[big hammer]

now i know they aren't a real HO, and i am considering zooting it up a little but a really want to retain the stock appearance. i would like to bump it up to at least 9:1 compression. does the stock engine have dished or flat top pistons? which is the best way to raise the compression on these engines?

['ol Pinion head]

Stock pistons are flat top cast with two small reliefs. Easiest way to up compression is pull the 5I's & install a pair of 5C-8's or 6X-8's. Both will be around 100cc chambers & will bump a stock bore 455 up around 9-1. 6X's actually started showing up on 350 & 400's in the spring of '75, you might even find a pair that date & are cheap. For my '73 TA project, I yanked the 4X-1H's and went with a pair of late '73 model 4X 400 heads, they even dated the car build. Picked em up for $30, bought Jim Hand's book & have nearly 20 hours in port work in them.

[Lloyd-TX]

Nice find, hammer, and welcome aboard!

Do yourself a HUGE favor - buy Jim Hand's "How to Build Max Performance Pontiac V8s" Engine book. Great info . . .

http://www.amazon.com/How-Build-Perf...8735256&sr=1-1

[muscle_collector]

post some pics please.

[big hammer]

thanks guys-- i'll post pics in a few days. i serendipidously found the car while vacationing in california, and made a quick deal on it. the car went into storage before i could take any pictures. it's getting shipped to ND right now and i should be picking it up from there on friday. then i'll take pics of it. it's silver and in terms of a minty showroom car i give it a 6 out of 10.

the interior is black now but according to the PHS documents was originally white. it is a numbers matching car.

[RATTCRUSHER455]

get a pair of 6x heads number four and put them behind the rear tires get a pair of 5c heads put them behind the front tires and go spend the money or a pair of real heads like 1970 55 h/o #64 heads and really go fast

[big hammer]

Originally Posted by RATTCRUSHER455

or a pair of real heads like 1970 55 h/o #64 heads and really go fast

i'll do that. there's so many of those heads out there you can't even give them away.

[big hammer]

#64 heads are 87 cc chambers? would that put me up closer to 9.8:1?

[2manyT/A'S]

You will likely NOT be happy for LONG with those heads on your 455.

The chamber is just too small for todays pump gas.

Overheating & detonation will likely result & have the potential to destroy your engine.

A set of 4x-6x 98 cc's with an 068 (455 HO) cam with Ram Air exhaust manifolds & you will make ALL the power you have traction for.

[RATTCRUSHER455]

run a fat head gasket back the timing a little use super and it will be fine, been running them for years no problems and still make more power than 6x junk 4x junk and 5c junk. what is all boils down to most people dont want to spend the money for the good heads and go the cheap way its been that way in the 80's and in the 90's right threw 00's and still here today.

[RATTCRUSHER455]

but if you really want to use 6x heads i have bunches of that crap laying around some i use to hold tarps down for my outside storage for my 455 motors

[big hammer]

what would the actual compression ratio be with my bottom end and 64 heads?

['ol Pinion head]

Most ignorant thing I've read on here in months. 6X & 5C heads have very favorable low lift flow characteristics. I've built with "64" & 6X castings on both 455's & 400's. All 64's are is expensive to find resto heads, & have been for the last decade. On today's pump gas, no need for 87cc cast iron heads on a 455 or 462.

[RATTCRUSHER455]

right at 10 to 1 maybe a little higher depends on the gasket and how fat your deck is if that scares you run 96 heads the other good head most people are afraid to run only because it costs more than a 6x 4x 5c junk they are 96 ccs and can run any hodgey gas you throw at them if you want them i have those also (i store those under the tarp )

['ol Pinion head]

64's on a 70 455 were stock advertised at 10.25-1 C/R. When one actually does the math on a never bored or decked 455, the actual C/R comes in around 9.7-1, 9.8-1. Once one starts boring & zero decks C/R will be little over 10-1

[67 Lamnas]

Originally Posted by RATTCRUSHER455

...... 6x junk 4x junk and 5c junk......

Seriously???

Originally Posted by 'ol Pinion head

....Most ignorant thing I've read on here in months......

I'd have to agree....maybe even years.

