[Cliff R]

A couple of observations.

You don't need an operable downshift solenoid in the TH400 with a well thought out Pontiac build. Matter of fact I unhook them on my vehicles. Instead I use my right hand to select lower gears if/as needed plus full control of the upshift points as well. Using the solenoid would for sure destroy the car or get me killed or seriously injured anyhow. If I were cruising along at 30 mph or so and went to full throttle the engine would try to rip the tires right off the rims if it shifted to low gear and I'd likely loose control of it and end up wrapped around a telephone pole.

I'd also add here the using Rhoads lifters on a RAIV cam has absolutely NOTHING to do with racing the car, or not. They are used to help offset the 80 something degrees of overlap and improve idle quality, vacuum production at idle speed, and improved throttle response and engine power right off idle and low RPM's. They work as advertised and take these somewhat "antiquated" engine designs and give them variable valve timing like modern engines. The downside is that they make noise doing it, which some folks can tolerate and others simply can not.

Advancing the cam has really nothing to do with engine noise unlessy you went so far the valves are smacking the pistons. In that event it would have bent them and you'd be walking anyhow. I've found that the RAIV cam likes to be at 109-110 ICL in a 455 build with moderate compression. Never used one in a 428 but I still wouldn't advance it very far, maybe 108-109ICL and run with it..........FWIW.....

[TRADERMIKE 2012]

Originally Posted by Cliff R

A couple of observations.

You don't need an operable downshift solenoid in the TH400 with a well thought out Pontiac build. As a matter of fact, I unhook them in my vehicles. Instead, I use my right hand to select lower gears if/as needed plus full control of the upshift points as well. Using the solenoid would for sure destroy the car or get me killed or seriously injured anyhow. If I were cruising along at 30 mph or so and went to full throttle the engine would try to rip the tires right off the rims if it shifted to low gear and I'd likely lose control of it and end up wrapped around a telephone pole.

I'd also add here the using Rhoads lifters on a RAIV cam has absolutely NOTHING to do with racing the car or not. They are used to help offset the 80 something degrees of overlap and improve idle quality, vacuum production at idle speed and for improved throttle response and engine power right off idle and low RPM's. They work as advertised and take these somewhat "antiquated" engine designs to give them variable valve timing, like modern engines. The downside is that they make noise while doing it, which some folks can tolerate and others simply cannot.

Advancing the cam has really nothing to do with engine noise unless you went so far, the valves are smacking the pistons. In that event it would have bent them and you'd be walking anyhow. I've found that the RAIV cam likes to be at 109-110 ICL in a 455 build with moderate compression. Never used one in a 428 but I still wouldn't advance it very far, maybe 108-109ICL and run with it..........FWIW.....

" I'd also add here the using Rhoads lifters on a RAIV cam has absolutely NOTHING to do with racing the car, or not. They are used to help offset the 80 something degrees of overlap and improve idle quality, vacuum production at idle speed, and improved throttle response and engine power right off idle and low RPM's. They work as advertised and take these somewhat "antiquated" engine designs and give them variable valve timing like modern engines. The downside is that they make noise doing it, which some folks can tolerate and others simply cannot".

What you said in the above quote concerns me at this time. I have successfully completed a rebuild on my 1967 TH 400 Trans. and after testing and tuning I replaced the vacuum Modulator and procured a rebuilt Valve body and we ran into a different issue. The car has been off the road for the past 2 years dealing with the Trans, so I went through the Tri-power Carbs. because they too have been sitting.

Prier too rebuilding the Trans. we installed the "041" Cam and then we advanced it 6 degrees at the Crank and so 3 degrees at the Cam, without ever degreeing the Motor. Currently as we test and tune seem to have a vibration that did not exist - ever. We took a hose and listened with our ears all around the Engine to isolate where the vibration/noise was coming from, and came up with some theories. First, we looked at the Torque converter to Fly wheel and the bolts were tight. Then we checked the Drive shaft and found no problem there. Then I remembered we had advanced the Cam timing and are currently reversing that procedure installing the Cam with zero advance. I plan on purchasing a degreeing wheel kit. We just removed the intake Manifold to inspect the pushrods and Lifters, then we spun each Pushrod when the Cam lobe circle was on top to check the Valve lash on these Johnson almost new Lifters. The almost new Chrome Moly HD Pushrods to Rocker Arm to top of Valves looks well and to spec. and no Metal is on top of the Vally area. The only thing wrong is the crossover exhaust in the Heads are missing 25% material and need to be replaced. We spun the Motor using our push button to starter tool and no noise or ad-moralities noted. While I order the Gaskets, I will need to reassemble this HO 428 ci Pontiac Motor, I will pull the Oil pan to inspect the inner pan for Metal and plan to cut open the remote Oil filter looking for metal too. Perhaps the noise/ Vibration went away by zeroing the Cam chain Gears? I won't know until I run the Motor so, I best check all while I am this deep into this Engine. Once I inspect the lower half of the Block, then we will spin the motor once again.

If anybody (friend or foe) has any input here, please advise me.

P.S. I am so tempted to remove these Heads, ones that I have never removed since owning this project vehicle.

[Jay S]

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

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.

[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.

[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.

[West Coast GTO]

Just last year the machine shop installed the rods backwards to the pistons ala Chevrolet and had to reheat/press out / install the correct way.
The conversation went, "chamfer backwards at crank with piston notch correct". He said" it will be OK, we do that like all Chevys and Fords".
I said " Nope chamfer correct, notch correct and you can't change piston locations to correct this because you balanced it and I paid for the pistons in correct relationship with crank, right?"

"Right"