The 455 started in 1970, correct? They had higher compression than the '71 and on, right? How do the later heads flow compared to the '70 heads? Did the low compression heads just have larger combustion chambers? Could a person install domed pistons in a "low compression" motor to bring it to life? Did the "low compression" motors come with a smaller cam? What kind of power ( hp and tq ) could I expect out of a stock "low compression" motor? It can always be improved on , right? I know there are alot of questions, but, I figured that while I had your attention.............ask away!
Hi, not to toot my own horn or anything but my 72 full weight GSX clone has gone a best of 11:31 so far on a 9.7 to 1 motor and pump gas with a hydraulic cam, but it is not the most street friendly setup out there, I mean I can drive it just fine on the street but like say my mom would have a heck of a time. My wife has driven it a couple times and loved it. I would bet others have gone faster than this on pump gas motors. I have no idea what this translates to in hp/torque numbers, I would assume around 500 hp and 520-540 torque? Tom
Yes, the 455 started in 1970. Yes, they had higher compression than 71-later The 75-76 heads are open chamber and had much lower compression. I'm not sure about flow differences stock for stock. Maybe someone else can answer that Only the 75-76 had significantly larger combustion chambers. The major difference relating to compression was the piston dish. The 1970's had less dish than the 71-laters (which from everything I've seen/read were essentially the same piston). A person could install "domed" pistons, but there are several choices out there that will give good compression with the 70-74 heads. I'm guessing there were a variety of cam differences from 1970 -1976 455's throughout the different Buicks that they were in. I don't know what the different specs were by make/model though. There are guys running some good ET's with low compression motors, although they're running forged pistons. I know Jerry Roslie (gotbuick) has seen an 11.03 on a 9.3:1 motor with some very good aluminum Stage 2 heads. Rick Henderson has gone 11.6's with similar compression with some really good iron heads in a 4000 lb car with 3.42's. Good heads with a matched combo seem to be the key.:TU:
Does anyone know the hp/tq ratings for the 455 from '70 on? Are there any years to totally avoid? What years were the 430's and what car did they come in? What years were the 400's and what car di they come in?
Here is a link that will answer most of your questions except the torque. http://viragotech.com/BUI-68-82.rtf I got the link from here: http://www.buickpartsdirectory.com/all_links.htm Pretty good site.:TU:
Buicks don't really use "domed" pistons. A "flat top" piston in a BB Buick yields about 12:1 compression (Depending on several factors). BB Buick heads have relativly small combustion chambers (68-78cc) compared to other makes.
Also beginning in 72 the rating methodology changed from gross to SAE which is around a 20-25% difference. Torque 1970 510 ft lbs 1971 450-460 depending on the 455 variant 1972 360-390 " " " " ". 1973 same as 72 1974 270-375 depending on the 455 variant. Also remember the hp rating were just a paper figure to meet the 10 to 1 weght to Hp limitation for intermediate cars imposed at that time by GM.
As long as I've been around I didn't know that. I see folk on the net get fouled up on the gross and net HP #'s all the time; but, I didn't realize that a ratio guideline was in place. What does that do to the ratings of the heavier cars ratings as far as skewing them? I mean ie a 4000# car ratio works out to max of 400hp, right so a heavier car would be understated in hp rating to meet guideline if it was rated less than 400hp. o No:
I think they assumed a lot of 3600 pound cars on average so they rated a lot of cars 360 hp --remember. GTOs , 442s etc. Thus the 10 to 1 mandate was just met although in some cases just on paper. So let's take the same 455 stage 1 engine in a riv ifor 1970 and compare it to a GS. It got a 370 hp rating whereas the same stage 1 GS got a 360. Why? Because of its higher weight there was no danger the Riv would exceed the 10 to 1 ratio and I suspect it was not considered an intermediate size. The actual hp at 5000? rpm on the factory dyno was 376. (Per D. Manner the godfather of the engine at Buick)
ya, you have to set the base HP assuming the lightest weight car it's going to be used in our you're going to start getting some uncomfortable questions about why the same basic motor assembly produces +40hp in a heavier weight car for no good reason. as always, you can safely ignore the bureaucrats with a wink and a nudge BUT you HAVE to give them a fig leaf to hide behind. Buick engine overview at TA Performance you'll see that 430's were available from 67-69 and then it was the 455 from 70-76 photo comparison of some factory 455 pistons, courtesy of the Buick Performance club listing of casting numbers for blocks with head chamber size and 'hi-flow' factory heads highlighted courtesy of Atlanta Buick now that i think on it, i'm not sure why i'm reposting all of this instead of just linking it
Here is the homepage for navigation purposes for my site: www.buickpartsdirectory.com Thanks for the plug dude!:TU:
