9.0/1 Compression Ratio Engines

[C9x]

New guy here.

Was wondering if there's any information on 9.0/1 CR engine building?

I'm running a 462" late Buick (455 .030 over), very mild cam, shot-peened rods, forged pistons, roller rockers, balanced, 750 Edelbrock carb jetted for the altitude (3300'), 1 7/8" primary and 3 1/2" collector headers in a 32 roadster.
MSD 6AL and Mallory Unilite.

Starts easy, runs good and I really like being able to run 87 octane summer or winter.

Reason I ask is, I have another 455 Buick to build.
Thinking 9.5/1 CR on this one and a pair of Edelbrocks Aluminum heads should bring it just a touch over 10/1.
A pair of 500 cfm Carters go on this engine, headers and the rest of the build will be similar to the engine above.

This engine also goes in a street driven roadster.

Light cars and lotsa torque are a lot of fun.

Thought I'd ask about 9.0/1 CR builds to see if I'm overlooking something critical.

I did a search, but found nothing.

[Cammer]

Choosing and bolting parts together without a well thought out plan often leaves an engine owner disappointed with results.

I can not stress enough the need for a comprehensive plan before starting any engine build!

You need to consider the unique characteristics of the 455 Buick engine before making any build decisions.

A stock 455 Buick will provide plenty of power for your car. Are you considering the dual four barrels just for looks? A single four barrel carburetor with the proper manifold can be set up to easily outperform your chosen dual Carter setup.

I had a light T roadster in my past running a stock 401 Buick and wide asphalt racing tires. This car would easily light up the rear tires at highway speeds with but a gentle touch on the go pedal.

Keep us in the loop as your build progresses.

[seattle smitty]

The reaction you are likely to get here is that you don't first pick a compression ratio and then build whatever engine to that compression. The compression ratio is determined after a lot of other things are known, such as combustion chamber and piston crown shapes, port and valve details, camshaft specs, and much more, not to mention gearing and weight and intended use of the vehicle, and of course, the preferred fuel octane.

[Ol' CW]

Your cam choice is closely related to your CR as this will affect the dynamic compression. This is very basic stuff, but even if you're limited to one choice on block, heads intake etc, your cam needs to work with the static CR or you are wasting your time

DV has written some good stuff about this and Keith Black has a easy-to-use dynamic compression calculator on their site; or the easiest thing to do is call your cam company with the particulars for your engine and they'll make a recommendation

Agree, the dual 4bbl is just for looks on a street motor or dual plane intake. Lots of extra headache to set up for less power and mileage.

[Cammer]

These shops are proficient in Buick engines:

Home

TA Performance Products Inc.

The 455 Buick cylinder heads are limited by pushrod location and porting them can prove frustrating. Most will drill out and sleeve pushrod holes. The center head bolt boss should be drilled out and a substantial steel sleeve installed to protect port integrity after porting. Larger valves can be installed as dictated by desired power levels. I provide this information as a reference to the amount of research needed for a good engine build.

I do not usually make specific part recommendations over the internet. The above listed shops can assist you in component selection for your unique build.

By now you can see the importance of planning your engine build.

[C9x]

Thanks for the information gentlemen.

Fwiw, the dual quad setup was at the recommendation of Kenne-Bell who in fact recommended dual 750's, but I chose 500's as well as 9.0/1 CR mainly for running low or mid-octane gas on the street, but also at the nostalgia drags once in a while.
My aim was mid-range torque with an occasional run up to 5500 rpm.

Since the car is so light - 2300# sans top and 4-point roll bar, 2400# with - getting the maximum HP was not a necessity.

Just a moderate build did the trick and the car's run fine for 48,000 miles so far.

Reasonable gearing (3.70 diff) helps as well, but after Septembers street drags on Beale Street in Old Town Kingman, Arizona in September a 3.00 diff goes in for a little better gas mileage.

I've had four different cams and several intake setups on the car and have pretty much settled on the present combo with it's very mild cam (260 - 266 degrees advertised duration) and the Edelbrock Performer with Edelbrock 750 carb jetted/rodded for the altitude - 3300'.

