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Discussion Starter #1
I need some advice/info on a problem I am having with my motor.

I have about 1500 miles on my 350 long block, and it has been smoking on start up for quite some time now. I had a lot of heating problem at first and I thought the excessive heat may have melted the valve seals or damaged them in some way to cause the smoking on start up.

This weekend I pulled my engine to do some cleanup work on the fire wall, just hiding wiring and cleaning it up.

Anyway, when I pulled the plugs all the plugs had oil on the threads.

I looked into the exhaust ports and the valves were wet with oil and they have a lot of carbon/gunk on them. Anyway they don't look like a 1500 mile motor.

After I pulled the motor I looked at the intake ports and the valves look like the exhaust valves with carbon and gunk on them. I pulled the heads and took out an exhaust valve and there are no seals what so ever. I pulled an intake valve and there is a seal on them. It didn't have the oring on the upper part of the stem, but there was a seal lower down on the guide. All Intake valves had the same seals and there are no seals on the exhaust valves at all.

I checked the casting numbers on the heads, 354434, and the info I found say there are a 262/305 head.

The motor ran so I know that they fit and work, but why would anyone do this? Is there some advantage to using a 262/305 head on a 350? And why aren't there any seals on the exhaust valves?

Thanks in advance, any advice will be help full.

Kevin
 

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Measure the bore maybe its not a 350 either. Maybe just used some cheap heads he had lying around. 350's are 4.00 inch bore , 305's are what 3.750 I think?
 

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Discussion Starter #3
Measure the bore maybe its not a 350 either. Maybe just used some cheap heads he had lying around. 350's are 4.00 inch bore , 305's are what 3.750 I think?
Jim383,

The bore is 4.00" and the casting numbers indicate a 350.

Casting #10066036.

I think you maybe right on the junk heads, and that makes me not feel too good about the shop I bought the long block from.

Also make me wonder how the bottom end is.
 

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262/395 heads on a 350 and missing valve seals

Hey Now, a couple of questions, Are there any numbers stamped on top of the pistons?; like .30 or .40 indicating block was bored. Second The two valves you have out or removed the keepers and springs; Can you wriggle the valves side to side while in the guide, with out springs and keepers? If you can, the heads may need more work than they are worth. Sincerely, "Bill's" II :)
 

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Discussion Starter #5
Bill's II,

Yes, pistons are .060 over and I can still see the cross hatch from the hone in all the cylinders.

As for the valves I removed 1 intake and 1 exhaust from the same cylinder and they were both fairly tight in the guide. No lateral play and they were smooth and easy to move up and down in the guide, so I think the guides are OK, at least the 2 I checked.

I should also mention that I did do a leak down test; engine removed, all rockers disconnected (all valves closed), and intake off.

The results of the leak down weren't impressive, all cylinders were about the same with about 35-40 percent leakage. Bear in mind I was using a Harbor Freight leakage tester, and engine was cold.

My plan going forward, as of now, it changes by the minute, is to reseal the heads, put it back together and save my pennies and run it till it dies and get a stroker short block. Or I may buy some aluminum heads and trash the old ones. See I changed may plan faster than I can type this.

I am not too concerned at this point about the bottom end because all cylinders were basically the same, my oil pressure was very good and I don't hear or feel any rod knocks.

Is it a common thing to not seal the exhaust valves or did someone screw up when they done this set of heads?

Maybe a Friday afternoon at 4 PM rebuild on the heads, maybe the engine too... who knows.

Thanks

Kevin
 

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Might try cleaning them and using some valve compound on them. Adding new seals.

BTW Friday 4 pm. I'd be gone already. Lol. :yes:
 

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Cyl Heads

From what you have described, it is possible the heads never had a valve job. GM went to an umbrella (shedder) type exhaust seal in the early 1980s. It is not uncommon for all eight ex guides and ex valve stems to be worn enough to cause oil consumption even with new valve seals.....Remove the heads and send them to a machine shop for repair.
 

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Discussion Starter #8
ism duce,

That's probably what I am going to do.

I'll send them out for a quote and see what it takes to fix them.

