The Stovebolt Site Forums The Shop Area The HiPo Shop Head work?

I am planning on milling the head for a 235.I am going to take .100 th off the head,sink the valves .100th" and trim .100th" off the valve Stims.anyone else done this? Did it make a difference ?

Why?

I just wondered if it made much difference in power.It should bring compression up from 7 to 1, to somewhere around 9 to 1. Maybe a little more.

Why do you think you need to cut the valve tips .100"? Sinking the valves that much will require you to also shim the valve springs a lot also. Sinking the valve that much also will kill the airflow thru the SSR and probably nullify most of any gain you get from the compression increase.

My experience is that the most restriction comes from the exhaust port flow/design on this head and further recessing the valve into an already tight corner exacerbates this problem. Start by zero decking the block and investigating pop up pistons before polluting your valve train geometry with head milling.

I am no expert on head flow for sure.As I understand it ,if the valves are not sunk as much as the head. Is milled,they will come in contact with the piston.I have not heard of a replacement piston that will increase compression for this engine,Maybe there is one available? If there is that would certianly be worth looking in to,but I would think a dome type piston would still contact the valve.I have high pressure springs that will work after the valves are sunk.The valve Stims would have to be trimmed to keep the geometry correct.I understand how all of that works.What I don't understand is how it would affect the air flow enough to off set the gain from the compression increase.I maybe wrong ,but I would think these engines were lower compression,because they were coming from a early design ,that we're made to start by hand crank.As electric starters proved to work,the compression increased,and air flow and engine design got better.

Well another misunderstanding people have about compression is that they think or assume a little gives you a lot in return, and it doesn't. On your engine for example, you may increase yours by 2 full compression points, but it might only give you a 10 HP increase in power on an otherwise stock engine.
Airflow into an engine is very sensitive to abrupt changes in the airstream. Even though sinking a valve by almost an 1/8" may not seem like much to you, it is a huge jump as the head sees it. And it will change the relationship and flow of air as it transitions over the SSR drastically. Porting technology has increases many hundreds of percent since the days of California Bill and others and much has been learned that they didn't even know back then. The closer the valve moves towards the SSR, it makes the radius smaller and hurts the velocity and it restricts the incoming charge in a bad way.
As far as pistons go, dome pistons are available from Ross and others that will raise the compression the correct way, and leave the valve relationship where it needs to stay since you don't have to try to compensate, so you gain on two levels instead of on one and losing on another.

I would do the pistons and maybe clean the ports up. Maybe there's a nice cam available also.

I already got. A cam from Howard's cams.I could do pistons if I can get them.I am not really looking to make a lot more power,but do want to get the most for the money I spent.That's why I am asking ? here.If I wanted a lot of power I would go with a different engine that I know more about.I want to do something that is more like done in the 50's and 60's.I want my truck to be a resto mod, that I can drive and take to the local car shows and local sonics drive in.Many go with a v8,I like that as well ,and know it cost less for what you get.I don't want to do that with this truck.I want a old school cool kind of look.I want it to appear to be stock,yet little things changed,so when others hear it run and see small changes know it's been tinkered with.

Do some minor head work/clean up of ports, maybe gasket match the ports? Thinner head gasket? CP-CARRILLO. Ask for Mike. (929)567-9000. They show je pistons and arias with 9.1. Also there's a flatlander site. Forged components for a 235. The rods are long as heck though. Good luck.

The milling job you're describing has already been done for you- - - -just use an 848 casting number head. Chevy raised the compression that way starting in 1956, I believe. Recessing the valve doesn't present a problem because the flat part of the head where the intake sits is milled away, so no shrouding happens. Yes, it's necessary to trim the intake stems to maintain proper geometry with the recessed stems. Do yourself a favor and fit some 1.6" diameter exhaust valves, and pocket port the head to accommodate the bigger valves. They're identical to small block V8 exhaust valves, so they're plentiful and cheap.

You won't raise the compression two ratios by milling .100"- - - -whomever told you that was ignorant or a liar. If you've got much over stock lift on the intake valve lobe of the cam, consider flycutting the top of the piston a little to assure you don't get valve-to-piston contact. A .030" thick solid copper head gasket used to be available to stovebolt hotrodders- - - -not sure if it's still being made.
Jerry