dont know if this is the right forum,but I'll try.I have a set of gm cast heads #3998920 All I can find is a year 72-75.I'm would like to use these on a 406 sbc and need to know if thier junk or can be made into something half decent.Thanks

 

Well what I came up with was that they were used on '72-'73 350s and have 76cc chambers. That right there would tell me that they are too small for a 406. Then again, I'm no cylinder head guru.

 

Yeah I did a little research thier your basic 76cc open chamber smog basically junk!

 

Well even if they were the good stuff from around 69-71 I would think that the ports on heads designed for a 350 would be too small to feed a 406. I could be wrong though.

 

They will not make good power. Go aftermarket - heads are cheap these days.

 

There are no OEM heads for a smallblock from before the late 80s worth anything more than scrap iron unless you want a numbers matching setup.

The late 80s L98 heads will cleany outdo the 202 fuelie stuff and the LT1/Vortec stuff puts them to shame, hell they outdo the GM "Bowtie" race heads from the 80s. As said the aftermarket has a LOT of inexpensive options too.

To bring a set of crappy 60s-70s heads up to running condition you will likely spend what a new set of Vortecs would cost and still have less potential.

 

I wouldn't bother with vortecs on a 406.

Do some research and buy a good head aftermarket that will get you where you want to be

 

Thanks for the input guys.I will be going aftermarket on the cyl heads

 

For a out of the box head, look at a Dart Platinum or the New Pro 1's they are the best as cast out of the box heads for a SBC. Best bang for the buck by far. In the end you will spend the same money on a set of heads as you would getting those junk stock castings to work.

Bret

 

Just to be clear I was not trying to recommend Vortecs, just trying to make a point about how much it would cost to rework junk as opposed to how affordable some of the newer better stuff is.

The Vortecs offer limited intake manifold selection and I believe some slight header complication, great BUDGET head for mild stuff but for something like this the aftermarket has a lot to offer.

 

I'll second that emotion.

Mike....You're still alive!!

Call me sometime.