1.94 Valve in Chevy 305 Heads (416 castings)

[68maliblue]

I'm working on a set of 416 casting 305 Chevy heads. The valve job is gone on these and they already have 1.84" valves. I'd like to go to 1.94 valves to save them but it seems like unshrouding the valve will make the chamber walls too thin. I see a lot of people are grinding out the chambers but the castings I have are pretty thin. I checked them with dividers and best I can tell they are .15" thick in the areas in question. Even taking .050" out of the chamber seems to be too much for comfort. How thin can you make the combustion chamber wall and expect it to live? If you have to move the centerline of the valve to make the 1.94" valve work, the low $$$ appeal of these heads goes away very fast. What are you guys doing to fit 1.94 valves on these heads?

[F-BIRD'88]

You don't need to "deshroud the whole thingy..
Most of the air goes in and towards the plug.
Spreay the garden hose thru the intake port to see the pattern.. The chamber wall right beside the intake valve only needs slight deshrouding.

[F-BIRD'88]

How much space between the edge of the 1.84" valve and the chamber wall do you have now?
(red arrow)
At this point I don't think you need to deshroud right there any more than you are comfortable with. Its just not a high flow area.

When mine are done the chamber volume is 61-62cc (1.94/1.60 valves) before any deck milling.

You're right about keeping the total all in net cost in check on these..

[mag2555]

You should contact Ferrea or Manely and see now much it would be to get eight 1.94” valves cut down to 1.92”, it’s probably not much of a additional cost.

[68maliblue]

Here’s a picture of the chamber with the tightest clearance to a 1.94 valve

43CFBE6B-F61C-4251-8195-A4FCE92B01D7.jpeg

[PRH]

Just cut the valves down to 1.90”.
Easily done, even in a hobby lathe.

[F-BIRD'88]

Are these heads going on a 350 or a 305 engine?

[68maliblue]

307 so its going to be fine with 1.94 valves as its got another .125" of bore diameter over the 305. It's another low $$ build. Got the complete short block for $30 with minimal bore wear. Can't feel a ridge on the cylinder walls. Gave it a dingleberry hone and cast rings and new main and rod bearings. Crank/rod clearances are on the high side but OK. Cam is a regrind solid cam 224/224 @ .050" on 108 LSA. Highest cost of this whole build is going to be the cylinder heads.

[F-BIRD'88]

Might try this Melling/Elgin low cost solid , after.
Melling #22402. Elgin #E-1131-P

282/290. 240/250 .521"/.521". 106LSA. 104/108 .024"

[68maliblue]

Thanks F-Bird. This will be a street driven car so that cam seems a little large for a 307 unless I put some gears in it.

[F-BIRD'88]

Yes, gearz is good, especially with lil sbc's.

[F-BIRD'88]

With it going on a 307, minimum combustion chamber volume increase so as to get a performance friendly compression ratio should be a priority vs agressive deshrouding, anyway. Get the ports working.

They pour big but stock mininum cross sectional area is
small.. You can fix that with thru porting.
They need agressive porting. Don't be shy, but also keep the intake port flange opening to a 1205 gasket size.
Many get carried away here. The big gains are deeper in the ports.

I save money by drilling and pinning the stock rocker studs vs $$ machining for screw in studs and guide plates.

[Walter R. Malik]

When "Dart" produced their head for a 305 with a 1.940" intake valve they moved the intake guide toward the exhaust so, de-shrouding the chamber was not necessary.

The same thing can be done here ... if you have the capability.

[68maliblue]

Took apart the other cylinder head and found this ugly exhaust seat. All the other seats look serviceable. This seat is recessed .060” and it looks like they just hit it with a 45 deg cut all the way out to the intake. Is this head scrap or can a replacement exhaust seat be installed without hitting water?

[PRH]

The only concern with repairing that hole is going to be how close to the water jacket does the pocket for the required oversized seat get?
How large does the seat have to be to get out into new material, so the height can be restored?

If you’re paying to have work done, it’s pretty easy to reach the point where the casting isn’t worth fixing.

Machine the seat pocket, look for an obvious breach into the water jacket....... if it looks good, pressure test it.
If it passes, install the seat and carry on.

When it’s just “normal” seat recession, that someone else hasn’t screwed with......... I’ve had the seats be close to .200” down into the port and still repair that with a normal replacement seat.
It’s when the replacement seat OD needs to be quite a big larger than would normally be used in whatever head you’re working on, that the risk for getting to water jacket goes up.