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Thanks for the info Jim. I'm definitely interested in things I can do to stiffen the frame. And, this is a good time to make that decision. I'll be checking this out soon.
The seller of my car had purchased a new rear sway bar but never installed it. I was planning on using it. I'll check out the boxed lower arms. Are there any negatives? I've heard before that the factory designed these to flex.

I have decided that I want to buy a GForce transmission crossmember. They are very beefy. That will also help with frame stiffening. Not only is the factory crossmember flimsy, it mounts in rubber at the frame. I'm scratching my head as to why they did that on these cars.
I think the unboxed arms might flex a little, but I don't think you will get much flex out of a boxed lower control arm other than from the rubber bushings. You don't want the rear suspension to be too stiff as it can cause steering issues when you go into hard corners. You can make the suspension too stiff and going with a large diameter rear sway bar can do this as there isn't the weight on the rear of the car as there is in the front to "work" the sway bar.

The rubber mounts on the crossmember are more than likely to prevent drivetrain vibration & noise from traveling to the frame - it dampens it. Some who use the harder polyurethane bushings/body mounts note that the car's interior can pick up more noise when compared to the factory rubber bushings.

The polyurethane body bushing can also help to stiffen the chassis, as would solid mounts. The complaint is that they can "squeak" due to the material used. I went with the polygraphite body bushings which are said to eliminate that issue as the graphite in the bushings acts as a lubricant if the body/frame flexes. I got mine from PST, but can't remember if I got the hardware from them or sourced it as a kit from someone else.

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Oh how much I regret installing poly in my 87 GTA. Once the tires start ageing a bit you start feeling every road imperfection vibrating in the dash. And who owns a third gen transam knows what i am talking about when you mention plastics.

Not to mention the squeaking you get where the bush rubs a body part!!

Will surely never do it again as long as I am not building a track car.
 

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Pontiac was late to the game regarding rear sway bars as Delorean didn't believe in them. They were being installed in Olds A bodies and the Chevelle Z16 as early as 65. It wasn't until 1970 that they were installed across the GM high performance A body lineup.
 

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Discussion Starter #44
The seller of the car gave me these:

He told me the rear one was bought new and never installed.
The other one is a used fatter than stock front bar. He told me what it came off of but I can't recall what but said it would fit. The stock front bar was still on the car when I got it so I have that too.

He also gave me a bunch of new parts to rebuild the front with. Energy Suspension poly bushings for both A-arms, idler arm, ball joints and tie rod ends which are all GL McQuay Norris brand. I see those are made in Taiwan which makes me leary. I always go with Moog and prefer their Problem Solver line. Not sure if those A-arm bushings would squeak or not. I'm kind of leary of using those too. Also Energy Suspension for sway bar end links and A-arm snubbers. He did not have a center-link and it needs a new one. The one I took out was shot.
 

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Discussion Starter #45
I think the unboxed arms might flex a little, but I don't think you will get much flex out of a boxed lower control arm other than from the rubber bushings. You don't want the rear suspension to be too stiff as it can cause steering issues when you go into hard corners. You can make the suspension too stiff and going with a large diameter rear sway bar can do this as there isn't the weight on the rear of the car as there is in the front to "work" the sway bar.

The rubber mounts on the crossmember are more than likely to prevent drivetrain vibration & noise from traveling to the frame - it dampens it. Some who use the harder polyurethane bushings/body mounts note that the car's interior can pick up more noise when compared to the factory rubber bushings.

The polyurethane body bushing can also help to stiffen the chassis, as would solid mounts. The complaint is that they can "squeak" due to the material used. I went with the polygraphite body bushings which are said to eliminate that issue as the graphite in the bushings acts as a lubricant if the body/frame flexes. I got mine from PST, but can't remember if I got the hardware from them or sourced it as a kit from someone else.

!
I've never had a car that came with a crossmember where the frame connections were in rubber before. It would seem a good rubber tranny mount would take car of any drive-train vibration. I put one of those G-Force crossmembers on my '83 El Camino SS and found it superb. It did feel like the it stiffened the frame too.

