Compression Ratio & Pump Gas?

[Jake1798]

Hey guys,

Just ordered a pair of World Sportsman II 64cc heads for my '76. The guy who I am dealing with told me with my setup I should be running around 10:1 compression and that I will be fine running premium fuel. I just wanted to check to make sure that premium fuel will handle that compression ratio. Thanks.

-Jake

 

[Lucy64]

I had a new smallblock built last year and it is also 10:1. It runs fine on the pump high test gas. From what I was told that is about as high compression as you should go on pump gas.

 

[LVMYVT76]

What else are you going to do to your motor?

 

[Jake1798]

What else are you going to do to your motor?

Nothing. I have already purchased and installed (with the exception of the intake and carb):

Pro Form Aluminum Roller Rockers
Crane Cam Engergizer Hyrdaulic Camshaft & Lifters With .454" Lift
Edelbrock Performer 600cfm Carb W/ Electric Choke #1406
Edelbrock EPS Intake (non -EGR) #2701
World Sportsman II 64cc Cylinder Heads

-Jake

 

[Lucy64]

You will have no problem at all running pump gas on this setup at 10:1.

 

[Jake1798]

You will have no problem at all running pump gas on this setup at 10:1.

Okay thanks very much Lucy.

-Jake

 

[Evolution1980]

I second that...

My ZZ4 is 10:1 compression and runs just fine on 93 octane

 

[GerryLP]

Hey guys,

Just ordered a pair of World Sportsman II 64cc heads for my '76. The guy who I am dealing with told me with my setup I should be running around 10:1 compression and that I will be fine running premium fuel. I just wanted to check to make sure that premium fuel will handle that compression ratio. Thanks.

-Jake

Jake,

Perhaps you can check the cubic centimeters (cc's) on the piston top (once the the old heads are removed), and then cc the head chambers, and then you'll be on your way (there are other measurements to be made) to accurately determine the compression ratio (CR) for your engine. This way, you won't have to guess whether or not which gas to use (to avoid the inherent problems).

A kit will cost you about $130 dollars from the average performance vendor, or perhaps you're lucky enough to have a neighbor, friend, or relative who has one of these cc'ing kits. I pieced mine together for abut $82 dollars.

I can tell you from personal experience that depending on your own goals on the performance for this engine...(Let's face it, can there really be such thing as having too much horsepower on one's engine???)...that once you work all the tuning and adjustments possible, and if you still cannot get to your goal, then you'll start to second guess the actual CR in your engine.

GerryLP:cool

 

[Glensgages]

You will have no problem at all running pump gas on this setup at 10:1.

My Z28 runs-on Sunoco Ultra 94 with 10.3+ compression, but I think the camshaft, with 244* @.050"-lift, helps bleed-off some squeeze.....

 

[Jack]

Jake:
ZZ4 has more cam (than energizer) that helps bleed off CR and has aluminum heads that help reduce knock (WPS2 are iron) ... apples & oranges.

What is Jake's original motor (&CR)??? if L48 (dished 4VR piston) or L82 (flat 2VR piston) makes a difference ...if block has ever been machined it makes a difference. What head gasket (thickness) is used with WPS2? New CR w/ WPS2 64cc may well be less than 10:1 ... may be real close to 9:1.

Handy & rather accurate CR calculator (if you know some of your combo's specs):
http://www.campbellenterprises.com/Race math calculators.htm#Compression ratio calculator

Bottom line ... if 76 C3 block & pistons are stock OE ... you'll be able to run some grade of pump gas w/ WPS2 64cc ... may not require hi-test ... you may need to tinker with the ignition timing.