[toomanybirds]

Originally Posted by 2manyT/A'S

Well Mark,your post this morning inspired me to go digging in the "uncharted areas" of my basement & thought these might interest the HO guys.
According to the sheet they will ALSO work in the "other" round port 455 (2nd fastest) as well as any other 71-76 455.

As I understand it,a high compression round port 455 was planned as the ULTIMATE large displacement Pontiac motor for 1970 & I'm guessing GM comissioned TRW to design these pistons (perhaps as an OEM application),but with the premature DEATH of high compression engines for 71,there was NO OEM market for them.

One of our contributers here (from the Great White North) has a set of these in a 72 HO with the domes cut down to reduce chamber volume.

These pistons are TRW L2394F. Not too rare or unusual. They may even still be available from Sealed Power, I haven't checked in a few years. I have 2 sets in my parts stash. They have grooves machined for floating wrist pins, and lock rings are included with a set.

They were designed to be used with 455HO and SD455 heads to give about 10.5:1 with a standard bore size. It was common to smooth the "bumps" from the domes to improve combustion efficiency. I believe HO Specialties marketed these pistons and recommended removing the "bumps."

I doubt these were a GM design, as all of the Pontiac high compression engines used smaller cylinder head chambers, not domed pistons.

[Lloyd-TX]

Used those pistons - with the "bumps" milled off and domes polished - in my '75 T/A w/ a 455SD engine MANY years back. I knew a LOT less back then than I do now, but it ran OK. Upper 11's @ 112 with a TH400 and 4.10's.

[2manyT/A'S]

Originally Posted by toomanybirds

I doubt these were a GM design, as all of the Pontiac high compression engines used smaller cylinder head chambers, not domed pistons.

I personally find it hard to believe that TRW would have tooled up a SPECIFIC piston in 1973 for "dead horse" low production big cube engine.

As I recall,in that year,muscle cars were DEAD,insurance rates were outrageous & we were lining up to buy junk gas (on every other day)

The SD's (few as they were) hadn't hit the streets yet.

With a total run of 7000 or less? engines/cars built and NO hi-octane pump gas available to support the fat compression ratio,they just WOULDN'T have done it.

I wasn't suggesting they were RARE,just the "hot ticket" in the mid-70's and thought some of the "younger guys" might be interested,if they hadn't seen them before.

[johnta1]

I don't know when they first came out, but the TRW SD pistons were specifically made for the SD, narrower opening for the rod.
They wouldn't work with the stock rods.

I had a set in 77, and they worked great, using the HO setup like Lloyd said.

[OVERULD]

Originally Posted by 2manyT/A'S

I've heard that engine is now in an OTG.

S'A\Tynam2:

uoY thgim tnaw ot evah flesruoy dekcehc rof aixelsyd.


JB

[2manyT/A'S]

Originally Posted by OVERULD

S'A\Tynam2:

uoY thgim tnaw ot evah flesruoy dekcehc rof aixelsyd.


JB

!dooG llac

[toomanybirds]

Originally Posted by johnta1

I don't know when they first came out, but the TRW SD pistons were specifically made for the SD, narrower opening for the rod.
They wouldn't work with the stock rods.

I had a set in 77, and they worked great, using the HO setup like Lloyd said.

The L2423F TRW flat-top replacement pistons for the SD455 were exactly the same piston as the OEM pistons. The only difference being the part number. (TRW was the supplier for GM)

The SD455 pistons had a single "trough" valve relief and were made to fit only the SD forged rods which had a narrower small end than the non-SD cast rods. These stock pistons would need to be machined in order to be used with the wider cast rods.

The L2394F domed "racing pistons" are machined wider to fit non-SD cast rods. If the L2394F pistons are used with forged SD rods, there is excess gap or "play" between the piston pin boss and the rod. This is not a problem with stock wrist pins. But, if thin wall "light weight" wrist pins are used, wrist pin failure could occur.

The L2394F domed pistons were made for, and marketed for, use in both 455HO and SD455 engines.

TRW made a number of "racing pistons" with domes for use in many different types and brands of engines. Many of these were low production engines.

[johnta1]

Hmmm, I'll have to see if I can find that SD piston/rod.
Could have swore it was only for the SD rod.
There was another number for the 'normal' rod.

[goathead455]

Originally Posted by 2manyT/A'S

One of our contributers here (from the Great White North) has a set of these in a 72 HO with the domes cut down to reduce chamber volume.

10 years ago that car acheived almost "legendary status" at the dragstrips in the area.

Totally STOCK looking, especially under the hood,it made Pontiac BELIEVERS out of countless Ford,Chev & Dodge guys with TONS of aftermarket speed parts on THEIR cars.

