Oliver gurus

Can anyone tell me how big you can take the valves on a 310 12 port head? Also does anyone know what cfm a stock 310 head is? Are the valves the biggest restrictions for a 310 or is it the intake? Any infomation would be great!

Thanks,

I have an 88 with a 310 which has had extensive head work. Prior to doing the head work(porting & polishing and bigger valves) when put on a flow bench we found that the exhaust flowed more than the intake.
I've been told by several high performance engine builders that the exhaust should flow 85% of what the intake flows, so lets say your intake flows 100cfm's then your exhaust should flow 85cfm's. With all this being said my stock head flowed 178cfm's on the intake and 188cfm's on the exhaust, after installing the biggest intake and exhaust valves that we could stuff in the head we ended up with 1.9" intake valves and 1.75 exhaust valves. I also have a set of Murphy's high ratio rockers and a good cam grind, after all this we ended up with 235cfm's on the intake and 224cfm's on the exhaust @ .600 lift. I've been told that you can possibly get a few more cfm's but in my case I'm afraid of going through the water jacket. I would say that the 1.9 valve is the biggest valve that you use because the valve sits in the combustion chamber and will get shrouded. In my case I actually had to lay back the sides of the chamber to help the flow. You have to keep in mind that as you remove material from the chamber walls you also take away compression.

I would say that the intake manifold is the biggest restriction. With all the head work I did I still couldn't get it to rev more than 4200 rpm's and keep in mind I built this tractor to be a high rpm puller. Then I built a custom intke and exhaust header and through a holley 4 barrel carb on it and now it will rev to 6,000,
I don't rev the motor that high but I do take it up to 5'000 rpm's all he time.The horsepower increase was incredible. I hope this info helps.

This is great information! Thank you very much for your response. I may need to pick your brain more in the future,as I'm learning as I go about building pulling engines.

Do you know what rpm the stock flywheel will hold?

Look into using a 310D head its crossflow It might save you money in the long run.

I would not exceed 3,000 rpm's with a stock flywheel. The stock flywheel is a ticking time bomb once you exceed that rpm.
If you have a good machine shop in your area, they should be able to easily make a steel one for you.
Just use the old one as a template, although if you are going to build your engine up, then you might want to install a double disc clutch. I've done all of this so if you need any info, I can help.