putting a non-supercharged 3800 series II engine in my 84 fiero, is the camaro flywheel already the right balance?

i know its gotta be turned to .840 on the face, but im wondering if it has to be balanced or if its already the right balance since they are both 3800 series II motors.

matthew

the sc motor has a diff imbalance than the non sc, so if ur going to use the non sc flywheel, on a non sc 3800 u dont need to worry about balancing issues

from the best of my knowledge

This week I took a Camaro 3.8 flywheel to a machine shop to have it cut down to 0.840" for a 3800NA Series II (non-SC) swap and the machinist needed the flexplate from the new motor to balance the modified flywheel the same as the flexplate. I anticipated this so I had the flexplate with me. If I were you I would do the same thing.

Best of luck.
Jim C.

[This message has been edited by SeattleRedFormula (edited 03-18-2006).]

it really depends on what your after. If your pretty much doing a stock engine just bold it oun there. You can run a flywheel that is almost 16 grams out before you start to feel it and i doubt the milling process has changed the imbalance that much. However if your planning on doing a lot of mods i would have it rebalanced somtimes on a high HP engine you'll feel a not so perfect flywheel during hard accelaration or high rpm for a long time. If you do decide to have it balance take them your pressureplate and have them do it as a unit, you'll have to do it every time you change the pressureplate but it will be perfect and you won't have to wounder if its your clutch assembly if you do get a little vibration.

pred1tor83 is correct. The n/a camaro 3800 balance is the same as the n/a FWD 3800 balance. However, experience has shown some of the balancing holes drilled into the 3800 camaro flywheel were drilled into the face which means, during machining, these holes will be reduced or eliminated. So some balance-matching may still be required.

-ryan

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power corrupts. absolute power corrupts absolutely.

Custom Computer Tuning | Engine Conversions | Turbocharging | www.gmtuners.com

ok, i got a flywheel from a 1999 camaro 3800 v6, Now i know it says to turn it down to .840, but is that the overall depth of the flywheel, or just the depth of the face?

does anyone have a diagram of what needs to be done, i want the machine shop to do it right the first time.

matthew

the whole thickness of the flywheel needs to be .84" top to bottom.... then you can decide if u want to balance it or not, and the machine shop SHOULD know how to do that!

quote Originally posted by m0sh_man: ok, i got a flywheel from a 1999 camaro 3800 v6, Now i know it says to turn it down to .840, but is that the overall depth of the flywheel, or just the depth of the face? does anyone have a diagram of what needs to be done, i want the machine shop to do it right the first time. matthew

You got that right!!!!!! Do it right the first time. I had to get another flywheel because the machine shop machined it to the wrong dimension or atleast the correct dimension but to the wrong surfaces. Not really sure if I told him wrong or just a mis-communication.
What ever its now .840 from mounting surface at the crank flange to the clutch surface. No charge.

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" DRIVE IT LIKE YOU LOVE IT"

[This message has been edited by ohio86se (edited 03-19-2006).]

I guess I will use this thread as the "information" thread about the 3800NA flywheel vs the 3800SC flywheel. If you remember this subject came up in another thread which has the 3800 FAQ posted I have been working on for some time.

The first thing I notice about people that are suppose to be in the " KNOW " about helping others with correct information.... they should be posting and telling some numbers to indicate they have actually pursued the investigation of said information. Just to show some pictures and say… ‘balance the flywheel because this picture shows a smaller weight’ is useless information. We don’t know how the 3800NA flywheel really is without measuring and understanding the true imbalance built into it.

Lets think about it. If someone is going to tell you the thickness of cutting the flywheel, we expect a measurement in thousands of a inch. We see .840 thrown around all the time. Personally, if you just measure the stock 2.8 flywheel and see that the measurement is taken from the crank flange to the disc surface, this is what we are going to be looking for on the 3800 flywheel so the disc and pressure plate are in the correct location for the slave to do its work releasing the clutch and fully engaging the clutch. I have found .860 gives a better feel to the petal on the 88's. Its only .020 difference here... but when the slave is throwing 1.1 inches, thousandths makes a big difference.

