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Old 01-13-2011, 01:34 PM
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1968 Z/28 engine fuel requirements

Let me start by listing the engine specs for a 1968 June built engine. These specs are from z/28 fact books and other articles/manuals not strait from my brain.
Holly 800 cfm carb., Chevy aluminum high rise intake manifold, 2.02” 1.60” double hump heads, I believe they are 64cc’s. “30/30” solid lifter cam with .452” intake and .455” exhaust lift, 229 degree intake duration and 237 exhaust (both measured at .050” tappet lift) and 78 degrees of overlap (at 0 lift). 11:1 forged aluminum pistons with floating pins, shot peened rods, forged steel large journal crank (2-bolt mains probably the weakest link).

Can I run on 93 pump fuel? The previous owner did and said he didn't have any problems. I hear so many different opinions. More questions to come...

Thanks,
Dave

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Old 01-13-2011, 01:58 PM
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Quote:
Originally Posted by 1968z28dave
Let me start by listing the engine specs for a 1968 June built engine. These specs are from z/28 fact books and other articles/manuals not strait from my brain.
Holly 800 cfm carb., Chevy aluminum high rise intake manifold, 2.02? 1.60? double hump heads, I believe they are 64cc?s. ?30/30? solid lifter cam with .452? intake and .455? exhaust lift, 229 degree intake duration and 237 exhaust (both measured at .050? tappet lift) and 78 degrees of overlap (at 0 lift). 11:1 forged aluminum pistons with floating pins, shot peened rods, forged steel large journal crank (2-bolt mains probably the weakest link).

Can I run on 93 pump fuel? The previous owner did and said he didn't have any problems. I hear so many different opinions. More questions to come...

Thanks,
Dave
Try it and see how it reacts. If it pings that can be managed in several different ways which include:

- back off the timing till it stops

- richen the mixture till it stops

- source the carb air from outside the engine room to get cooler air

- reduce the engine operating temperature

One, some, or all of these can be used.

In addition to just backing the timing down, if it only detonates in places changing the timing curve to a slower rate can help. Also, the use of alcohol/water injection is very useful and these systems are inexpensive and don't require tearing the engine apart for installation, this is an old and effective trick.

Bogie
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Old 01-13-2011, 02:00 PM
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Yes you can get by on 93 but keep the RPMs down. I run a BB 396/12.5:1 cr As long as I keep it under 5500 it does fine. You may want to choose a brand name gas and tune your engine to it.
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