I've heard some warnings about using poly bushings in rear control arms in that they can cause the suspension to bind. Boxed arms would seem like that would add to the problem. But maybe boxed arms with stock type rubber bushings are OK in that regard. I kept rubber in the rear of my El Camino and did not box the arms. I did install a sway bar, air bags inside the springs and used mono-tube shocks. I am so happy with the way that car feels and rides, I was thinking about going the same route with my GTO. But I may consider boxing the lower arms.

Btw, this is my El Camino and was my last project that I finished 2 years ago. I've owned the car over 25 years and this was my second refresh go around with it.

 

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I've never had a car that came with a crossmember where the frame connections were in rubber before. It would seem a good rubber tranny mount would take car of any drive-train vibration. I put one of those G-Force crossmembers on my '83 El Camino SS and found it superb. It did feel like the it stiffened the frame too.

I've heard some warnings about using poly bushings in rear control arms in that they can cause the suspension to bind. Boxed arms would seem like that would add to the problem. But maybe boxed arms with stock type rubber bushings are OK in that regard. I kept rubber in the rear of my El Camino and did not box the arms. I did install a sway bar, air bags inside the springs and used mono-tube shocks. I am so happy with the way that car feels and rides, I was thinking about going the same route with my GTO. But I may consider boxing the lower arms.

Btw, this is my El Camino and was my last project that I finished 2 years ago. I've owned the car over 25 years and this was my second refresh go around with it.


The boxed control arms is not necessarily about making them stiffer. They are boxed so when you install the sway bar and run the bolts through the arms and tighten them, they don't crush.

You could use stock arms and cut a length of tubing to insert in between the open bottom/sides of the arms so when you tighten them, the tube will keep the sides of the control arms from folding in when you tighten the through bolts.

You can buy a kit to box what you already have as well:

 

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Factory front bar is 1" in diameter for 68-69 GTOs. 1 1/8" was stock for the 70. Thats the limit I would go without modifying the front bar frame mounting holes for the 1 1/4" or larger bars.
7/8" was the stock rear bar diameter for 70-72.
The front suspension really sucks on the 64-72 A bodies. The best thing you can do is to add some quality tubular upper A arms that will relocate the upper ball joint with adding a 1/2" taller upper ball joint to really improve the suspension geometry. Even adding the tall BJ to stock arms is an improvement . I do feel rubber or Delrin bushings are fine for the street.
The lower arm is known to crack around the ball joint area and needs a thorough inspection.

Center links are available from MOOG and Proforged. The Proforged will be a better fit with the grease fittings in the right places. Moog has moved a lot of production overseas to India and other Asian countries. The construction appears to be the same as before but I was a little wary of their ball joints. I bought mine from UMI.

My rear axle guy wanted to install polys in the upper arm mounting ears of the axle. He has seen a number of rubber bushings begin to crack and fail after 3 or 4 years which he attributes to poor rubber quality. I had him install roto-joints instead which with will allow the axle to float some rather than bind up. I kept the rubber bushings in the upper and lower arms to keep the noise and vibration to a minimum although I haven't made up my mind yet whether to install roto-joints in the axle end of the lowers too.

Last time I looked, AMES still carried Genuine GM rubber pads for the crossmember. I would imagine the rubber quality is better than the aftermarket.





Roto-Joints

1E670FFA-C596-402A-AD2E-E342CD65B97C_1_201_a.jpeg




Rear Crossmember Reinforcement Brackets

57DD9872-50AC-4D6A-9510-9E1501623589_1_201_a.jpeg
 

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Discussion Starter #48
Thanks for all of the advice. I will continue to process and figure out what I want to do. Just measured the sway bars I've got. My stock front bar was indeed a 1". The used front bar I got from the seller is 1 1/4". The new rear bar I got from him is 1".

