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73 pontiac 455

  
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73 pontiac 455

 
jlwebbga jlwebbga
New User | Posts: 3 | Joined: 01/10
Posted: 01/14/10
06:11 AM

I have a 1971 Pontiac Lemans...I am interested in putting a 73 455 in it...It previously had a 350.... The 455 currently has 7k3 heads and I have a set of 62 heads I would like to put on them instead. I know I will have to install dished pistons to use with the heads... But question is would it be worth it. I know the 62 heads has more compression, but they are registered more H.P, but how much more will they give this motor... Last question is what cam, intake,carb would be good with these heads...and what would be the compression...

Thanks,
Jlwebbga  

barneyformula barneyformula
Addict | Posts: 3306 | Joined: 01/07
Posted: 01/14/10
07:14 AM

To start with, are you sure that number mk3 is right, the closest number I show in either of my references is 7k3 which came on 72 400/250hp with 96cc chambers and 2.11" intakes and 1.77" exhausts. The 62 heads have the same size valves and smaller combustion chambers at 72-75cc. Don't get too hung up on factory HP ratings, as many times two engines with the same heads/cam/intake/exhaust systems would be rated at different HP depending on the application. All late 60's to mid 70's d-port heads (with the same valve sizes) will flow similar amounts of air out-of-the-box, leaving combustion chamber size (and screw-in rocker studs) as the only variable. Also remember that in 1972, manufacturers switched to SAE testing to rate engines and the same engine that was rated at 300hp in 70/71 was re-rated to 250hp in 72, making comparison very difficult.
Ideally the best piston design for a big bore engine such as a Pontiac V8 is a flat-top piston with the deck height as close to zero as possible to create the ideal "quench". However, a dish piston is the only way to get a streetable CR with the heads you want to use. I would use whichever head gives you the best CR without going over 9.5:1 with available dished pistons.
Steve  
A little help... 'cause we don't all have to learn the hard way!

Pontiacman8 Pontiacman8
Moderator | Posts: 5775 | Joined: 02/08
Posted: 01/14/10
08:09 AM

+1  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

jlwebbga jlwebbga
New User | Posts: 3 | Joined: 01/10
Posted: 01/14/10
09:28 AM

Hey pontiacman what does +1 mean  

barneyformula barneyformula
Addict | Posts: 3306 | Joined: 01/07
Posted: 01/14/10
09:32 AM

It just means he agrees with my post, seems to be a new thing, I just noticed it a few weeks ago. Sure saves a bunch of typing and it gives positive reinforcement that others agree with a posted opinion. Hope what I wrote helps you with your 455, that'll really wake up your Lemans!
Steve

PS: I re-read your first post and I forgot to answer the rest of your questions. As for the intake/carb, you can't go very wrong with the factory 4bbl manifold and Q-jet or if you prefer aftermarket, the Edelbrock Performer with a 750carb (your pick) using vacuum secondaries. The cam really needs to be picked based on the trans/rear gearing/tire size combo, taking into consideration the CR that you settle on and the manner in which you intend to drive the car. Let us know.  
A little help... 'cause we don't all have to learn the hard way!

Pontiacman8 Pontiacman8
Moderator | Posts: 5775 | Joined: 02/08
Posted: 01/14/10
09:34 AM

Yep, exactly what it means.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

jlwebbga jlwebbga
New User | Posts: 3 | Joined: 01/10
Posted: 01/14/10
10:00 AM

Thanks alot for the input it will really help..But last question what compression do you think I will be ranging with the 62 heads and the 7k3 heads...Because I want to use what is best for performance....BTW I'm using a TH350 and have 3.31 posi rearend and the tires are pretty much factory size for the car.....

Thanks again,
Jlwebbga  

barneyformula barneyformula
Addict | Posts: 3306 | Joined: 01/07
Posted: 01/14/10
01:32 PM

The 7k3 heads will put you right around 9.4:1 with a .030 over 455 using flat-top pistons assuming they haven't been milled a bunch. The 62 heads will require dished pistons to get the CR down enough for pump gas. A couple of COMP cams that will work well for you are listed below, just copy and paste each link into your address bar. These will be nice streetable cams with a ton of torque. Some other guys have their own favorites and I'm certain you will get a few other recommendations to pick from.
Steve




XE268H: http://www.compcams.com/Cam_Specs/CamDetails.aspx?csid=1203&sb=2

275DEH: http://www.compcams.com/Cam_Specs/CamDetails.aspx?csid=1209&sb=2  
A little help... 'cause we don't all have to learn the hard way!

Brazil Brazil
Addict | Posts: 3945 | Joined: 06/09
Posted: 01/16/10
08:00 AM

The +1 and so on thing is kind of us Pontiac folks new version of "LOL" (never have determined what that means - I thought it meant lots of love, I was wondering why so many people loved me until I was informed that was not what it stood for). But we need our own language anyway. I think Pontiacman8 started it - not sure, but it does give a positive nod to good advice.

I liked the way "idrivejunk" started one of his posts with "HOW",  That captured the whole nature of the beasts that we love to work on - after all, Pontiac is named after an American Indian tribe. woo woo woo woo!

OK, back to business.  

barneyformula barneyformula
Addict | Posts: 3306 | Joined: 01/07
Posted: 01/16/10
08:43 AM

LOL means laugh out loud, or a short form of HAHAHAHAH  
A little help... 'cause we don't all have to learn the hard way!

Pontiacman8 Pontiacman8
Moderator | Posts: 5775 | Joined: 02/08
Posted: 01/16/10
08:51 AM

Exactly.
No I don't start it it was started on one of the Chevy sites and does save some typing.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

idrivejunk idrivejunk
Addict | Posts: 5139 | Joined: 12/09
Posted: 01/16/10
11:19 AM

HOW(dy) tribesmen- Heap big wampum for all!

+1 I had to ask about the plusses! Laugh  I love getting them.

BTW (by the way)
FYI (for your information)
TMI (too much information)
IMO (in my opinion)
IMHO (in my humble opinion)
ROTFL (rolling on floor laughing)
LMAO (laughed my ass off)

are a few common acronyms...in internet speak. FYI Laugh  
idrivejunk

tuffnuff tuffnuff
Moderator | Posts: 2567 | Joined: 12/09
Posted: 01/16/10
06:27 PM

idjunkman,,,
what does Fuque U mean,,, in english BTW
Smile  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

tuffnuff tuffnuff
Moderator | Posts: 2567 | Joined: 12/09
Posted: 01/16/10
06:29 PM

Hmmmm,,,
Brazil warrior make plenty papoose too
LOL
Smile  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

idrivejunk idrivejunk
Addict | Posts: 5139 | Joined: 12/09
Posted: 01/16/10
07:18 PM

tuff you pickin on me? LOL  Y'all pay no attention to this guy- unless you want to learn a thing or two.... Laugh  
idrivejunk

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