Heads on a 305

[junior3382]

I have a small project going with a friend of mine, and before we get to involved, we wanted to ask this question. Is it difficult to replace the heads on a 305? Its an earlky 80's K10 pickup, 4x4. Thats all I know. He doesn't want to have it done, and I thought it sounded like fun. But what should we look for? any known issues we should look for?

Thanks for all the help.

[mrjohnwayne]

not hard at all. The most difficult thing is setting the valve lash which still isnt hard.

[junior3382]

I am sorry if this shows my total inexperience in this partcular area, but what is a valve lash? we are getting a complete head and gasket kit. will that already be set?

[mrjohnwayne]

valve lash is the gap between the rocker arm and valve stem. It is set after you have replaced the heads, pushrods, and rocker arms.

[junior3382]

Is there a special tool for this? I have tooled around with motors before, you know the stupid stuff, starters, tune-ups, even rplaced a fwd motor in a grand am once, that was fun.... but I have never heard of this term. Now I know what you are saying makes sense, but I still don't think I grasp it perfectly. After we put the heads on, slip in the push rods and tighten the bolts to spec, whats next? We thought we could just lift one off, and put the other in, so I would hate to see us screw this up. I am all for trying new things, and my buddy knows this, but I like to be able to understand it first. Thats why I started visiting here, you guys have answered a lot of questions for me. So if I am missing something, please tell me. Does that make sense?

[75K30]

You are not going to need any special tools. O.K. a couple will help, but you really don't need anything special. Mrjohnwatne is talking about adjusting the valves. You are going to have to adjust the valves after you install the heads.
You will have to check the heads to make sure thay are flat, and not warped, or they will never seal, and you will be removing the heads again. If you machine the heads to make them true, you will be removing material from them, and the new head gasket will have a different installed heigth than the heigth it was when it was removed. This has an affect on the valve adjustment since the pushrod remains the same length.

Alright the procedure.
You are gong to get dirty, you are probably going to burn yourself, and you may invent a couple of new words. you will not like doing this, and after it is done, you will not look foward to ever doing it again.
Can you tell I don't like to do this.
Adjust only one side at a time, no need to make a mess on both sides because you can only get to one side at a time. Use oil restrictors, (here is the special tool) for the rockers, or use a butchered valve cover that has the top removed to gain access to the rockers.
After you have assembled everything, and you have tightened the rockers down to zero lash. This is a tight rocker that is only tight enough to allow the pushrod to spin when the valve is closed. make sure all of the valves are this way.
Start the engine, and loosen one of the valves, a little. You should hear it clatter quite a bit more than the others. I try to use a stethoscope for this procedure. It helps me hear the individual rockers. Slowly tighten the rocker until the clatter goes away, then tighten the nut 1/4 to 1/2 turn. This will set the pintle. Repet for the rest of the valves, and button that side up. Then when you are satisfied, you get to do the other side. I like to check the oil at this point, and add some, because you are going to spray more oil around, and you do not want to run the risk of running the engine low. This is true for after you complete the other side. Make sure you dont run this thing dry.
After all of the valves are set, it should be very quiet, and the engine should run smooth. If you hear any rocker clatter, or the truck seems to be running poorly, you will be running the valves again, so take your time, and have some patience.
Best bet is to buy a book on valve adjustment. It will have pictures, and explain in better detail the procedure, and explain why.
You are capable of doing this, just have to read a little.

[junior3382]

Okay, that is definitely a more detailed explanation, thank you 75K30. I knew it would not be as simple as one off one on. And yes I know we will get dirty, but that is half the fun right? I wanted the experience, and I know the satisfaction will be there when we are finished. As for the book, would the Haynes manual have what we need, or do we need to find a specialty book? Between the two of us, i know we can do this, but there will be beer involved.....lol.... so I will let you guys know how we made out. Anyways, is the valve adjustment all we need to worry about?

[bradrhale]

do NOT overtorque the head bolts. or undertorque them for that matter. torque them down in the proper order and not just which ever bolt is next in line. the head will not seat properly doing it that way.

[75K30]

Seems to me that bradrhale covered the torque of the heads, note, they do have a sequence, so we have discussed the valves. On this site I have seen plenty of guys having troubles with distributor installation, so make sure you don't get confused with the removal, and installation, and you guys should be alright.
As for the books, you could use a haynes, or chiltons, but these are very practical bosks. Good ones, but perhaps a little too comprehensive, and maybe a little too redundant with info you already know. Instaed I might lean towards a specialty book ,for modifying, or "Hot Rodding" the small block chevy. This will have detailed instructions for doing a simple valve adjustment, and it will describe how you can pick up some extra ponnies with little modification. Don't get me wrong, your buddies 305 willl never be a hot rod, but you are mechanically at the level where you can appreciate a book with a little more knowledge written into it. These alternative books offer decent descriptions, and opinion on why a modification works over another option.
Either way, it is up to you, heak, buy a couple of books, it never hurts to have knowledge...

Good luck with your project..

[junior3382]

I went to NAPA this morning and they have a book just for chevy engines. Now this is just a work truck, and way to ugly to turn into a projct, but your right, you never know what a little more knowledge will get you. And I did know about the order of the head bolts and have the tourque specs for those to.. We borrowed a beautiful Tourque wrench for this too... anyways, this will be next weekends proiject, I will let you guys know how we did.