I'm not looking for extreme performance but maybe some improvement and a good ride. I won't drive this car that hard. Mostly cruising and some highway travelling.
For that reason, I think I'll stay with the stock A-arms in the front. I did some research on these Energy Suspension A-arm bushings I have and they say if you use their grease with them, they won't squeak. Also did some research on the McQuay Norris parts I have and it appears they are good quality. My inclination now is to use all these parts. Only thing I need to buy is a center link.

My inclination right now on the rear is to go ahead and get that boxing kit to box the lower arms and use rubber bushings on both uppers and lowers. I will want to get the best quality there is for those. I also think the control arm braces are something I will do.

Pretty certain I want to get the GForce transmission crossmember. I don't like the idea of the rubber mounts for the stock one at all. I think this adds a very large amount of stiffness to the frame. I am thinking that I will stay with rubber body mounts but again will want to get the best quality out there for them.
 

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If you're going to use the 1 1/4" bar I highly recommend that you modify the mounting brackets to frame mounting holes. The threaded frame holes are very thin and only have a few threads to hold the bracket bolts. The bigger bar places more stress on these threads with the end result of having the mounting bolt fall out. Had this problem with my 70 SS El Camino.
The fix is to have a 1/4" flat stock pre-drilled and threaded to match your mounting bracket bolt spacing. Insert the bar into the frame from the front. Hold in place with the mounting bolts.
You will also find that the mounting brackets for the bigger bar are of course bigger to fit the larger bushing and may or may not match up to the frame holes. The 1" bar brackets will not fit the 1 1/4" bushings. The aftermarket brackets are slotted and do not have this problem.
 

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Discussion Starter #50
Appreciate that advice. I may start out using the stock bar and decide if I think it's OK or not before going any further.

An update today:
While cleaning up my shop and organizing parts today, I decided to remove the axle bearings from the axles that I had on the floor. It was the last thing I hadn't dismantled.

Not good news. At some point in the past life of this car, the d/s axle bearing had seized and it scored the axle. The bearing was replaced anyway. Once I split and removed the retaining ring, the bearing was loose on the axle. It also appears to me that this got very hot when that bearing failed.
You can see the smaller diameter on the axle where the bearing sits. Strange looking pits too:


Pretty sure that even though the bearing hadn't failed on the p/s axle, the owner at the time decided to replace that bearing too. It was an identical part. The mechanic didn't do a great job as you can see the mark he made right in front of where the seal rides:


This axle is Ok to use though. But I can't in good conscience
use the other that had the seized bearing. I'd appreciate some advice here.
Look for a used original or buy a new aftermarket axle? Or replace both with new aftermarket axles? In all the cars I've had I've never had to replace an axle before so this is new territory for me.
 

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Tom's Kick Ass Axles is where I bought my axles from for my Elco. It's axles looked like yours.
American made and very good quality.
I bought new studs too.



6A97E3B7-6B10-44BA-BD97-EA15E70FCD72.jpeg
 

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Discussion Starter #52 (Edited)
That's where I've always bought my rear end parts. Unfortunately Tom passed away a year or two ago. Before he passed, he tried to sell the business but there were no takers so he just liquidated the inventory.

Edit:
The web address you provided is working. Maybe someone did buy the business. But the catalog does say 2017.
 

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I heard the family has continued the business. The website is new since I last visited a few months ago and it is dated 2020 for what's its worth.
 

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Discussion Starter #54
I just ordered a set of the Yukon axles that are 1541H Alloy.
Now I'm trying deciding on where to buy the rest of the parts I need for the rear.

I'm now thinking about going with 3.55 gears instead of using the stock 3.23. I think it will be a little bit better of a match with what my plans are.
I've already have a new Lunati 60902 cam and lifters that the seller gave me. I like the specs on this cam. SPECS
My tire diameter should be 27.5" and I'm planning on a 200-4R automatic and an Edelbrock Pro Flo 4 mpfi setup.
I calculate that a 3.55 rear would yield just a touch over 2,000 rpm at 70 mph. The 2.74 first gear would also give a 9.73 torque multiplication which I think would be good using a normal converter rather than a high stall.

