[ITSBACK]

Interesting situation. I bought my 428 as an unfired rebuilt motor. It is a 68 428HO 390hp motor. I changed the heads to a set of Paul Spotts ported #62 heads with the chambers opened to 82cc that according to Paul flow at least 250 and a Crower 60243 with 1.65 roller rockers and a 66 tripower. Stock rods and KB hypers and deck height is .025 in the hole.This motor had a flex plate on it which I didn't think ahead enough and removed and sold it at a swap meet as my car is a 4 speed car but now is a TKO 600.
Here's the problem. I got rid of flex plate and have nothing to balance flywheel. I ordered new flywheel from SD and I can just put it in and try it when car is all done and it may be OK but it may not. Spoke with Dave through emails and he pretty much has confirmed what I kinda figured may be the case. It might work and it might not. At the moment the motor is in the the rolling chassis, which is easy to remove and install as opposed to when the car is all together and its a pain in the ass. I spoke with motor guy and he said anywhere from $700-$800 as just a short block if nothing is needed. I can take it all down and reassemble it myself which will be cheaper. I hate to have to pull it apart but what's the popular opinion, do it now or maybe later?

[72LuxuryLeMansLa.]

Originally Posted by ITSBACK

Interesting situation. I bought my 428 as an unfired rebuilt motor. It is a 68 428HO 390hp motor. I changed the heads to a set of Paul Spotts ported #62 heads with the chambers opened to 82cc that according to Paul flow at least 250 and a Crower 60243 with 1.65 roller rockers and a 66 tripower. Stock rods and KB hypers and deck height is .025 in the hole.This motor had a flex plate on it which I didn't think ahead enough and removed and sold it at a swap meet as my car is a 4 speed car but now is a TKO 600.
Here's the problem. I got rid of flex plate and have nothing to balance flywheel. I ordered new flywheel from SD and I can just put it in and try it when car is all done and it may be OK but it may not. Spoke with Dave through emails and he pretty much has confirmed what I kinda figured may be the case. It might work and it might not. At the moment the motor is in the the rolling chassis, which is easy to remove and install as opposed to when the car is all together and its a pain in the ass. I spoke with motor guy and he said anywhere from $700-$800 as just a short block if nothing is needed. I can take it all down and reassemble it myself which will be cheaper. I hate to have to pull it apart but what's the popular opinion, do it now or maybe later?

I am no expert but here is what I would do. Take it down, ditch the stock rods and Hypers for forged parts and balance it all. I would also zero deck it. It's just me but I will not build a short block without forged rods and pistons, zero decking and balancing.
At the very least it must be balanced!

[track73]

Here's a thought. I have a '56 Buick Special. In the factory Buick engine repair manual, it says to rebalance an engine in the car (322's were externally balanced) you can take out clutch bolts one at a time and use longer bolts and add washers to them. Do that around the clutch until you find the sweet spot. When you hit the spot where it runs the smoothest, drill the opposite side and reinstall the original bolts. This may take some tinkering but it will save time and money if it works. Before computerized balancers, we used to balance tires with our Hunter balancer and our ear on the fender. From what I learned from HO, Pontiacs are externally balanced to 5 inch ounces.

Now please you purests, please don't rag on me I'm just giving an opinion.

[ITSBACK]

I have a set of H beams I was saving for my other 428, with is a 67 428HO 4 speed motor which is already machined .030 with new can bearings and freeze plugs installed. The plan for that one is SD Old Faith full and have them port the original 670's. Maybe sell this short block and buy forged pistons and just do the 67 motor now.

[geeteeohguy]

I would simply take the new flywheel down to the machine shop and have it zero balanced for $40. Bolt it on and go. No worries.

[ITSBACK]

Dave said the new PRW flywheels come with a bolt on weight. To have a neutral balance flywheel you take off the weight. He said they sometimes still need to be tweeked a bit. But if the motor was externally balanced wouldn't a neutral flywheel result in an unbalanced rotating assembly? It would be great if I knew it was internally balanced. The builder supposedly builds circle track motors so you suspect he did some sort of balancing.

[geeteeohguy]

If the new flywheel has a weight on it, it probably already is zero balanced. Zero balancing is just that: no heavy side/area. Easy enough to check. And a zero balanced flywheel can't mess up the rest of the balance job, unless the old flywheel was weighted to compensate for the rest of the rotating assembly. I guess that's the $64 question.

[Half-Inch Stud]

Have the flywheel & Pressureplate combo balanced, no offset.

leave the clutch at home.

