? I finally spoke with the machinist though. Im luckily that he didnt get too far.
71 Scout 2
New member
All IH sv engines with factory internals use the same series of bearings. Meaning that the main, rod, camshaft will have the same o.d. And width (except the main thrust bearing) between a 152, 196, 266, 304, 345, 392. The connecting rod and crankshaft I.d. And main/crankshaft thrust bearing width vary with the service diameter of the crankshaft journals.
So in simple terms, yes, the bearings will work on either style of connecting rods.
It's not so much that the connecting rods (stock form) are different weights. When an engine in mass produced by the thousands there is a spec range for every part made. If everything had to identical, the cost for production would be too much. So there is a range that allows for an increased profit margin and quicker/easier production.
To make things simple, even though the two different styles of connecting rods (stock) didn't weigh the same, they are close enough to say they weigh the same. To give you an idea just how close the two styles are, go grab 5 small metal paperclips, those paperclips weigh more then the difference of my two example connecting rods (stock). It just happened that the two examples I was working with at the time weighed in like they did. The next connecting rods I compare might be just the opposite of the two I posted.
If you're going to balance an IH sv v8 engine. You need to balance it as an assembly. Meaning; flywheel, crankshaft, harmonic balancer hub, connecting rods, pistons, wristpins (locks if required), rings, rod bearings and all the bolts and nuts that hold the assembly together. The person doing the balancing will also add a small amount for oil in/on the rotating assembly.
So in simple terms, yes, the bearings will work on either style of connecting rods.
It's not so much that the connecting rods (stock form) are different weights. When an engine in mass produced by the thousands there is a spec range for every part made. If everything had to identical, the cost for production would be too much. So there is a range that allows for an increased profit margin and quicker/easier production.
To make things simple, even though the two different styles of connecting rods (stock) didn't weigh the same, they are close enough to say they weigh the same. To give you an idea just how close the two styles are, go grab 5 small metal paperclips, those paperclips weigh more then the difference of my two example connecting rods (stock). It just happened that the two examples I was working with at the time weighed in like they did. The next connecting rods I compare might be just the opposite of the two I posted.
If you're going to balance an IH sv v8 engine. You need to balance it as an assembly. Meaning; flywheel, crankshaft, harmonic balancer hub, connecting rods, pistons, wristpins (locks if required), rings, rod bearings and all the bolts and nuts that hold the assembly together. The person doing the balancing will also add a small amount for oil in/on the rotating assembly.
Last edited:
My parts manual for 72 - 73 full size only shows one part number for rod bearings.
Imo -- there is no need to
lighten rods or polish / lighten the crankshaft in an IH (or any) engine that is not going to "see" 5000 rpm
unless you want "bragging rights" over beer with your buddies...
(makes more "sense" in a race engine that "sees" / runs at 7000 - 8000 rpm...)
as stated before, you should have the rods / pistons balanced -- reread robertk's posts #22, #25 and #26 in this thread.
If the crankshaft / flywheel / harmonic balancer come from one engine; then I think you do not need to balance the crankshaft.
But, michael mayben, robertk, or Jeff can speak more authoritatively than I on this subject.
If these three pieces come from more than one engine; then all three should be balanced. The engines were externally balanced on the assembly line when new.
The crankshaft should be dynamically balanced -- I do not know if the harmonic balancer should be attached -- again robertk knows more than I on the subject. Though he did not state exactly what he did on his 152 as far as balancing the crankshaft.
I believe the flywheel should be balanced by itself.
Hth
Imo -- there is no need to
lighten rods or polish / lighten the crankshaft in an IH (or any) engine that is not going to "see" 5000 rpm
unless you want "bragging rights" over beer with your buddies...
(makes more "sense" in a race engine that "sees" / runs at 7000 - 8000 rpm...)
as stated before, you should have the rods / pistons balanced -- reread robertk's posts #22, #25 and #26 in this thread.
If the crankshaft / flywheel / harmonic balancer come from one engine; then I think you do not need to balance the crankshaft.
But, michael mayben, robertk, or Jeff can speak more authoritatively than I on this subject.
If these three pieces come from more than one engine; then all three should be balanced. The engines were externally balanced on the assembly line when new.
The crankshaft should be dynamically balanced -- I do not know if the harmonic balancer should be attached -- again robertk knows more than I on the subject. Though he did not state exactly what he did on his 152 as far as balancing the crankshaft.
I believe the flywheel should be balanced by itself.
Hth
Robert Kenney
Super Moderator
Just have the rotating assy balanced. and ignore all of the other stuff although some is relevant to much of a good thing is still to much of a good thing.
The guy doing the balancing will need one set of rings, one set of rod bearings, all of your new pistons, all of your rods, all of your wrist pins, the crank, the front crank hub or harmonic balancer and the flywheel or flex plate. If you are real critical the pressure plate needs to be doweled and balanced to the and with the flywheel.
