[TRADERMIKE 2012]

Originally Posted by Kenth

Offset piston pins reduce piston slap and decrease thrust load, NOT the opposite.
Reverse the pistons and you´ll get piston slap and increased load on thrust side.

Mike wants to know:
Would I be wrong if I took the Piston off the Wrist Pin and reassembled them correctly?

Can I remove the Pins with my Bushing driver kit or do I need to press them out?

I might be able to remove the wrist pin using the drivers in the bushing removal kit with a small Hydraulic jack using stuff in the shed?

If I can't remove the Pins, I will take them to the Machine shop that repairs the Heads.

Why would a racer get more HP by pointing the notch backward?

[TRADERMIKE 2012]

Originally Posted by Jay S

Was the engine in question using oil? I would leave the short block alone if it is ok.

You said:" I reverse hung the pistons to reduce the force on the piston skirt on the thrust side. Especially on cast pistons in performance builds".

Mike wants to know: With my original Pistons, could this be the reason for the notch installed toward the rear?


I have honed out a ton of 10K mile engines that were using oil, that had the correct piston orientation, honed them, with new rings, and then the oil consumption stopped and ran for years. Sometimes the rings do not brake in correct or bore are not straight after engines are bore out.

I have hung Pontiac pistons on backward, and done other brands also, I never remember one using oil? Maybe I am just lucky, but I have done a lot more than one engine with the pistons reversed, several 455 Pontiacs too.. I reverse hung the pistons to reduce the force on the piston skirt on the thrust side. Especially on cast pistons in performance builds. These days, with modern pistons, there is no offset most of the time, I don’t even think of it.

I bought this second-hand project with plenty of miles, it was not running when it was installed in the 1979 Pontiac TA. We manufactured a custom wiring harness for under the hood off the schematics in the book ourselves. Since I got this Engine running, I have only less that 10 k miles on it over the last 10 years. It runs strong and I recently discovered a noise in it. I still have not found the reason for that noise. The Engine never smoked and is clean inside, we installed new Valve guide seals both on the Exhaust and umbrella seals on the Intake side. We suspect reverb in the exhaust Manifold could be the culprit, since there were dime size holes in the crossover block off plugs that we installed during my ownership. We believe that we caused this by running this engine in the tent cover outside were it lives, when we inserted 4" dryer type hose over the 2-1/2 exhaust pipe with metal tape and ran a 10' length outside the tent so we would not smell fumes while we ran the car. We think we blew the dime size holes in the crossover plugs @ that time. This is when the change in Motor sound started. The car has been off the road for 2 years and we rebuilt the Trans. during that time. Now that we are on the road testing and tuning the Trans. and getting the bugs out of the rebuild, the Trans is great. For all I know the noise is gone once I install the new crossover block off plugs that keep the heat from under the center carb. on my Tri-powers. We found no metal in the crank area; we opened the oil filter and found no metal there either. We pulled the Heads and they need Exhaust seats.

What I need to know is if the noise is gone with the work that I have already done, how would I precede here? Do I just take my chances and assume that the reverb was the noise and just live with the Piston being backward and enjoy the extra HP? Put the degree wheel on the Engine and send the Heads out and put it back together? This is what I was just going to do. I think there are miles left on the bottom end yet that I would like to milk out for another 50 k miles? I think the rings are good for now too. The Heads seem to be the very necessary part at this time for them to be repaired. The Piston walls have .005 - .010" clearance between the Piston and cylinder wall, is that good? The Cylinder walls are not scratched and last time I measured the CR with and without oil it was fine. The long-term plan is to use this engine up, rebuild it and sell it to someone that needs a stock 1967 YK code 428ci HO engine with the Tri-power option and use that money to purchase a modern motor for this Vehicle.

[Cliff R]

No, you can NOT press or drive the pins out of the pistons at home with a punch and a BFH. This requires a press and piston holding fixture to keep from destroying the pistons. Even with a "cradle" under them sometimes they still get damaged and need replaced.

Two things. Since the engine needs all this work, pull it out of the vehicle and put it on an engine stand. It takes about an hour to pull it, then minutes to take it all apart and find out what' s going on wit h the rods and pistons. They may simply be installed backwards in the block and you can move them to the other bank and the notches will now be facing the correct way, plus the offset wil improve ring seal as it side-loads the pistons as the engineers intended.

Doing all this work laying over the fenders is at least 10 times MORE diffciult, and now you need to jack it up and pull the oil pan to get the pistons out. At that point it's 85 percent out anyhow, so just go ahead and pull it out the rest of the way so you can effectively clean everything up before putting it back together........FWIW......

