72' Buick engine with 69 heads

[Guest]

I have a 1972 buick GS350 engine with 1969 heads. It has been bored to 40 over and the crank is 10 under. I plan to put a 760 eddlebrock carburator on the stock intake. I plan to port and polish the intake, and put headers on. This is going in a 1984 Buick Regal 2dr. What will the compression be? What cam should I use? What headers will fit? Will the stock motor pads work? I've never done this befor so I could use all the info I can get. The carburator is being used because it was free.

[Sgt Art]

Sounds like a project. My 2 cents is to find a formula previously worked up in a Magazine like Hot Rod or one of the other publications that cater to what want to do. No point tring to reinvent the wheel. The reason I say this, is I've seen so many guys (myself included) who throw a bunch of money into parts only to be disappointed with the results. Generally speaking, (and parts store guys will verify this) most guys go for the biggest of everything. Many times, that's a mistake. A big cam with a rumpty-rump idle really sucks in traffic, great for the track though. I think a 760 cfm carb is probably going to be more than you need. I had a 650 cfm square on a 455 and it ran great. I was surprised but when you consider you seldom run flat out with all four bores open, it made sense. Smooth idle with good off the line accelleration. There's almost no way for me to know you're compression ratio as there are too many variables. Tip, go no higher than 9.5:1. You'll be happy you did as your car should run fine on most pump gas and will last longer. On that note, have you had hardened inserts added to those 69 model heads? You may need them as I doubt they were engineered for today's unleaded fuels. Lastly, I don't like headers. I believe you'll see less than 10 percent increase in HP and you'll never "feel" it. They're noisy, they crack and aren't worth the hassle. Instead, put your money into a good duel exhaust system. There's a page somewhere here or a link for Buick performance engines, find it it will really help you. Good luck.

[Guest]

Thanks for the reply. I agree with you on the carburator bot since it was free I thought I would try it. I think I will take your advice on the headers also.

As for the cam, so far I have only found three. One was stock, one was for a motor home and one was for street raceing. Right now I'm thinking of the raceing cam.

[Turbo Loyd]

[color:"blue"]You can find the information to calculate your compression ratio at:

NHRA specs for engines

The formula for compression ratio is:

Compression Ratio = (C / N * 16.39) / (H + G+ R + D) + 1

Where:

B Bore (inches) 3.8

S Stroke (inches) 3.85

C Cubic Inch Disp. 349.3082208

N Number of Cyls 8

H Head Volume 51.00

G Head Gasket 13.84

R Piston Relief 17.30

D Deck Clearance 6.92

For:

Head volume 51cc

Gasket 0.02 thick

Piston dish 17.3 cc

Deck 0.01 from top of piston to top of block

Your CR is 9.01 with std bore and 9.2 with 0.04 overbore

I would use the 72 heads since they had 50 ccs instead of 51 ccs and the seats were hardened as mentioned above.

The stock gasket in 72 was 0.041 inches thick reducing the CR so make sure you use the thinner gasket.

I have this formula set up in an Excel file for easy use. For a copy E-mail me.

For cams be sure to check with TA Performance, Postons or AMP. See Charlie Evan's cam guide at:

Cam tables for 455

This will give you an idea of what is out there. The guys at AMP will be more than happy to guide you.

Finally there is a Buick 350 Forum at:

Small Block Tech

They will help you with lots of great information and tips. According to that group the 750 cfm carb should work out fine.

Sounds like a great project. The V8 board also has a Regal Forum for tips for what else to change in that Regal.

Hope this helps

[Guest]

Buick big blocks came from the factory with 730cfm rochester carbs until 1972 at which time they stepped up to 800cfm rochester carbs. I seem to recall an article in an old Kenne-Bell newsletter where they bolted a 1000cfm holley onto an otherwise completely stock GS455 and cut .25 sec off it's e.t. Also I was informed by a fellow gearhead(buick fanatic) that Buick started using hardened exhaust valve seats as early as 1965 because even back then they knew that side of the head got hotter and the better seats would help. If anyone out ther can verify this I would appreciate this. As far as going too big on the carb; Car Craft did an article on carbs in the last year that showed even though "the formula" for carb size((cu.in. x rpm) / 3456) x (volumetric efficiency of the engine = cfm needed)) indicated one size carb, the dyno showed that way bigger actually worked better in some cases.