All components need to be separate and unassembled.
That is all you need to worry your self with as a good balancing firm will do the rest. I leave nothing to chance when building an engine period and pretty much end of story.
Like robertc stated you are not building a race motor but any motor will vibrate if not balanced correctly. A 35 year old motor cannot be associated to any factory build specs so please "do not" try to convince some one that the factory specs or rod weights are relevant here without even seeing the parts. That is just blowing smoke and irresponsible.
and ignore all of the other stuff although some is relevant to much of a good thing is still to much of a good thing. The guy doing the balancing will need one set of rings, one set of rod bearings, all of your new pistons, all of your rods, all of your wrist pins, the crank, the front crank hub or harmonic balancer and the flywheel or flex plate. If you are real critical the pressure plate needs to be doweled and balanced to the and with the flywheel.
All components need to be separate and unassembled.
That is all you need to worry your self with as a good balancing firm will do the rest. I leave nothing to chance when building an engine period and pretty much end of story.
Like robertc stated you are not building a race motor but any motor will vibrate if not balanced correctly. A 35 year old motor cannot be associated to any factory build specs so please "do not" try to convince some one that the factory specs or rod weights are relevant here without even seeing the parts. That is just blowing smoke and irresponsible.
Robert Kenney
Super Moderator
If you have r2 rods that is fine. The r2 denoted the better rod. The big difference is where the neck(I-beam) of the rod transitions to the big end. That big fillet allows the rod to take a bunch more tensile loading without distorting the bearing bore and distribute the compressive bearing loading way better. You won't break them with your setup.
I couldn't remember if you had a auto to I through in the pressure plate reference for safety.
Yes, I would assume so...
My 72 - 73 IH full size parts manual shows 216114r12 as the 345 rod.
Something you have to keep in mind -- as IH "revised" / "updated" parts they increased the r# -- r1 was the first version; rnn were later versions.
My personal point of view is that you need 8 rods with the same part number -- which is what you seem to have.
From a balance perspective (as 71 Scout 2 pointed out), there is probably only 1/2 gram to maybe 2 grams of weight between the lightest to the heaviest rod.
This does not seem to be much, but you will have a "better" engine if the weights are "equaled out"... With balancing
hth
My 72 - 73 IH full size parts manual shows 216114r12 as the 345 rod.
Something you have to keep in mind -- as IH "revised" / "updated" parts they increased the r# -- r1 was the first version; rnn were later versions.
My personal point of view is that you need 8 rods with the same part number -- which is what you seem to have.
From a balance perspective (as 71 Scout 2 pointed out), there is probably only 1/2 gram to maybe 2 grams of weight between the lightest to the heaviest rod.
This does not seem to be much, but you will have a "better" engine if the weights are "equaled out"... With balancing
hth
Robert Kenney
Super Moderator
This is where I had /have the problem with the argument that the rods are intended to be interchangeable. How in the heck( self censored) can you say with any certainty that is still true. No one has seen the old rods from 78ih let alone weighed them so how can you say they are still at an IH spec weight.
These statements are absolutely irresponsible and we will not allow them to continue. We can not make statements based on unknown facts. The weights May very well be oem but they May very well not be. Lets error on the safe side.
I bet I can come up with 10 known sv engine builds where the guy has taken a grinder to the small and large end of the rod in an attempt to lighten them. When the crank is bobed and spun the counterweights are then modified to the new lightened rods. How do you think those weights correlate to the IH spec now????? How do you know that the engine in question here is a virgin.
Very few of these sv motors are still virgin and untouched.
The total rod weight is not entirely relevant to a 8v balance. The Bob weight that is attached to the rod journals is a very accurate calculated mass. It is a combination of many things like rotating, reciprocating weights in predetermined factors.
If ya got time to read here is a good write up on balancing a "v" engine. It ain't so simple!! crankshaft balance factors
Very few of these sv motors are still virgin and untouched.
These statements are absolutely irresponsible and we will not allow them to continue. We can not make statements based on unknown facts. The weights May very well be oem but they May very well not be. Lets error on the safe side.
I bet I can come up with 10 known sv engine builds where the guy has taken a grinder to the small and large end of the rod in an attempt to lighten them. When the crank is bobed and spun the counterweights are then modified to the new lightened rods. How do you think those weights correlate to the IH spec now????? How do you know that the engine in question here is a virgin.
Very few of these sv motors are still virgin and untouched.
The total rod weight is not entirely relevant to a 8v balance. The Bob weight that is attached to the rod journals is a very accurate calculated mass. It is a combination of many things like rotating, reciprocating weights in predetermined factors.
If ya got time to read here is a good write up on balancing a "v" engine. It ain't so simple!! crankshaft balance factors
Very few of these sv motors are still virgin and untouched.
Last edited:
- Status