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blakethechop 01-06-2013 08:12 PM

455 pistons and gaskets

after some advise for my 455 pontiac .has anyone used these pistons they are 0cc to increase compression.also what are some options for thin head gaskets without having to o ring i really appreciate all the help im getting
cheers blake:thumbup:

cobalt327 01-07-2013 01:52 AM


Originally Posted by blakethechop (Post 1631586)

after some advise for my 455 pontiac .has anyone used these pistons they are 0cc to increase compression.also what are some options for thin head gaskets without having to o ring i really appreciate all the help im getting
cheers blake:thumbup:

I've never used those exact pistons, but KB are OK pistons- just pay attention to any recommendations they may have regarding the top ring gap and piston-to-wall clearance.

Also, the -060 is for a 0.060" oversize piston (Summit's catalog listing makes it look like that p/n is for a standard piston). -030 would be a 0.030" over, etc. So be sure to order the right oversize for your engine. The machinist will need to assess the condition of your block to give you his oversize recommendation.

Then you have to order the pistons and give them to the machinist for him to measure before doing the final hone. The type of ring used (plain, moly, etc.) needs to be known as well so the hone finish is correct for the rings being used.

cobalt327 01-07-2013 02:02 AM

BTW, those pistons use a 1/16" second ring so a 'normal' Pontiac 455 ring set won't work.

MouseFink 01-07-2013 08:11 AM

If you use those pistons (flat top) make sure you have 1971-1979 cylinder heads with no less than 90 CC combustion chamber volume or you will forced to use a large percentage of 108 octane racing fuel. The alternative would be to machine a dish in the L2359NF pistons. The L2359NF or L2359F pistons are Sealed Power VMS 75 alloy which is a thicker medium eutectic silicon alloy forging. The top of those pistons will take a dish .300"deep x 3.00" diameter.

With no less than 90 CC combustion chambers, and Fel Pro 8518PT head gaskets that have .039" crushed thickness, your 455 engine will have 10.6:1 static compression ratio. That is borderline for 93 octane pump gas with the initial timing advance set where the engine will run best. There may be off the shelf dished pistons available for the 455 engine but they are smog pistons made of 4032 hypereutectic 18% silicon alloy. My 455 engines had 1963 heads with 70 CC combustion chambers and had 11.8:1 compression ratio. I had to use 100% 108 octane VP C-12 racing fuel with the initial timing set anywhere.

Standard 455 Pontiac rings are 5/64" top / 1/16" second / 3/16" oil. The 455 engine has high thrust loading so GM used a 1/16" second ring in an attempt to reduce cylinder wall wear. The 455 SD racing engines used 1/16" top and second rings and the pistons were forged 2618 (2% silicon) eutectic alloy. The forged pistons and 455 SD/RA-IV camshaft is the reason why the team of engineers who developed the optional 455 SD engines were fired in 1975. . The 455 SD engine could not comply with emissions tests mandated by the revised 1970 EPA Clean Air Act, even after it was tested and equipped with the relatively mild 1966 HO / Tri-power and 1969-70 Ram Air III camshaft. The 1/16" rings and the low silicon pistons had too much blow-by before they reached operating temperature. .

cobalt327 01-07-2013 11:21 PM

He has 4X 455 heads that he has to use, big chambers, no prob. w/too much CR. Good catch on the ring size, though. Was looking at the 428 KB's

Mr. P-Body 01-10-2013 07:23 AM

455 ring pack has a 5/64" top ring, 1/16" second ring and 3/16" oil ring. Stock dimensions. The increase in stroke from 4" to 4.210" added significant wear to the second ring, so the size reduction was made before the engine went into production.

The Speed Pro L2359F is FAR superior to the KB piston. We use them (KBs) for ash trays. The Icon forgings, however, are every bit as good, if not better than the Speed Pros, and lighter, for about the same money.

In order for a "flat top" piston'd 455 to make under 9.5:1 (accepted limit for 93 octane and iron heads on a Pontiac) requires 98 CCs in the chamber/dish, not including the gasket. Purge the term "get away with" from your vocabulary. Do it right.