[Jay S]

Reverse hanging pistons has been tested and done over the years by lots of big names, David Vizard, Joe Sherman, Smokey Yunick, most recently Motor trend engine masters. Richard Holdener.

There is supposedly a slightly difference in acceleration at some RPMs. There has never been any quantitative numbers that show an increase or decrease in anything when it come to piston offset though. It is pretty much all BS.. Engine masters did an engine where they pulled all the pistons out and moved each piston and rod to the opposite engine bank. With dyno pulls before and after, and got the exact same numbers, with in 1 HP! No honing, rings were not changed, no changes other than moving the pistons to the opposite bank. It did nothing.

If it was not using oil before, I would not change the pistons to the other direction. If it had a rod knock you will have the pistons out anyway. Do what ever you want, change them back to stock, leave them reversed, I don’t think it matters. The piston orientation did not cause any of the current issues.

I have never been able to hear a difference in piston slap. I think on some engines i hear a slightly difference in the exhaust tone with the pistons reverse hung. But how do you quantify that…you really can’t..

[track73]

I would try Rhodes lifters. The best of both worlds., plus an easy fix..

[Jay S]

I think you have (a little) more risk of having an issue down the road by removing the pressed fit pins to change the way the pistons are hung than you do if you let them be. Personally I would only change than back if the pistons were free floating.

[78w72]

Connecting 4" dryer hose to 2.5" exhaust pipes wont cause any problems with back pressure, its almost 2x bigger than the factory exhaust pipes, mechanics/shops use extension hoses on the exhaust like that all the time during the winter months when they need to run an engine inside the shop... nor will it blow out exhaust crossover filling from reverberation. block off plates are known to get blown out just from the normal exhaust gases over time.

[track73]

I would try Rhodes lifters. The best of both worlds., plus an easy fix..

[Skip Fix]

My first 455 with the RAIV heads the machinist swapped the pistons on purpose. He was an old Pontiac NHRA Stocker and felt that helped make a little more power.

[Stan Weiss]

Originally Posted by Skip Fix

My first 455 with the RAIV heads the machinist swapped the pistons on purpose. He was an old Pontiac NHRA Stocker and felt that helped make a little more power.

Skip,
Back in the day that was SOP on an NHRA Stocker.

Stan

[Kenth]

Originally Posted by Jay S

I think you have (a little) more risk of having an issue down the road by removing the pressed fit pins to change the way the pistons are hung than you do if you let them be. Personally I would only change than back if the pistons were free floating.

Switch banks on rods and pistons assemblies reduce the risk to zero.

[Jay S]

Originally Posted by Kenth

Switch banks on rods and pistons assemblies reduce the risk to zero.

Yep!

[TRADERMIKE 2012]

Originally Posted by track73

I would try Rhodes lifters. The best of both worlds., plus an easy fix..

Please send me a video clip of your motor with the road's lifters, so I can determine whether or not I can stand the different noise they incur!

[TRADERMIKE 2012]

Originally Posted by Kenth

Switch banks on rods and pistons assemblies reduce the risk to zero.

I am Glad to hear I can do that, so, I don't have to remove the Pistons at all from the Rods, thank you for that heads up idea!

[TRADERMIKE 2012]

Originally Posted by Jay S

I think you have (a little) more risk of having an issue down the road by removing the pressed fit pins to change the way the pistons are hung than you do if you let them be. Personally, I would only change than back if the pistons were free floating.

Naturally your proposal is my easiest way out, If I can be sure that the noise that I experienced in the Engine was caused by reverb (read the entire post) ,then I can move on and live with the reversed Pistons, all I want is to drive the last miles out of this Engine. The Head work should be the main thing for me to do at this time. When I put the Engine back together, I plan on blocking off the crossovers at the Heads. Can someone explain the reverb (I think) I heard/noise in Engine. Since I have Headers to collector and no cross over "X" beyond the collectors, no mufflers and the exhaust exits the Diffuser and then the dual Tail pipes.

I fear that the only way I am going to know if there is still a noise in this Engine is to assemble it and run it, in hopes it was only reverb that I caused myself. Has anybody had experience in this reverb area that I think That I experienced? Remember prior to the Trans breaking, I had no noise in the bottom end, then I rebuild the Trans. and install it, then test the vehicle Trans, get the bugs out of the Trans. and then I hear the lower noise. The Heads get pulled; the crossovers have dime size holes in them.

