This is my first big block build-up, so this might be a dumb question. I have a set of #781 heads that I am thinking about using, so I was tearing them down the other day. Underneath each exhaust valve spring there was one shim. This I have seem before. Under each intake valve spring, however, there was a thick rotating washer that the valve spring set on. I have put together a few sets of small-block heads, and have never seen these. Do all big block heads have these? and if so do they just go under the intake valve springs?

Also, other than cutting the heads for 2.19/1.88 valves, what are some other things that would help the performance of these heads?

Porting, maybe polishing if it makes you feel good and definitely go with the larger valves. I did the porting myself, minor polishing, larger valves and when my heads returned from the shop, the springs had those washers under them. I forgot what they are for specifically , but these guys can tell you. :D

There exhaust valve rotators. For performance applications they are removed and discarded. In their place, a hardened .300" thick washer is used which are sold by many of the major cam companies...their called exhaust rotator spacers.

Originally posted by THE DUDE:
This is my first big block build-up, so this might be a dumb question. I have a set of #781 heads that I am thinking about using, so I was tearing them down the other day. Underneath each exhaust valve spring there was one shim. This I have seem before. Under each intake valve spring, however, there was a thick rotating washer that the valve spring set on. I have put together a few sets of small-block heads, and have never seen these. Do all big block heads have these? and if so do they just go under the intake valve springs?

Also, other than cutting the heads for 2.19/1.88 valves, what are some other things that would help the performance of these heads? =
Mark,
They are rotators & are under the exhaust spring not the intake.
Not all Rat heads have them but most do.
Comp makes a spacer to replace them, looks like a thick shim.
SB's had them on a lot of heads but they were on top of the exhaust spring & were part of the retainer.
You don't want them in any performance application.

Find a shop that knows how to cut seats & the angles leading to them properly.
Just putting the larger valves in won't do much unless you do a decent job of cutting the throat under the valve & cleaning up the chamber side.

What works pretty fair if there is enough material to work with is 15-30-45-60- & 75 into the throat on the intake & 10 or 15, -35-45-& a full radius to the 75 in the throat for the exhaust.

Then you can clean the "pocket" under these cuts down into the bowl area of the ports.
Grind all the rough casting flash & crap out of the ports, leave the intake on the rough side, like 80 grit or so.

Spend your time in the bowl area & around the guides.
Just clean the short turn of sharp edges, do not lower it towards the valve seat.

You can gasket match the intake but don't expect much in the way of gains here as this is the best flowing & largest part of the port.
Just use the gasket to get them all the same size & make the intake manifold runner just slightly smaller then the head but unless the gasket is close to the size of the head opening don't just make the head bigger because the gasket is.

You can polish the chamber & exhaust & raise the exhaust as much as possible towards the header, at preferably as high as the header is.
The floor of the exhaust port can be cleaned up but don't lower it or try to "match" it to the header at the bottom.

This should keep you busy for a few minutes :D

Hello Mike,

Any worthwhile gains to be made reshaping the combustion chambers? I recall reading in How to Hot Rod BBC they recommend increasing the size of the chamber etc near the exhaust side. I assume this entails grinding to the head gasket area as well smoothing out some of that area to improve "swirl charateristics".

What is you take on this?

Originally posted by MonteMan454:
Hello Mike,

Any worthwhile gains to be made reshaping the combustion chambers? I recall reading in How to Hot Rod BBC they recommend increasing the size of the chamber etc near the exhaust side. I assume this entails grinding to the head gasket area as well smoothing out some of that area to improve "swirl charateristics".

What is you take on this? =
On the exhaust side you will aid flow by unshrouding towards the gasket but don't know about changing the swirl as I haven't tested swirl.
I also use the 15 deg top cutter on the intake to open the chamber towards the gasket with a "plunge" at the wall to unshroud the valve & it really seems to help low lift flow.

To add, It's been about 10 years since I have ported a set of rat heads as I normally just don't have the time anymore but I do a lot of "creative" valve jobs on circle track stuff that cannot be ground on. & have done a "few" flow tests over the years.
I have picked up the flow pretty good on a lot of heads by just doing a decent valve job on something someone has hamburgered up assuming they left enough material to work with graemlins/angry.gif

There are some excellent heads out there now so unless you are going to do a lot of the porting work yourself I feel you are probably money ahead spending it on a good set of heads.
Unless of course you have a friend that will work for beer that you can trust with your parts :D
It doesn't take a lot of work on something like the 781's to make power after a real good valve job & some simple unshrouding has been done.
You don't need to play Joe Mondello, just clean up the sharp edges & smooth the chamber & ports along with a port match & a little bowl work.
BTW, port match does not mean gasket match ;)

Thanks for the replies guys! :D