[Matt Meaney]

if you take the oil pan off, you will be able to see how the engine was balanced. check the pads on the piston (where the pin goes through) for drill marks/ weight removed. also check the pads on the caps of the rods for machining. usually the piston and rod that are the lightest are left alone and the heavier ones are lighted by taking away metal to match the lightest. then look at the crank counter weights for weight taken away or added. then if the harmonic balancer is untouched, chances are really good it's been internally balanced. put a zero balanced fly wheel on and your done.

[ITSBACK]

Well the plan at this point is to break it down and get the rotating assembly balanced with the new flywheel and balancer. The first thing I will do though is remove the oil pan and take a look at the internals to see if any material has been removed from the pistons , rods, or crank. The motor did not have a balancer on it when I picked it up. I appreciate all the info. When I finally get to it I will update the post.

[lust4speed]

Have to disagree with most of you. I've had engines balanced both internally (zero) and externally depending on what they were going in. Either balance requires the pistons to be equalized in weight if the balance is done properly. There's a chance that heavy metal would be used in the crank weights for a zero balance, and this would be easy to spot.

I would lean towards this engine still being externally balanced since the builder retained the stock rods, and it appears to be a fairly stock build. Any possibility of contacting the builder? He probably has a habit of doing all builds the same, and even if he doesn't remember this exact build, he might confirm the method he always uses.

[steve25]

Pull it apart and do it right, its the only way to change out the more than likly weak stock oil pump drive rod anyway!
Look at it this way, one small slice of gasket or silicone gasket maker left in the pan will surly at some point get stuck in the pump bypass ball, and then your not only pulling the pan off, but yankin the motor to pull the pan amd work like a a Human!

[c sheeder]

Pontiac engines were all internally balanced from the factory.....most machine shop try to keep it balanced the way they were........u should have a neutral balanced harmonic balancer and your fly wheel or flex plate will b neutral balanced also.....IT IS INTERNALLY BALANCED

[lust4speed]

Whoops, Pontiac engines were all externally balanced from the factory. Pontiac did use a neutral balanced damper on the front, but used the flywheel/flexplate to complete the engine balance.

[c sheeder]

Lust for speed u r wrong pontiac engines were INTERNALLY BALLANCED from the factory....I have built several Pontiac motors....have had harmonic balancer issues on stock engines......the flywheel and balancer a 0 balanced because they r internally balanced.....check it out call Paul Spotts or butlers....the majority of the Pontiac engines were internally balanced....u need to do a little more research.....

[GOAT WHORE]

Originally Posted by c sheeder

Lust for speed u r wrong pontiac engines were INTERNALLY BALLANCED from the factory....I have built several Pontiac motors....have had harmonic balancer issues on stock engines......the flywheel and balancer a 0 balanced because they r internally balanced.....check it out call Paul Spotts or butlers....the majority of the Pontiac engines were internally balanced....u need to do a little more research.....

Pontiac flywheels/flexplates from the factory had a 6oz/in imbalance in them.

[jonmachota78]

Originally Posted by c sheeder

Lust for speed u r wrong pontiac engines were INTERNALLY BALLANCED from the factory....I have built several Pontiac motors....have had harmonic balancer issues on stock engines......the flywheel and balancer a 0 balanced because they r internally balanced.....check it out call Paul Spotts or butlers....the majority of the Pontiac engines were internally balanced....u need to do a little more research.....

Are you talking about those cheby motors with the pontiac valve covers??

[AG]

Stock motors are externally balanced like goatwhore said, slight enough where it is very easy to internally balance when using lighter aftermarket parts without any mallory metal. I've never had to use mallory even with stock rods and heavy TRW pistons.

[MrWrestlingII]

Here's a quote from Mr. P-Body (Jim Lehart) in an old thread along with a couple of links with some good information he provided on balancing...

A Pontiac is not internally balanced. There is a slight imbalance at the rear (about 6"-oz.). You can clearly see the factory "balance" when you look at a flexplate. There are a series of smaller holes on one side, not there on the other side. Unlike Chevy and Ford, Pontiac removed material from one side, rather than add material to the "other". That being said, it's not difficult to "convert" the Pontiac to internal, recommended only for racing. If "external", the balancer and/or flexplate/flywheel must be attached during the process. For the Pontiac, no need for the balancer, but definitely the flywheel/flexplate.


http://forums.maxperformanceinc.com/...=balancing+101

http://forums.maxperformanceinc.com/...01#post4211898