View Full Version : More head questions?

06-28-2006, 04:21 PM
I hate to keep beating this dead horse but I have another question on the 259 head to 232 block, head swap. I received alot of info on valve choices, valve seal choices, valve guide choices, rocker assembly swapping, notching the block for clearence etc.. I finally found a good automotive machine shop that isn't scared of Studebaker heads [scared into jacking up the price]. Regarding shaving the heads the number given to me by Ted Harbit was .060. I'm assuming that this returns the engine to its previous compression ratio [7-1 or 7.5-1]. Though I'm planning to supercharge this engine, in case it does not work out how much would I need to remove from these heads [535976] to get closer to 8-1 C/R? When shaving Stude. heads how much is safe and how much can be removed before getting into valve train and intake fitment issues? Thanks all,

Darryl C. Lewallen

06-28-2006, 05:03 PM
I wouldn't shave them more than 0.060. You can use thin head gaskets to gain a little more.

Gary L.
1954 Commander Starliner (restomod)
1959 DeLuxe pickup (restomod)

06-28-2006, 05:24 PM
I would not mill them down any farthur than to get them flat. As soon as you jack up the inches you also raise the compression ratio. When the heads are milled the intake ports don't match anymore and you have to mill the intake manifold to get it to realign right. Too much trouble to get a little extra compression and todays gas sucks. Unless you are going to E85.

06-28-2006, 08:35 PM
I know very little about it but have been told superchargers and higher compression are not a good mix. Is it a question of degree?

06-28-2006, 10:50 PM
Everything is relative. Static compression ratio, boost pressure and camshaft duration are a multi-variable equation. Current microprocessor technology, even with the junk gas we have today, can supercharge a 10:1 compression ratio to 10-12psi and it will work just fine.

Studebaker's 1957 Golden Hawk with the standard short duration camshaft was limited to 7.5:1 compression ratio with only 5-6psi boost. By 1963-64, the Studebaker R2, with premium gas was happy with 9:1 and as much as 7psi. The longer duration R1-2 camshaft bled off enough compression to make it work.

Some of today's top fuel dragsters run only 6:1 compression, but are loading the cylinders with so much fuel and boost pressure, they almost hydro-lock.

thnx, jv.


06-29-2006, 12:11 AM
As I understand it,a supercharger gives you "virtual" compression - meaning that you are forcing more mixture into the cylinders to burn, and therefore you need lower compression when you super (or turbo) charge than when you don't. I am far from an expert on supercharging, I suggest you contact Mr. Harbit, the expert, and ask him again. Be sure he understands that you intend to supercharge this engine, and the amount of boost you expect to run. Do this before you mill anything.

06-29-2006, 01:35 AM
Every engine has 'virtual compression'. The static compression ratio usually referre to is the size of the combustion chamber to that of the cylinder plus combustion chamber, plus head gasket and any piston dish..

The actual cranking pressure is affected by the duration of the camshaft. Take an R1 10.25 c.r. engine and install a regular Stude V8 camshaft and the cranking pressure jumps from 185 to 210 psi. Take a regular 8.5 c.r. Stude and install an R1 cam and the cranking compression drops from 160 to 130.

Add a supercharger and as the RPMs go up and the boost rises, the cylinder filling jumps from the 80% of a normally aspirated engine to 110-150% of a boosted engine. The pressure goes up accordingly, and all of a sudden the 9:1 R2 compression developes the same pressure at high RPMs like it is 12:1.

As mentioned earlier, each engine parameter affects the pressure the cylinders experience. To discuss whether a particular compression ratio and boost pressure are compatable, we also have to know the camshaft duration, the RPM vs boost curve and whether there are any electronic control functions involved.

thnx, jv.


06-29-2006, 06:10 PM
I was just looking for an easy way to achieve an 8-1 compression ratio in case the supercharger didn't work out. I've heard that 8-1 is about max for an older designed engine and even without the blower it would be OK. Thanks,

Darryl C. Lewallen