[70 Dream]

Originally Posted by BruceWilkie

For the OP I suggest low enough compression you can "limp home" on cheapest gas available should you go somewhere need gas and they are out of premium.

Bruce, your comment above was not helpful in any way. The board can correct me if I'm wrong, but I thought the purpose of the PY Forums is all about knowledgeable members helping less knowledgeable members (like me) and sharing info, not looking down their noses at them. By the way, my name isn't "The OP," it's Harry.

[BruceWilkie]

Originally Posted by 70 Dream

Bruce, your comment above was not helpful in any way. The board can correct me if I'm wrong, but I thought the purpose of the PY Forums is all about knowledgeable members helping less knowledgeable members (like me) and sharing info, not looking down their noses at them. By the way, my name isn't "The OP," it's Harry.

Harry... far from looking down my nose. Sorry it seemed that way to you. What I posted was info that could help you understand how cam choice affects actual compression which affects fuel octane compatibility. Also provided an excellent link on detonation and preignition. How is that not sharing info???

It wasnt my intent to give you my suggestion on approximate compression and cam choice. You have decisions to make not me. You want highway gearing and good idle with strong performance best I can tell. You want no worry fuel choice too it appears. Generally this suggests a modest cam choice and modest compression. The more you push boundaries the more issues you have to overcome.

The following combo works well in my wifes 69 bird convertible @ 3800 lb with driver full tank. 2.56 gear with powertax posi, non sticky regular BFG TA Radial 255/60-15, T400 2200 stall convertor(A freebie B+M from a parts car). 406 CI 9.7 compression home ported 1969 #46 heads with large valves, crower 60916 hyd cam and P65 dual quad with 1" 4 hole spacers topped with two 750 AFB's. Car has been driven thousands of miles since 2004 when this combo went together including the 1000 mile drive from our old home to our new home. Around town gets 12-14 mpg (carbs set tandem or progressive) and highway it gets 15-16 mpg. Performance is very good, idle quality very good(Deb says sounds too stock), around 15-16 in idle vacuum neutral (800 rpm) and in gear about 13 with a 750 rpm idle. Not a racer but it has gone down a track a few times with a best of 13.05 104 mph and spinning 60 ft times in the 2.20's. Certainly enough there to go mid twelves with traction(probably better with gear swap). Car only uses 1st and 2nd down the track. Recently sold the Dual quads and for now my RPM 780 holley are on there until I can put together an EFI. Car seems to run the same maybe a tid weaker up past 5000. Car usually runs on 93 no issue if stuck with 92 but 89 has worked ok except when hot it lightly pings from around 4k rpm up, and pushed hard and could probably tune around it If I wanted.

Our combo is not your combo. A 428 or 455 would have different results. There are choices that could net better or worse results. I'm not going to dictate what I think you should run. Thats your choice your decision to live with!


Cliff fwiw you seem to have good gas in Ohio. All our trips regardless of vehicle the fillups in Ohio net us our best MPG.(even fighting Cleveland, Columbus, Cincinatti traffic) NY gas we lose 2mpg. TN maybe 1/2 to 1 mpg.