If too much maybe I'll be forced to by some AFR's.:devil:

Thanks

Kevin
 

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With the reduced price of aluminum heads both new and used now, I wouldn't even consider using those low performance heads. Find out what cc your old heads have if your happy with the compression ratio then look for some aluminum ones with larger valves and a similar cc size although aluminum heads with tolerate more compression without spark knock if you don't get crazy with timing. Just my 2 cents worth.
 

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Discussion Starter #10
monkeyy337,

Already been checking them out...these bad heads may just be a blessing in disguise.

Thanks

Kevin
 

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305 heads on a 350 is not so bad. It has been said in some of the articles I've read that the 305s swirl the fuel for better distribution and firing. also the 305s give a smaller cc and seem to produce a lot of low end torque. That's the way it works on my 74. the heads are stock 305 with the smaller valves. I've got a set of 2.02 350 heads on another 350 I have. It has a big cam and hi compression pistons so I really can't compare them.
I like the aluminum heads idea are there any proven aluminum heads on stock chevy 350s that work well on a 1980 block? haven't found any info on that yet so any help is appreciated.


D
 

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Those heads have a 60 cc chamber which is very small for a smog head---small valves as well--1.72' intakes . A machine shop in Tennessee built the engine in my Nova for the guy i bought the car from. It's a 383 & it had the same heads on it you have. I had detonation problems running even 6* initial timing with 93 octane. I ripped those off & bought a set of aluminum big valve large port heads---now i can run 12* initial & 91 octane if i want. Chevrolet used 2 different seal styles on their heads---FACTORY SEAL KITS had umbrella & o-rings,but the umbrellas for the exhaust valve stems were a high temp. material & different color . My advice to you---ditch those heads & save some weight & headaches---well worth it !
398500
 

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A decent aluminum head will probably wake the engine up. The 305 head was never designed with performance in mind. No way I'd spend money on the 305 heads if I could swing something else. Even a entry level vortec head would be a big improvement.
 

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listening to the posts, heads only, here's what I've got 1980 350 truck block, 305 heads of unknown characteristics, an edelbrock 600 with edelbrock manifold and headman headers. compression in the 140 to 150 range. there is a magazine article of 305 heads on a 350. findings were better combustion pattern, smaller cc, batter low end torque.
So then assuming as you say going to a Vortex head. I'd use one with the same cc as the steel heads. so what's so improved i na vortex head?
 

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listening to the posts, heads only, here's what I've got 1980 350 truck block, 305 heads of unknown characteristics, an edelbrock 600 with edelbrock manifold and headman headers. compression in the 140 to 150 range. there is a magazine article of 305 heads on a 350. findings were better combustion pattern, smaller cc, batter low end torque.
So then assuming as you say going to a Vortex head. I'd use one with the same cc as the steel heads. so what's so improved i na vortex head?
In simple terms the difference is air flow. Think about your engine as a big air pump. The more air you can get thru your heads the more power it will have. The 305 heads have small valves and small ports. When you bolt on a head that has larger valves and better ports you free up air flow and in turn make the engine breathe better. This will also make your engine more efficient which will probably make it get better fuel mileage if driven moderately. It's no different than a person with asthma or COPD. They are limited because they cannot get enough air into their body to make them breathe good. Headers do not do anything other than create better air flow out of the engine. You cannot get air in unless you get it out. On a small block chevy engine the heads/camshaft is very important to performance.
 

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Also, get the smallest chamber they offer, it's going to be a bigger chamber than you have now but you don't want to lose too much compression.
 

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Another important thing to consider is how far your current piston is down in the cylinder at TDC, and what piston it has now. Your current head has a 65cc chamber. For example, if your down in the hole 0.030 now, and then you replace these heads with a 68cc chamber head, you may not be able to run a thin enough head gasket to make even 9:1 compression without replacing pistons. If you do decide to change cylinder heads, you might also want to consider 0 decking the block which might give you more of a cylinder head/head gasket selection. Nice thing is that it's a small block Chevy and there's lots of parts available. While the heads are off you can check all this stuff out, document it, and plan for the future.
 
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