What is the tell tale sign your SBC chevy heads are going bad? When the guides are bad what are the signs? I was thinking about getting some summit racing heads, cast iron. Using some roller rockers 1.5 this makes the hp smoothe. I got a valve that seems to either stick or something. When I pull out I can hear it on the right side, there is no misfire but a hard tap.
do a compression test if you have no compression in any cyl. then one of the valves is gone. what bi have found is the guides wear first then with the valve rattling around in a bad guide it takes out the seat.
Sounds like an exhaust leak to me if it is on one blank under power. If you are going to spend money on new heads buy aluminum. They breathe better and they are always repairable..... about the same money.
When you have a bad guide, it will tend to use a bunch of oil. If you remove the spring, the stem will have a bunch of play. Clearance varies, but it is usually 0.003 or less. I have seen well worn guides that make no noise at all. A deceleration rattle could be a rod bearing. There is no reason to spend extra bucks on aluminum heads. Cast iron heads can flow very well and are durable if you have good, thick castings. I highly recommend having thick wall guides installed by a good builder. Don't use thinwalls or have your existing guides knurled. This tends to be very temporary in my experience. Summit used to sell rebuilt heads. I helped a friend sell parts from a motor with older summit heads. They were mismatched castings and one had a weld. I don't think they still sell this garbage, but they do have some very good deals on iron Dart heads. You will still be able to save cash by having your heads rebuilt, provided that you are satisfied with the valve size and castings. If you have a tired motor and put on good heads, oil consumption around the rings will probably increase.
There was a thread recently on whether or not to knurl guides and the general consensus was that knurling is OK if there is a slight amount of wear and it is done properly, and there was nothing wrong with thin wall inserts. Oil consumption is not increased by new valve work. If you notice oil use after a valve job, it was there before the head work and you just thought that you only needed to do the heads.
Now, about your problem; You failed to give a very specific description of the noise. An exhaust leak is possible, does it go away when it warms up and do you have a manifold that is loose, or maybe headers? It also could be you need to adjust your rocker arms, this will show up more when the motor is cold as you said "when I pull out."
For a cheap rebuilder you plan to sell, well, then it may be OK. If it is your pride and joy and you want a lot of trouble free miles, spend a few bucks more. What do thick wall guides cost? About $8 ea. installed? If you make the top end sealing better, you can see more oil consumption around worn rings. Experience and physics......some will argue with it.
I had bad guides replaced last year. The engine would idle fine, but would SOMETIMES buck or backfire under power (highway speeds). One or two valves had a rattle, but nothing very bad. Just slightly louder than normal. When I did my compression check the bad cylinders were low and oil on the rings did NOT help. I had new guides installed and a valve job. Engine runs fine now. I would not have the guides knurled as this fix will not last many miles and the labor cost would be about the same as new guides.
If I rev the motor it would backfire. After the car warmed up I would here this sound when I pull up or take off. Noisey not a smoothe take off. If you rev the motor while it's in park, there is no misfire. I have a 1955 Chevy 2 dr ht it has the summit cast iron heads with roller rockers. This motor sound good and takes off very smoothe. I just bought a street rod (1940chevy coupe) It also has a SBC 350 however it fails an comparsion. Nothing like the 55 chevy. It must be the heads. I think I will go with the Summit racing heads(cast iron) with roller rockers. I also have a stock intake will a performance intake make a difference as well?
Wouldn't a cylinder leakdown test or just putting some air in give you an idea where the leak is? Did you check your plugs over? Wires? Look at the simple cheap stuff before going to the expense of new heads.
compression test and like others have said check the cap/wires. It could be simple like a broke spring or a bad lifter, pull the valve cover , you could have a broken rocker. it's a bit messy but you could run it w/o a valve cover and see if all is working properly on that side.
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