I have a '65 327 block that is currently in the machine shop. My roadster originally came with a 327/365 and I would like rebuild a version of this engine that will be able to run on modern 93 octane pump gas, as this will be an occasional driver for me. I will be using the stock fuelie heads with 2.02 intakes, stock Winters aluminum intake and the original Holley carburetor. The machine shop is advising against doing a stock rebuild, instead recommending a set of flat top pistons and mild cam with a compression ratio about 9.6:1, claiming a stock rebuild (11:1 pistons and 30-30 cam) won't run well on 93 pump gas. Additional info: Car has a 3.70 rear and I'm going to be swapping the Muncie for a Tremec TKX close ratio 5-speed. The machinist also advised against using a Comp Cams Nostalgia Plus 239/246 hydraulic cam, which interests me, as it has a exhaust sound similar to the 30-30 solid lifter cam. I'm fairly new to the small block world, so I'm looking for some professional opinions as to the right direction to go. I'm sure I'm not the first guy to ask these questions about this particular engine. Greatly appreciate any insights. Thanks

 

Welcome to the forums! Not sure how many people want to jump into this subject. I loved the 327 from years in the past and had several. Machinist is really trying to dial you back, I can see his point about the fuel, It's sometimes hard to find a fuel blend for a High performance engine that works well. You could compromise and go 10.5:1 pistons. I would consider using roller camshafts for the reason of no zinc in new motor oils. (you can always add zinc or buy racing oils) Not sure if there are issues using roller cams in that engine. They do make mechanical roller lifters also. (to get that solid lifter sound) Or build it the way you want it. It's your money! This is a tough subject, to many options. Good Luck. Tell us what you decide.

 

Welcome to the forum.

I don't remember what the octane rating was in the '60s. I had a '68 GTO that was stock and it ran fine on regular. While not a professional, personally I would think with timing adjustments, you could probably run on 93 with your proposed setup.

A quick Google search revealed that premium could be as high as 98 in the '60s and some Sunoco stations had 102. Does the owner's manual say what octane reading fuel to use?

I would recommend using alcohol-free gas unless you plan on modifying your fuel system to handle ethanol.

 

The 60`s and 70`s used lead in its fuel that made a difference in the octane ratings of today. No ethnoil in the gas would be a good idea. If non ethnoil fuel availability in your area is a problem you might want to consider that with compression ratios you choose.

 

The mention of the removal of lead in gasoline reminds me that you should have the shop install hardened valve seats in your heads. Besides raising the octane, the other purpose of lead in gasoline was to prevent valve seat recession. I've read articles though that stated that unless the engine is under a heavy load continuously for a long period, valve seat recession won't occur.

While the addition of lead to gasoline increased the octane rating, 93 octane without lead is the same as 93 octane with lead tho.

 

Your machinist is trying to build an engine for you that you can run pump gas WITHOUT additives. If you want or need more than he is offering remember you will be stuck buying additives. Hardened exhaust seats are a must. Seat erosion WILL occur over time, even under light loads. A choice only you can make but your machinist is not wrong.

 

You might ask, why can modern engines run 10.5 compression and even higher yet still run Ethanol pump gas? The answer is they do not use a carburetor and mechanical points distributor. Modern electronics manage variable ignition timing and there is an ignition knock sensor to retard ignition under load (and they have hardened valve seats and ethanol compatible seals). With your vintage approach, you have NO protection against engine knock, which means you have to retard timing (defeating your performance) or risk early detonation and permanent engine damage. You could do your build and replace your Holley with a modern day throttle body fuel injection along with an electronic distributor to get close to the same approach as a modern engine. I'm not a fan but Holley Sniper and others fit in place of your standard carburetor with just a couple of extra wires and also extra fuel lines and high pressure pump in the fuel tank. There ain't no free lunch.

With the build you propose your only other option is to buy 100 - 104 octane gas by the barrel (like VR Racing) if you have a place to store it, and then add it to your non ethanol gas to increase the octane. Octane is linear so if you have one gallon of 93 octane and add one gallon of 104 octane you end up with 2 gallons of 98.5 octane.

 

Well said. Sunoco 260 GT Plus 104 Octane Race Unleaded Fuel sells for $105/5 gallons on eBay. It was cheaper at another website though.

Of course this octane is the average of the old research octane and the motor octane ratings. In this case, the old research octane would be 110. I don't know when they went to the new average rating but probably around the time they went to unleaded gas.