[Half-Inch Stud]

Originally Posted by OG68

Same here. '68 40 over WT. All stock parts, 068 cam, 16 heads measured at 71 cc. RA manifolds from Ames. I used ICON 14 cc dished pistons. CR came out to 9.65 with .039 head gasket.

How clean-sounding does it run with 87 at WOT?

[OG68]

I had a cam bearing failure during the original engine break-in Stripped and cleaned block and rebuilt again.
Replaced the cam with a Crower and cylinder heads with Edelbrock D port 72s.

.040 over
4.160" bore
Stock ’N’ crank .020/.020
RPM 5140 I-Beam 6.625 press fit rods.
Icon C891-040 pistons 14cc dish
Hastings rings 4.160”, 2M644040, 1/16"x1/16"x3/16" Plasma Moly rings
Felpro 1016 .039" head gaskets
Edelbrock ‘D’ port heads; 72 cc, 2.11 intake, 1.66 exhaust
Crower 60242 Cam
Butler 60# ‘Pro’ oil pump
Crower ‘Cam Saver’ lifters
Butler Pushrods.
Melling Timing set with ‘Morse’ chain, Steel timing and crank gears
Crower Stainless Steel 1.5 full roller rockers
Stock cast iron intake
Stock Qjet built by Cliffs High Performance
Stock points distributor
Clevite 77 Main Bearings -.20
Clevite 77 Rod Bearings -.20
Powerbond Balancer PBO-PB1056ST

Engine is overbuilt for its intended usage. I know I could have installed flat top pistons and still be able to run on 91 but I've sank enough money and time into it already.

Second engine break-in went well and I currently have about 50 miles on it, so I don't know about 87. I'll probably not chance going that low.
But after I run a few tankfuls of 91, I'll start blending some 89 and see how it runs.

[b-man]

I would probably build it with Icon forged pistons. Built my 421 using dished Ross forged pistons and they were expensive at $750 over a decade ago.

I just had a 2276cc air cooled VW engine built for my pickup using Icon pistons and have another one in the works using Icon as well, they’re a little over $100 each for the 3.700” (94mm) size I’m using.

The Sealed Power / TRW pistons are great but I don’t care for the pressed wrist pins, the weight really isn’t the issue.

I’ve had engines with original factory cast pistons and they were fine. One was a low-12s / high-11s bracket race 455 so they do well no problem in performance street engines as well.

[Gary H]

I use Icon pistons in about 75% of my engine builds for customers. which are 2618 alloy. The other 25% of the street engines I use DSS pistons with a 4032 alloy. Both are forged pistons with a good ring pack, 1/16, 1.16, 3/16., but the 4032 run a little quieter on start-up. Either one is commonly available, and will do the job. With your heads, #16's, I'd run a dished piston to reduce the compression ratio.

[scott70]

Surprised nobody has mentioned autotech pistons yet.

[scott06]

Originally Posted by 1969GTO

Funny you should ask.
I am dropping my engine off to Paul Spotts of Spotts Performance in PA tomorrow 04/04/26.
I am having the same type of build done to my numbers matching 1968 GTO 400 engine.
I am using my YS block, 16 heads, original cast intake, QJet, distributor, crank shaft and rods.
The piston brand I don't remember but the compression will be knocked down to around 9.5.
I will also include RAM AIR Restorations exhaust manifolds and PYPES exhaust with an X pipe.
Contact Paul for more info on his builds.

I just got an engine from Paul (65 -389) he really likes the Icons. We used ross in my 65 to get the dish right, but ICON and Ross are what he uses most.

The ross pistons were really nice , they were pricey but do it once. 25 cc dish to keep the compression down on my small chamber heads

[scott06]

Originally Posted by b-man

Built my 421 using dished Ross forged pistons and they were expensive at $750 over a decade ago.

.

The ross dished ones I just got were about $1200 with pins and rings. These are the semi custom ones where they cnc the dish you want from an instock blank

[chiphead]

Originally Posted by scott70

Surprised nobody has mentioned autotech pistons yet.

I used Autotec pistons for my 433 build and they are very nice pieces. Got them in 2019. I read that they were bought by private equity in 2023. Not sure if that affected price or quality.

[carcrazy]

I went with Ross on my last build.

[tooski]

I bought DSS off the shelf pistons for my upcoming 433 build. I would have to get custom pistons otherwise. Their CH distance put them at .005 in the hole on my decked block. Along with the 14 cc dish puts the cr at 9.9. Down from 10.1 in the 406 with speed pro and stock rods.

['ol Pinion head]

Originally Posted by scott70

Surprised nobody has mentioned autotech pistons yet.

Have a set of Autotecs with slight domes for one of my 71 455 HO builds. Chose the AutoTecs for the tight wall clearance 4032 alloy &, the reasonable at the time upcharge for the slight domes. That was from Shannon's Engr years ago.

Once i can have my 72 T/A's block sonic tested, will choose a sizing for it's pistons. Will be another set of AutoTecs or possibly custom Icons, again w a slight dome.

[P@blo]

DSS 455 040 18cc dish off the shelf piston and ring kit here. Block was squared and decked as per normal operation and got the thumbs up from my machine shop.

[scott70]

Originally Posted by 'ol Pinion head

Have a set of Autotecs with slight domes for one of my 71 455 HO builds. Chose the AutoTecs for the tight wall clearance 4032 alloy &, the reasonable at the time upcharge for the slight domes. That was from Shannon's Engr years ago.

Once i can have my 72 T/A's block sonic tested, will choose a sizing for it's pistons. Will be another set of AutoTecs or possibly custom Icons, again w a slight dome.

Through Paul I just got a set of custom 4.191 auto techs 4032 with a 1.501 CH. Little under 1100.00 with rings and floating pins.

[tom s]

I get Autotec from Paul K for all of my builds.No issue at all.Tom

[rohrt]

Originally Posted by steve25

Just to add this snippet, pistons with the stock size 5/64” 5/64” rings last a lot longer seal wise.
Yes, there’s more friction and hp loss above 5K, but so what on a street motor.

Steve can you expand on this? First I head of the metric ring packs not lasting. I have heard of less parasitic drag.

Notes
1mm, 1mm, 3mm ring pack.
1/16th, 1/16th, 3/16th ring pack (1/16 = 1.5mm)
stock LS engines use a 1.5mm / 1.5mm / 3.0mm
Pontiac 400/428 (1967-1979): Generally uses 5/64", 5/64", 3/16" packs

[Dragncar]

Guys are seeing power gains with the new trick .7 mm ring packs. Lots of new tech in that area.
I used my Ross old school 1/6" ring pack pistons in my 461. But, I had Total Seal back cut some ported rings for less tension and used that flat wire spring steel for spacers under those rings. Everything turned out great, but a lot of work fitting it all. Never again, I will buy new pistons next time with metric rings.

[VCho455]

Originally Posted by Tim Corcoran

Hmmmmm Pontiac used cast pistons from the factory and I don't recall anyone having problems with cast pistons on a street car. They are plenty strong for street use and last a long time due to closer piston to bore clearance. And the rings last longer with a tight piston to bore as the piston isn't rocking as much.

I have to agree. All the pistons I broke (Back in when all I could afford was cast pistons) were from rods or valves failing first. However with part quality level we see today I'm not sure that holds true anymore.