Now about this balancing... I finally went to a machine shop that specializes in balancing flexplates and flywheels for NASCAR type engines. I had them show me exactly what the machine looked like and how it all functioned.

This is where no one else has bothered to provide the information so everyone can be a little more educated in this subject.

The STOCK 3800 SC flexplate will imbalance at 217 grams to 212 grams in 3 flexplates I had with me...

The CUT down version 3800 NA flywheel will imbalance at 194 grams. I only had one cut flywheel with me at the time.

So, what is the percent of 'safe' .... ? Bear racing indicates that there is a 10% tolerance in OEM casting measurements.

So, 10% of 215 grams is 21.5 grams... So, we can be +21.5 or – 21.5 grams if our baseline is 215 from the stock flexplate. Now, I am pretty sure that the 3800NA flywheel is always going to be short on grams, and not ever plus.. We have already seen that NA flexplates have a smaller amount of weight material than the 3800SC flexplates. It is difficult however to know what is going on with the 3800NA flywheel because the weight is cast into the flywheel and extends around the flywheel different than the flexplates.

So, if the CUT flywheel I had at the machine shop was 194 grams, it was within 10%... HOWEVER, Bear Racing indicates that you will feel 20 grams of imbalance if it is wrong.

Now we take 215 – 21.5 and we have 193.5... Oops.... Now we have a 3800NA flywheel that imbalanced 194... This flywheel is off enough that it can be felt with poly mounts at idle for sure. Is it going to knock a bearing out? Bear racing indicates that it is within GM tolerances.

So, I guess I can say that I am very lucky that I have installed about 10 manual applications with no idle vibration to speak of. Now that I know the location of the imbalance needed to be counter drilled, I can do it myself to the tune of about 20 grams. I plan to try this on another flywheel in about 2 weeks to see if my calculations are correct to getting close to the magic 215 grams imbalance.

It cost $100 for imbalance work at Bear machine per unit. I dropped $500 there so you guys had this information.

Loyde

[This message has been edited by FastFieros (edited 03-19-2006).]

quote Originally posted by FastFieros: The first thing I notice about people that are suppose to be in the " KNOW " about helping others with correct information.... they should be posting and telling some numbers to indicate they have actually pursued the investigation of said information. Just to show some pictures and say… ‘balance the flywheel because this picture shows a smaller weight’ is useless information. We don’t know how the 3800NA flywheel really is without measuring and understanding the true imbalance built into it.

Are you incapable of posting in a thread I participate in without taking a jab at me? Just wondering...

quote Now about this balancing... The STOCK 3800 SC flexplate will imbalance at 217 grams to 212 grams in 3 flexplates I had with me... The CUT down version 3800 NA flywheel will imbalance at 194 grams. I only had one cut flywheel with me at the time. So, what is the percent of 'safe' .... ? Bear racing indicates that there is a 10% tolerance in OEM casting measurements.

What? 10% tolerance in OEM casting measurements? 10% of what? "Casting measurements" is a little too vague and doesn't tell us specifically what Bear Racing is talking about here. But one thing is I think is pretty certain: I think it's safe to say GM isn't letting stuff go out the door with a 20 gram imbalance; but if you say so...