Also, be certain to install new FORGED connecting rods. Don't let ANYONE convince you you don't need them. The original rods are a cast steel, and were inadequate when NEW, much less 40 years later... RPM rods make a nice replacement for a reasonable price (about the same cost as new bolts and resizing the old rods).

Be sure to get Jim Hand's "How to Build Max-performance Pontiac V8s" by SA Designs. It's the most current study of the ol' Injun. There's a "rewrite" in process, but none of the original "players" were consulted. The "tractor motor" crowd has hijacked the book. It's okay. Still TONS of good info on modern builds "out there". And we HAVE learned how to build Pontiacs that rev just like any other brand... (we shifted Dirty Bird @ 9,200, a 475 CID Pontiac blown/alcohol, about 2,200 HP) But they STILL make a bunch more low-end than the "other" GM engines that are popular among the racer crowd.



cobalt327 01-10-2013 02:26 PM


Originally Posted by Mr. P-Body (Post 1633015)
...9.5:1 (accepted limit for 93 octane and iron heads on a Pontiac)


Originally Posted by cobalt327
The OP's 4X 455 heads w/a 0.060" cut and FT pistons and a 0.041" quench will give him right at 9.1:1; 9.5:1 is the max I, or anyone who knows what they're talking about regarding Pontiac engines w/iron heads would recommend he use, anyway.

blakethechop, you would do well to follow the recommendations shown here regarding Pontiac CR w/iron heads.

MouseFink 01-10-2013 03:06 PM

1967-1970 GTO/Firebird 400 heads
455 CI
11.8:1 static compression ratio
10.8:1 dynamic compression ratio
Melling SPC-8 Ram Air IV camshaft
Comp Cams 863 limited travel lifters
Richmond 4-speed
3.64:1 rear cogs
BF Goodrich Drag radials.
100% VP C-12 108 octane racing fuel

Run with the funny cars.

Mr. P-Body 01-13-2013 10:53 AM


Funny cars? Hydraulic cams?

It's very important to most folks today, to run well on "pump gas", 93 or lower octane. Using 108 in a street car is not practical. The Pontiac chamber is "unique", both a blessing and a curse. When octane is right, timing is right and the engine is "happy", the chamber provides good power and lower emmissions than most others of the era. That same efficiency makes them very prone to detonation when things aren't EXACTLY right (erred on the side of "danger", not "caution").


MouseFink 01-13-2013 02:16 PM

Cool aid quality pump gas is bad now and is getting worse so people must build their emissions engines accordingly.

Providing that you have an engine that does not have emissions restrictions, such as those without a catalytic converter you can get 12:1 static compression ratio, 9.4:1 dynamic compression ratio, and 220 lb. cranking cylinder pressure would be the limit before you must O-ring the block.

Get it with an "Old School" 1970 455 CI Pontiac, 1967 GTO/Firebird 400 heads (#670), Comp Cams 041H Ram Air IV camshaft, Borg Warner Super T10 with a 2.64 low, 3.90:1 gears, 100%, VP C12, 108 octane racing fuel at $14 per gallon and plenty of "bite" fills the bill nicely.

Mr. P-Body 01-14-2013 08:37 AM

Still not sure what you're driving at here. The "funny car" reference?

The "recipe" you supplied for an old Pontiac is from the 1970s. Race gas and high compressin are for RACE CARS, not street cars. With that cam/head combination, the engine will make MAYBE 450 HP, be out of breath at 5,800 and in general, be a slug except in a light car with stiff gears.

Today, we take a completely different approach to building a powerful Pontiac. Porting the heads is paramount. The little intake ports are fine for a "stocker", but won't let a 455 rev.

While it may not be "necessary" to rev a Pontiac hard to make power (unlike the SBC), why not have "both"? It's nearly impossible to "tune" the low-end power "out". So, add parts to make it breath, and will make low-end power AND rev. Solid lifters also make a HUGE difference in performance. If the budget can stand it, solid rollers are "the best". Comp has some very nice "street" grinds in the XE series, just for the lower compression and higher revs.

It's not uncommon at all, to have 550-600 HP and 600 lb ft. with 93 octane, under 6,000. How about spinning it to 7.500? WOO-HOO!


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