I think when the vehicle was taken off the road after realizing the Trans. was shot and we innovated the exhaust tailpipe extension using a 4" dryer metal hose adding 10' to the overall length, then taped the extension to the exhaust pipe, we caused the back pressure to blow out the crossover plugs @ the Head. We clearly heard the sound difference after running the car in the tent say 5 times. So now I test-drive the car, not knowing there are holes at the crossovers and Wala, a new noise suddenly manifests itself... I will say it again, This Engine has a strong bottom end and after installing the TH 400 rebuilt and test and tunning numerous times ran stronger and stronger as we eliminated the Trans. bugs.

Thus, the Heads were not yet removed while testing the vehicle that have holes in the crossovers. So, I feel that if I send out the Heads for rebuilding and install a complete gasket set and install the block off plugs at the exhaust plugs at each Header problem solved, without touching the lower end yet. I like to fix one thing at a time so I know what fixes what. Don't get me wrong, I could pull this motor, but only if I have to. The other thing that I am Leary about is rebuilding the upper end, as I have changed all the removable wearing parts already, plus, the Heads complete the top end build correctly, is spinning the bottom of the motor. I can't tell you how many times that I have heard that occurring?

So, the real question is what do we all know about reverb and the correct way to assemble an Exhaust system. Since I left out the crossovers past the collectors and did not install the mufflers and used the dryer hose etc... just mistake after mistake causing an anomalous noise in this engine? Also, when building the TH 400, I had to make many choices along the way as I am doing now, one more hurdle to leap, usually my intuition is the best thing to go by. All your help is very valuable and I thank you all for your input. Never say never and never say allways...

[TRADERMIKE 2012]

Originally Posted by Stan Weiss

Skip,
Back in the day that was SOP on an NHRA Stocker.

Stan

What is "SOP"? Plus, the person who originally rebuilt this Engine, post factory, knew what they were doing, now that I hear things like this!

Here is what they did:
(1) Pistons on backwards, a racer thing.
(2) Water Jackets are blocked in certain areas along the Block only, did not see any ones blocked on the Heads. Pontiac modification, for lack of better terms!
(3) This 1967 Pontiac 428 ci HO is supposed to have a Quadrajet Carb., However this one uses the 1966 Intake and Tri-power ones!
(4) Should have a 066,067,068 type Cam, this came with the 1956 only Tri-power Cam, that can only be purchased over the counter, generally racers would know this!
(5) This Block bears special #'s and letters, by the second builder, on the P.S front left side of the Head, upside down and along the left edge. STANDARD OPERATING PROCEDURE, JUST FIGURED IT OUT ,THANKS

[TRADERMIKE 2012]

Originally Posted by 78w72

Connecting 4" dryer hose to 2.5" exhaust pipes won't cause any problems with back pressure, it's almost 2x bigger than the factory exhaust pipes, mechanics/shops use extension hoses on the exhaust like that all the time during the winter months when they need to run an engine inside the shop... nor will it blow out exhaust crossover filling from reverberation. block off plates are known to get blown out just from the normal exhaust gases over time.

Good to know on one end bad on the other, might mean I have another problem.

I will ask this: Since after taping and sealing the connection from the Exhaust tips to the 4" metal dryer hose, we eventually heard the Engine make a different sound and when we added an additional rubber to plastic material from a lawn type blower to the end of the metal hose about another 6', the diameter was greater, than that of the 4" metal hose and that was also taped together using metal duct tape as well. Combined 16' approx. length made a change in motor sound, I quickly stopped this procedure, I originally thought that I may have disturbed the Exhaust Valve seals? Note: I had replaced the Valve seals within 10 k miles that I put on this second-hand project. It is unknown what the full mileage is on this engine?

So, could you explain to me "what the difference in motor sound" occurred while I had the dryer hose attachment installed and why I all of a sudden heard a different sound that doesn't belong after test driving this vehicle on the road, without yet discovering the holes in the crossover plugs?

[Cliff R]

Your logic is flawed some when it comes to getting this engine up and running well. Although you are getting a LOT of good advice here, this is what needs to happen.

Pull the engine, remove the pan and swap the pistons/rods so the notches are toward the front of the block.