I am also going to order an Auburn Gear posi carrier for it. I've had good luck with them. I'm also going try and find new Timken bearings for the pinion, carrier and axle bearings.
 

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Do you plan on lowering engine compression? That cam would be better for a 9.0 compression engine. I would not use it in a stock compression 400. The 112 LSA may build more cylinder pressure and thus suited better for a low compression.

3.55's would be a good choice. I assume the torque converter has some slip or is it lock-up? I am not familiar enough with these. If it has a little slip, then you'll be hitting 70 MPH a little over 2,000, maybe 2,200 RPM's which should be good.
 

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Discussion Starter #56
Yes. The seller also provided me with new pistons and told me he figured about 9.0. He's an experienced mechanic and I didn't doubt him on it.
The pistons are 40 over and block has been bored but not final honed. The seller also gave me new piston rings ready to put on. The heads have all been redone and were not milled. The block was not decked.



Here's a link to the piston specs:
Keith Black KB Performance Pistons KB346-040

The rings are Mahle 11D04CD1
 

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Discussion Starter #57
Hoping to hear from you Jim. I'd appreciate your comments on the info in my last post.

New updates:

So as I said, I have new Yukon axles on order. I have already received the Auburn Gear posi unit. Everything else for the rear should come in early next week. I ordered a complete differential kit by Standard Gear which includes seals, gasket and Timken bearings for the carrier and pinion. Also on order are a Dana 3.55 ring and pinion gear set and Timken axle bearings and seals.
I called the guy I've used a few times in the past to set up my new gears and that's a no-go. He's 81 and not doing these anymore. I'll have to find somebody new. Got a few leads.

I did visit the guy that's done upholstery for me in the past and he agreed he would do the seats for the car and the convertible top down the road when I'm ready for that. He said call him after the first of the year and he should be ready for me to drop off the seats.

I got all set up to be ready to start blasting the frame. It might not be tomorrow as there is a 20-30% chance of rain. If it rains, I've got another tarp to keep the frame from getting wet. I'll also need to keep an eye on the weather to make sure it's a good temperature to be spraying epoxy primer. Once I get the frame blasted, I don't want it to sit for very long before spraying. It needs to be above 60 to spray SPI epoxy and I'll need to have it sprayed early enough in the day so it's dry enough to move into the shop. Can't let it get below 60 for the first 48 hours after it's sprayed. Right now the forecast from Saturday going forward looks really good to be able to get it done.

 

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Discussion Starter #58
At about 10:30 AM I decided it looked like it wasn't going to rain today. So I got started with blasting the frame. My wife got a couple of photos of me in action:


Late in the day my neighbor stopped by again. He said he could tell by how much my compressor was running that I must be blasting today. And again, great timing I just completed getting it 3/4 completed and needed help to turn the frame over.
So I'll be ready to get the frame blasting complete tomorrow.



Just for an fyi, I used up about 2 - 50 lb bags of blasting media to do what I did today. I used the coal slag called Black Diamond that Tractor Supply has for $9 a bag. I also reclaimed what I could sweep up from the concrete twice.
 

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At about 10:30 AM I decided it looked like it wasn't going to rain today. So I got started with blasting the frame. My wife got a couple of photos of me in action:


Late in the day my neighbor stopped by again. He said he could tell by how much my compressor was running that I must be blasting today. And again, great timing I just completed getting it 3/4 completed and needed help to turn the frame over.
So I'll be ready to get the frame blasting complete tomorrow.



Just for an fyi, I used up about 2 - 50 lb bags of blasting media to do what I did today. I used the coal slag called Black Diamond that Tractor Supply has for $9 a bag. I also reclaimed what I could sweep up from the concrete twice.