Don't forget the factory pistons starting in '75 had a chamfer that lowered the compression a few extra tenths over the '74 earlier pistons.

The 4X and especially the 6X castings are an EXCELLENT choice for a street engine if you want to raise your compression ratio. Nunzi amongst others have known this for years.

[455Grandville]

Originally Posted by 2manyT/A'S

You will likely NOT be happy for LONG with those heads on your 455.

The chamber is just too small for todays pump gas.

Overheating & detonation will likely result & have the potential to destroy your engine.

A set of 4x-6x 98 cc's with an 068 (455 HO) cam with Ram Air exhaust manifolds & you will make ALL the power you have traction for.

x 2 with the 6X heads; I yanked the original 200 horse weezer out my 75 GV (with around 23K orig miles) and dropped in a mild 455 with 6x's (the larger 98 cc 400 versions) , a little more cam, R/A resto manifolds, a 1971 Intake, and some other mild upgrades and the difference was night & day.

Originally Posted by 'ol Pinion head

Most ignorant thing I've read on here in months. 6X & 5C heads have very favorable low lift flow characteristics. I've built with "64" & 6X castings on both 455's & 400's. All 64's are is expensive to find resto heads, & have been for the last decade. On today's pump gas, no need for 87cc cast iron heads on a 455 or 462.

Indeed.

[RATTCRUSHER455]

hey it does not matter to me what heads you guys want to run if people want to run 6x junk i have that both in 8 and 4 versions for sale , if people want some 5c i have that trash also, if people want 4x to my dismay i have to many of that crap to, but if people want better heads like 64 heads and 96 heads yes i have them but in limited extra supply because i run both 64 and 96 heads on many of my 455 engines and by the way that i run with zero detonation issues but i always have extra pairs laying around for educated buyers who are not afraid to spend a little more money for a better head and back in the 80's the head of choice for the street was not the 6x it was the 96 head its the limited availabilty of the 96 head that makes a 6x a back seat well if i have to choice and we also have to factor in the cost 6x heads if your lucky will fetch 150.00 per pair a set of 96 heads fetch 450.00 and 64 heads sell for 800 plus with out even trying and its not the resto guys buying them its the 455 crowd with money and serious power in there future

[455Grandville]

Originally Posted by RATTCRUSHER455

hey it does not matter to me what heads you guys want to run if people want to run 6x junk i have that both in 8 and 4 versions for sale , if people want some 5c i have that trash also, if people want 4x to my dismay i have to many of that crap to, but if people want better heads like 64 heads and 96 heads yes i have them but in limited extra supply because i run both 64 and 96 heads on many of my 455 engines and by the way that i run with zero detonation issues but i always have extra pairs laying around for educated buyers who are not afraid to spend a little more money for a better head and back in the 80's the head of choice for the street was not the 6x it was the 96 head its the limited availabilty of the 96 head that makes a 6x a back seat well if i have to choice and we also have to factor in the cost 6x heads if your lucky will fetch 150.00 per pair a set of 96 heads fetch 450.00 and 64 heads sell for 800 plus with out even trying and its not the resto guys buying them its the 455 crowd with money and serious power in there future

Educated ? You know just because you cannot hear detonation does not mean it's not happening. By the time you hear it; it's usually really bad.
I set mine at 9.3:1 and unless I can by 93 octane (which is not always available) it's a problem. Many stations sell 91- 92 octane as their Premium and if you're on a long trip , that might be all you can get.
You mention these other heads, but you failed to mention the CC size; the book may give a ballpark factory number, but in reality they will vary because machining at the factory in 1970 had alot more variance; so you're going have ones with even less CC's. Add into the fact some may need to be milled even more, or have been milled before and you might be over 10 : 1.

That's a problem with cast iron heads on pump gas -

[RATTCRUSHER455]

howdy brad

i am very sure if i was having detonation problems in any one of my 455 eingines with 64 heads it would have shown its ugly head by now 12- 15 years later and trust me i am not one of those afraid to stand on them.

my only trick will be to get a xf block to run hard with a set of 614's on the pump in my 70 t/a that we are frame uping