This round port T/A was driven to track on street tires with the sticky tires in the back seat & once installed would run LOW 12 second ET's all day long.

I've heard that engine is now in an OTG. (perhaps we will get an UPDATE?)

It is true that this engine is now in my GTO.
The TRW pistons are still in place but got treated to some Eagle rods this past spring along with new rings and bearings.
As soon as the engine was together the car ws driven to Oregon for the Tiger Run GTO show,getting close to 16 mpg on the 2000 mile round trip.
Last month I finally made it to the drag strip and the car ran 12.43@110 in poor air conditions(4500')
Next year when I can tune the car a bit I hope to get into the 11's but I'll have to wait and see as the track is closed for the season now.
There is the update you asked for.
The Trans Am with the HO was a very fun car and caught alot of people off guard.
In the early to mid 90's there weren't nearly as many 12 second street cars as there is now,especially ones with Q-jets and exhaust manifolds.
The car ran a best of 12.06 but that was in great conditions at a sea level track,it would run 12 teens in the heat of summer.
Here are a couple of pics of the T/A.
I will post some of the GTO later.

[OVERULD]

Nice! The smoke from the burn out matches the color of the car very nicely.

BJ

[Father&Son73T/A]

Originally Posted by 2manyT/A'S

Well Mark,your post this morning inspired me to go digging in the "uncharted areas" of my basement & thought these might interest the HO guys.
According to the sheet they will ALSO work in the "other" round port 455 (2nd fastest) as well as any other 71-76 455.

As I understand it,a high compression round port 455 was planned as the ULTIMATE large displacement Pontiac motor for 1970 & I'm guessing GM comissioned TRW to design these pistons (perhaps as an OEM application),but with the premature DEATH of high compression engines for 71,there was NO OEM market for them.

One of our contributers here (from the Great White North) has a set of these in a 72 HO with the domes cut down to reduce chamber volume.

10 years ago that car acheived almost "legendary status" at the dragstrips in the area.

Totally STOCK looking, especially under the hood,it made Pontiac BELIEVERS out of countless Ford,Chev & Dodge guys with TONS of aftermarket speed parts on THEIR cars.

This round port T/A was driven to track on street tires with the sticky tires in the back seat & once installed would run LOW 12 second ET's all day long.

I've heard that engine is now in an OTG. (perhaps we will get an UPDATE?)

So,these could be used on 73-74 L-75's?

[goathead455]

Originally Posted by goathead455

It is true that this engine is now in my GTO.
The TRW pistons are still in place but got treated to some Eagle rods this past spring along with new rings and bearings.
As soon as the engine was together the car ws driven to Oregon for the Tiger Run GTO show,getting close to 16 mpg on the 2000 mile round trip.
Last month I finally made it to the drag strip and the car ran 12.43@110 in poor air conditions(4500')
Next year when I can tune the car a bit I hope to get into the 11's but I'll have to wait and see as the track is closed for the season now.
There is the update you asked for.
The Trans Am with the HO was a very fun car and caught alot of people off guard.
In the early to mid 90's there weren't nearly as many 12 second street cars as there is now,especially ones with Q-jets and exhaust manifolds.
The car ran a best of 12.06 but that was in great conditions at a sea level track,it would run 12 teens in the heat of summer.
Here are a couple of pics of the T/A.
I will post some of the GTO later.

I should add that the Trans Am is an automatic and the GTO has a standard transmission.

[Wareagle]

For a 71-72 455HO engine what compression would you have with 69-70 RAM AIR IV Heads.

[johnta1]

Over 11.5 CR

[Wareagle]

Originally Posted by johnta1

Over 11.5 CR

Thanks - I know of a fellow in Switzerland that has them on his 71-72 ? 455HO T/A
- more info to follow.

[2manyT/A'S]

You DON'T want to go there!

72CC heads (round OR D port) on a 455 makes TONS of power with INCURABLE DETONATION.

It's not a suitable combination for street driving/pump gas.

[Wareagle]

Heres the 455HO T/A ( RAM AIR IV Heads ) 1.07 mark-partway through this video - he's been driving it for years to shows and races . SDRoger ( 73 SD455 T/A 4 spd ) who I met in Switzerland told me about this unique T/A -- COOL.
http://www.youtube.com/watch?v=D08qJ0XP3kQ

[Wareagle]

I just got a email from SDRoger-- he says his friends 71 455HO T/A ( RAM AIR IV Heads ) runs fine -no problem getting 98 oct.pump gas and shell has 100 oct. pump gas were he lives .

[2manyT/A'S]

http://cgi.ebay.com/ebaymotors/ws/eB...3AIT&viewitem=

Wonder what they will net?

[goathead455]

Flatlander Racing still shows these as available.
Their price is $63 per piston.