The engineers at Pontiac knew more about this that anyone else and they offset them for a reason. I can tell you from accidentally installing a set backwards 40 years ago that EVERYTHING get better when you put them in the RIGHT DIRECTION. The testing done by a few good folks over the years did NOT include putting 100,000 miles on a 406 SBC in a K-5 Blazer with the first 10,000 miles having the pistons in the block with the offset the WRONG direction. That engine from day one just didn't run right or sound right. It was one of those things with this hobby that you just can't put your finger on and leaves you wondering what was missed during a pretty expensive engine build. I had NO IDEA whatsoever what was wrong with it, so yanked it back out and after hours of examining everything scattered all over a work bench I found the issue. The HY-DUTY pistons I bought were all facing the WRONG direction in the block....BINGO!! Nailed it! Back together and FLAWLESS for another 90,000 miles!!!!!!!!!!!!!

Forget this blocking the exhaust crossoever thing unless your intake is getting to hot down there in Florida that's it's boiling the fuel out of the carbs at a stoplight. NOTHING good comes from blocking off exhaust crossovers in a street engine aside from you loose thermal efficiency designed into that system by the engineers so you reap the benefits of quicker warm-ups, improved fuel economy, power, and able to effectively burn a leaner mixture thus being able to keep a little extra money in your pocket from the improved MPG's.

As I follow your threads I simply don't undertand this "one step at a time" thing. You have the engine down in the vehicle which is at least 10 times (I'm being conservative here) more difficult that removing it and doing all that work on an engine stand. I get all that, and sometimes due to limited resourses we have to work a little harder with things. However you have discovered a major issue and now the pan needs to come off to remove the rods and pistons. Take a step back, take a deep breath, forget trying to find an easy way out and take the plunge. In the big scheme of things the end result will be well worth the extra effort.......IMHO and FWIW........

[TRADERMIKE 2012]

[QUOTE=Cliff R;6445994] Your logic is flawed some when it comes to getting this engine up and running well. Although you are getting a LOT of good advice here, this is what needs to happen.

Pull the engine, remove the pan and swap the pistons/rods so the notches are toward the front of the block.

The engineers at Pontiac knew more about this than anyone else and they offset them for a reason. I can tell you from accidentally installing a set backwards 40 years ago that EVERYTHING gets better when you put them in the RIGHT DIRECTION. The testing done by a few good folks over the years did NOT include putting 100,000 miles on a 406 SBC in a K-5 Blazer with the first 10,000 miles having the pistons in the block with the offset the WRONG direction. That engine from day one just didn't run right or sound right. It was one of those things with this hobby that you just can't put your finger on and leaves you wondering what was missed during a pretty expensive engine build. I had NO IDEA whatsoever what was wrong with it, so I yanked it back out and after hours of examining everything scattered all over a work bench, I found the issue. The HY-DUTY pistons I bought were all facing the WRONG direction in the block....BINGO!! Nailed it! Back together and FLAWLESS for another 90,000 miles!!!!!!!!!!!!!

Forget this blocking the exhaust crossover thing unless your intake is getting too hot down there in Florida that's it's boiling the fuel out of the carbs at a stoplight. NOTHING good comes from blocking off exhaust crossovers in a street engine aside from you lose thermal efficiency designed into that system by the engineers so you reap the benefits of quicker warm-ups, improved fuel economy, power, and able to effectively burn a leaner mixture thus being able to keep a little extra money in your pocket from the improved MPG's.

As I follow your threads, I simply don't understand this "one step at a time" thing. You have the engine down in the vehicle which is at least 10 times (I'm being conservative here) more difficult than removing it and doing all that work on an engine stand. I get all that, and sometimes due to limited resources we have to work a little harder with things. However, you have discovered a major issue and now the pan needs to come off to remove the rods and pistons. Take a step back, take a deep breath, forget trying to find an easy way out and take the plunge. In the big scheme of things, the end result will be well worth the extra effort.......IMHO and FWIW........[/QUOTE

Mikes reply:

I listened to your advice when building the Th 400 and was successful in that endeavor, prudence says to listen to you now!

you said: "Forget this blocking the exhaust crossover thing unless your intake is getting too hot down there in Florida that's it's boiling the fuel out of the carbs at a stoplight. NOTHING good comes from blocking off exhaust crossovers in a street engine aside from you lose thermal efficiency designed into that system by the engineers so you reap the benefits of quicker warm-ups, improved fuel economy, power, and able to effectively burn a leaner mixture thus being able to keep a little extra money in your pocket from the improved MPG's.

Mikes reply: YES, that is exactly what is happening! I have to run rec-89-90 with no alcohol down here in South Florida and I have made many changes to the coolant system over the years to keep this particular motor, in this vehicle, to "not vapor lock", so, I must keep the crossover block plug in play. However, since the Pistons were installed backwards and is a big deal, then, I have no recourse but to fix that issue. I am convinced that pulling the Crank and pistons is the only way that I am truly going to repair someone's blunder and figure out if there are any other issues that I can't determine without going all the way. The way the vehicle is set up currently the motor mounts are disconnected and the Oil pan is accessible.

