deciding to pull heads or not
 

I am doing a refresh of my pontiac 350, 1970. i was just going to do total gasket kit, timing set, and valve seals. my compression check before pulling the motor were all around 140 each cylinder, so i figure the head gaskets are good. It overheated a bunch of times so i just completed flushed the block with the freeze plugs out. and working on the WP plate and clearances. but i took a look at the top of the valves from the intake. and they're pretty carboned up.

reason i didnt want to pull the heads is b/c i didn't want to have the cast heads planed before installing. ( if i even need too)?

anyway, carbon on top of valves prob no effect on engine performance, esp any overheating.? the valve seats are prob ok, but the valve stem seems wet when i look in the exhaust port.

i'm attahcing a pic of the valve. i can send the valve stem from the exhaust port if that helps

thanks

First of any heads from 1970 will need new oil control O-rings on the valve stems, especially after a overheating session they just crumble into peices .

Next up that gray color in that Intake port is Exh pollution, so it looks like your Intake valves are not sealing as they should.

You might be opening a can of worms if you take them off, that carbon is probably from oil deposits from the guides leaking. If you just take them apart to clean them up and put them back on, it will just show up again. I’d guess it may need guide seals while you have them off.

That looks like a significant amount of carbon on the back of the intake valves. Yes, could be opening up a can of worms if you pull the engine down. Honestly, you need to look at your overall goals for the engine and the car, how much $$ your willing/able to spend on it. Leaving the heads on and just replacing leaking gaskets and valve seals will probably solve the external oil leak issues but little else. Your giving up significant HP and driveability and fuel economy by not removing the heads, having them surfaced if needed and a good valve job performed, possibly guide liners. Also the heads could be cut for PC style positive seals at this time. That all cost $$$ however. Hard to give an exact number but based on that caked up intake valve, your probably giving up at least 40 HP leaving the heads on and not performing some service.

Thanks guys. Alright for now I will probably take the heads off and take a good look. Maybe I’ll get lucky and the guides will be ok -ish. I can clean the valves. Lap them ? New guide seals and oil o ring. New keepers and see how it goes.

I didn’t really plan on machining to positive seals just yet.

I plan on a full gasket kit from butler so I’ll have the new head gaskets as well. And just install the stock black valve seals even though the positive seals I know are better.

I just know my limits. I’ve never messed with valve guides nor valve seats. So those I can’t do. But I can clean them up and handle seals.

Can’t make it worse. I hope haha.

I’ll attach a picture for fun of the large chunk that power washed out of my water jacket

You can try lapping the valves by means of a fine lapping compound ( not the course stuff) but after the two or three overheating session you posted about the lapping process might only serve to show you how badly the valves need to be trued up and a overall valve job done, and we have not even talked about the guides yet!

If you use a wire wheel to clean up the chambers be sure to use a no harm Brass wire type when you get near the valve seats.

This check out process will not be a quick since it takes a long time to get all the valve faces clean enough to allow a lapping stick to suck down and hold onto to it well.


Is that chunk of crap that came out of your cooling system metalic at all, as in responding to a magnet?

Crap like that forms from ancient antifreeze and it being cut with tap water with its high mineral content which will practically guarantee a motor overheating session in time.

By the looks of that crap from your cooling system I would be very surprised if your water pump impeller was not well on the way to being shot.

A caution i would take is i wouldn't take the heads apart unless i was going all the way, refrain from valve rotation, they may or may not rotate naturally which leads to uneven seat wear and if you rotate a valve you may risk upsetting a working seal

you could re'seal the upper end of valves before pulling heads then pull and clean the heads and reinstall

once removed and on the ground soak back of valves with a strong cleaner and pressure wash early in process then take them to a warm dry area when done cleaning

now after a wash you risk rust in valve guides reason for warm dry place .. and i would rubber mallet tap open each valve every day or couple days, a day or two before install i would lay heads flat and use a thinner motor oil dripped down valve stem in the ports so it will run into the guide clearance to avoid a dry startup there