Granted, not as many changes as you folks get into with dyno tuning et al, but enough to make it interesting.

Subjective, I know, but it seems the dual quads run a little harder than does the single 750.
Probably going to learn the truth no matter which way it goes after our local dragstrip goes in.

From a lot of the Buick oriented reading I've done, it looks like I'm on the right track with this particular combo.

I think too, using one of the bigger cams I have stored away for the 10/1 CR engine will work ok.

Trouble for most amateurs is they don't have a dyno and have to make reasonably good guesses right up front.

In any event, I enjoy this site greatly and like reading what David writes as well as what others have to say.

Thanks again.

[Packard V8]

FWIW, the desktopdynosim programs are fun and will point the way. They can show the crossover points where more cam, more compression drop off. However, they can't show where it will ping. I don't see you getting into any trouble at 10:1 with aluminum heads and a light car.

The one real mistake I see you about to make is thinking you can run "one of the bigger cams I have stored away" with "a 3.00 diff goes in for a little better gas mileage." That will be a miserable combination. Bigger cams need lower gears. With a 3:00 diff, the engine will at cruise way below the sweet spot and fighting the overlap. Choose one - big cam/low gears or short cam/high gears. For a bigger, peakier cam (230@050" and above) I always choose the highest sustained cruise speed I'm ever likely to be holding and gear for the top of the torque curve there. Whichever way you go, stay with a 180-degree intake.

thnx, jack vines

[C9x]

Originally Posted by Packard V8

FWIW, the desktopdynosim programs are fun and will point the way. They can show the crossover points where more cam, more compression drop off. However, they can't show where it will ping. I don't see you getting into any trouble at 10:1 with aluminum heads and a light car.

The one real mistake I see you about to make is thinking you can run "one of the bigger cams I have stored away" with "a 3.00 diff goes in for a little better gas mileage." That will be a miserable combination. Bigger cams need lower gears. With a 3:00 diff, the engine will at cruise way below the sweet spot and fighting the overlap. Choose one - big cam/low gears or short cam/high gears. For a bigger, peakier cam (230@050" and above) I always choose the highest sustained cruise speed I'm ever likely to be holding and gear for the top of the torque curve there. Whichever way you go, stay with a 180-degree intake.

thnx, jack vines

Agreed on the big cam and high gears.
The 3.00 diff goes into the 32 roadster.

I probably explained it poorly, but the yet-to-be-built 10/1 engine goes into a different roadster.
This one a 31 A on 32 frame rails - a traditional and popular hot rod - with chassis set up for drag racing now and then.

Gearing and tire size will about equal the overall gearing combo of the 32 with its present 3.70 diff and in fact the 31 will be about 5% lower overall.

Weight looks like it will come in at about 2200#.

Part of the reason for building the new roadster is that I had some parts left over from the 32 build and even though they're not quite right for optimum output they're there and I plan to use them.
I can always make changes later....


As an aside, every bracket racer I know is striving for maximum output with their engine, but it seems a modest engine in a light car with gears that won't allow the engine to be overly stressed by high rpms in the traps is the way to go.

Consistency is the key and if the car runs a half second slower or 8-10 mph slower it won't be a problem for me.

I like the aspect of running a hydraulic cam, street type carburetor, change the oil and go to the races far better than a faster machine that requires thrashing on it between rounds....

[JohnBlazeLTZ]

I know I am probably just cluttering up your post with this comment but my dad has a Buick Rivera with a mostly stock 425 Super Wild Cat and dual 4 barrels and as heavy as that car is...the tires will still roast...great cars them Buicks.

[C9x]

Originally Posted by JohnBlazeLTZ

I know I am probably just cluttering up your post with this comment but my dad has a Buick Rivera with a mostly stock 425 Super Wild Cat and dual 4 barrels and as heavy as that car is...the tires will still roast...great cars them Buicks.

You're not cluttering, always interesting to hear about Buicks on the street.

I'm amazed at how easy some fairly modest 455 powered Buicks get into the 10 second range.