[Aussie XAXB]

I've been playing around with Desktop Dyno2000 and came up with a very interesting cam for my 351C. My only concern is that the duration would be too short for the amount of compression.

I have an Australian 351C with the Australian 302C closed chambered 2V heads. The intake valve is 2.055" and the exhaust is 1.660" and they will be pocket ported. I suspect (popular with these heads) to have 11:1 compression on the pistons. I won't know for sure until I take the engine part and measure the piston spec's.

I want to build the engine for mid range torque or about 2,000-5,500 RPM and DD2000 came up with the following...

The cam on the intake side only has 213* duration at .050" lift. It has 228* on the exhaust though. Is the 213* figure too short with this compression? Will the dynamic compression shoot up too high to run the car on the street? I expect to put in premium gas (93 octane) and occasionally 100 unleaded octane to be mixed in. It ran well on 91 octane, but did even better on a mixture of 93 and 100. Never had a knock or ping.

The car will have a 5-speed manual and weighs about 3,350 pounds. The rear gear will be about a 3.25 - 3.75:1 with 26-27 inch tires. The car will be driven on the street to cruises and car shows as well as for fun. It will not be a daily driver. I will also take it down the drag track a few times I am sure.

Thanks for any input.

Steve

 

[IanRiordan]

Clevelands, by virtue of their bizarre cooling system tend to run hot out here, so what works in winter may not in summer.
There are no hard and fast rules on comp vs cam timing - restrictor plate engines run MUCH higher compression than unrestricted and get away with it because you need to burn oxygen to generate heat and the less oxygen you can burn the less heat you generate.

 

[Aussie XAXB]

I thought there is some "magic" about compression ratio vs. cam timing. Hhhmmm.

The car will not be driven during the winter and the occasional run down the track will only be for fun, not competition.

Steve

 

[Rick WI]

It would be almost unheard of to be able to run AN ACTUAL 11:1 compression at 213 duration camshaft, old style iron heads on 93 pump gas.

Before you come to any conclusions on what you currently have you need to tear down the motor, measure everything and calculate what your current compression really is. I doubt you have 11:1 right now if your running 91 octane pump gas with no detonation.

 

[curtis73]

Agreed. If you truly have 11:1, I'd consider more than 213*. Cranking pressures will be much too high for pump gas. 104 octane territory there.

225-230 is a little more in the middle I would think.

 

[bullheimer]

i'm with them try this when you figure your stuff out. also make sure you buy your timing gears for a 1970 motor, that way you will run a gazillion times better than with a later or new smog crap era set.
http://216.178.81.108/forums/showthread.php?t=469761&highlight=compression

 

[Aussie XAXB]

Thanks for all the input guys. I know I need to take the thing apart to confirm exactly what I have but I have to work on the body and get it back into shape first. The problem is I really need to let this car sit while I do suspension on another driveable car. I can't resist doing the planning on this one though.

I found some more info about this online, I think at a car magazine website. They recommend about the same thing when it comes to duration and compression.

I have no idea what the cam that is in the engine is like. The car pulled incredibly from 60 mph on up though.

Steve