quote So, 10% of 215 grams is 21.5 grams... So, we can be +21.5 or – 21.5 grams if our baseline is 215 from the stock flexplate. Now, I am pretty sure that the 3800NA flywheel is always going to be short on grams, and not ever plus.. We have already seen that NA flexplates have a smaller amount of weight material than the 3800SC flexplates. It is difficult however to know what is going on with the 3800NA flywheel because the weight is cast into the flywheel and extends around the flywheel different than the flexplates. So, if the CUT flywheel I had at the machine shop was 194 grams, it was within 10%... HOWEVER, Bear Racing indicates that you will feel 20 grams of imbalance if it is wrong. Now we take 215 – 21.5 and we have 193.5... Oops.... Now we have a 3800NA flywheel that imbalanced 194... This flywheel is off enough that it can be felt with poly mounts at idle for sure. Is it going to knock a bearing out? Bear racing indicates that it is within GM tolerances. So, I guess I can say that I am very lucky that I have installed about 10 manual applications with no idle vibration to speak of. Now that I know the location of the imbalance needed to be counter drilled, I can do it myself to the tune of about 20 grams. I plan to try this on another flywheel in about 2 weeks to see if my calculations are correct to getting close to the magic 215 grams imbalance.

I don't think idle vibrations were the main concern here. 20 grams out-of-balance is something you may or may not feel at 800rpm, but I can assure you that you are going to feel something at 6000+rpms. From reading your post I guess I am a little confused here. On one note you are telling us that a 20gram imbalance is nothing to be worried about. But later on in the same post you say you can probably do the balancing yourself; although you don't have the proper equipment to do so. From your own statements you say you can calculate where to drill holes and how deep to drill them to arrive at the correct imbalance; but earlier in the same post you said GM had a 10% tolerance in casting measurements???!!! So if there is a 10% tolerance across all 3800 flywheels ever produced, how are you going to know exactly where to drill holes to do this balancing yourself on each flywheel without the proper balancing equipment???

quote It cost $100 for imbalance work at Bear machine per unit. I dropped $500 there so you guys had this information. Loyde

You spent $500 to find something out that we already knew just from a mere side-by-side comparison of parts. But hey, now you have provided us with specifcs and I am sure everybody appreciates that. I may not have spent that kind of money on something I already knew was different; but I have better things to do with my money... Speaking of which, when I was in college actually running machines like a crank balancer; we were trained/instructed to get the balance as close a possible. I remember one specific case where I spent about 2 hours to get my 350 SBC crank balanced within 0.5 grams of perfect. Just for giggles, I called around to a few local machine shops today to find out what their recommended specs where when they did balance jobs for guys walking in off the street... 1 gram was the figure I was told. That's right, 1 gram for a balance job for Joe Blow off the street; not race engines.

I think the whole point I am trying to communicate here is if you are going to spend a couple of thousand dollars doing this type of swap; what is another hundred or so to make sure the balance is as correct as possible? I don't know where Loyde is getting his info that 20 grams is "acceptible", but I can assure you the level of quality I am used to working with is a lot more specific than a "10% tolerance". But to each his own, I guess. Perhaps I am just a perfectionist when it comes to this sort of stuff.

over on clubgp, the recommendation is to use the crankshaft balancer from the same engine that the flywheel/flexplate comes from. This may or may not have any bearing on this discussion since I believe we have to machine it in our applications anyway.

I only know that when the machine shop did my flywheel ( both times) they came back with balance hole cut into them. He is very well known in this area for doing all kinds of auto machine shop work including crank balancing. I told him I wanted the flywheel to be imbalance the same as the flexplate that came of my engine. It was my fault I had to have it done twice. Whether it needed to be Im not fully convinced but all I is that he added holes for imbalanace as the the flexplate is making it so the engine wont know what its turning. Its was only $50 extra to do this extra work so go ans have it done. If I didnt have felxplate with me he would have required me to supply him with the complete rotating assy from the 3800sc. im sure what ever was done could not have made things worse.

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" DRIVE IT LIKE YOU LOVE IT"

I'm with darth on this one you will definatly feel a flywheel thats 20 grams out. through personal experiance I've found that 16 grams is about as far out as you can go with out feeling it but because there is a good possibility that your pressure plate is only goin to be balanced down to 10 or 15 grams your more then likley gonna feel a vibration. At work nothing more then 0.0 or 0.1 is accepted on flexplates flywheels or complete rotating assemblys. I also retract my previous statement about not rebalancing, I didn't realize the F body flywheel was balanced on two planes. (friction side and crank side)