want to Upgrade a 455 1972 Stage 1 Stock - What is best route?

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I am thinking about adding more horsepower to the 455 by upgrading Cam and heads.  Then will alter carb to a more robust cfm to 820 with ne intake manifold...  also add converter for gas to get quicker to the rpm where hp RPM range is at...


i realize this is a very large upgrade, but any facts to do it or not too.. or what heads and carb should be used since I do not want to alter the hood... btw, this is going into a 68 GS, not a 72 with the hood scoop already there.


Thanks much.



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Rather than all of the "g750cood to talk about at the cruise" stuff, why not go more toward efficiency?  Which should also unlock some better driveability at the same time?


You can brag about how much carb, how much cam, what it dyno'd at, etc.  BUT if it doesn't scatter stuff until it get to a higher rpm, what real good is it on the street in normal driving?  The driving range you're normally in, rather than at the top of the rpm band!  Less total power, but more useable in daily driving rpm levels (i.e., TORQUE) is what burns the tires off-idle, NOT 6000rpm horsepower!


As these were emissions engines, an optimized centrifugal advance curve in the distributor, one which BUICKS like (not the generic Chevy motor!!!), plus a good vacuum advance curve, plus a more-optimized fuel curve in the QJet or 750cfm street carb helps in the efficient power orientation, too.


I'm NOT mentioning self-learning fuel injection for a few reasons.  One of which is that I've PM'd with some people who have them and never could get the fuel mixture just right for their engines.  One was from a forum user who had one put on his Buick 430 Electra, which did high-teens economy on the highway, but now doesn't get past 8mpg.  Not sure what went wrong, but something did.  So, with all of the newer carbs, as the Street Demon, I tend to lean toward bolt-on carbs, then finessing them for the application.  PLUS, the cost of these EFI kits is still not a cost-effective (from fuel savings) compared to a $500.00 (or less) new carb.  Be that as it may.


Upping the compression can help, probably, but I'm not sure how that could be done on that motor.  With just heads or with pistons, or combinations thereof.  MUCH has been learned in combustion chamber dynamics since that engine was designed, by observations.


Exhaust system?  Probably should be 2.50" pipe as a good size for that size motor, with some quieter low-restriction mufflers.  A "torque" motor that "rpms" can be a good thing, but it shouldn't need to go to 6000rpm to get results.  Aim more for 5000rpm as the top rpm.


Get the car so it has super-sharp off-idle throttle response and similar when cruising at 1500rpm levels.  You'll have more fun and spend less money getting there.


Just some thoughts,


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How and what one does often is a function of one's budget, AND the guy at the local speed shop that wants to help one with one's budget ;)


Street engines, and engines for trailered race-cars are two different items. The rest of this post is directed toward a street engine.


Three external (read less expensive than internal) options are: (A) carburetion (maybe), (B) distributor, and (C) exhaust.


Covering the distributor first - most of the US V-8's by 1972 had very little initial advance, and a distributor that cranked in the rest. Not a distributor guy, so will leave specs to those that are; but more initial advance (up to a point) is generally a good thing.


Willis (NTX5467) covered the exhaust.


As far as the carburetor/intake manifold: Lots of early 1970's Buick carbs were 800 CFM, and the Pontiac and Chevy dudes have been migrating them to Pontiacs and Chevvies for years. The fact that the WOT is 800 is nowhere near as important as the fact that the primary side is 200 versus 150 for the 750 CFM carbs. When Carter brought out the TQ in 1969 (race-only), and folks used them on performance street-cars, it was found that the transition from primary to secondary was MUCH smoother using the slightly larger primary. Buick figured that out in 1970, and Pontiac performance engines used larger primary carbs beginning in 1971. By 1976, virtually all of the Q-Jets were 800 (200/600).


For street use in street RPM ranges, the aftermarket intakes will gain style points, AND LOSE LOW-END TORQUE! Your choice, style or torque.


So, suggestions:


(A) carburetor - determine if yours is a 750 or 800. If 750, acquire an 800 (Q-Jet or the Carter GM TQ). If you go with the Q-Jet, buy Cliff Ruggles book on the Q-Jet. (OPINION) NOTHING new will outperform either of these two on the street, and probably won't come close unless set up by a professional.

(A-sub-a) manifold - stock Buick

(B) distributor - talk to a distributor dude, nothing wrong with a modified (curve) GM original.

(C) exhaust - 2 1/2 inch pipes, and good mufflers. Personally, I DETEST tube-headers on the street (really like to be able to listen to music).


The above should be good for a healthy performance increase, and won't bust the budget.


Have fun.




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Posted (edited)

Thanks for the great info NTX and carbking.... 


Actually, I gave the go ahead over the weekend to the custom garage that will be doing the upgrade...


One determination was the carb - currently, the stock (I believe) rochester carb is on it.. do not know cfm...  but I will be getting an 820 cfm pro series... the mechanic/engineer has used these in the past and feels comfortable - I know they are expensive...  $650-800 


I am getting a new alum manifold to better match the larger carb.


Getting all new electrical.... MSD Distributer/Coil/Ignition Firecore Spark Plug wiring


With that, with the point that was made with RPM, placing a converter in to get the engine to better rev to where the HP and torque is at quicker and smoother... hopefully, there will not be any hesitation in the gas flow how I have now.. meaning, when I floor the gas, there is that initial 1/2 second stall hesitation and then things kick in


Finally, since I was getting so much into the upgrade - I decided to go ahead and change the larger alum heads and cam for the 455...  do not know that ,info yet. but I know I will be pushing the compression to 10:1 or so...


btw, I think I have 2.5" exhaust already.  I need to double check...  because the headers where not in the price of the upgrade.


So, that is the new upgrades... My existing 455 was upgraded about 7K ago too with mainly stock stuff - still runs great, just got used to the zoom.. and want more of a zoom...


Likewise, all this started because I was leaking a little oil from my manifold that I needed to fix...


Again, any thoughts are welcome...  


I will keep everyone posted...  Likewise, I will place before and after pics along with during the build pics...





Edited by Takis (see edit history)

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2 hours ago, Takis said:



If the car is still together, run three 0-60 times and get an average.


Once the modifications are done, do the same thing, and compare the results.


You may be surprised.



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