I can disassemble the Crank in the car, the Block will be lighter after pulling the Crank and pistons for me and then, if it is necessary to remove the short Block, I will have to get my Engine puller back, that I loaned to my brother, in NW Florida. P.S. I agree that the engineers at Pontiac knew what they were building. The schematic that I posted online depicts some of the 428 ci Blocks water Jackets have been closed off; this is an indication of a Pontiac coolant mod. Someone online, in the past, mentioned a Pontiac mod. and posted it on PY. Are you familiar with coolant mod? I need to know if the mod. is complete as is or have they made a mistake there as well.

[JSchmitz]

[QUOTE=TRADERMIKE 2012;6446001]

Originally Posted by Cliff R

Your logic is flawed some when it comes to getting this engine up and running well. Although you are getting a LOT of good advice here, this is what needs to happen.

Pull the engine, remove the pan and swap the pistons/rods so the notches are toward the front of the block.

The engineers at Pontiac knew more about this than anyone else and they offset them for a reason. I can tell you from accidentally installing a set backwards 40 years ago that EVERYTHING gets better when you put them in the RIGHT DIRECTION. The testing done by a few good folks over the years did NOT include putting 100,000 miles on a 406 SBC in a K-5 Blazer with the first 10,000 miles having the pistons in the block with the offset the WRONG direction. That engine from day one just didn't run right or sound right. It was one of those things with this hobby that you just can't put your finger on and leaves you wondering what was missed during a pretty expensive engine build. I had NO IDEA whatsoever what was wrong with it, so I yanked it back out and after hours of examining everything scattered all over a work bench, I found the issue. The HY-DUTY pistons I bought were all facing the WRONG direction in the block....BINGO!! Nailed it! Back together and FLAWLESS for another 90,000 miles!!!!!!!!!!!!!

Forget this blocking the exhaust crossover thing unless your intake is getting too hot down there in Florida that's it's boiling the fuel out of the carbs at a stoplight. NOTHING good comes from blocking off exhaust crossovers in a street engine aside from you lose thermal efficiency designed into that system by the engineers so you reap the benefits of quicker warm-ups, improved fuel economy, power, and able to effectively burn a leaner mixture thus being able to keep a little extra money in your pocket from the improved MPG's.

As I follow your threads, I simply don't understand this "one step at a time" thing. You have the engine down in the vehicle which is at least 10 times (I'm being conservative here) more difficult than removing it and doing all that work on an engine stand. I get all that, and sometimes due to limited resources we have to work a little harder with things. However, you have discovered a major issue and now the pan needs to come off to remove the rods and pistons. Take a step back, take a deep breath, forget trying to find an easy way out and take the plunge. In the big scheme of things, the end result will be well worth the extra effort.......IMHO and FWIW........[/QUOTE

Mikes reply:

I listened to your advice when building the Th 400 and was successful in that endeavor, prudence says to listen to you now!

you said: "Forget this blocking the exhaust crossover thing unless your intake is getting too hot down there in Florida that's it's boiling the fuel out of the carbs at a stoplight. NOTHING good comes from blocking off exhaust crossovers in a street engine aside from you lose thermal efficiency designed into that system by the engineers so you reap the benefits of quicker warm-ups, improved fuel economy, power, and able to effectively burn a leaner mixture thus being able to keep a little extra money in your pocket from the improved MPG's.

Mikes reply: YES, that is exactly what is happening! I have to run rec-89-90 with no alcohol down here in South Florida, and I have made many changes to the coolant system over the years to keep this particular motor in this vehicle to not vapor lock, so I must keep the crossover block plug in play. However, since the Piston s were installed in backwards is a big deal, then I have no recourse to fix that issue, I am convinced that pulling the Crank and pistons is the only way I am truly going to repair someone's blunder and figure out if there are other issues that I can't determine without going all the way. The way the vehicle is set up currently the motor mounts are disconnected and the Oil pan is accessible. I can disassemble the Crank in the car, the Block will be lighter after pulling the Crank and pistons for me and then if it is necessary to remove the short Block, I will have to get my Engine puller back that I loaned to my brother in NW Florida.

Don't need to pull the crank to flip pistons/rods around (unless I missed that you want to pull the crank for another reason lol). Rods have a direction also. Make sure all are correct this time.