Saw your post over at PY and the answers you got on the engine parts. The D-dish pistons are fine as I recall they were 14CC's which is used to lower compression based on the heads you are using, the #16's which are said to be 72 CC's, but could be more or less a few cc's due to the valve job and valve choice. The only way to know with 100% accuracy would be to CC the heads yourself or let a shop do it. I have a post that describes how to CC your own heads for cheap. Then you will know exactly what you have and can use that number to better achieve an accurate compression number using the Wallace Compression Calculator.

If you KB pistons are similar to mine in deck height, my pistons were .020" down in the hole - which you can use in the Wallace Calculator. The thing you want to do is get a good quench number of .040" between the flat piston top area of that D-dish and the flat area of the head that surrounds the combustion chamber. Knowing what the pistons are down in the hole, which can be measured once the pistons are installed and you get one of them up to TDC, you can then decide what head gasket thickness you might want to go with to get that quench nearest to 040". From my reading, anything under .060" is acceptable, but not optimum, with .040" your best number. Some will go tighter, but that makes me nervous as parts get worn. I have my pistons set at a .047" quench which I am fine with.

One guy mentioned he did not like your lifters. The lifters, depending on manufacturer, have different C-clips that hold the guts together and inside the lifter body. The factory lifters use a simple wire style C-clip. The better hi-performance lifters will use a snap ring style clip. I have included a photo that shows you. The lifter on the left has the wire type and the lifter on the right has the snap ring type. It is said that if you like to rev your engine high, that the wire type clips can pop out whereas the snap ring type will hang in there and stay in place.

The roller tipped rockers should be fine. I have a set going on my 455 build. However, over on PY the complaint seems to be that the rocker ball does not seat/fit well in the rocker arm cup. I have not examined mine to confirm or deny that statement, but will take a look at mine. I think I might paint the rocker ball and rocker cup using a black Sharpie, then insert the rocker ball and move it about and see what kind of wear pattern I see. If I see a bad pattern where the two are not meshing well, then the PY guys may be correct and I may not use them. Sometimes problems do arise and it could have been an early batch when they were first introduced - I don't know. Many use them, so how bad can they be off? I did use the Comp Cams 1.5 stamped rockers on my previous 400CI build and these are stronger than factory and have a more accurate/consistent 1.5 ratio that the factory rockers did not. They also have the grooved rocker arm balls which I prefer over the factory smooth surfaced rocker arm balls. So I would not hesitate to use these should the roller tip rockers not meet my expectations.

You will most likely be able to use the factory length pushrods, but always a good idea to check your rocker arm geometry to make sure the rocker arm is hitting the center of the valve stem tip and not off center too far back or forward.

The frame looks good. I too used the Black Beauty and did my best to recover what I could using the tarp method you are using and then sifting the sand and re-using it. I seems to me that it cuts better first time around and after a second use, time to just not re-use it and toss it. I have the same set-up, but after using the pressurized tank for some time, tips will of course wear out, the hose cracked and split, the sand flow valve wore out, and any kind of moisture that gets into the tank with the sand will clog it up - and then the fight is on. LOL I have capped off the air supply that pressurizes the tank at the top and just use the blaster in a conventional manner as you would one of the inexpensive open canister type sand blasters. I still tighten the top cap which seems to take on some pressurization which makes the sand then flow and I can blast my part.

Lifter C-clips.JPG
 

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Discussion Starter #60
Thanks for the info Jim. I'll respond to you later regarding it.

Finished blasting.
Total blasting time including reloading the blaster was about 8 - 9 hours. Consumed 2 1/2 bags of Black Diamond media. I never discard media. What I do is add about 25% new to what I reclaim. Been doing it that way ever since I started using this blaster and it's always seemed to work well. These blasters are finicky but once you get a procedure down that works for you, they work really well. It sure can be frustrating at first and patience is required.
I don't know if it will be warm enough tomorrow to spray the epoxy primer. If the temperature of the frame gets up to 65 degrees early enough in the day, I might be able to do it.
Almost looks like it's painted gray when in the sun but it's just blasted steel:


Headed out now to clean up the mess and reclaim the media.
 
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